unicode-collation-0.1.3.6: Haskell implementation of the Unicode Collation Algorithm

Copyright | (c) 2021 John MacFarlane
License | BSD-2-Clause
Maintainer | John MacFarlane <jgm@berkeley.edu>
Safe Haskell | None
Language | Haskell2010

Text.Collate

Description

This library provides a pure Haskell implementation of the Unicode Collation Algorithm, allowing proper sorting of Unicode strings.

The simplest way to use the library is to use the `IsString` instance of `Collator` (together with the `OverloadedStrings` extension):

    >>> import Data.List (sortBy)
    >>> import qualified Data.Text.IO as T
    >>> mapM_ T.putStrLn $ sortBy (collate "en-US") ["𝒶bc","abC","𝕒bc","Abc","abç","äbc"]
    abC
    𝒶bc
    𝕒bc
    Abc
    abç
    äbc

Note the difference from the default sort:

    >>> import Data.List (sort)
    >>> import qualified Data.Text.IO as T
    >>> mapM_ T.putStrLn $ sort ["𝒶bc","abC","𝕒bc","Abc","abç","äbc"]
    Abc
    abC
    abç
    äbc
    𝒶bc
    𝕒bc

A `Collator` provides a function `collate` that compares two texts, and a function `sortKey` that returns the sort key. Most users will just need `collate`.

    >>> let de = collatorFor "de"
    >>> let se = collatorFor "se"
    >>> collate de "ö" "z"
    LT
    >>> collate se "ö" "z"
    GT
    >>> sortKey de "ö"
    SortKey [0x213C,0x0000,0x0020,0x002B,0x0000,0x0002,0x0002]
    >>> sortKey se "ö"
    SortKey [0x22FD,0x0000,0x0020,0x0000,0x0002]

To sort a string type other than `Text`, the function `collateWithUnpacker` may be used. It takes as a parameter a function that lazily unpacks the string type into a list of `Char`.

    >>> let seCollateString = collateWithUnpacker "se" id
    >>> seCollateString ("ö" :: String) ("z" :: String)
    GT

Because `Collator` and `Lang` have `IsString` instances, you can just specify them using string literals, as in the above examples. Note, however, that you won't get any feedback if the string doesn't parse correctly as a BCP47 language tag, or if no collation is defined for the specified language; instead, you'll just get the default (root) collator. For this reason, we don't recommend relying on the `IsString` instance.

If you won't know the language until run time, use `parseLang` to parse it to a `Lang`, handling parse errors, and then pass the `Lang` to `collatorFor`.

    >>> let handleParseError = error  -- or something fancier
    >>> lang <- either handleParseError return $ parseLang "bs-Cyrl"
    >>> collate (collatorFor lang) "a" "b"
    LT

If you know the language at compile-time, use the `collator` quasi-quoter and you'll get compile-time errors and warnings:

    >>> :set -XQuasiQuotes
    >>> let esTraditional = [collator|es-u-co-trad|]
    >>> let esStandard = [collator|es|]
    >>> collate esStandard "Co" "Ch"
    GT
    >>> collate esTraditional "Co" "Ch"
    LT

Note that the unicode extension syntax for BCP47 can be used to specify a particular collation for the language (here, Spanish "traditional" instead of the default ordering; the alias `trad` is used because of length limits for BCP47 keywords).

The extension syntax can also be used to set collator options. The keyword `kb` can be used to specify the "backwards" accent sorting that is sometimes used in French:

    >>> collate "fr" "côte" "coté"
    GT
    >>> collate "fr-u-kb" "côte" "coté"
    LT

The keyword `ka` can be used to specify the variable weighting options which affect how punctuation and whitespace are treated:

    >>> collate "en-u-ka-shifted" "de-luge" "de Luge"
    LT
    >>> collate "en-u-ka-noignore" "de-luge" "de Luge"
    GT

The keyword `kk` can be used to turn off the normalization step (which is required by the algorithm but can be omitted for better performance if the input is already in NFD form (canonical decomposition).

    >>> let noNormalizeCollator = [collator|en-u-kk-false|]

The keyword `kf` can be used to say whether uppercase or lowercase letters should be sorted first.

