TFL/utils.ML
changeset 10769 70b9b0cfe05f
child 16854 fdd362b7e980
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/TFL/utils.ML	Wed Jan 03 21:20:40 2001 +0100
@@ -0,0 +1,78 @@
+(*  Title:      TFL/utils.ML
+    ID:         $Id$
+    Author:     Konrad Slind, Cambridge University Computer Laboratory
+    Copyright   1997  University of Cambridge
+
+Basic utilities.
+*)
+
+signature UTILS =
+sig
+  exception ERR of {module: string, func: string, mesg: string}
+  val C: ('a -> 'b -> 'c) -> 'b -> 'a -> 'c
+  val itlist: ('a -> 'b -> 'b) -> 'a list -> 'b -> 'b
+  val rev_itlist: ('a -> 'b -> 'b) -> 'a list -> 'b -> 'b
+  val end_itlist: ('a -> 'a -> 'a) -> 'a list -> 'a
+  val itlist2: ('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> 'c -> 'c
+  val pluck: ('a -> bool) -> 'a list -> 'a * 'a list
+  val zip3: 'a list -> 'b list -> 'c list -> ('a*'b*'c) list
+  val take: ('a -> 'b) -> int * 'a list -> 'b list
+end;
+
+structure Utils: UTILS =
+struct
+
+(*standard exception for TFL*)
+exception ERR of {module: string, func: string, mesg: string};
+
+fun UTILS_ERR func mesg = ERR {module = "Utils", func = func, mesg = mesg};
+
+
+fun C f x y = f y x
+
+fun itlist f L base_value =
+   let fun it [] = base_value
+         | it (a::rst) = f a (it rst)
+   in it L
+   end;
+
+fun rev_itlist f =
+   let fun rev_it [] base = base
+         | rev_it (a::rst) base = rev_it rst (f a base)
+   in rev_it
+   end;
+
+fun end_itlist f =
+   let fun endit [] = raise UTILS_ERR "end_itlist" "list too short"
+         | endit alist =
+            let val (base::ralist) = rev alist
+            in itlist f (rev ralist) base
+            end
+   in endit
+   end;
+
+fun itlist2 f L1 L2 base_value =
+ let fun it ([],[]) = base_value
+       | it ((a::rst1),(b::rst2)) = f a b (it (rst1,rst2))
+       | it _ = raise UTILS_ERR "itlist2" "different length lists"
+ in  it (L1,L2)
+ end;
+
+fun pluck p  =
+  let fun remv ([],_) = raise UTILS_ERR "pluck" "item not found"
+        | remv (h::t, A) = if p h then (h, rev A @ t) else remv (t,h::A)
+  in fn L => remv(L,[])
+  end;
+
+fun take f =
+  let fun grab(0,L) = []
+        | grab(n, x::rst) = f x::grab(n-1,rst)
+  in grab
+  end;
+
+fun zip3 [][][] = []
+  | zip3 (x::l1) (y::l2) (z::l3) = (x,y,z)::zip3 l1 l2 l3
+  | zip3 _ _ _ = raise UTILS_ERR "zip3" "different lengths";
+
+
+end;