src/Tools/Compute_Oracle/am_interpreter.ML
changeset 23174 3913451b0418
child 23663 84b5c89b8b49
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Tools/Compute_Oracle/am_interpreter.ML	Thu May 31 20:55:33 2007 +0200
@@ -0,0 +1,162 @@
+(*  Title:      Tools/Compute_Oracle/am_interpreter.ML
+    ID:         $Id$
+    Author:     Steven Obua
+*)
+
+signature ABSTRACT_MACHINE =
+sig
+
+datatype term = Var of int | Const of int | App of term * term | Abs of term
+
+datatype pattern = PVar | PConst of int * (pattern list)
+
+type program
+
+exception Compile of string;
+val compile : (pattern * term) list -> program
+
+exception Run of string;
+val run : program -> term -> term
+
+end
+
+structure AM_Interpreter : ABSTRACT_MACHINE = struct
+
+datatype term = Var of int | Const of int | App of term * term | Abs of term
+
+datatype pattern = PVar | PConst of int * (pattern list)
+
+datatype closure = CVar of int | CConst of int
+                 | CApp of closure * closure | CAbs of closure
+                 | Closure of (closure list) * closure
+
+structure prog_struct = TableFun(type key = int*int val ord = prod_ord int_ord int_ord);
+
+datatype program = Program of ((pattern * closure) list) prog_struct.table
+
+datatype stack = SEmpty | SAppL of closure * stack | SAppR of closure * stack | SAbs of stack
+
+exception Compile of string;
+exception Run of string;
+
+fun clos_of_term (Var x) = CVar x
+  | clos_of_term (Const c) = CConst c
+  | clos_of_term (App (u, v)) = CApp (clos_of_term u, clos_of_term v)
+  | clos_of_term (Abs u) = CAbs (clos_of_term u)
+
+fun term_of_clos (CVar x) = Var x
+  | term_of_clos (CConst c) = Const c
+  | term_of_clos (CApp (u, v)) = App (term_of_clos u, term_of_clos v)
+  | term_of_clos (CAbs u) = Abs (term_of_clos u)
+  | term_of_clos (Closure (e, u)) = raise (Run "internal error: closure in normalized term found")
+
+fun strip_closure args (CApp (a,b)) = strip_closure (b::args) a
+  | strip_closure args x = (x, args)
+
+fun len_head_of_closure n (CApp (a,b)) = len_head_of_closure (n+1) a
+  | len_head_of_closure n x = (n, x)
+
+
+(* earlier occurrence of PVar corresponds to higher de Bruijn index *)
+fun pattern_match args PVar clos = SOME (clos::args)
+  | pattern_match args (PConst (c, patterns)) clos =
+    let
+        val (f, closargs) = strip_closure [] clos
+    in
+        case f of
+            CConst d =>
+            if c = d then
+                pattern_match_list args patterns closargs
+            else
+                NONE
+          | _ => NONE
+    end
+and pattern_match_list args [] [] = SOME args
+  | pattern_match_list args (p::ps) (c::cs) =
+    (case pattern_match args p c of
+        NONE => NONE
+      | SOME args => pattern_match_list args ps cs)
+  | pattern_match_list _ _ _ = NONE
+
+(* Returns true iff at most 0 .. (free-1) occur unbound. therefore check_freevars 0 t iff t is closed *)
+fun check_freevars free (Var x) = x < free
+  | check_freevars free (Const c) = true
+  | check_freevars free (App (u, v)) = check_freevars free u andalso check_freevars free v
+  | check_freevars free (Abs m) = check_freevars (free+1) m
+
+fun count_patternvars PVar = 1
+  | count_patternvars (PConst (_, ps)) = List.foldl (fn (p, count) => (count_patternvars p)+count) 0 ps
+
+fun pattern_key (PConst (c, ps)) = (c, length ps)
+  | pattern_key _ = raise (Compile "pattern reduces to variable")
+
+fun compile eqs =
+    let
+        val eqs = map (fn (p, r) => (check_freevars (count_patternvars p) r;
+                                     (pattern_key p, (p, clos_of_term r)))) eqs
+    in
+        Program (prog_struct.make (map (fn (k, a) => (k, [a])) eqs))
+    end
+
+fun match_rules n [] clos = NONE
+  | match_rules n ((p,eq)::rs) clos =
+    case pattern_match [] p clos of
+        NONE => match_rules (n+1) rs clos
+      | SOME args => SOME (Closure (args, eq))
+
+fun match_closure (Program prog) clos =
+    case len_head_of_closure 0 clos of
+        (len, CConst c) =>
+        (case prog_struct.lookup prog (c, len) of
+            NONE => NONE
+          | SOME rules => match_rules 0 rules clos)
+      | _ => NONE
+
+fun lift n (c as (CConst _)) = c
+  | lift n (v as CVar m) = if m < n then v else CVar (m+1)
+  | lift n (CAbs t) = CAbs (lift (n+1) t)
+  | lift n (CApp (a,b)) = CApp (lift n a, lift n b)
+  | lift n (Closure (e, a)) = Closure (lift_env n e, lift (n+(length e)) a)
+and lift_env n e = map (lift n) e
+
+fun weak prog stack (Closure (e, CApp (a, b))) = weak prog (SAppL (Closure (e, b), stack)) (Closure (e, a))
+  | weak prog (SAppL (b, stack)) (Closure (e, CAbs m)) = weak prog stack (Closure (b::e, m))
+  | weak prog stack (Closure (e, CVar n)) = weak prog stack (List.nth (e, n) handle Subscript => (CVar (n-(length e))))
+  | weak prog stack (Closure (e, c as CConst _)) = weak prog stack c
+  | weak prog stack clos =
+    case match_closure prog clos of
+        NONE => weak_last prog stack clos
+      | SOME r => weak prog stack r
+and weak_last prog (SAppR (a, stack)) b = weak prog stack (CApp (a,b))
+  | weak_last prog (s as (SAppL (b, stack))) a = weak prog (SAppR (a, stack)) b
+  | weak_last prog stack c = (stack, c)
+
+fun strong prog stack (Closure (e, CAbs m)) =
+    let
+        val (stack', wnf) = weak prog SEmpty (Closure ((CVar 0)::(lift_env 0 e), m))
+    in
+        case stack' of
+            SEmpty => strong prog (SAbs stack) wnf
+          | _ => raise (Run "internal error in strong: weak failed")
+    end
+  | strong prog stack (clos as (CApp (u, v))) = strong prog (SAppL (v, stack)) u
+  | strong prog stack clos = strong_last prog stack clos
+and strong_last prog (SAbs stack) m = strong prog stack (CAbs m)
+  | strong_last prog (SAppL (b, stack)) a = strong prog (SAppR (a, stack)) b
+  | strong_last prog (SAppR (a, stack)) b = strong_last prog stack (CApp (a, b))
+  | strong_last prog stack clos = (stack, clos)
+
+fun run prog t =
+    let
+        val (stack, wnf) = weak prog SEmpty (Closure ([], clos_of_term t))
+    in
+        case stack of
+            SEmpty => (case strong prog SEmpty wnf of
+                           (SEmpty, snf) => term_of_clos snf
+                         | _ => raise (Run "internal error in run: strong failed"))
+          | _ => raise (Run "internal error in run: weak failed")
+    end
+
+end
+
+structure AbstractMachine = AM_Interpreter