--- /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