fasto unzipped

fasto/Fasto/SymTab.fs

@@ -0,0 +1,37 @@
+(* A polymorphic symbol table. *)
+
+module SymTab
+
+open System
+
+(*
+A symbol table is just a list of tuples identifiers and values. This allows for
+easy shadowing, as a shadowing binding can be quickly placed at the head of the
+list.
+*)
+type SymTab<'a> = SymTab of (string * 'a) list
+
+let empty () = SymTab []
+
+let rec lookup n tab =
+  match tab with
+    | SymTab [] -> None
+    | SymTab ((n1,i1)::remtab) ->
+        if n = n1
+        then Some i1
+        else lookup n (SymTab remtab)
+
+let bind n i (SymTab stab) = SymTab ((n,i)::stab)
+
+let remove n (SymTab stab) =
+    SymTab (List.filter (fun (x, _) -> x <> n) stab)
+
+let removeMany ns (SymTab stab) =
+  SymTab (List.filter (fun (x, _) ->
+            not (List.exists (fun y -> y = x) ns)) stab)
+
+let combine (SymTab t1) (SymTab t2) = SymTab (t1 @ t2)
+
+let fromList l = SymTab l
+
+let toList (SymTab lst) = lst