    >>> collate "en-u-kf-upper" "A" "a"
    LT
    >>> collate "en-u-kf-lower" "A" "a"
    GT

These options be combined:

    >>> collate "de-DE-u-co-phonebk-kb-false-ka-shifted" "Udet" "Über"
    LT

Options can also be set using the functions `setVariableWeighting`, `setNormalization`, `setUpperBeforeLower`, and `setFrenchAccents`:

    >>> let frC = setFrenchAccents True [collator|fr|]
    >>> collate frC "côte" "coté"
    LT

Synopsis

- data Collator
- collate :: Collator -> Text -> Text -> Ordering
- collateWithUnpacker :: Collator -> forall a. Eq a => (a -> [Char]) -> a -> a -> Ordering
- collatorFor :: Lang -> Collator
- collator :: QuasiQuoter
- rootCollator :: Collator
- newtype SortKey = SortKey [Word16]
- sortKey :: Collator -> Text -> SortKey
- renderSortKey :: SortKey -> String
- data VariableWeighting
  - = NonIgnorable
  - | Blanked
  - | Shifted
  - | ShiftTrimmed
- data CollatorOptions = CollatorOptions {
  - optLang :: Maybe Lang
  - optVariableWeighting :: VariableWeighting
  - optFrenchAccents :: Bool
  - optUpperBeforeLower :: Bool
  - optNormalize :: Bool
  }
- collatorOptions :: Collator -> CollatorOptions
- collatorLang :: Collator -> Maybe Lang
- setVariableWeighting :: VariableWeighting -> Collator -> Collator
- setNormalization :: Bool -> Collator -> Collator
- setFrenchAccents :: Bool -> Collator -> Collator
- setUpperBeforeLower :: Bool -> Collator -> Collator
- tailorings :: [(Lang, Collation)]
- module Text.Collate.Lang

# Documentation

data Collator Source #

#### Instances

Instances details

IsString Collator Source # |
Instance details Defined in Text.Collate.Collator Methods fromString :: String -> Collator Source #

collate :: Collator -> Text -> Text -> Ordering Source #

Compare two `Text`s

collateWithUnpacker :: Collator -> forall a. Eq a => (a -> [Char]) -> a -> a -> Ordering Source #

Compare two strings of any type that can be unpacked lazily into a list of `Char`s.

collatorFor :: Lang -> Collator Source #

Returns a collator based on a BCP 47 language tag. If no exact match is found, we try to find the best match (falling back to the root collation if nothing else succeeds). If something other than the default collation for a language is desired, the `co` keyword of the unicode extensions can be used (e.g. `es-u-co-trad` for traditional Spanish). Other unicode extensions affect the collator options:

- The `kb` keyword has the same effect as `setFrenchAccents` (e.g. `fr-FR-u-kb-true`).
- The `ka` keyword has the same effect as `setVariableWeight` (e.g. `fr-FR-u-kb-ka-shifted` or `en-u-ka-noignore`).
- The `kf` keyword has the same effect as `setUpperBeforeLower` (e.g. `fr-u-kf-upper` or `fr-u-kf-lower`).
- The `kk` keyword has the same effect as `setNormalization` (e.g. `fr-u-kk-false`).

collator :: QuasiQuoter Source #

Create a collator at compile time based on a BCP 47 language tag: e.g., `[collator|es-u-co-trad|]`. Requires the `QuasiQuotes` extension.

rootCollator :: Collator Source #

Default collator based on DUCET table (`allkeys.txt`).

newtype SortKey Source #

Constructors

SortKey [Word16] |

#### Instances

Instances details

Show SortKey Source # |
Instance details Defined in Text.Collate.Collator Methods showsPrec :: Int -> SortKey -> ShowS Source # show :: SortKey -> String Source # showList :: [SortKey] -> ShowS Source #
Eq SortKey Source # |
Instance details Defined in Text.Collate.Collator Methods (==) :: SortKey -> SortKey -> Bool Source # (/=) :: SortKey -> SortKey -> Bool Source #
Ord SortKey Source # |
Instance details Defined in Text.Collate.Collator Methods compare :: SortKey -> SortKey -> Ordering Source # (<) :: SortKey -> SortKey -> Bool Source # (<=) :: SortKey -> SortKey -> Bool Source # (>) :: SortKey -> SortKey -> Bool Source # (>=) :: SortKey -> SortKey -> Bool Source # max :: SortKey -> SortKey -> SortKey Source # min :: SortKey -> SortKey -> SortKey Source #

sortKey :: Collator -> Text -> SortKey Source #

The sort key used to compare a `Text`

renderSortKey :: SortKey -> String Source #

Render sort key in the manner used in the CLDR collation test data: the character '|' is used to separate the levels of the key and corresponds to a 0 in the actual sort key.

data VariableWeighting Source #

`VariableWeighting` affects how punctuation is treated. See http://www.unicode.org/reports/tr10/#Variable_Weighting.

