1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188
|
(************************************************************************)
(* * The Coq Proof Assistant / The Coq Development Team *)
(* v * Copyright INRIA, CNRS and contributors *)
(* <O___,, * (see version control and CREDITS file for authors & dates) *)
(* \VV/ **************************************************************)
(* // * This file is distributed under the terms of the *)
(* * GNU Lesser General Public License Version 2.1 *)
(* * (see LICENSE file for the text of the license) *)
(************************************************************************)
(** Module implementing basic combinators for OCaml option type.
It tries follow closely the style of OCaml standard library.
Actually, some operations have the same name as [List] ones:
they actually are similar considering ['a option] as a type
of lists with at most one element. *)
(** [has_some x] is [true] if [x] is of the form [Some y] and [false]
otherwise. *)
let has_some = function
| None -> false
| _ -> true
let is_empty = function
| None -> true
| Some _ -> false
(** Lifting equality onto option types. *)
let equal f x y = match x, y with
| None, None -> true
| Some x, Some y -> f x y
| _, _ -> false
let compare f x y = match x, y with
| None, None -> 0
| Some x, Some y -> f x y
| None, Some _ -> -1
| Some _, None -> 1
let hash f = function
| None -> 0
| Some x -> f x
exception IsNone
(** [get x] returns [y] where [x] is [Some y].
@raise IsNone if [x] equals [None]. *)
let get = function
| Some y -> y
| _ -> raise IsNone
(** [make x] returns [Some x]. *)
let make x = Some x
(** [bind x f] is [f y] if [x] is [Some y] and [None] otherwise *)
let bind x f = match x with Some y -> f y | None -> None
let filter f x = bind x (fun v -> if f v then x else None)
(** [init b x] returns [Some x] if [b] is [true] and [None] otherwise. *)
let init b x =
if b then
Some x
else
None
(** [flatten x] is [Some y] if [x] is [Some (Some y)] and [None] otherwise. *)
let flatten = function
| Some (Some y) -> Some y
| _ -> None
(** [append x y] is the first element of the concatenation of [x] and
[y] seen as lists. *)
let append o1 o2 =
match o1 with
| Some _ -> o1
| None -> o2
(** {6 "Iterators"} ***)
(** [iter f x] executes [f y] if [x] equals [Some y]. It does nothing
otherwise. *)
let iter f = function
| Some y -> f y
| _ -> ()
exception Heterogeneous
(** [iter2 f x y] executes [f z w] if [x] equals [Some z] and [y] equals
[Some w]. It does nothing if both [x] and [y] are [None]. And raises
[Heterogeneous] otherwise. *)
let iter2 f x y =
match x,y with
| Some z, Some w -> f z w
| None,None -> ()
| _,_ -> raise Heterogeneous
(** [map f x] is [None] if [x] is [None] and [Some (f y)] if [x] is [Some y]. *)
let map f = function
| Some y -> Some (f y)
| _ -> None
(** [fold_left f a x] is [f a y] if [x] is [Some y], and [a] otherwise. *)
let fold_left f a = function
| Some y -> f a y
| _ -> a
(** [fold_left2 f a x y] is [f z w] if [x] is [Some z] and [y] is [Some w].
It is [a] if both [x] and [y] are [None]. Otherwise it raises
[Heterogeneous]. *)
let fold_left2 f a x y =
match x,y with
| Some x, Some y -> f a x y
| None, None -> a
| _ -> raise Heterogeneous
(** [fold_right f x a] is [f y a] if [x] is [Some y], and [a] otherwise. *)
let fold_right f x a =
match x with
| Some y -> f y a
| _ -> a
(** [fold_left_map f a x] is [a, f y] if [x] is [Some y], and [a] otherwise. *)
let fold_left_map f a x =
match x with
| Some y -> let a, z = f a y in a, Some z
| _ -> a, None
let fold_right_map f x a =
match x with
| Some y -> let z, a = f y a in Some z, a
| _ -> None, a
(** [cata f a x] is [a] if [x] is [None] and [f y] if [x] is [Some y]. *)
let cata f a = function
| Some c -> f c
| None -> a
(** {6 More Specific operations} ***)
(** [default a x] is [y] if [x] is [Some y] and [a] otherwise. *)
let default a = function
| Some y -> y
| _ -> a
(** {6 Smart operations} *)
module Smart =
struct
(** [Smart.map f x] does the same as [map f x] except that it tries to share
some memory. *)
let map f = function
| Some y as x -> let y' = f y in if y' == y then x else Some y'
| _ -> None
end
(** {6 Operations with Lists} *)
module List =
struct
(** [List.cons x l] equals [y::l] if [x] is [Some y] and [l] otherwise. *)
let cons x l =
match x with
| Some y -> y::l
| _ -> l
(** [List.flatten l] is the list of all the [y]s such that [l] contains
[Some y] (in the same order). *)
let rec flatten = function
| x::l -> cons x (flatten l)
| [] -> []
let map f l =
let rec aux f l = match l with
| [] -> []
| x :: l ->
match f x with
| None -> raise_notrace Exit
| Some y -> y :: aux f l
in
try Some (aux f l) with Exit -> None
end
|