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src/Tools/Compute_Oracle/am_interpreter.ML

author | wenzelm |

Sun, 08 Jul 2007 19:51:58 +0200 | |

changeset 23655 | d2d1138e0ddc |

parent 23174 | 3913451b0418 |

child 23663 | 84b5c89b8b49 |

permissions | -rw-r--r-- |

replaced exception TableFun/GraphFun.DUPS by TableFun/GraphFun.DUP;

(* 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