Constructors

NonIgnorable | Don't ignore punctuation (Deluge < deluge-)
Blanked | Completely ignore punctuation (Deluge = deluge-)
Shifted | Consider punctuation at lower priority (de-luge < delu-ge < deluge < deluge- < Deluge)
ShiftTrimmed | Variant of Shifted (deluge < de-luge < delu-ge)

#### Instances

Instances details

Show VariableWeighting Source # |
Instance details Defined in Text.Collate.Collator Methods showsPrec :: Int -> VariableWeighting -> ShowS Source # show :: VariableWeighting -> String Source # showList :: [VariableWeighting] -> ShowS Source #
Eq VariableWeighting Source # |
Instance details Defined in Text.Collate.Collator Methods (==) :: VariableWeighting -> VariableWeighting -> Bool Source # (/=) :: VariableWeighting -> VariableWeighting -> Bool Source #
Ord VariableWeighting Source # |

Instance details

Defined in Text.Collate.Collator

Methods

compare :: VariableWeighting -> VariableWeighting -> Ordering Source #

(<) :: VariableWeighting -> VariableWeighting -> Bool Source #

(<=) :: VariableWeighting -> VariableWeighting -> Bool Source #

(>) :: VariableWeighting -> VariableWeighting -> Bool Source #

(>=) :: VariableWeighting -> VariableWeighting -> Bool Source #

max :: VariableWeighting -> VariableWeighting -> VariableWeighting Source #

min :: VariableWeighting -> VariableWeighting -> VariableWeighting Source #

data CollatorOptions Source #

Constructors

CollatorOptions |

Fields

- optLang :: Maybe Lang

  `Lang` used for tailoring. Note that because of fallback rules, this may be somewhat different from the `Lang` passed to `collatorFor`. This `Lang` won't contain unicode extensions used to set options, but it will specify the collation if a non-default collation is being used.

- optVariableWeighting :: VariableWeighting

  Method for handling variable elements (see http://www.unicode.org/reports/tr10/, Tables 11 and 12).

- optFrenchAccents :: Bool

  If True, secondary weights are scanned in reverse order, so we get the sorting "cote côte coté côté" instead of "cote coté côte côté"

- optUpperBeforeLower :: Bool

  Sort uppercase letters before lower

- optNormalize :: Bool

  If True, strings are normalized to NFD before collation elements are constructed. If the input is already normalized, this option can be set to False for better performance.

#### Instances

Instances details

Show CollatorOptions Source # |
Instance details Defined in Text.Collate.Collator Methods showsPrec :: Int -> CollatorOptions -> ShowS Source # show :: CollatorOptions -> String Source # showList :: [CollatorOptions] -> ShowS Source #
Eq CollatorOptions Source # |
Instance details Defined in Text.Collate.Collator Methods (==) :: CollatorOptions -> CollatorOptions -> Bool Source # (/=) :: CollatorOptions -> CollatorOptions -> Bool Source #
Ord CollatorOptions Source # |

Instance details

Defined in Text.Collate.Collator

Methods

compare :: CollatorOptions -> CollatorOptions -> Ordering Source #

(<) :: CollatorOptions -> CollatorOptions -> Bool Source #

(<=) :: CollatorOptions -> CollatorOptions -> Bool Source #

(>) :: CollatorOptions -> CollatorOptions -> Bool Source #

(>=) :: CollatorOptions -> CollatorOptions -> Bool Source #

max :: CollatorOptions -> CollatorOptions -> CollatorOptions Source #

min :: CollatorOptions -> CollatorOptions -> CollatorOptions Source #

collatorOptions :: Collator -> CollatorOptions Source #

The options used for this `Collator`

collatorLang :: Collator -> Maybe Lang Source #

Deprecated: Use (optLang . collatorOptions)

`Lang` used for tailoring. Because of fallback rules, this may be somewhat different from the `Lang` passed to `collatorFor`. This `Lang` won't contain unicode extensions used to set options, but it will specify the collation if a non-default collation is being used.

setVariableWeighting :: VariableWeighting -> Collator -> Collator Source #

Set method for handling variable elements (punctuation and spaces): see http://www.unicode.org/reports/tr10/, Tables 11 and 12.

setNormalization :: Bool -> Collator -> Collator Source #

The Unicode Collation Algorithm expects input to be normalized into its canonical decomposition (NFD). By default, collators perform this normalization. If your input is already normalized, you can increase performance by disabling this step: `setNormalization False`.

setFrenchAccents :: Bool -> Collator -> Collator Source #

`setFrenchAccents True` causes secondary weights to be scanned in reverse order, so we get the sorting `cote côte coté côté` instead of `cote coté côte côté`. The default is usually `False`, except for `fr-CA` where it is `True`.

setUpperBeforeLower :: Bool -> Collator -> Collator Source #

Most collations default to sorting lowercase letters before uppercase (exceptions: `mt`, `da`, `cu`). To select the opposite behavior, use `setUpperBeforeLower True`.

tailorings :: [(Lang, Collation)] Source #

An association list matching `Lang`s with tailored `Collation`s.

module Text.Collate.Lang