# Racket Mode ¶

## Table of Contents

- Introduction
- Install, Update, and Uninstall
  - Use Emacs 28.1 or newer with NonGNU ELPA
  - Configure Emacs to use MELPA
  - Install
  - Minimal Racket
  - Uninstall
  - Update
    - Upgrading all packages
    - Updating just Racket Mode
- Configure
  - Which major mode to use
  - Key bindings
  - Font-lock (syntax highlighting)
  - Completion at point
  - Completion in minibuffer
  - Xref (definitions and references)
  - Indent
  - paredit
  - smartparens
  - Appearance of parentheses
  - Edit buffers and REPL buffers
  - eldoc
  - Start faster
  - Inserting Unicode math symbols
  - Ligatures
- Architecture
- Reference
- Commands
  - Edit
    - racket-mode
    - racket-insert-lambda
    - racket-insert-symbol
    - racket-fold-all-tests
    - racket-unfold-all-tests
    - racket-tidy-requires
    - racket-trim-requires
    - racket-base-requires
    - racket-add-require-for-identifier
    - racket-indent-line
    - racket-smart-open-bracket-mode
    - racket-insert-closing
    - racket-cycle-paren-shapes
    - racket-backward-up-list
    - racket-input-mode
    - racket-align
    - racket-unalign
    - racket-complete-at-point
  - Hash Langs
    - racket-hash-lang-mode
    - racket-hash-lang-backward
    - racket-hash-lang-forward
    - racket-hash-lang-up
    - racket-hash-lang-down
    - racket-hash-lang-C-M-q-dwim
  - Explore
    - racket-xp-mode
    - racket-xp-describe
    - racket-xp-documentation
    - racket-xp-next-definition
    - racket-xp-previous-definition
    - racket-xp-next-use
    - racket-xp-previous-use
    - racket-xp-next-error
    - racket-xp-previous-error
    - racket-xp-tail-up
    - racket-xp-tail-down
    - racket-xp-tail-next-sibling
    - racket-xp-tail-previous-sibling
    - racket-documentation-search
    - racket-describe-mode
    - racket-describe-search
  - Run
    - racket-repl-mode
    - racket-run
    - racket-run-and-switch-to-repl
    - racket-run-module-at-point
    - racket-repl
    - racket-repl-describe
    - racket-repl-documentation
    - racket-racket
    - racket-profile
    - racket-profile-mode
    - racket-logger
    - racket-logger-mode
    - racket-debug-mode
    - racket-repl-clear
    - racket-repl-clear-leaving-last-prompt
  - Test
    - racket-test
    - racket-raco-test
  - Eval
    - racket-send-region
    - racket-send-definition
    - racket-send-last-sexp
  - Collections
    - racket-open-require-path
  - Macro expand
    - racket-stepper-mode
    - racket-expand-file
    - racket-expand-region
    - racket-expand-definition
    - racket-expand-last-sexp
  - Packages
    - racket-package-refresh
    - list-racket-packages
    - racket-package-mode
    - describe-racket-package
  - Other
    - racket-debug-toggle-breakpoint
    - racket-mode-start-faster
    - racket-mode-start-slower
- Variables
  - General variables
    - racket-program
    - racket-command-timeout
    - racket-memory-limit
    - racket-error-context
    - racket-user-command-line-arguments
    - racket-browse-url-function
    - racket-xp-after-change-refresh-delay
    - racket-xp-highlight-unused-regexp
    - racket-xp-add-binding-faces
    - racket-xp-eldoc-level
    - racket-documentation-search-location
    - racket-expand-hiding
  - Hash lang variables
    - racket-hash-lang-token-face-alist
    - racket-hash-lang-module-language-hook
  - REPL variables
    - racket-repl-buffer-name-function
    - racket-submodules-to-run
    - racket-repl-history-directory
    - racket-history-filter-regexp
    - racket-images-inline
    - racket-imagemagick-props
    - racket-images-keep-last
    - racket-images-system-viewer
    - racket-images-do-not-use-svg
    - racket-pretty-print
    - racket-repl-command-file
    - racket-repl-echo-sent-expressions
  - Other variables
    - racket-doc-index-directory
    - racket-doc-index-predicate-function
    - racket-indent-curly-as-sequence
    - racket-indent-sequence-depth
    - racket-pretty-lambda
    - racket-smart-open-bracket-enable
    - racket-logger-config
    - racket-before-run-hook
    - racket-after-run-hook
    - racket-sexp-comment-fade
  - Experimental debugger variables
    - racket-debuggable-files
  - Showing information
    - racket-show-functions
  - Running racket and raco commands in a shell or terminal
    - racket-shell-or-terminal-function
  - Racket input method
    - racket-input-prefix
    - racket-input-translations
- Configuration functions
  - Showing information
    - racket-show-pseudo-tooltip
    - racket-show-echo-area
    - racket-show-header-line
    - racket-show-pos-tip
  - Associating edit buffers with REPL buffers
    - racket-repl-buffer-name-shared
    - racket-repl-buffer-name-unique
    - racket-repl-buffer-name-project
    - racket-project-root
  - Browsing file URLs with anchors
    - racket-browse-url-using-temporary-file
  - Configuring back ends
    - racket-add-back-end
  - Running racket and raco commands in a shell or terminal
    - racket-shell
    - racket-term
    - racket-ansi-term
    - racket-vterm
- Faces
  - All
    - racket-keyword-argument-face
    - racket-reader-quoted-symbol-face
    - racket-reader-syntax-quoted-symbol-face
    - racket-here-string-face
    - racket-xp-def-face
    - racket-xp-use-face
    - racket-xp-unused-face
    - racket-xp-tail-target-face
    - racket-xp-tail-position-face
    - racket-xp-binding-lang-face
    - racket-xp-binding-lang-use-face
    - racket-xp-binding-import-face
    - racket-xp-binding-import-use-face
    - racket-xp-binding-local-face
    - racket-xp-binding-local-use-face
    - racket-logger-config-face
    - racket-logger-topic-face
    - racket-logger-fatal-face
    - racket-logger-error-face
    - racket-logger-warning-face
    - racket-logger-info-face
    - racket-logger-debug-face
    - racket-doc-link-face
    - racket-ext-link-face
    - racket-doc-output-face
    - racket-doc-litchar-face
    - racket-repl-message
    - racket-repl-prompt
    - racket-repl-value
    - racket-repl-error-message
    - racket-repl-error-location
    - racket-repl-stdout
    - racket-repl-stderr
    - racket-hash-lang-text

## Introduction ¶

The Racket Mode package consists of a variety of Emacs major and minor modes, including:

- `racket-mode`: A major mode to edit `.rkt` files. Generally assumes `#lang racket`.
- racket-hash-lang-mode: An alternative to `racket-mode` using behavior specified by a `#lang` for colors, indent, expression navigation, etc. Experimental.
- racket-xp-mode: A minor mode to enhance either edit mode. Explain and explore code, similar to background check-syntax in Dr Racket.
- `racket-repl-mode`: A major mode to run programs and use a REPL.
- Various other modes to support specific features:
  - racket-logger-mode
  - racket-profile-mode
  - racket-debug-mode

For code, issues, and pull requests, see the Git repo.

To sponsor this work, see GitHub Sponsors or PayPal.

## Install, Update, and Uninstall ¶

The most common way to use Racket Mode is to install from a package archive like MELPA or NonGNU ELPA.

Some people also use a system like straight.el.

Note that Racket Mode is only available on MELPA (not “MELPA Stable”), and is available as a “rolling release” from NonGNU ELPA.

### Use Emacs 28.1 or newer with NonGNU ELPA ¶

Emacs 28.1 or newer comes configured to use NonGNU ELPA, in which case you can skip ahead to Install.

With older versions of Emacs, you can use MELPA.

### Configure Emacs to use MELPA ¶

Following is a quick guide that may work for you. (For definitive instructions and the latest trouble-shooting tips, please see https://melpa.org/#/getting-started.)

- Add the following to your ‘`~/.emacs`’ or ‘`~/.emacs.d/init.el`’:

    (require 'package)
    (add-to-list 'package-archives
                  '("melpa" . "https://melpa.org/packages/")
                  t)
    (package-initialize)

- Restart Emacs.

> NOTE: If you ever get an error message about “contacting a host” or “downloading an archive”, the problem is not unique to Racket Mode. Please see https://melpa.org/#/getting-started.

### Install ¶

When Emacs is configured to use NonGNU ELPA or MELPA:

1. Type `M-x` `package-initialize` `RET` .
2. Type `M-x` `package-refresh-contents` `RET` .
3. Type `M-x` `package-install` `RET` `racket-mode` `RET` .

> NOTE: If you get an error message about “contacting a host” or “downloading an archive”, the problem is not unique to Racket Mode. Please see https://melpa.org/#/getting-started.

### Minimal Racket ¶

If you have installed the minimal Racket distribution (for example by using the homebrew formula) Racket Mode needs some additional Racket packages. A simple way to get all these packages is to install the `drracket` Racket package. In a command shell:

    raco pkg install --auto drracket

A more-targeted approach is instead to install these specific packages and their dependencies:

    raco pkg install --auto data-lib errortrace-lib macro-debugger-text-lib rackunit-lib racket-index scribble-lib drracket-tool-text-lib

If you do not want to use `racket-xp-mode`, then you can omit `drracket-tool-text-lib`.

On a headless server, you might want to omit `gui-lib`. Unfortunately, `racket-doc` depends on `gui-lib`. On the one hand, if you uninstall `racket-doc` and `gui-lib`, you will no longer be able to access documentation when using a Racket Mode back end running there. On the other hand, if you leave `gui-lib` installed, you should be careful to run the Racket Mode back end using `xvfb-run racket`.

### Uninstall ¶

To uninstall Racket Mode, simply type `M-x` `package-delete` `RET` `racket-mode` `RET` .

You should probably also exit and restart Emacs.

### Update ¶

#### Upgrading all packages ¶

The “easy path” provided by Emacs is to update all packages to their latest versions. Although you might not want to do this — see next section — here is how to do so:

1. Use `M-x` `package-initialize`.
2. Use `M-x` `package-refresh-contents`.
3. Use `M-x` `list-packages`. It should display a message like “42 packages can be upgraded; type ‘U’ to mark them for upgrading.”.
4. Press `U` as suggested to mark them all.
5. Press `x` to execute.

After such a mass update, it might be wise to exit and restart Emacs.

> NOTE: If you get an error message about “contacting a host” or “downloading an archive”, the problem is not unique to Racket Mode. Please see https://melpa.org/#/getting-started.

#### Updating just Racket Mode ¶

Updating all packages sometimes is more than you want. For example, maybe you will discover that some packages have changed in ways that require you to take time to learn about, change customizations, and so on.

To update just Racket Mode:

1. Uninstall.
2. Optional but most reliable: Exit and restart Emacs.
3. Install again. This will install the latest version.

## Configure ¶

Although Racket Mode can be customized with many Variables, there is only one that you might need to set: racket-program. This is the name or pathname of the Racket executable. It defaults to `Racket.exe` on Windows else `racket`.

On Windows or Linux, this default will probably work for you.

On macOS, downloading Racket doesn’t add its `bin` directory to your `PATH`. Even after you add it, GUI Emacs doesn’t automatically use your path (unless you use the handy exec-path-from-shell package). Therefore you might want to set `racket-program` to a complete pathname.

You can `setq` this directly in your Emacs init file (‘`~/.emacs`’ or ‘`~/.emacs.d/init.el`’), or, use `M-x` `customize`, as you prefer.

### Which major mode to use ¶

Racket is a programming language.

Racket is also a “language-oriented programming language”. Most Racket source files contain a ‘#lang‘ line. The lang may be an s-expression lang like `racket`, or an at-expression lang like `scribble/manual`, or something completely different like `datalog` or `rhombus`.

The Racket Mode package offers a choice of two major modes to use in buffers for viewing and editing source code. Each has pros and cons.

Whereas `racket-mode` is in the tradition of Emacs `lisp-mode` and `scheme-mode` and assumes s-expression langs, `racket-hash-lang-mode` takes the approach of DrRacket to work for all langs.

