diff options
Diffstat (limited to 'lib/option.ml')
| -rw-r--r-- | lib/option.ml | 36 |
1 files changed, 21 insertions, 15 deletions
diff --git a/lib/option.ml b/lib/option.ml index 85efdd44..942fff48 100644 --- a/lib/option.ml +++ b/lib/option.ml @@ -6,7 +6,7 @@ (* * GNU Lesser General Public License Version 2.1 *) (************************************************************************) -(*i $Id: option.ml 11576 2008-11-10 19:13:15Z msozeau $ i*) +(*i $Id$ i*) (** Module implementing basic combinators for OCaml option type. It tries follow closely the style of OCaml standard library. @@ -20,7 +20,7 @@ let has_some = function | None -> false | _ -> true - + exception IsNone (** [get x] returns [y] where [x] is [Some y]. It raises IsNone @@ -34,11 +34,11 @@ let make x = Some x (** [init b x] returns [Some x] if [b] is [true] and [None] otherwise. *) let init b x = - if b then + if b then Some x else None - + (** [flatten x] is [Some y] if [x] is [Some (Some y)] and [None] otherwise. *) let flatten = function @@ -48,7 +48,7 @@ let flatten = function (** {6 "Iterators"} ***) -(** [iter f x] executes [f y] if [x] equals [Some y]. It does nothing +(** [iter f x] executes [f y] if [x] equals [Some y]. It does nothing otherwise. *) let iter f = function | Some y -> f y @@ -60,7 +60,7 @@ 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 = +let iter2 f x y = match x,y with | Some z, Some w -> f z w | None,None -> () @@ -92,11 +92,17 @@ let fold_left2 f a x y = | _ -> 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 = +let fold_right f x a = match x with | Some y -> f y a | _ -> a +(** [fold_map f a x] is [a, f y] if [x] is [Some y], and [a] otherwise. *) +let fold_map f a x = + match x with + | Some y -> let a, z = f a y in a, Some z + | _ -> a, None + (** [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 @@ -112,20 +118,20 @@ let default a = function (** [lift f x] is the same as [map f x]. *) let lift = map -(** [lift_right f a x] is [Some (f a y)] if [x] is [Some y], and +(** [lift_right f a x] is [Some (f a y)] if [x] is [Some y], and [None] otherwise. *) let lift_right f a = function | Some y -> Some (f a y) | _ -> None -(** [lift_left f x a] is [Some (f y a)] if [x] is [Some y], and +(** [lift_left f x a] is [Some (f y a)] if [x] is [Some y], and [None] otherwise. *) let lift_left f x a = match x with | Some y -> Some (f y a) | _ -> None -(** [lift2 f x y] is [Some (f z w)] if [x] equals [Some z] and [y] equals +(** [lift2 f x y] is [Some (f z w)] if [x] equals [Some z] and [y] equals [Some w]. It is [None] otherwise. *) let lift2 f x y = match x,y with @@ -137,18 +143,18 @@ let lift2 f x y = (** {6 Operations with Lists} *) module List = - struct + 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) - | [] -> [] + | [] -> [] end @@ -157,8 +163,8 @@ end module Misc = struct - (** [Misc.compare f x y] lifts the equality predicate [f] to - option types. That is, if both [x] and [y] are [None] then + (** [Misc.compare f x y] lifts the equality predicate [f] to + option types. That is, if both [x] and [y] are [None] then it returns [true], if they are bothe [Some _] then [f] is called. Otherwise it returns [false]. *) let compare f x y = |