langs a-z

Task/Search-a-list/Standard-ML/search-a-list.ml

@@ -0,0 +1,15 @@
+fun find_index (pred, lst) = let
+  fun loop (n, [])    = NONE
+    | loop (n, x::xs) = if pred x then SOME n
+                                  else loop (n+1, xs)
+in
+  loop (0, lst)
+end;
+
+val haystack = ["Zig","Zag","Wally","Ronald","Bush","Krusty","Charlie","Bush","Bozo"];
+
+app (fn needle =>
+       case find_index (fn x => x = needle, haystack) of
+            SOME i => print (Int.toString i ^ " " ^ needle ^ "\n")
+          | NONE   => print (needle ^ " is not in haystack\n"))
+    ["Washington", "Bush"];