- `racket-mode` is the original, “classic” mode for `#lang racket` and related s-expression languages. It is implemented entirely in Emacs and does not need Racket Mode’s back end racket process running. Font-lock (coloring) uses rules for a fixed set of identifiers from `racket` lang and popular modules like `racket/match`. Indentation uses rules for a fixed set of forms, and may be customized.
- `racket-hash-lang-mode` uses font-lock (colors) and indentation determined by the lang; to get this information it does need the Racket Mode’s back end racket process running. Although basic editing should feel fast, you might notice some delay when indenting. You might see colors appear after a small delay (but it will not block editing). Speaking of colors, they will be “plainer” than `racket-mode` – just colors for tokens like numbers, comments, strings, and keywords. This looks similar to DrRacket. However you can enhance this in various ways; see the discussion of racket-hash-lang-module-language-hook.

You can use different major modes for different kinds of files:

- For editing `.rkt` files and s-expression langs, which mode to use is personal preference.
- For `.scrbl` and at-expression langs like `scribble/manual`, `racket-hash-lang-mode` is probably better than `racket-mode`. (Note there is also an unrelated `scribble-mode` package.)
- For non-s-expression langs like `datalog` or `rhombus` (`.rhm`), `racket-hash-lang-mode` is definitely better than `racket-mode`. (Note there is also an unrelated `rhombus-mode` package.)

You can use `auto-mode-alist` to tell Emacs which major mode to use initially for certain file extensions. Also, in a buffer you can use `M-x racket-mode` and `M-x racket-hash-lang-mode` to switch between them.

### Key bindings ¶

To customize things like key bindings, you can use `racket-mode-hook` in your Emacs init file to modify `racket-mode-map`. For example, although `C-c C-c` is bound by default to the `racket-run` command, let’s say you wanted `F5` to be an additional binding:

    (add-hook 'racket-mode-hook
              (lambda ()
                (define-key racket-mode-map (kbd "<f5>") 'racket-run)))

Likewise for `racket-repl-mode-hook` and `racket-repl-mode-map`.

### Font-lock (syntax highlighting) ¶

> Note: The alternative major mode racket-hash-lang-mode disables all of the following behavior and uses colors determined by the #lang.

Font-lock (as Emacs calls syntax highlighting) can be controlled using the variable `font-lock-maximum-decoration`, which defaults to `t` (maximum). You can set it to a number, where `0` is the lowest level. You can even supply an association list to specify different values for different major modes.

Historically you might choose a lower level for speed. These days you might do so because you prefer a simpler appearance.

Racket Mode supports four, increasing levels of font-lock:

- `0`: Just strings, comments, and `#lang`.
- `1`: `#:keyword` and self-evaluating literals like numbers, quoted symbols (including symbols with spaces delimited by `|` characters), and `#rx` and `#px` regular expressions.
- `2`: Identifiers in `define`-like and `let`-like forms.
- `3`: Identifiers provided by `racket`, `typed/racket`, `racket/syntax`, and `syntax/parse`. (This level effectively treats Racket as a language, instead of a language for making languages.).

### Completion at point ¶

In Emacs, a major mode may supply a “completion-at-point function”. This function is used by manual completion commands like `complete-symbol` (bound by default to `C-M-i` ), as well as by auto-completion packages like `company-mode`.

- `racket-mode` supplies `racket-complete-at-point`, which simply supplies the same symbols that it knows how to font-lock. This does not require the Racket Mode back end to be running. But of course the completion candidates do not correspond to your program’s definitions or those it imports. This is a static, “better than nothing” fallback.
- `racket-xp-mode` — an optional minor mode that enhances `racket-mode` — supplies `racket-xp-complete-at-point`, which uses a static analysis to find local and imported binding names. Although this requires the Racket Mode back end to be running — and will automatically start it — it does not require the edit buffer to be `racket-run`. This also supplies meta data usable by the `company-capf` backend.
- `racket-repl-mode` supplies `racket-repl-complete-at-point`, which uses the result of `namespace-mapped-symbols` on the program currently running in the REPL.

These completion functions are set by default. (However, `racket-xp-mode` is not enabled by default. To do so: racket-xp-mode.)

If you want `TAB` to do completion as well as indent, add the following to your Emacs init file:

    (setq tab-always-indent 'complete)

This changes the behavior of Emacs’ standard `indent-for-tab-command`, to which `TAB` is bound by default in `racket-mode` and `racket-repl-mode`.

### Completion in minibuffer ¶

Sometimes Racket Mode asks for input in the minibuffer. To do so it uses the standard Emacs function `completing-read`, so as to be compatible with all Emacs packages that enhance `completing-read`, such as helm, ivy, ido-completing-read+, vertico, and so on.

(Earlier versions of Racket Mode sometimes used `ido-completing-read`. If you have upgraded Racket Mode and miss that, simply install the ido-completing-read+ package.)

### Xref (definitions and references) ¶

Several modes support the Emacs commands

- `M-.` `xref-find-definitions`
- `M-?` `xref-find-references`
- `M-,` `xref-pop-marker-stack`

To do so, each mode adds a local hook for `xref-backend-functions`:

- racket-mode: `#'racket-mode-xref-backend-function`
- racket-xp-mode: `#'racket-xp-xref-backend-function`
- racket-repl-mode: `#'racket-repl-xref-backend-function`

If you prefer, you can remove the local hook — e.g. for `racket-mode`: `(remove-hook 'xref-backend-functions #'racket-mode-xref-function t)`.

You can `M-x customize-group` and enter `xref` to adjust some other settings. For example, the customization variable `xref-prompt-for-identifier` controls which commands prompt you and when. You might prefer to set it to `nil`.

If you use `paredit`, by default it binds `M-?` to `paredit-convolute-sexp`. You can change that binding in `paredit-mode-map` allowing the global binding for `M-?` to be used, or, pick some other key for `xref-find-references` in the global map.

Finally, what to expect:

- Racket does not have a global or project-wide database of definitions and references.
- Various modules can export identifiers with the same symbolic value – for example a different “define” is provided by `racket/base`, `typed/racket/base`, and other modules.
- A module can import something, then rename, contract, and re-export it.

As a result, to find a definition, it is necessary to know exactly which identifier is meant — either by expanding the module (as is done by `racket-xp-mode`) or by actually running it (`racket-repl-mode`). Once known, we can usually find the definition site, even through a chain of renaming and/or contract-wrapping exports. In addition, when point is on a module within `require` form, we can usually find the source file. (In plain `racket-mode` edit buffers not enhanced by `racket-xp-mode`, the only thing that `xref-find-definitions` does is visit relative requires, e.g. `foo.rkt` in `(require "foo.rkt")`.)

As for finding references, the default xref implementation is used, which greps for strings among a project’s files. Although `racket-xp-mode` can sometimes do better, using `drracket/check-syntax` for definitions and references within the current buffer, beyond those it also falls back to the default implementation.

In any case, using the Emacs xref API allows for consistent command names, shortcut keys, and even a special buffer to navigate among references and visit each source location.

### Indent ¶

> Note: The alternative major mode racket-hash-lang-mode disables all of the following behavior and uses indentation determined by the #lang.

Indentation can be customized in a way similar to lisp-mode and scheme-mode: racket-indent-line.

(Indentation preserves your line breaks. If you want to use an auto-reformatter — an expressive pretty printer that chooses line breaks while computing an optimal layout — the Racket package fmt is supported by the Emacs package emacs-format-all-the-code.)

### paredit ¶

> Note: If you use racket-hash-lang-mode, see racket-hash-lang-module-language-hook for how to enable/disable paredit based on the specific #lang.

If you use paredit, you might want to add keybindings to `paredit-mode-map`:

- Bind the curly brace keys to `paredit-open-curly` and `paredit-close-curly`.
- Bind whatever keys you prefer for `paredit-wrap-square` and `paredit-wrap-curly`.

For example, with `use-package`:

    (use-package paredit
      :ensure t
      :config
      (dolist (m '(emacs-lisp-mode-hook
                   racket-mode-hook
                   racket-repl-mode-hook))
        (add-hook m #'paredit-mode))
      (bind-keys :map paredit-mode-map
                 ("{"   . paredit-open-curly)
                 ("}"   . paredit-close-curly))
      (unless terminal-frame
        (bind-keys :map paredit-mode-map
                   ("M-[" . paredit-wrap-square)
                   ("M-{" . paredit-wrap-curly))))

Starting c. November 2022, paredit binds the `RET` key to its own command. Unfortunately this is not compatible with interactive modes — including but not limited to `racket-repl-mode` — which expect `RET` to be bound to a command to submit your input to the REPL. In other words, if you type an expression and hit `RET` , nothing will happen and the REPL will seem frozen. You `M-x racket-repl-submit` to proceed.

If you want to use paredit with interactive modes, their advice is to remove the binding from `paredit-mode-map` (note that this will also disable it for all buffers, including editing buffers). One way you can do this for all related keys:

    (dolist (k '("RET" "C-m" "C-j"))
      (define-key paredit-mode-map (kbd k) nil))

### smartparens ¶

> Note: If you use racket-hash-lang-mode, see racket-hash-lang-module-language-hook for how to enable/disable smartparens based on the specific #lang.

If instead of paredit you prefer smartparens, you can use the default configuration it provides for Lisp modes generally and for Racket Mode specifically:

    (require 'smartparens-config)

### Appearance of parentheses ¶

If you prefer parentheses to appear “dimmed”, see paren-face.

If you prefer the opposite, see rainbow-delimiters.

### Edit buffers and REPL buffers ¶

By default, all `racket-mode` edit buffers share one `racket-repl-mode` buffer, named `*Racket REPL*`. For example, if you run foo.rkt, the REPL prompt changes to `foo.rkt>`, and the REPL is inside the file module namespace. If you then run bar.rkt, the REPL prompt changes to `bar.rkt>`, and you are in that namespace.

If you prefer, you can use more than one REPL buffer, by customizing the variable racket-repl-buffer-name-function:

- Share a REPL buffer among files belonging to the same project; each REPL buffer is named `*Racket REPL <project-name>*`.
- A unique REPL buffer for each edit buffer, similar to Dr Racket; each REPL buffer is named `*Racket REPL <file.rkt>*`.
- You can also define your own, custom function.

You can customize where the REPL buffer is displayed by adding an item to the Emacs variable `display-buffer-alist`. A good regular expression to use for this would be `\\`\\*Racket REPL`. For example, if you wanted to make the REPL buffer appear in a new frame:

    (add-to-list 'display-buffer-alist
                 '("\\`\\*Racket REPL"
                   (display-buffer-reuse-window
                    display-buffer-pop-up-frame)
                   (reusable-frames . 0)
                   (inhibit-same-window . t)))

### eldoc ¶

Various modes add local hooks to `eldoc-documentation-functions`.

- The minor mode `racket-xp-mode` adds hooks to document the identifiers at point or at an apparent s-expression application head position. The identifiers are documented from check-syntax annotations. You may customize the variable racket-xp-eldoc-level to choose how much information is shown.
- The major mode `racket-repl-mode` adds hooks to describe the namespace identifers at point or at an apparent s-expression application head position. The description is a signature from surface syntax, or a Typed Racket type, or a “bluebox” for the namespace identifier.

Tip: With an `eldoc-documentation-strategy` of `eldoc-documentation-default`, these hooks show info about point when available, or else for the s-expression application head. You may change that to `eldoc-documentation-compose` to show info for both positions when available.

Tip: Some people use the third-party package `eldoc-box` to show information in a child frame (near point, or in a corner of the main frame) instead of the echo area.

Note: Racket Mode does not support the “old” eldoc API that uses `eldoc-documentation-function`, singular.

### Start faster ¶

You can use racket-mode-start-faster to make the Racket REPL start faster.

### Inserting Unicode math symbols ¶

To insert various Unicode math symbols, you can:

- Use a command: See racket-insert-symbol.
- Use an Emacs input method, which you can enable in a buffer using a minor mode: See racket-input-mode.

### Ligatures ¶

Prior to Emacs 28.0.50, things like `auto-composition-mode` or `ligature-mode` that use `composition-function-table` to display ligatures can cause Emacs to freeze. This can happen when an Emacs overlay displays a string containing such a ligature. Although the problem is not limited to Racket Mode, it affects the overlays created by `racket-show-pseudo-tooltip`, as used by `racket-xp-mode`. The only known work-around is to change the value of `racket-show-functions` to something “boring” such as `(racket-show-echo-area)`.

## Architecture ¶

Racket Mode consists of a single Emacs front end, and one or more processes running a back end written in Racket.1

A back end is responsible for commands that cannot be implemented in Emacs Lisp, as well as supplying zero or more REPLs.

