diff options
Diffstat (limited to 'lib/monad.ml')
-rw-r--r-- | lib/monad.ml | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/lib/monad.ml b/lib/monad.ml index a1714a41..2e55e969 100644 --- a/lib/monad.ml +++ b/lib/monad.ml @@ -64,6 +64,9 @@ module type ListS = sig its second argument in a tail position. *) val iter : ('a -> unit t) -> 'a list -> unit t + (** Like the regular {!CList.map_filter}. The monadic effects are threaded left*) + val map_filter : ('a -> 'b option t) -> 'a list -> 'b list t + (** {6 Two-list iterators} *) @@ -138,6 +141,14 @@ module Make (M:Def) : S with type +'a t = 'a M.t = struct | a::b::l -> f a >> f b >> iter f l + let rec map_filter f = function + | [] -> return [] + | a::l -> + f a >>= function + | None -> map_filter f l + | Some b -> + map_filter f l >>= fun filtered -> + return (b::filtered) let rec fold_left2 r f x l1 l2 = match l1,l2 with |