Module GapiLens

module GapiLens: sig .. end
Functional lenses.

Based on F# implementation in FSharpx (see src/FSharpx.Core/Lens.fs for the original implementation)
See also


type ('a, 'b) t = {
   get : 'a -> 'b; (*Functional getter*)
   set : 'b -> 'a -> 'a; (*Functional setter*)
}
Lens type definition
val modify : ('a, 'b) t -> ('b -> 'b) -> 'a -> 'a
Updates a value through a lens

Combinators


val compose : ('a, 'b) t -> ('c, 'a) t -> ('c, 'b) t
Sequentially composes two lenses
val pair : ('a, 'b) t -> ('c, 'd) t -> ('a * 'c, 'b * 'd) t
Pairs two lenses
val cond : ('a -> bool) ->
('a, 'b) t -> ('a, 'b) t -> ('a, 'b) t
Selects a lens checking a predicate.

cond pred lensTrue lensFalse: pred is applied to source. If true, lensTrue is selected. If false, lensFalse is selected.


State monad integration


val get_state : ('a, 'b) t -> 'a -> 'b * 'a
Gets a value from the state monad.
val put_state : ('a, 'b) t -> 'b -> 'a -> unit * 'a
Puts a value in the state monad.
val modify_state : ('a, 'b) t -> ('b -> 'b) -> 'a -> unit * 'a
Modifies a value in the state monad.

Stock lenses


val ignore : ('a, unit) t
Trivial lens
val id : ('a, 'a) t
Identity lens
val first : ('a * 'b, 'a) t
Gets/sets the first element in a pair
val second : ('a * 'b, 'b) t
Gets/sets the second element in a pair
val head : ('a list, 'a) t
Gets/sets the first element in a list
val tail : ('a list, 'a list) t
Gets/sets the tail of a list
val for_hash : 'a -> (('a, 'b) Hashtbl.t, 'b option) t
Lens for a particular key in a hashtable
val for_assoc : 'a -> (('a * 'b) list, 'b option) t
Lens for a particular key in an associative list
val for_array : int -> ('a array, 'a) t
Lens for a particular position in an array
val for_list : int -> ('a list, 'a) t
Lens for a particular position in a list
val option_get : ('a option, 'a) t
Lens for extracting the value from an option type (same as Option.get)

List combinators


val list_map : ('a, 'b) t -> ('a list, 'b list) t
Creates a lens that maps the given lens in a list

Isomorphism


val xmap : ('a -> 'b) -> ('b -> 'a) -> ('c, 'a) t -> ('c, 'b) t
Applies an isomorphism to the value viewed through a lens
module Infix: sig .. end
Infix operators
module StateInfix: sig .. end
Infix operators for the state monad