Although you can start and stop a back end with `racket-start-back-end` and `racket-stop-back-end`, a back end is normally started automatically when the front end needs to issue some command. This includes commands that do not involve `racket-run` or a REPL. For example `racket-xp-mode` issues commands to check your code and annotate the buffer, even if you do not run it. In other words, a back end supplies zero or more REPLs — a back end is not the same thing as a REPL.

To learn more about how many REPLs are used: See racket-repl-buffer-name-function.

In the common case there is only one back end, on the same local host as Emacs, and it is used for `.rkt` files in any directory.

However you can configure using any number of back ends on any number of local or remote host paths.

As one example, you can have multiple back ends on the local host. One back end is used for a project under a specific subdirectory, and the other back end for all others. (Perhaps one project needs Racket built from source, and everything else uses an installed, older version of Racket. By using different back ends, not only will `racket-run` use the desired version of Racket for a file, so will commands for documentation or visiting definitions.)

(Note: If you use various versions of Racket via `direnv` combined with the `envrc` Emacs package, you still need a distinct back end for each project. To arrange this, add or modify a `.dir-locals.el` file next to each `.envrc` file; See racket-add-back-end.)

Furthermore, you could work with a project located on a remote host, whose files you edit using TRAMP. You also want the back end to run there. For a remote host, Racket Mode copies its back end source files to the remote when necessary, and runs the back end using ssh.

Of course the remote can also use different back ends for different paths.

And of course you can have multiple remotes.

If you need any of these “fancy” configurations: See racket-add-back-end.

However by default a configuration is automatically created for one back end on the local host. For that very common case, you don’t need to configure anything.

## Reference ¶

The following sections are generated from the doc strings for each command, variable, or face. (As a result, some of the formatting might not be quite as nice or correct as in the previous sections.)

You can also view these by using the normal Emacs help mechanism:

- `C-h f` and enter the name of a command.
- `C-h v` and enter the name of a variable.

## Commands ¶

### Edit ¶

#### racket-mode ¶

`M-x` `racket-mode`

Major mode for editing Racket source files.

Key | Binding
`TAB` | `indent-for-tab-command`
`C-M-u` | racket-backward-up-list
`C-c C-p` | racket-cycle-paren-shapes
`C-c C-s` or `C-c C-.` | racket-describe-search
`C-c C-d` | racket-documentation-search
`C-c C-z` | `racket-edit-switch-to-repl`
`C-c C-e x` | racket-expand-definition
`C-c C-e f` | racket-expand-file
`C-c C-e e` | racket-expand-last-sexp
`C-c C-e r` | racket-expand-region
`C-c C-f` | racket-fold-all-tests
`)` or `]` or `}` | racket-insert-closing
`C-M-y` | racket-insert-lambda
`C-c C-l` | racket-logger
`C-c C-x C-f` | racket-open-require-path
`C-c C-o` | racket-profile
`C-c C-c` or `C-c C-k` | racket-run-module-at-point
`C-M-x` | racket-send-definition
`C-x C-e` | racket-send-last-sexp
`C-c C-r` | racket-send-region
`C-c C-t` | racket-test
`C-c C-u` | racket-unfold-all-tests

In addition to any hooks its parent mode `prog-mode` might have run, this mode runs the hook `racket-mode-hook`, as the final or penultimate step during initialization.

#### racket-insert-lambda ¶

`C-M-y`

Insert λ.

To insert Unicode symbols generally, see racket-input-mode.

#### racket-insert-symbol ¶

`M-x` `racket-insert-symbol`

Insert a symbol from racket-input-translations.

A command alternative to the “Racket” input method activated by racket-input-mode.

Presents a `completing-read` UI, in which the symbols that would be inserted are shown as annotations – a preview unlike what is currently provided by the Emacs UI for input method.

#### racket-fold-all-tests ¶

`C-c C-f`

Fold (hide) all test submodules.

#### racket-unfold-all-tests ¶

`C-c C-u`

Unfold (show) all test submodules.

#### racket-tidy-requires ¶

`M-x` `racket-tidy-requires`

Make a single, sorted “require” form for each module.

Use a single require-spec for each phase-level, sorted in this order: for-syntax, for-template, for-label, for-meta, and plain (phase 0).

Within each phase-level, sort require-specs by module name.

Format at most one module per line.

Simplify gratuitous require-specs. For example reduce (only-in m) to m and elide (combine-in).

See also: racket-trim-requires and racket-base-requires.

#### racket-trim-requires ¶

`M-x` `racket-trim-requires`

Like racket-tidy-requires but also delete unnecessary requires.

Use macro-debugger/analysis/check-requires to analyze.

The analysis:

- Needs the `macro-debugger-lib` package.
- Only works when the source file can be fully expanded with no

errors.

- Only works for requires at the top level of a source file using

#lang – not for requires inside submodule forms. Furthermore, the analysis is not smart about module+ or module* forms – it might delete outer requires that are actually needed by such submodules.

See also: racket-base-requires.

#### racket-base-requires ¶

`M-x` `racket-base-requires`

Change from “#lang racket” to “#lang racket/base”.

Using “racket/base” is a recommended optimization for Racket applications. Loading all of “racket” is slower and uses more memory.

Add explicit requires for imports that are provided by “racket” but not by “racket/base”.

Also do the equivalent of racket-trim-requires and `nil`. See those commands for additional notes and caveats.

Note: Currently this only helps change “#lang racket” to “#lang racket/base”. It does not help with other similar conversions, such as changing “#lang typed/racket” to “#lang typed/racket/base”.

#### racket-add-require-for-identifier ¶

`M-x` `racket-add-require-for-identifier`

Add a require for an identifier.

Useful when you know the name of an export but don’t remember from what module it is exported.

After you choose an identifier, this command will:

- Insert the identifier at point if not already there.
- Insert a “require” form and do racket-tidy-requires.

Caveat: This works only for identifiers that are documented. The mechanism is similar to that used for Racket’s “Search Manuals” feature. Today there exists no system-wide database of identifiers that are exported but not documented.

#### racket-indent-line ¶

`M-x` `racket-indent-line`

Indent current line as Racket code.

Normally you don’t invoke this command directly. Instead, because it is used as the value for the variable `indent-line-function` in racket-mode and racket-repl-mode buffers, it is used automatically when you press keys like RET or TAB. However you might refer to it when configuring custom indentation, explained below.

Following the tradition of `lisp-mode` and `scheme-mode`, the primary way to determine the indentation of a form is to look for a rule stored as a `racket-indent-function` property.

To extend, use your Emacs init file to

        (put SYMBOL 'racket-indent-function INDENT)

SYMBOL is the name of the Racket form like “test-case” and INDENT is an integer or the symbol “defun”. When INDENT is an integer, the meaning is the same as for lisp-indent-function and scheme-indent-function: Indent the first INDENT arguments specially and indent any further arguments like a body. (The number may be negative; see discussion below.)

For example:

        (put 'test-case 'racket-indent-function 1)

This will change the indent of `test-case` from this:

        (test-case foo
                   blah
                   blah)

to this:

        (test-case foo
          blah
          blah)

For backward compatibility, if `racket-indent-function` has no property for a symbol, a scheme-indent-function property is also considered, although the “with-” indents defined by scheme-mode are ignored. This is only to help people who may have extensive scheme-indent-function settings, particularly in the form of file or dir local variables. Otherwise prefer putting properties on `racket-indent-function`.

If no explicit rules match, regular expressions are used for a couple special cases:

- Forms that start with “begin” indent like “begin”.
- Forms that start with “def” or “with-” indent like “define”.

On the one hand this is convenient when you create your own “DRY” macros; they will indent as expected without you needing to make custom indent rules. On the other hand there can be false matches; for example a function or form named “defer” will indent like “define”. This is a known drawback and is unlikely to be fixed unless/until Racket macros someday support a protocol to communicate how they should be indented.

There is also automatic handling for:

- Forms that begin with a #:keyword (as found in contracts)
- Literal forms like #hasheq()
- Quoted forms when the variable racket-indent-sequence-depth is > 0.
- {} forms when the variable racket-indent-curly-as-sequence is not nil.

Finally and otherwise, a form will be indented as if it were a procedure application.

— — —

Note: Racket Mode extends the traditional Emacs lisp indent spec to allow a negative integer, which means that all distinguished forms should align with the first one. This style originated with “for/fold”, which has two distinguished forms. Traditionally those would indent like this:

        (for/fold ([x xs])
            ([y ys])            ; twice body indent
          body)

However the popularly desired indent is:

        (for/fold ([x xs])
                  ([y ys])      ; same as first distingushed form
          body)

This idea extends to optional distinguished forms, such as Typed Racket annotation “prefixes” in “for/fold”, “for/x”, and even “let” forms:

        (for/fold : Type
                  ([x xs])
                  ([y ys])      ; same as first distingushed form
          body)

#### racket-smart-open-bracket-mode ¶

`M-x` `racket-smart-open-bracket-mode`

Minor mode to let you always type `[`’ to insert `(` or `[` automatically.

Behaves like the “Automatically adjust opening square brackets” feature in Dr. Racket.

By default, inserts a `(`. Inserts a `[` in the following cases:

- `let`-like bindings – forms with `let` in the name as well as things like `parameterize`, `with-handlers`, and `with-syntax`.
- `case`, `cond`, `match`, `syntax-case`, `syntax-parse`, and `syntax-rules` clauses.
- `for`-like bindings and `for/fold` accumulators.
- `class` declaration syntax, such as `init` and `inherit`.

When the previous s-expression in a sequence is a compound expression, uses the same kind of delimiter.

To force insert `[`, use `quoted-insert`.

Combined with racket-insert-closing this means that you can press the unshifted `[` and `]` keys to get whatever delimiters follow the Racket conventions for these forms. When something like `electric-pair-mode` or `paredit-mode` is active, you need not even press `]`.

Tip: When also using `paredit-mode`, enable that first so that the binding for the `[`’ key in the map for racket-smart-open-bracket-mode has higher priority. See also the variable `minor-mode-map-alist`.

Tip: When using this with racket-hash-lang-mode, you may want to use racket-hash-lang-module-language-hook to enable it IFF the module langugage is something like “racket”.

This is a minor mode. If called interactively, toggle the `Racket-Smart-Open-Bracket mode` mode. If the prefix argument is positive, enable the mode, and if it is zero or negative, disable the mode.

If called from Lisp, toggle the mode if ARG is `toggle`. Enable the mode if ARG is nil, omitted, or is a positive number. Disable the mode if ARG is a negative number.

To check whether the minor mode is enabled in the current buffer, evaluate the variable racket-smart-open-bracket-mode.

The mode’s hook is called both when the mode is enabled and when it is disabled.

#### racket-insert-closing ¶

`]` or `)`

Insert a matching closing delimiter.

With `C-u` insert the typed character as-is.

This is handy if you’re not yet using something like `paredit-mode`, `smartparens-mode`, `parinfer-mode`, or simply `electric-pair-mode` added in Emacs 24.5.

#### racket-cycle-paren-shapes ¶

`C-c C-p`

Cycle the sexpr among () [] {}.

#### racket-backward-up-list ¶

`C-M-u`

Like `backward-up-list` but works when point is in a string or comment.

Typically you should not use this command in Emacs Lisp – especially not repeatedly. Instead, initially use `racket--escape-string-or-comment` to move to the start of a string or comment, if any, then use normal `backward-up-list` repeatedly.

#### racket-input-mode ¶

`M-x` `racket-input-mode`

A minor mode to enable the “Racket” input method.

The Racket input method lets you type racket-input-prefix, followed by a key sequence from racket-input-translations, directly in a buffer, to insert a symbol.

For example when racket-input-prefix is the default “\”, you can type “\All” and it is immediately replaced with “∀”.

To enable racket-input-mode (and the Racket input method) for all new buffers, put the following in your Emacs init file:

        (dolist (hook '(racket-mode-hook
                        racket-hash-lang-mode-hook
                        racket-repl-mode-hook))
          (add-hook hook #'racket-input-mode))

Tip: You may use the standard Emacs key C-\ to toggle the current input method.

Tip: If you don’t like the highlighting of partially matching tokens you can disable that using `input-method-highlight-flag`.

See the Emacs manual for other information about input methods.

Tip: Another way to use racket-input-translations is by using a command: racket-insert-symbol.

This is a minor mode. If called interactively, toggle the `Racket-Input mode` mode. If the prefix argument is positive, enable the mode, and if it is zero or negative, disable the mode.

