package containers
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Lazy Tree Structure

This structure can be used to represent trees and directed graphs (as infinite trees) in a lazy fashion. Like CCKList, it is a structural type.

type 'a sequence = ('a -> unit) -> unit
type 'a gen = unit -> 'a option
type 'a klist = unit -> [ `Nil | `Cons of 'a * 'a klist ]
type 'a printer = Format.formatter -> 'a -> unit

Basics

type +'a t = unit -> [ `Nil | `Node of 'a * 'a t list ]
val empty : 'a t
val is_empty : _ t -> bool
val singleton : 'a -> 'a t

Tree with only one label.

val node : 'a -> 'a t list -> 'a t

Build a node from a label and a list of children.

val node1 : 'a -> 'a t -> 'a t

Node with one child.

val node2 : 'a -> 'a t -> 'a t -> 'a t

Node with two children.

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

Fold on values in no specified order. May not terminate if the tree is infinite.

val iter : ('a -> unit) -> 'a t -> unit
val size : _ t -> int

Number of elements.

val height : _ t -> int

Length of the longest path to empty leaves.

val map : ('a -> 'b) -> 'a t -> 'b t
val (>|=) : 'a t -> ('a -> 'b) -> 'b t
val cut_depth : int -> 'a t -> 'a t

Cut the tree at the given depth, so it becomes finite.

Graph Traversals

class type 'a pset = object ... end

Abstract Set structure

val set_of_cmp : cmp:('a -> 'a -> int) -> unit -> 'a pset

Build a set structure given a total ordering.

val dfs : pset:'a pset -> 'a t -> [ `Enter of 'a | `Exit of 'a ] klist

Depth-first traversal of the tree.

val bfs : pset:'a pset -> 'a t -> 'a klist

Breadth-first traversal of the tree.

val force : 'a t -> [ `Nil | `Node of 'a * 'b list ] as 'b

force t evaluates t completely and returns a regular tree structure.

  • since 0.13
val find : pset:'a pset -> ('a -> 'b option) -> 'a t -> 'b option

Look for an element that maps to Some _.

Pretty-printing

Example (tree of calls for naive Fibonacci function):

let mk_fib n =
  let rec fib' l r i =
    if i=n then r else fib' r (l+r) (i+1)
  in fib' 1 1 1;;

let rec fib n = match n with
  | 0 | 1 -> CCKTree.singleton (`Cst n)
  | _ -> CCKTree.node2 (`Plus (mk_fib n)) (fib (n-1)) (fib (n-2));;

let pp_node fmt = function
  | `Cst n -> Format.fprintf fmt "%d" n
  | `Plus n -> Format.fprintf fmt "%d" n;;

Format.printf "%a@." (CCKTree.pp pp_node) (fib 8);;
val pp : 'a printer -> 'a t printer

A pretty-printer using S-expressions and boxes to render the tree. Empty nodes are not rendered; sharing is ignored.

  • since 0.9

Pretty printing in the DOT (graphviz) format

module Dot : sig ... end