add mem to CCHashTrie

src/data/CCHashTrie.ml

@@ -38,6 +38,8 @@ module type S = sig
 
   val add : key -> 'a -> 'a t -> 'a t
 
+  val mem : key -> _ t -> bool
+
   val get : key -> 'a t -> 'a option
 
   val get_exn : key -> 'a t -> 'a
@@ -115,14 +117,14 @@ end
   (*
   from https://en.wikipedia.org/wiki/Hamming_weight
 
-  //This uses fewer arithmetic operations than any other known  
+  //This uses fewer arithmetic operations than any other known
   //implementation on machines with fast multiplication.
   //It uses 12 arithmetic operations, one of which is a multiply.
   int popcount_3(uint64_t x) {
     x -= (x >> 1) & m1;             //put count of each 2 bits into those 2 bits
-    x = (x & m2) + ((x >> 2) & m2); //put count of each 4 bits into those 4 bits 
+    x = (x & m2) + ((x >> 2) & m2); //put count of each 4 bits into those 4 bits
-    x = (x + (x >> 4)) & m4;        //put count of each 8 bits into those 8 bits 
+    x = (x + (x >> 4)) & m4;        //put count of each 8 bits into those 8 bits
-    return (x * h01)>>56;  //returns left 8 bits of x + (x<<8) + (x<<16) + (x<<24) + ... 
+    return (x * h01)>>56;  //returns left 8 bits of x + (x<<8) + (x<<16) + (x<<24) + ...
   }
 *)
 
@@ -317,6 +319,10 @@ module Make(Key : KEY)
     try Some (get_exn_ k ~h:(hash_ k) m)
     with Not_found -> None
 
+  let mem k m =
+    try ignore (get_exn_ k ~h:(hash_ k) m); true
+    with Not_found -> false
+
   (* TODO: use Hash.combine if array only has one non-empty LEAF element? *)
 
   (* [left] list nodes already visited *)

src/data/CCHashTrie.mli

@@ -47,6 +47,8 @@ module type S = sig
 
   val add : key -> 'a -> 'a t -> 'a t
 
+  val mem : key -> _ t -> bool
+
   val get : key -> 'a t -> 'a option
 
   val get_exn : key -> 'a t -> 'a