If called from Lisp, toggle the mode if ARG is `toggle`. Enable the mode if ARG is nil, omitted, or is a positive number. Disable the mode if ARG is a negative number.

To check whether the minor mode is enabled in the current buffer, evaluate the variable racket-input-mode.

The mode’s hook is called both when the mode is enabled and when it is disabled.

#### racket-align ¶

`M-x` `racket-align`

Align values in the same column.

Useful for binding forms like “let” and “parameterize”, conditionals like “cond” and “match”, association lists, and any series of couples like the arguments to “hash”.

Before choosing this command, put point on the first of a series of “couples”. A couple is:

- A list of two or more sexprs: “[sexpr val sexpr …]”.
- Two sexprs: “sexpr val”.

Each “val” moves to the same column and is `prog-indent-sexp`-ed (in case it is a multi-line form).

For example with point on the “[” before “a”:

        Before             After

        (let ([a 12]       (let ([a   12]
              [bar 23])          [bar 23])
          ....)              ....)

        ([a . 12]          ([a   . 12]
         [bar . 23])        [bar . 23])

        (cond [a? #t]      (cond [a?   #t]
              [b? (f x           [b?   (f x
                     y)]                  y)]
              [else #f])         [else #f])

Or with point on the quote before “a”:

        (list a 12        (list a   12
              bar 23)           bar 23)

If more than one couple is on the same line, none are aligned, because it is unclear where the value column should be. For example the following form will not change; racket-align will display an error message:

        (let ([a 0][b 1]
              [c 2])       error; unchanged
          ....)

When a couple’s sexprs start on different lines, that couple is ignored. Other, single-line couples in the series are aligned as usual. For example:

        (let ([foo         (let ([foo
               0]                 0]
              [bar 1]            [bar 1]
              [x 2])             [x   2])
          ....)              ....)

See also: racket-unalign.

#### racket-unalign ¶

`M-x` `racket-unalign`

The opposite of racket-align.

Effectively does M-x `just-one-space` and `prog-indent-sexp` for each couple’s value.

#### racket-complete-at-point ¶

A value for the variable `completion-at-point-functions`.

Completion candidates are drawn from the same symbols used for font-lock. This is a static list. If you want dynamic, smarter completion candidates, enable the minor mode racket-xp-mode.

### Hash Langs ¶

#### racket-hash-lang-mode ¶

`M-x` `racket-hash-lang-mode`

Use color-lexer, indent, and navigation supplied by a #lang.

An experimental major mode alternative to racket-mode for source file edit buffers.

In your Emacs configuration, you may want to update the variable `auto-mode-alist` to use racket-hash-lang-mode for file extensions like “.rkt”, “.scrbl”, and/or “.rhm”.

Languages supply colors for lexer tokens like strings and comments; see the customization variable racket-hash-lang-token-face-alist. For more colors see the hook variable racket-hash-lang-module-language-hook, which can also be used to vary configurations per language.

A discussion of the information provided by a Racket language:

https://docs.racket-lang.org/tools/lang-languages-customization.html

Key | Binding
`TAB` | `indent-for-tab-command`
`RET` | `newline-and-indent`
`C-c C-z` | `racket-edit-switch-to-repl`
`C-c C-e x` | racket-expand-definition
`C-c C-e f` | racket-expand-file
`C-c C-e e` | racket-expand-last-sexp
`C-c C-e r` | racket-expand-region
`C-c C-f` | racket-fold-all-tests
`C-M-q` | racket-hash-lang-C-M-q-dwim
`C-M-b` | racket-hash-lang-backward
`C-M-d` | racket-hash-lang-down
`C-M-f` | racket-hash-lang-forward
`C-M-u` | racket-hash-lang-up
`C-M-y` | racket-insert-lambda
`C-c C-l` | racket-logger
`C-c C-x C-f` | racket-open-require-path
`C-c C-o` | racket-profile
`C-c C-c` or `C-c C-k` | racket-run-module-at-point
`C-M-x` | racket-send-definition
`C-x C-e` | racket-send-last-sexp
`C-c C-r` | racket-send-region
`C-c C-t` | racket-test
`C-c C-u` | racket-unfold-all-tests

In addition to any hooks its parent mode `prog-mode` might have run, this mode runs the hook `racket-hash-lang-mode-hook`, as the final or penultimate step during initialization.

#### racket-hash-lang-backward ¶

`C-M-b`

Like `backward-sexp` but uses #lang supplied navigation.

#### racket-hash-lang-forward ¶

`C-M-f`

Like `forward-sexp` but uses #lang supplied navigation.

#### racket-hash-lang-up ¶

`C-M-u`

Like `backward-up-list` but uses #lang supplied navigation.

#### racket-hash-lang-down ¶

`C-M-d`

Like `down-list` but uses #lang supplied navigation.

#### racket-hash-lang-C-M-q-dwim ¶

`C-M-q`

Fill or indent depending on lang lexer’s token at point.

When the lang lexer token is…

- “text”, for example in Scribble document text, do `fill-paragraph`.
- “comment”, do `fill-comment`.
- “whitespace”, give an error message.
- anything else, do `prog-indent-sexp`.

### Explore ¶

#### racket-xp-mode ¶

`M-x` `racket-xp-mode`

A minor mode that analyzes expanded code to explain and explore.

This minor mode is an optional enhancement to racket-mode edit buffers. Like any minor mode, you can turn it on or off for a specific buffer. If you always want to use it, put the following code in your Emacs init file:

        (require 'racket-xp)
        (add-hook 'racket-mode-hook #'racket-xp-mode)

Note: This mode won’t do anything unless/until the Racket Mode back end is running. It will try to start the back end automatically. You do not need to racket-run the buffer you are editing.

This mode uses the drracket/check-syntax package to analyze fully-expanded programs, without needing to evaluate a.k.a. “run” them. The resulting analysis provides information for:

- Visually annotating bindings – local or imported definitions and references to them.
- Visually annotating expressions in a tail position, as well as the enclosing expression with respect to which they are in a tail position.
- Completion candidates.
- Defintions’ source and documentation.

When point is on a definition or use, related items are highlighted using racket-xp-def-face and racket-xp-use-face – instead of drawing arrows as in Dr Racket. Information is displayed using the function(s) in the hook variable racket-show-functions; it is also available when hovering the mouse cursor.

Note: If you find these point-motion features too distracting and/or slow, in your `racket-xp-mode-hook` you may disable them:

      (require 'racket-xp)
      (add-hook 'racket-xp-mode-hook
                (lambda ()
                  (remove-hook 'pre-redisplay-functions
                               #'racket-xp-pre-redisplay
                               t)))

The remaining features discussed below will still work.

You may also use commands to navigate among a definition and its uses, or to rename a local definitions and all its uses:

- racket-xp-next-definition
- racket-xp-previous-definition
- racket-xp-next-use
- racket-xp-previous-use

In the following little example, not only does drracket/check-syntax distinguish the various “x” bindings, it understands the two different imports of “define”:

      #lang racket/base
      (define x 1)
      x
      (let ([x x])
        (+ x 1))
      (module m typed/racket/base
        (define x 2)
        x)

When point is on the opening parenthesis of an expression in tail position, it is highlighted using the face racket-xp-tail-position-face.

When point is on the opening parenthesis of an enclosing expression with respect to which one or more expressions are in tail position, it is highlighted using the face racket-xp-tail-target-face.

Furthermore, when point is on the opening parenthesis of either kind of expression, all of the immediately related expressions are also highlighted. Various commands move among them:

- racket-xp-tail-up
- racket-xp-tail-down
- racket-xp-tail-next-sibling
- racket-xp-tail-previous-sibling

The function `racket-xp-complete-at-point` is added to the variable `completion-at-point-functions`. Note that in this case, it is not smart about submodules; identifiers are assumed to be definitions from the file’s module or its imports. In addition to supplying completion candidates, it supports the “:company-location” property to inspect the definition of a candidate and the “:company-doc-buffer” property to view its documentation.

When you edit the buffer, existing annotations are retained; their positions are updated to reflect the edit. Annotations for new or deleted text are not requested until after racket-xp-after-change-refresh-delay seconds. The request is made asynchronously so that Emacs will not block – for moderately complex source files, it can take some seconds simply to fully expand them, as well as a little more time for the drracket/check-syntax analysis. When the results are ready, all annotations for the buffer are completely refreshed.

You may also set racket-xp-after-change-refresh-delay to nil and use the `racket-xp-annotate` command manually.

The mode line changes to reflect the current status of annotations, and whether or not you had a syntax error.

If you have one or more syntax errors, `next-error` and `previous-error` navigate among them. Although most languages will stop after the first syntax error, some like Typed Racket will try to collect and report multiple errors.

You may use `xref-find-definitions` `M-.` , `xref-pop-marker-stack` `M-x` `xref-pop-marker-stack`, and `xref-find-references`: racket-xp-mode adds a backend to the variable `xref-backend-functions`. This backend uses information from the drracket/check-syntax static analysis. Its ability to find references is limited to the current file; when it finds none it will try the default xref backend implementation which is grep-based.

Tip: This mode follows the convention that a minor mode may only use a prefix key consisting of “C-c” followed by a punctuation key. As a result, `racket-xp-control-c-hash-keymap` is bound to “C-c #” by default. Although you might find this awkward to type, remember that as an Emacs user, you are free to bind this map to a more convenient prefix, and/or bind any individual commands directly to whatever keys you prefer.

Key | Binding
`C-c # N` | `next-error`
`C-c # P` | `previous-error`
`C-c C-s` | racket-describe-search
`C-c # g` | `racket-xp-annotate`
`C-c C-.` | racket-xp-describe
`C-c C-d` | racket-xp-documentation
`C-c # j` | racket-xp-next-definition
`C-c # n` | racket-xp-next-use
`C-c # k` | racket-xp-previous-definition
`C-c # p` | racket-xp-previous-use
`C-c # r` | `racket-xp-rename`
`C-c # v` | racket-xp-tail-down
`C-c # >` | racket-xp-tail-next-sibling
`C-c # <` | racket-xp-tail-previous-sibling
`C-c # ^` | racket-xp-tail-up
`M-.` or `C-c # .` | `xref-find-definitions`
`C-c # ?` | `xref-find-references`

This is a minor mode. If called interactively, toggle the `Racket-Xp mode` mode. If the prefix argument is positive, enable the mode, and if it is zero or negative, disable the mode.

If called from Lisp, toggle the mode if ARG is `toggle`. Enable the mode if ARG is nil, omitted, or is a positive number. Disable the mode if ARG is a negative number.

To check whether the minor mode is enabled in the current buffer, evaluate the variable racket-xp-mode.

The mode’s hook is called both when the mode is enabled and when it is disabled.

#### racket-xp-describe ¶

`C-c C-.`

Describe the identifier at point.

The command varies based on how many `C-u` command prefixes you supply.

- `C-c C-.`

  Uses the symbol at point. If no such symbol exists, you are prompted enter the identifier, but in this case it only considers definitions or imports at the file’s module level – not local bindings nor definitions in submodules.

  - If the identifier has installed Racket documentation, then a simplified version of the HTML is presented in the buffer, including the “blue box”, documentation prose, and examples.
  - Otherwise, if the identifier is a function, then its signature is displayed, for example “(name arg-1-name arg-2-name)”.
- `C-u` `C-c C-.`

  Always prompts you to enter a symbol, defaulting to the symbol at point if any.

- `C-u` `C-u` `C-c C-.`

  This is an alias for racket-describe-search, which uses installed documentation in a racket-describe-mode buffer instead of an external web browser.

The intent is to give a quick reminder or introduction to something, regardless of whether it has installed documentation – and to do so within Emacs, without switching to a web browser.

This buffer is also displayed when you use `company-mode` and press F1 or C-h in its pop up completion list.

#### racket-xp-documentation ¶

`C-c C-d`

View documentation in an external web browser.

The command varies based on how many `C-u` command prefixes you supply.

- `C-c C-d`

  Uses the symbol at point. Tries to find documentation for an identifer defined in the expansion of the current buffer.

  If no such identifer exists, opens the Search Manuals page. In this case, the variable racket-documentation-search-location determines whether the search is done locally as with `raco doc`, or visits a URL.

- `C-u` `C-c C-d`

  Always prompts you to enter a symbol, defaulting to the symbol at point if any.

- `C-u` `C-u` `C-c C-d`

  Always prompts you to enter anything, defaulting to the symbol at point if any.

