Add Lwd.map_and_set

let-def · Dec 16, 2023 · 1517853 · 1517853
1 parent 1ed497d
commit 1517853
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diff --git a/lib/lwd/lwd.ml b/lib/lwd/lwd.ml
@@ -308,6 +308,8 @@ let peek = function
   | Operator ({desc = Var v; _}) -> v.binding
   | _ -> assert false
 
+let map_and_set f v = set v (f (peek v))
+
 (* Primitives *)
 type 'a prim = 'a t
 let prim ~acquire ~release =

diff --git a/lib/lwd/lwd.mli b/lib/lwd/lwd.mli
@@ -67,6 +67,9 @@ val peek : 'a var -> 'a
 (** Observe the current value of the variable, without any dependency
     tracking. *)
 
+val map_and_set : ('a -> 'a) -> 'a var -> unit
+(** Modify a variable based on its currently observed value. *)
+
 type +'a prim
 (** A primitive document. It can correspond, for example, to
     a primitive UI element.