`type 'a t =`

1. `| Node of 'a * 'a t list`
   (*

   The type of polymorphic trees

   *)

### Functions for placement

`module Place (X : Signature.Boxlike) : sig ... end`
`val gen_draw_arrows : 'c -> style:(Point.t -> Point.t -> 'c) -> corner:(Box.position -> 'a -> Point.t) -> 'a t -> 'c t`

draws arrows from a node to its children with a given style

`val draw : ('a -> Box.t) -> 'a t -> Command.t`

Draws a tree that has already been placed when one knows how to draw its elements.

### Useful functions

`val map : ('a -> 'b) -> 'a t -> 'b t`

apply a function everywhere in the tree

`val map2 : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t`

`map2 f` takes two trees of identical structure and applies the function `f` to every pair of nodes. Raise `Invalid_argument` if the trees do not have the same structure.

`val combine : 'a t -> 'b t -> ('a * 'b) t`

Transform a pair of trees into a tree of pairs. Raise `Invalid_argument` if the trees do not have the same structure.

`val split : ('a * 'b) t -> 'a t * 'b t`

Transform a tree of pairs into a pair of trees.

`val root_map : ('a option -> 'a -> 'b) -> 'a t -> 'b t`

`root_map f t` calls `f (Some father) node` for each node of `t` and its father. It calls `f None root`, where `root` is the root of the once, once at the beginning. A tree having the same structure is built with the results.

`val map_children : ('a -> 'a list -> 'b) -> 'a t -> 'b t`

`map_children f t` calls `f node children` for each node of `t` and its children. A tree having the same structure is built with the results

`val fold : ('a -> 'b -> 'a) -> 'a -> 'b t -> 'a`

Traverse the tree in a bottom-up, left-to-right order

`val fold_child : ('a -> 'b -> 'b -> 'a) -> 'a -> 'b t -> 'a`

Traverse the pairs of parent-child in the tree in a bottom-up, left-to-right order

`val filter : ('a -> bool) -> 'a t -> 'a t`

filter f t If for a node n of t f n is false then it doesn't appear in the result as well as its descendants. If f is false for the root node, invalid_argument is raised

`val filter_option : ('a -> 'b option) -> 'a t -> 'b t`

Suppress a subtree depending on a condition on the node

`val wrap_corner_box : ('a -> Box.t) -> (corner:(Box.position -> 'a -> Point.t) -> 'c) -> 'c`

`wrap_corner_box give_box f` returns `f` where its argument corner has been set

`module Overlays : sig ... end`

Tools for overlay aware trees

`module Overlays_Boxlike (X : Signature.Boxlike) : Signature.Boxlike with type t = X.t Overlays.spec`