  Proceeds directly to the Search Manuals page. Use this if you would like to see documentation for all identifiers named “define”, for example.

#### racket-xp-next-definition ¶

`C-c # j`

Move point to the next definition.

#### racket-xp-previous-definition ¶

`C-c # k`

Move point to the previous definition.

#### racket-xp-next-use ¶

`C-c # n`

When point is on a use, go to the next, sibling use.

#### racket-xp-previous-use ¶

`C-c # p`

When point is on a use, go to the previous, sibling use.

#### racket-xp-next-error ¶

`M-x` `racket-xp-next-error`

An obsolete alias for `next-error`.

#### racket-xp-previous-error ¶

`M-x` `racket-xp-previous-error`

An obsolete alias for `previous-error`.

#### racket-xp-tail-up ¶

`C-c # ^`

Go “up” to the expression enclosing an expression in tail position.

When point is on the opening parenthesis of an expression in tail position, go its “target” – that is, go to the enclosing expression with the same continuation as the tail expression.

#### racket-xp-tail-down ¶

`C-c # v`

Go “down” to the first tail position enclosed by the current expression.

#### racket-xp-tail-next-sibling ¶

`C-c # >`

Go to the next tail position sharing the same enclosing expression.

#### racket-xp-tail-previous-sibling ¶

`C-c # <`

Go to the previous tail position sharing the same enclosing expression.

#### racket-documentation-search ¶

`C-c C-d`

Search documentation.

This command is useful in several situations:

- You are not using racket-xp-mode for a racket-mode edit buffer, so racket-xp-documentation is not available.
- There is no racket-repl-mode buffer with a live namespace, so racket-repl-documentation is not available or helpful.
- You want to search for definitions provided by all modules – for example, the “define” syntax provided by racket/base, by typed/racket/base, and by other modules, as well definitions or topics that merely include “define”.

This command does not try to go directly to the help topic for a definition provided by any specific module. Instead it goes to the Racket “Search Manuals” page.

#### racket-describe-mode ¶

`M-x` `racket-describe-mode`

Major mode for viewing Racket documentation.

Many of the default key bindings are similar to `Info-mode`, as listed below.

To see “On this page” links, use `M-g i` for `imenu`, or, when `context-menu-mode` is enabled, right click the mouse.

Supports bookmarks: `bookmark-set`.

Supports org links: `org-store-link`, `org-insert-link`, and `org-open-at-point`.

Internal, intra-doc links – which go to other doc pages in the same racket-describe-mode buffer in Emacs – are given racket-doc-link-face unless the documentation specifies some non-default face.

External links – which are opened using the variable racket-browse-url-function, by default in an external web browser program – are given racket-ext-link-face.

Key | Binding
`<` | `beginning-of-buffer`
`>` | `end-of-buffer`
`q` | `quit-window`
`l` or `b` or `C-c C-b` | `racket-describe-back`
`x` | `racket-describe-browse-external`
`r` or `f` or `C-c C-f` | `racket-describe-forward`
`n` | `racket-describe-nav-next`
`p` | `racket-describe-nav-prev`
`C-^` | `racket-describe-nav-top`
`^` | `racket-describe-nav-up`
`i` or `C-c C-s` | racket-describe-search
`g` | `revert-buffer`
`DEL` or `S-SPC` | `scroll-down-command`
`SPC` | `scroll-up-command`

In addition to any hooks its parent mode `special-mode` might have run, this mode runs the hook `racket-describe-mode-hook`, as the final or penultimate step during initialization.

#### racket-describe-search ¶

`C-c C-.` or `C-c C-s`

Search installed documentation; view using racket-describe-mode.

### Run ¶

#### racket-repl-mode ¶

`M-x` `racket-repl-mode`

Major mode for Racket REPL.

You may use `xref-find-definitions` `M-.` and `xref-pop-marker-stack` `M-x` `xref-pop-marker-stack`: racket-repl-mode adds a backend to the variable `xref-backend-functions`. This backend uses information about identifier bindings and modules from the REPL’s namespace.

Key | Binding
`TAB` | `indent-for-tab-command`
`C-j` | `newline-and-indent`
`C-M-q` | `prog-indent-sexp`
`C-M-u` | racket-backward-up-list
`C-c C-s` | racket-describe-search
`C-c C-e x` | racket-expand-definition
`C-c C-e f` | racket-expand-file
`C-c C-e e` | racket-expand-last-sexp
`C-c C-e r` | racket-expand-region
`)` or `]` or `}` | racket-insert-closing
`C-M-y` | racket-insert-lambda
`C-c C-l` | racket-logger
`C-c C-c` | `racket-repl-break`
`C-c C-u` | `racket-repl-clear-input`
`C-c C-o` | `racket-repl-delete-output`
`C-c C-.` | racket-repl-describe
`C-c C-d` | racket-repl-documentation
`C-c C-\` | `racket-repl-exit`
`M-n` | `racket-repl-next-input`
`C-c C-n` | `racket-repl-next-prompt-or-run`
`M-p` | `racket-repl-previous-input`
`C-c C-p` | `racket-repl-previous-prompt-or-run`
`RET` | `racket-repl-submit`
`C-c C-z` | `racket-repl-switch-to-edit`

This mode runs the hook `racket-repl-mode-hook`, as the final or penultimate step during initialization.

#### racket-run ¶

`M-x` `racket-run`

Save the buffer in REPL and run your program.

As well as evaluating the outermost, file module, automatically runs the submodules specified by the customization variable racket-submodules-to-run.

See also racket-run-module-at-point, which runs just the specific module at point.

The command varies based on how many `C-u` prefix arguments you supply.

- `<f5>`

  Follows the racket-error-context setting.

- `C-u` `<f5>`

  Uses errortrace for improved stack traces, as if racket-error-context were set to “high”.

  This lets you keep racket-error-context set to a faster value like “low” or “medium”, then conveniently re-run when you need a better strack trace.

- `C-u` `C-u` `<f5>`

  Instruments code for step debugging. See racket-debug-mode and the variable racket-debuggable-files.

Each run occurs within a Racket custodian. Any prior run’s custodian is shut down, releasing resources like threads and ports. Each run’s evaluation environment is reset to the contents of the source file. In other words, like Dr Racket, this provides the benefit that your source file is the “single source of truth”. At the same time, the run gives you a REPL inside the namespace of the module, giving you the ability to explore it interactively. Any explorations are temporary, unless you also make them to your source file, they will be lost on the next run.

See also racket-run-and-switch-to-repl, which is even more like Dr Racket’s Run command because it selects the REPL window after running.

To visit error locations, move point there and press RET or mouse click. Or, use the standard `next-error` and `previous-error` commands from either the edit or REPL buffer.

#### racket-run-and-switch-to-repl ¶

`<f5>`

This is racket-run followed by selecting the REPL buffer window.

This is similar to how Dr Racket behaves.

To make it even more similar, you may add racket-repl-clear to the variable racket-before-run-hook.

#### racket-run-module-at-point ¶

`C-c C-k` or `C-c C-c`

Save the buffer and run the module at point.

Like racket-run but runs the innermost module around point, which is determined textually by looking for “module”, “module*”, or “module+” forms nested to any depth, else simply the outermost, file module.

#### racket-repl ¶

`M-x` `racket-repl`

Show a Racket REPL buffer in some window.

The intended use of Racket Mode’s REPL is that you `find-file` some specific file, then run it using a command like racket-run or racket-run-module-at-point. The resulting REPL will correspond to those definitions and match your expectations.

Therefore this racket-repl command – which is intended as a convenience for people who want to “just get a quick scratch REPL” – is actually implemented as running the file named in the customization variable racket-repl-command-file. When that file doesn’t exist, it is created to contain just “#lang racket/base”. You may edit the file to use a different lang, require other modules, or whatever.

#### racket-repl-describe ¶

`C-c C-.`

Describe the identifier at point.

The command varies based on how many `C-u` prefix arguments you supply.

- `C-c C-.`

  Uses the symbol at point. If no such symbol exists, you are prompted enter the identifier, but in this case it only considers definitions or imports at the file’s module level – not local bindings nor definitions in submodules.

  - If the identifier has installed Racket documentation, then a simplified version of the HTML is presented in the buffer, including the “blue box”, documentation prose, and examples.
  - Otherwise, if the identifier is a function, then its signature is displayed, for example “(name arg-1-name arg-2-name)”.
- `C-u` `C-c C-.`

  Always prompts you to enter a symbol, defaulting to the symbol at point if any.

- `C-u` `C-u` `C-c C-.`

  This is an alias for racket-describe-search, which uses installed documentation in a racket-describe-mode buffer instead of an external web browser.

The intent is to give a quick reminder or introduction to something, regardless of whether it has installed documentation – and to do so within Emacs, without switching to a web browser.

#### racket-repl-documentation ¶

`C-c C-d`

View documentation in an external web browser.

The command varies based on how many `C-u` command prefixes you supply.

- `C-c C-d`

  Uses the symbol at point. Tries to find documentation for an identifer defined in the current namespace.

  If no such identifer exists, opens the Search Manuals page. In this case, the variable racket-documentation-search-location determines whether the search is done locally as with `raco doc`, or visits a URL.

- `C-u` `C-c C-d`

  Prompts you to enter a symbol, defaulting to the symbol at point if any.

- `C-u` `C-u` `C-c C-d`

  Prompts you to enter anything, defaulting to the symbol at point if any.

  Proceeds directly to the Search Manuals page. Use this if you would like to see documentation for all identifiers named “define”, for example.

#### racket-racket ¶

`C-M-<f5>`

Use command-line racket to run the file.

Uses a shell or terminal buffer as specified by the configuration variable racket-shell-or-terminal-function.

#### racket-profile ¶

`C-c C-o`

Like racket-run-module-at-point but with profiling.

Results are presented in a racket-profile-mode buffer, which also lets you quickly view the source code.

You may evaluate expressions in the REPL. They are also profiled. Use `racket-profile-refresh` to see the updated results. In other words a possible workflow is: racket-profile a .rkt file, call one its functions in the REPL, and refresh the profile results.

Caveat: Only source files are instrumented. You may need to delete compiled/*.zo files.

#### racket-profile-mode ¶

`M-x` `racket-profile-mode`

Major mode for results of racket-profile.

Key | Binding
`q` | `quit-window`
`g` | `racket-profile-refresh`
`f` | `racket-profile-show-non-project`
`z` | `racket-profile-show-zero`
`.` or `RET` | `racket-profile-visit`

In addition to any hooks its parent mode `tabulated-list-mode` might have run, this mode runs the hook `racket-profile-mode-hook`, as the final or penultimate step during initialization.

#### racket-logger ¶

`C-c C-l`

Create the racket-logger-mode buffer.

#### racket-logger-mode ¶

`M-x` `racket-logger-mode`

Major mode for Racket logger output.

The customization variable racket-logger-config determines the levels for topics. During a session you may change topic levels using `racket-logger-topic-level`.

For more information see: https://docs.racket-lang.org/reference/logging.html

Key | Binding
`g` | `racket-logger-clear`
`n` | `racket-logger-next-item`
`p` | `racket-logger-previous-item`
`l` | `racket-logger-topic-level`
`w` | `toggle-truncate-lines`

In addition to any hooks its parent mode `special-mode` might have run, this mode runs the hook `racket-logger-mode-hook`, as the final or penultimate step during initialization.

#### racket-debug-mode ¶

`M-x` `racket-debug-mode`

Minor mode for debug breaks.

This feature is EXPERIMENTAL!!! It is likely to have significant limitations and bugs. You are welcome to open an issue to provide feedback. Please understand that this feature might never be improved – it might even be removed someday if it turns out to have too little value and/or too much cost.

How to debug:

1. “Instrument” code for step debugging.

   Use two `C-u` command prefixes for either racket-run or racket-run-module-at-point.

   The file will be instrumented for step debugging before it is run. Any imported files are also instrumented if they are in the variable racket-debuggable-files.

   The run will break at the first breakable position.

   Tip: After you run to completion and return to a normal REPL prompt, the code remains instrumented. You may enter expressions that evaluate instrumented code and it will break so you can step debug again.

2. When a break occurs, the racket-repl-mode prompt changes. In this debug REPL, local variables are available for you to use and even to `set!`.

   Also, in the racket-mode buffer where the break is located, racket-debug-mode is enabled. This minor mode makes the buffer read-only, provides visual feedback – about the break position, local variable values, and result values – and provides shortcut keys:

Key | Binding
`c` | `racket-debug-continue`
`g` | `racket-debug-go`
`?` | `racket-debug-help`
`n` | `racket-debug-next-breakable`
`N` | `racket-debug-next-breakpoint`
`p` | `racket-debug-prev-breakable`
`P` | `racket-debug-prev-breakpoint`
`h` | `racket-debug-run-to-here`
`SPC` | `racket-debug-step`
`u` | `racket-debug-step-out`
`o` | `racket-debug-step-over`
`!` | racket-debug-toggle-breakpoint

This is a minor mode. If called interactively, toggle the `Racket-Debug mode` mode. If the prefix argument is positive, enable the mode, and if it is zero or negative, disable the mode.

If called from Lisp, toggle the mode if ARG is `toggle`. Enable the mode if ARG is nil, omitted, or is a positive number. Disable the mode if ARG is a negative number.

To check whether the minor mode is enabled in the current buffer, evaluate the variable racket-debug-mode.

The mode’s hook is called both when the mode is enabled and when it is disabled.

#### racket-repl-clear ¶

Delete all text in the REPL.

A suitable value for the hook racket-before-run-hook if you want the REPL buffer to be cleared before each run, much like with Dr Racket. To do so you can use `customize`, or, add to your Emacs init file something like:

(add-hook ’racket-before-run-hook #’racket-repl-clear)

See also the command racket-repl-clear-leaving-last-prompt.

#### racket-repl-clear-leaving-last-prompt ¶

`M-x` `racket-repl-clear-leaving-last-prompt`

Delete all text in the REPL, except for the last prompt.

### Test ¶

#### racket-test ¶

`C-<f5>` or `C-c C-t`

Run the “test” submodule.

Put your tests in a “test” submodule. For example:

        (module+ test
          (require rackunit)
          (check-true #t))

Any rackunit test failure messages show the location. You may use `next-error` to jump to the location of each failing test.

With `C-u` uses errortrace for improved stack traces. Otherwise follows the racket-error-context setting.

With `C-u` `C-u` also runs the tests with coverage instrumentation and highlights uncovered code using `font-lock-warning-face`.

See also:

- racket-fold-all-tests
- racket-unfold-all-tests

#### racket-raco-test ¶

`M-x` `racket-raco-test`

Use command-line raco test to run the “test” submodule.

Uses a shell or terminal buffer as specified by the configuration variable racket-shell-or-terminal-function.

### Eval ¶

#### racket-send-region ¶

`C-c C-r`

Send the current region (if any) to the Racket REPL.

See the customization variable racket-repl-echo-sent-expressions.

#### racket-send-definition ¶

`C-M-x`

Send the current definition to the Racket REPL.

See the customization variable racket-repl-echo-sent-expressions.

#### racket-send-last-sexp ¶

`C-x C-e`

Send the expression before point to the Racket REPL.

The expression may be either an at-expression or an s-expression.

When the expression is a sexp comment, the sexp itself is sent, without the #; prefix.

See the customization variable racket-repl-echo-sent-expressions.

### Collections ¶

#### racket-open-require-path ¶

`C-c C-x C-f`

Like Dr Racket’s Open Require Path.

Type (or delete) characters that are part of a module path name. “Fuzzy” matches appear. For example try typing “t/t/r”.

Choices are displayed in a vertical list. The current choice is at the top, marked with “->”.

- C-n and C-p move among the choices.
- RET on a directory adds its contents to the choices.
- RET on a file exits doing `find-file`.
- C-g aborts.

### Macro expand ¶

#### racket-stepper-mode ¶

`M-x` `racket-stepper-mode`

Major mode for Racket stepper output.

Used by the commands racket-expand-file, racket-expand-definition, racket-expand-region, and racket-expand-last-sexp.

Key | Binding
`n` or `j` | `racket-stepper-next-item`
`p` or `k` | `racket-stepper-previous-item`
`g` | `racket-stepper-refresh`
`RET` | `racket-stepper-step`

In addition to any hooks its parent mode `special-mode` might have run, this mode runs the hook `racket-stepper-mode-hook`, as the final or penultimate step during initialization.

#### racket-expand-file ¶

`C-c C-e f`

Expand the racket-mode buffer’s file in racket-stepper-mode.

Uses the `macro-debugger` package to do the expansion.

You do not need to racket-run the file first; the namespace active in the REPL is not used.

If the file is non-trivial and/or is not compiled to a .zo bytecode file, then it might take many seconds before the original form is displayed and you can start stepping.

With `C-u` behaves as if racket-expand-hiding were ’disabled.

#### racket-expand-region ¶

`C-c C-e r`

Expand the active region using racket-stepper-mode.

Uses the `macro-debugger` package to do the expansion.

With `C-u` behaves as if racket-expand-hiding were ’disabled.

#### racket-expand-definition ¶

`C-c C-e x`

Expand the definition around point using racket-stepper-mode.

Uses the `macro-debugger` package to do the expansion.

With `C-u` behaves as if racket-expand-hiding were ’disabled.

#### racket-expand-last-sexp ¶

`C-c C-e e`

Expand the sexp before point using racket-stepper-mode.

Uses the `macro-debugger` package to do the expansion.

With `C-u` behaves as if racket-expand-hiding were ’disabled.

### Packages ¶

#### racket-package-refresh ¶

`M-x` `racket-package-refresh`

Refresh the local copy of package catalogs.

Will make HTTP requests to remote catalog servers. May take a few seconds to complete.

#### list-racket-packages ¶

`M-x` `list-racket-packages`

Open a racket-package-mode buffer for the active back end.

#### racket-package-mode ¶

`M-x` `racket-package-mode`

Major mode for Racket package management.

The list of packages is equivalent to “raco pkg show -all” on the active back end – that is, all packages installed manually or as dependencies – plus packages available from your configured catalogs, assuming you have run the command racket-package-refresh.

On each row you can press RET to `describe-racket-package`, which opens a buffer where you can view details, and use buttons to install/update/remove the package.

Key | Binding
`RET` | `racket-package-describe`

In addition to any hooks its parent mode `tabulated-list-mode` might have run, this mode runs the hook `racket-package-mode-hook`, as the final or penultimate step during initialization.

#### describe-racket-package ¶

`M-x` `describe-racket-package`

Describe details of a Racket package.

Depending on the package status, buttons let you install, update, and/or remove the package and its dependencies. These convenience buttons are equivalent to using the command line on the active back end to do “raco pkg {install update remove} –auto”. For other operations, you still need to use “raco pkg” yourself; see https://docs.racket-lang.org/pkg/cmdline.html.

Detail values are links when possible:

- The Catalog (when “https://pkgs.racket-lang.org”) links to the package’s web page, which may have additional details not available locally.
- The Source links to the repo’s web page or local filesystem.
- The Directory for an installed package opens a dired buffer.
- Each Dependencies name links to details about that package.
- For installed packages, each Modules item links to the local file. There is also a button to each module’s locally installed documentation, if any.

If the package is available from a catalog, additional details will be shown, assuming you have run the command racket-package-refresh.

### Other ¶

#### racket-debug-toggle-breakpoint ¶

`M-x` `racket-debug-toggle-breakpoint`

Add or remove a breakpoint.

Each breakpoint has a condition and a list of actions.

The condition is a Racket expression that is evaluated in a context where local variables exist. Examples:

- “#t” means break always.
- If the code around the breakpoint is something like “(for ([n 100]) _)”, then a condition like “(zero? (modulo n 10))” is every 10 times through the loop.

Actions is a list of symbols; you may specify one or more. The action symbols are:

- “break” causes a break, enabling racket-debug-mode.
- “log” and “print” display information about local variables to the logger or REPL output, respectively. Although racket-debug-mode already shows these values “in situ” when you reach a break, this may be useful if you want a history. Specifying “log” or “print”, but not “break”, is equivalent to what many debuggers call a watchpoint instead of a breakpoint: Output some information and automatically resume.

Note: Although racket-debug-mode provides a convenient keybinding, you may invoke this command anytime using M-x.

Note: If you’re warned that point isn’t known to be a breakable position, that might be because it truly isn’t, or, just because you are not in racket-debug-mode and the breakable positions aren’t yet known. Worst case, if you set a breakpoint someplace that is not breakable, it is ignored. With a few exceptions – such as close paren positions that are tail calls – most open parens and close parens are breakble positions.

#### racket-mode-start-faster ¶

`M-x` `racket-mode-start-faster`

Compile Racket Mode’s .rkt files for faster startup.

Racket Mode is implemented as an Emacs Lisp “front end” that talks to a Racket process “back end”. Because Racket Mode is delivered as an Emacs package instead of a Racket package, installing it does not do the `raco setup` that is normally done for Racket packages.

This command will do a `raco make` of Racket Mode’s .rkt files, creating bytecode files in `compiled/` subdirectories. As a result, when a command must start the Racket process, it will start somewhat faster.

On many computers, the resulting speed up is negligible, and might not be worth the complication.

If you run this command, ever, you will need to run it again after:

- Installing an updated version of Racket Mode. Otherwise, you might lose some of the speed-up.
- Installing a new version of Racket and/or changing the value of the variable racket-program. Otherwise, you might get an error message due to the bytecode being different versions.

To revert to compiling on startup, use racket-mode-start-slower.

#### racket-mode-start-slower ¶

`M-x` `racket-mode-start-slower`

Delete the “compiled” directories made by racket-mode-start-faster.

## Variables ¶

### General variables ¶

#### racket-program ¶

Pathname of the Racket executable or command line to launch it.

- If the value of this variable is a string, it will be interpreted as a simple command without arguments.
- If it is a list of strings, the first element will be taken to be the executable, and the rest of the list command line arguments to pass to it before any other arguments.

Note that a back end configuration can override this with a non-nil `racket-program` property list value. See racket-add-back-end.

#### racket-command-timeout ¶

How many seconds to wait for command server responses.

Note: This is mostly obsolete, fortunately, because it applies only to commands that must block the Emacs UI until they get a response. Instead most Racket Mode commands these days receive their response asychronously.

#### racket-memory-limit ¶

Terminate the Racket process if memory use exceeds this value in MB.

Changes to this value take effect upon the next racket-run. A value of 0 means no limit.

Caveat: This uses Racket’s `custodian-limit-memory`, which does not enforce the limit exactly. Instead, the program will be terminated upon the first garbage collection where memory exceeds the limit (maybe by a significant amount).

#### racket-error-context ¶

The amount of context for error messages.

Each increasing level supplies better context (“stack trace”) for error messages, but causing your program to run more slowly.

- low corresponds to compile-enforce-module-constants #t and compile-context-preservation-enabled #f.
- medium corresponds to compile-enforce-module-constants #f and compile-context-preservation-enabled #t, which disables some optimizations like inlining.
- high corresponds to medium plus the use of errortrace, which extensively instruments your code and therefore might cause it to run significantly slower.

Tip: Regardless of this setting, you can enable high errortrace for a specific racket-run or racket-run-module-at-point by using `C-u` . This lets you normally run with a lower, faster setting, and re-run when desired to get a more-helpful error message.

#### racket-user-command-line-arguments ¶

List of command-line arguments to supply to your Racket program.

Accessible in your Racket program in the usual way — the parameter `current-command-line-arguments` and friends.

This is an Emacs buffer-local variable — convenient to set as a file local variable. For example at the end of your .rkt file:

        ;; Local Variables:
        ;; racket-user-command-line-arguments: ("-f" "bar")
        ;; End:

Set this way, the value must be an unquoted list of strings. For example:

        ("-f" "bar")

The following values will not work:

        '("-f" "bar")
        (list "-f" "bar")

#### racket-browse-url-function ¶

Function to call to browse a URL.

Defaults to racket-browse-url-using-temporary-file on macOS and `browse-url-browser-function` on other platforms.

#### racket-xp-after-change-refresh-delay ¶

Seconds to wait before refreshing racket-xp-mode annotations.

Set to nil to disable automatic refresh and manually use `racket-xp-annotate`.

#### racket-xp-highlight-unused-regexp ¶

Only give racket-xp-unused-face to unused bindings that match this regexp.

The default is to highlight identifiers that do not start with an underline, which is a common convention.

#### racket-xp-add-binding-faces ¶

Have racket-xp-mode fontify binding identifier sites.

A ’font-lock-face property is added for bindings from:

- the module language, using racket-xp-binding-lang-face and racket-xp-binding-lang-use-face.
- other imports, using racket-xp-binding-import-face and racket-xp-binding-import-use-face.
- local definitions, using racket-xp-binding-local-face and racket-xp-binding-local-use-face.

This has a visible effect only when there is not also a ’face property applied by the major mode’s fontification.

#### racket-xp-eldoc-level ¶

How much documentation to show via `eldoc`.

Used by `racket-xp-eldoc-point` and `racket-xp-eldoc-sexp-app`.

- Minimal: Only the help-echo string.
- Summary: Also the signature a.k.a. “blubox” from the documentation.
- Complete: Also the complete prose documentation.

A third-party package like `eldoc-box` can be useful for all but the minimal level. Even some bluebox signatures can take many lines to show on screen.

#### racket-documentation-search-location ¶

The location of the Racket “Search Manuals” web page. Where racket-documentation-search, racket-xp-documentation and racket-repl-documentation should look for the search page.

- If the value of this variable is the symbol “local”, open the search page from the local documentation, as with “raco doc”.
- Otherwise, the value is a string recognizable by `format`, with “%s” at the point at which to insert the user’s search text after applying `url-hexify-string`. Apart from “%s”, the string should be a properly encoded URL.

#### racket-expand-hiding ¶

The macro hiding policy for commands like racket-expand-file.

### Hash lang variables ¶

#### racket-hash-lang-token-face-alist ¶

An association list from color-lexer token symbols to face symbols.

Note: In many Racket languages, the lexer classifies tokens for identifiers as ’symbol. In many programs, a majority of the source consists of identifiers at binding definition and use sites. Therefore the appearance of “symbol” tokens is significant, and a matter of personal preference.

- If you prefer a “plainer” appearance, similar to Dr Racket: Add ’symbol with the value ’default. This gives an explicit ’face property that prevails over any ’font-lock-face property that a minor mode might apply to enhance the basic fontification.
- If you prefer a more “colorful” appearance, similar to “classic” racket-mode: Do not map ’symbol tokens in this list. See racket-hash-lang-module-language-hook for ideas.

Note: Some tokens are hardwired and not customizable by this list: Comment tokens use the face `font-lock-comment-face`, sometimes blended with other faces. Parenthesis tokens use the face `parenthesis` if defined, as by the paren-face package. String tokens use `font-lock-string-face`. Text tokens, e.g. Scribble text, use the face racket-hash-lang-text.

#### racket-hash-lang-module-language-hook ¶

Hook run when the module language changes.

Typically in Emacs each language gets its own major mode. As a result, the major mode hook is your opportunity to express preferences. However racket-hash-lang-mode handles radically different kinds of hash langs in one major mode. And a given buffer can change langs when you edit the “#lang” line. As a result, `racket-hash-lang-mode-hook` is not useful for per-lang configuration. Instead you need a kind of “sub major mode hook”. This is that hook.

The hook is run when a file is first visited, and thereafter whenever the “#lang” line is edited – provided that results in different language info; for example changing from “#lang racket” to “#lang racket/base” will not run the hook.

The function is called with a string returned by the lang’s “module-language” info key. This info key is supplied automatically when a language is defined using syntax/module-reader:

https://docs.racket-lang.org/syntax/reader-helpers.html#%28mod-path._syntax%2Fmodule-reader%29.

Otherwise a lang might not supply this and the value will be nil.

The hook is useful when you want to vary Emacs behavior in ways that go beyond what a lang can describe. This may include enabling “fancy” or “classic” Emacs behaviors only for s-expression langs.

For example, maybe you want to use `paredit-mode` when it is suitable for the module language, else `electric-pair-local-mode`:

      (defun my-hook (module-language)
        (let ((rackety
               (member module-language
                       (list "racket" "racket/base"
                             "typed/racket" "typed/racket/base"))))
          (electric-pair-local-mode (if rackety -1 1))
          (paredit-mode (if rackety 1 -1))))
      (add-hook 'racket-hash-lang-module-language-hook #'my-hook)

A similar tactic can be used for `smartparens`. In general, neither of these modes is likely to work well unless the hash-lang uses racket for drracket:grouping-position, in which case racket-hash-lang-mode uses the classic racket-mode syntax-table for the buffer. Otherwise you should not enable one of these modes, and instead just use the simple delimiter matching of `electric-pair-local-mode`, as configured by racket-hash-lang-mode.

As another example, if you prefer more colors than just tokens, choices include:

- Enable racket-xp-mode in `racket-hash-lang-mode-hook` and in the module language hook locally set racket-xp-add-binding-faces:

      (setq-local racket-xp-add-binding-faces t)

OR

- Use some of the regexp search-based fontification from classic racket-mode for rackety module languages:

      (require 'racket-font-lock)
      (if rackety
          (font-lock-add-keywords nil
                                  (append racket-font-lock-keywords-2
                                          racket-font-lock-keywords-3))
        (font-lock-remove-keywords nil
                                   (append racket-font-lock-keywords-2
                                           racket-font-lock-keywords-3)))

### REPL variables ¶

#### racket-repl-buffer-name-function ¶

How to associate racket-mode edit buffers with racket-repl-mode buffers.

The default is nil, which is equivalent to supplying racket-repl-buffer-name-shared: One REPL buffer is shared.

Other predefined choices include racket-repl-buffer-name-unique and racket-repl-buffer-name-project.

This is used when a racket-mode buffer is created. Changing this to a new value only affects racket-mode buffers created later.

Any such function takes no arguments, should look at the variable `buffer-file-name` if necessary, and either `setq-default` or `setq-local` the variable `racket-repl-buffer-name` to a desired racket-repl-mode buffer name. As a result, racket-run commands will use a buffer of that name, creating it if necessary.

#### racket-submodules-to-run ¶

Extra submodules to run.

This is a list of submodules. Each submodule is described as a list, to support submodules nested to any depth.

This is used by commands that emulate the DrRacket Run command:

- racket-run
- racket-run-and-switch-to-repl `<f5>`

It is NOT used by commands that run one specific module, such as:

- racket-run-module-at-point `C-c C-k` or `C-c C-c`
- racket-test `C-<f5>` or `C-c C-t`
- racket-profile

#### racket-repl-history-directory ¶

Directory for racket-repl-mode history files.

#### racket-history-filter-regexp ¶

Input matching this regexp are NOT saved on the history list. Default value is a regexp to ignore input that is all whitespace.

#### racket-images-inline ¶

Whether to display inline images in the REPL.

#### racket-imagemagick-props ¶

Use ImageMagick with these properties for REPL images.

When this property list is not empty – and the variable racket-images-inline is true, and Emacs is built with with ImageMagick support – then `create-image` is called with “imagemagick” as the type and with this property list.

For example, to scale images whose width is larger than 500 pixels, supply (:max-width 500).

#### racket-images-keep-last ¶

How many images to keep in the image cache.

#### racket-images-system-viewer ¶

The image viewer program to use for `racket-view-image`.

#### racket-images-do-not-use-svg ¶

Do not use SVG to render images?

Note: This value is used only when starting a back end – not for each run. If you change this, for it to take effect you must restart by using `racket-start-back-end`.

#### racket-pretty-print ¶

Use pretty-print instead of plain print?

When true, before each run set global-port-print-handler to use pretty-print from racket/pretty, which is suitable for s-expressions.

Note: A configure-runtime submodule might replace this initial value with its own global port print handler – for example to implement printing a non-s-expression syntax.

#### racket-repl-command-file ¶

Name of the file used by racket-repl.

#### racket-repl-echo-sent-expressions ¶

Should commands that send an expresion to the REPL echo it there?

The echoed expression and “ => ” are displayed using the face racket-repl-message to distinguish them from result values.

Affects racket-send-last-sexp, racket-send-region, and racket-send-definition.

### Other variables ¶

#### racket-doc-index-directory ¶

Directory for racket-describe-search doc index files.

#### racket-doc-index-predicate-function ¶

A function used by racket-describe-search to filter results.

The default value, the `always` function, filters nothing.

The function is given four string arguments – TERM, WHAT, FROM-LIBS, and FAMILIES – and should return whether to include the item in the list of completion candidates. An example that limits candidates to the “Rhombus” family:

(lambda (_term _what _from-libs families) (string-equal families “Rhombus”)

#### racket-indent-curly-as-sequence ¶

Indent `{}` with items aligned with the head item?

This is indirectly disabled if racket-indent-sequence-depth is 0. This is safe to set as a file-local variable.

#### racket-indent-sequence-depth ¶

To what depth should racket-indent-line search.

This affects the indentation of forms like ’() ‘() #() – and {} if racket-indent-curly-as-sequence is t — but not #’() #‘() ,() ,@(). A zero value disables, giving the normal indent behavior of DrRacket or Emacs `lisp-mode` derived modes like `scheme-mode`. Setting this to a high value can make indentation noticeably slower. This is safe to set as a file-local variable.

#### racket-pretty-lambda ¶

Display lambda keywords using λ. This is DEPRECATED.

Instead use `prettify-symbols-mode` in newer verisons of Emacs, or, use racket-insert-lambda to insert actual λ characters.

#### racket-smart-open-bracket-enable ¶

This variable is obsolete and has no effect.

Instead of using this variable, you may bind the `[` key to the `racket-smart-open-bracket` command in the `racket-mode-map` and/or `racket-repl-mode-map` keymaps.

#### racket-logger-config ¶

Configuration of racket-logger-mode topics and levels.

The topic “*” respresents the default level used for topics not assigned a level. Otherwise, the topic symbols are the same as used by Racket’s `define-logger`.

The levels are those used by Racket’s logging system: “debug”, “info”, “warning”, “error”, “fatal”.

For more information see: https://docs.racket-lang.org/reference/logging.html

The default value sets some known “noisy” topics to be one level quieter. That way you can set the “*” topic to a level like “debug” and not get overhwelmed by these noisy topics.

#### racket-before-run-hook ¶

Normal hook done before various Racket Mode run commands.

Here “before” means that the racket-repl-mode buffer might not exist yet.

When hook functions are called, `current-buffer` is that of the edit buffer when the run command was issued. If a hook function instead needs the racket-repl-mode buffer, it should get that from the variable `racket-repl-buffer-name`.

#### racket-after-run-hook ¶

Normal hook done after various Racket Mode run commands.

Here “after” means that the run has completed and the REPL is waiting at another prompt.

When hook functions are called, `current-buffer` is that of the buffer when the run command was issued. If a hook function instead needs the racket-repl-mode buffer, it should get that from the variable `racket-repl-buffer-name`.

#### racket-sexp-comment-fade ¶

How much to fade faces used in s-expression comment bodies.

A number from 0.0 to 1.0, where 0.0 is 0% fade and 1.0 is 100% fade (invisible).

This feature works by creating faces that are alternatives for faces used in s-expression comments. The alernative faces use a faded foreground color. The colors are recalculated automatically after you change the value of this customization variable and after any `load-theme`. However in other circumstances you might need to use `racket-refresh-sexp-comment-faces`.

### Experimental debugger variables ¶

#### racket-debuggable-files ¶

Used to tell racket-run what files may be instrumented for debugging.

This isn’t yet a defcustom becuase the debugger status is still “experimental”.

Must be either a list of file name strings, or, a function that takes the name of the file being run and returns a list of file names.

Each file name in the list is made absolute using `expand-file-name` with respect to the file being run and given to `racket-file-name-front-to-back`.

### Showing information ¶

#### racket-show-functions ¶

An “abnormal hook” variable to customize `racket-show`.

This is a list of one or more functions.

Each such function must accept two arguments: STR and POS.

STR is one of:

- Non-blank string: Display the string somehow.
- Blank string: Hide any previously displayed string.
- nil: Hide any persistent UI that might have been created. For instance racket-show-header-line hides the header line.

POS may be nil when STR is nil or a blank string.

Otherwise POS is the buffer position – typically the end of a span – that the non-blank STR describes.

A function that shows STR near POS should position it not to hide the span, i.e. below and/or right of POS. Examples: racket-show-pseudo-tooltip and racket-show-pos-tip.

A function that shows STR in a fixed location may of course ignore POS. Examples: racket-show-echo-area and racket-show-header-line

### Running racket and raco commands in a shell or terminal ¶

#### racket-shell-or-terminal-function ¶

How racket-racket and racket-raco-test run commands.

The function should accept a command string, not including a newline, get or create a suitable buffer, send the command, and send a newline or enter.

Predefined choices include racket-shell, racket-term, racket-ansi-term, and racket-vterm.

### Racket input method ¶

#### racket-input-prefix ¶

A prefix used by the “Racket” input method.

This string is prepended to the key sequence strings in racket-input-translations, when setting up the input method.

Using some non-nil, non-blank prefix avoids conflicts between key sequences and portions of normal words. For example “oint” would insert “∮” while you’re typing “point” – but not “\oint”.

If you change this setting manually with `setq` (instead of using the customization buffer or `setopt`) you need to call `racket-input-setup` in order for the change to take effect.

#### racket-input-translations ¶

A list of translations.

Each element is (KEY-SEQUENCE-STRING TRANSLATION-STRING).

Used by the “Racket” input method activated by racket-input-mode, as well as by the racket-insert-symbol command.

If you change this setting manually with `setq` (instead of using the customization buffer or `setopt`) you need to call `racket-input-setup` in order for the change to take effect.

## Configuration functions ¶

### Showing information ¶

#### racket-show-pseudo-tooltip ¶

`(racket-show-pseudo-tooltip str &optional pos)`

Show using an overlay that resembles a tooltip.

This is nicer than racket-show-pos-tip because it:

- Doesn’t flicker while navigating.
- Doesn’t disappear after a timeout.
- Performs well when `x-gtk-use-system-tooltips` is nil.

On the other hand, this does not look as nice when displaying text that spans multiple lines or is too wide to fit the window. In that case, we simply left-justify everything and do not draw any border.

#### racket-show-echo-area ¶

`(racket-show-echo-area str &optional _pos)`

Show things in the echo area.

A value for the variable racket-show-functions.

This does not add STR to the “Messages” log buffer.

#### racket-show-header-line ¶

`(racket-show-header-line str &optional _pos)`

Show things using a buffer header line.

A value for the variable racket-show-functions.

When there is nothing to show, keep a blank header-line. That way, the buffer below doesn’t “jump up and down” by a line as messages appear and disappear. Only when V is nil do we remove the header line.

#### racket-show-pos-tip ¶

`(racket-show-pos-tip str &optional pos)`

Show things using `pos-tip-show` if available.

A value for the variable racket-show-functions.

### Associating edit buffers with REPL buffers ¶

#### racket-repl-buffer-name-shared ¶

`(racket-repl-buffer-name-shared)`

Share one racket-repl-mode buffer per back end.

A value for the variable racket-repl-buffer-name-function.

#### racket-repl-buffer-name-unique ¶

`(racket-repl-buffer-name-unique)`

Each racket-mode edit buffer gets its own racket-repl-mode buffer.

A value for the variable racket-repl-buffer-name-function.

#### racket-repl-buffer-name-project ¶

`(racket-repl-buffer-name-project)`

Share a racket-repl-mode buffer per back end and per project.

A value for the variable racket-repl-buffer-name-function.

The “project” is determined by racket-project-root.

#### racket-project-root ¶

`(racket-project-root file)`

Given an absolute pathname for FILE, return its project root directory.

The “project” is determined by trying, in order:

- `projectile-project-root`
- `vc-root-dir`
- `project-current`
- `file-name-directory`

### Browsing file URLs with anchors ¶

#### racket-browse-url-using-temporary-file ¶

`(racket-browse-url-using-temporary-file url &rest _args)`

Browse a URL via a temporary HTML file using a meta redirect.

A suitable value for the variable racket-browse-url-function.

Racket documentation URLs depend on anchors – the portion of the URL after the # character – to jump to a location within a page. Unfortunately on some operating systems and/or versions of Emacs, the default handling for browsing file URLs ignores anchors. This function attempts to avoid the problem by using a temporary HTML file with a meta redirect as a “trampoline”.

Although the intent is to provide a default that “just works”, you do not need to use this. You can customize the variable racket-browse-url-function instead to be `browse-url`, or `browse-url-browser-function` in case have have customized that, or indeed whatever you want.

### Configuring back ends ¶

#### racket-add-back-end ¶

`(racket-add-back-end directory &rest plist)`

Add a description of a Racket Mode back end.

Racket Mode supports one or more back ends, which are Racket processes supporting REPLs as well as various other Racket Mode features.

DIRECTORY is a string describing a `file-name-absolute-p` directory on some local or remote server.

When a back end’s DIRECTORY is the longest matching prefix of a buffer’s `default-directory`, that back end is used for the buffer.

DIRECTORY can be a local directory like “/” or “/path/to/project”, or a `file-remote-p` directory like “/user@host:” or “/user@host:/path/to/project”.

Note that you need not include a method – such as the “ssh” in “/ssh:user@host:” – and if you do it is stripped: A back end process is always started using SSH. Even if multiple buffers for the same user+host+port use different methods, they will share the same back end.

Practically speaking, DIRECTORY is a path you could give to `find-file` to successfully find some local or remote file, but omitting any method. (Some remote file shorthand forms get expanded to at least “/method:host:”. When in doubt check `buffer-file-name` and follow its example.)

In addition to being used as a pattern to pick a back end for a buffer, DIRECTORY determines:

- Whether the back end is local or remote.
- When remote, any explicit user and port used to make SSH connections (as opposed to relying on values from ~/.ssh/config).
- Other properties get reasonable defaults based on whether the back end is local or remote, as described below.

After DIRECTORY, the remainining arguments are optional; they are alternating :keywords and values describing some other properties of a back end:

- :racket-program

  When not nil this is used instead of the value of the customization variable racket-program.

- :remote-source-dir

  Where on a remote host to copy the back end’s *.rkt files when they do not exist or do not match the digest of the local files. This must be `file-name-absolute-p` on the remote. Only supply the localname there (not a full `file-remote-p`). The default value is “/tmp/racket-mode-back-end”.

- :windows

  Whether the back end uses Windows style path names. Used to translate betwen slashes and backslashes between the Emacs front end (which uses slashes even on Windows) and the Racket back end (which expects native backslashes on Windows).

- :restart-watch-directories

  A list of `directory-name-p` strings. Each directory, and recursively its subdirectories, will be watched for file system changes. After any changes are detected, the next racket-run (or racket-run-module-at-point etc.) command will ask you if it should restart the back end for you. This may be helpful when you are changing source files used by the back end.

The default property values are appropriate for whether DIRECTORY is local or remote:

- When DIRECTORY is remote, :windows defaults to nil.
- Otherwise, :windows defaults to a value based on `system-type`.

Although the default values usually “just work” for local and remote back ends, you might want a special configuration. Here are a few examples.

        ;; 1. A back end configuration for "/" is
        ;; created automatically and works fine as a default
        ;; for buffers visiting local files, so we don't need
        ;; to add one here.

        ;; 2. However assume we want buffers under /var/tmp/8.0
        ;; instead to use Racket 8.0.
        (racket-add-back-end "/var/tmp/8.0"
                             :racket-program "~/racket/8.0/bin/racket")

        ;; 3. A back end configuration will be created
        ;; automatically for buffers visiting file names like
        ;; "/ssh:user@linode", so we don't need to add one here.
        ;;
        ;; If ~/.ssh/config defines a Host alias named "linode",
        ;; with HostName and User settings, a file name as simple as
        ;; "/linode:" would work fine with tramp -- and the
        ;; automatically created back end configuration would work
        ;; fine, too.

        ;; 4. For example's sake, assume for buffers visiting
        ;; /ssh:headless:~/gui-project/ we want :racket-program instead
        ;; to be '("xvfb-run" "racket").
        (racket-add-back-end "/ssh:headless:~/gui-project/"
                             :racket-program '("xvfb-run" "racket"))

If you use various versions of Racket by setting PATH values via direnv, .envrc files and `envrc-global-mode`, then you need a distinct back end for each such project subdirectory. One approach is to use racket-add-back-end for each project in your Emacs init file. Another way to is to have a .dir-locals.el file alongside each .envrc file:

        ((nil . ((eval . (racket-add-back-end default-directory)))))

### Running racket and raco commands in a shell or terminal ¶

#### racket-shell ¶

`(racket-shell cmd)`

Run CMD using `shell`.

A value for the variable racket-shell-or-terminal-function.

#### racket-term ¶

`(racket-term cmd)`

Run CMD using `term`.

A value for the variable racket-shell-or-terminal-function.

#### racket-ansi-term ¶

`(racket-ansi-term cmd)`

Run CMD using `ansi-term`.

A value for the variable racket-shell-or-terminal-function.

#### racket-vterm ¶

`(racket-vterm cmd)`

Run CMD using `vterm`, if that package is installed.

A value for the variable racket-shell-or-terminal-function.

## Faces ¶

### All ¶

#### racket-keyword-argument-face ¶

Face for `#:keyword` arguments.

#### racket-reader-quoted-symbol-face ¶

Face for symbols quoted using ’ or ‘.

This face is given only to symbols directly quoted using the reader shorthands ’ or ‘. All other directly quoted values, including symbols quoted using “quote” or “quasiquote”, get the face `font-lock-constant-face`.

#### racket-reader-syntax-quoted-symbol-face ¶

Face for symbols quoted using #’ or #‘.

This face is given only to symbols directly quoted using the reader shorthands #’ or #‘. All other directly quoted values, including symbols quoted using “syntax” or “quasisyntax”, get the face `font-lock-constant-face`.

#### racket-here-string-face ¶

Face for here strings.

#### racket-xp-def-face ¶

Face racket-xp-mode uses when point is on a definition.

#### racket-xp-use-face ¶

Face racket-xp-mode uses when point is on a use.

#### racket-xp-unused-face ¶

Face racket-xp-mode uses to highlight unused requires or definitions.

#### racket-xp-tail-target-face ¶

Face racket-xp-mode uses to highlight targets of a tail position.

#### racket-xp-tail-position-face ¶

Face racket-xp-mode uses to highlight expressions in a tail position.

#### racket-xp-binding-lang-face ¶

Face racket-xp-mode gives to the module language name.

See the variable `nil`.

#### racket-xp-binding-lang-use-face ¶

Face racket-xp-mode gives uses of bindings imported from the module language.

See the variable `nil`.

#### racket-xp-binding-import-face ¶

Face racket-xp-mode gives to imported module names.

See the variable `nil`.

#### racket-xp-binding-import-use-face ¶

Face racket-xp-mode gives uses of imported bindings.

See the variable `nil`.

#### racket-xp-binding-local-face ¶

Face racket-xp-mode gives to local definitions.

See the variable `nil`.

#### racket-xp-binding-local-use-face ¶

Face racket-xp-mode gives to uses of local definitions.

See the variable `nil`.

#### racket-logger-config-face ¶

Face for racket-logger-mode configuration.

#### racket-logger-topic-face ¶

Face for racket-logger-mode topics.

#### racket-logger-fatal-face ¶

Face for racket-logger-mode fatal level.

#### racket-logger-error-face ¶

Face for racket-logger-mode error level.

#### racket-logger-warning-face ¶

Face for racket-logger-mode warning level.

#### racket-logger-info-face ¶

Face for racket-logger-mode info level.

#### racket-logger-debug-face ¶

Face for racket-logger-mode debug level.

#### racket-doc-link-face ¶

Face racket-describe-mode uses for links within documentation. Note: When some special face is already specified by the documentation, then to avoid visual clutter this face is NOT also added.

#### racket-ext-link-face ¶

Face racket-describe-mode uses for external links. See the variable racket-browse-url-function.

#### racket-doc-output-face ¶

Face racket-describe-mode uses for Scribble @example or @interactions output.

#### racket-doc-litchar-face ¶

Face racket-describe-mode uses for Scribble @litchar.

#### racket-repl-message ¶

Face racket-repl-mode uses for messages from the back end.

#### racket-repl-prompt ¶

Face racket-repl-mode uses for prompts.

#### racket-repl-value ¶

Face racket-repl-mode uses for `print`-ed values.

#### racket-repl-error-message ¶

Face racket-repl-mode uses for error messages.

#### racket-repl-error-location ¶

Face racket-repl-mode uses for error locations.

#### racket-repl-stdout ¶

Face racket-repl-mode uses for output to current-output-port.

#### racket-repl-stderr ¶

Face racket-repl-mode uses for output to current-error-port.

#### racket-hash-lang-text ¶

Face racket-hash-lang-mode uses for text tokens.

#### Footnotes

##### (1)

Racket Mode’s Racket code is delivered as part of the Emacs package — not as a Racket package. Delivering both Emacs and Racket code in one Emacs package simplifies installation and updates. The main drawback is that the Racket code is not automatically compiled, as would normally be done by `raco pkg install`. To address this: See racket-mode-start-faster.