(* Title: Tools/Compute_Oracle/am_interpreter.ML
ID: $Id$
Author: Steven Obua
*)
signature AM_BARRAS =
sig
include ABSTRACT_MACHINE
val max_reductions : int option ref
end
structure AM_Interpreter : AM_BARRAS = struct
open AbstractMachine;
datatype closure = CDummy | 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 * (closure*closure) list) list) prog_struct.table
datatype stack = SEmpty | SAppL of closure * stack | SAppR of closure * stack | SAbs of stack
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)
| clos_of_term (Computed t) = clos_of_term t
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")
| term_of_clos CDummy = raise (Run "internal error: dummy in normalized term found")
fun resolve_closure closures (CVar x) = (case List.nth (closures, x) of CDummy => CVar x | r => r)
| resolve_closure closures (CConst c) = CConst c
| resolve_closure closures (CApp (u, v)) = CApp (resolve_closure closures u, resolve_closure closures v)
| resolve_closure closures (CAbs u) = CAbs (resolve_closure (CDummy::closures) u)
| resolve_closure closures (CDummy) = raise (Run "internal error: resolve_closure applied to CDummy")
| resolve_closure closures (Closure (e, u)) = resolve_closure e u
fun resolve_closure' c = resolve_closure [] c
fun resolve_stack tm SEmpty = tm
| resolve_stack tm (SAppL (c, s)) = resolve_stack (CApp (tm, resolve_closure' c)) s
| resolve_stack tm (SAppR (c, s)) = resolve_stack (CApp (resolve_closure' c, tm)) s
| resolve_stack tm (SAbs s) = resolve_stack (CAbs tm) s
fun resolve (stack, closure) =
let
val _ = writeln "start resolving"
val t = resolve_stack (resolve_closure' closure) stack
val _ = writeln "finished resolving"
in
t
end
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
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")
(*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
| check_freevars free (Computed t) = check_freevars free t
fun compile cache_patterns const_arity eqs =
let
fun check p r = if check_freevars p r then () else raise Compile ("unbound variables in rule")
fun check_guard p (Guard (a,b)) = (check p a; check p b)
fun clos_of_guard (Guard (a,b)) = (clos_of_term a, clos_of_term b)
val eqs = map (fn (guards, p, r) => let val pcount = count_patternvars p val _ = map (check_guard pcount) (guards) val _ = check pcount r in
(pattern_key p, (p, clos_of_term r, map clos_of_guard guards)) end) eqs
fun merge (k, a) table = prog_struct.update (k, case prog_struct.lookup table k of NONE => [a] | SOME l => a::l) table
val p = fold merge eqs prog_struct.empty
in
Program p
end
type state = bool * program * stack * closure
datatype loopstate = Continue of state | Stop of stack * closure
fun proj_C (Continue s) = s
| proj_C _ = raise Match
exception InterruptedExecution of stack * closure
fun proj_S (Stop s) = s
| proj_S (Continue (_,_,s,c)) = (s,c)
fun cont (Continue _) = true
| cont _ = false
val max_reductions = ref (NONE : int option)
fun do_reduction reduce p =
let
val s = ref (Continue p)
val counter = ref 0
val _ = case !max_reductions of
NONE => while cont (!s) do (s := reduce (proj_C (!s)))
| SOME m => while cont (!s) andalso (!counter < m) do (s := reduce (proj_C (!s)); counter := (!counter) + 1)
in
case !max_reductions of
SOME m => if !counter >= m then raise InterruptedExecution (proj_S (!s)) else proj_S (!s)
| NONE => proj_S (!s)
end
fun match_rules prog n [] clos = NONE
| match_rules prog n ((p,eq,guards)::rs) clos =
case pattern_match [] p clos of
NONE => match_rules prog (n+1) rs clos
| SOME args => if forall (guard_checks prog args) guards then SOME (Closure (args, eq)) else match_rules prog (n+1) rs clos
and guard_checks prog args (a,b) = (simp prog (Closure (args, a)) = simp prog (Closure (args, b)))
and match_closure (p as (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 p 0 rules clos)
| _ => NONE
and weak_reduce (false, prog, stack, Closure (e, CApp (a, b))) = Continue (false, prog, SAppL (Closure (e, b), stack), Closure (e, a))
| weak_reduce (false, prog, SAppL (b, stack), Closure (e, CAbs m)) = Continue (false, prog, stack, Closure (b::e, m))
| weak_reduce (false, prog, stack, Closure (e, CVar n)) = Continue (false, prog, stack, case List.nth (e, n) of CDummy => CVar n | r => r)
| weak_reduce (false, prog, stack, Closure (e, c as CConst _)) = Continue (false, prog, stack, c)
| weak_reduce (false, prog, stack, clos) =
(case match_closure prog clos of
NONE => Continue (true, prog, stack, clos)
| SOME r => Continue (false, prog, stack, r))
| weak_reduce (true, prog, SAppR (a, stack), b) = Continue (false, prog, stack, CApp (a,b))
| weak_reduce (true, prog, s as (SAppL (b, stack)), a) = Continue (false, prog, SAppR (a, stack), b)
| weak_reduce (true, prog, stack, c) = Stop (stack, c)
and strong_reduce (false, prog, stack, Closure (e, CAbs m)) =
(let
val (stack', wnf) = do_reduction weak_reduce (false, prog, SEmpty, Closure (CDummy::e, m))
in
case stack' of
SEmpty => Continue (false, prog, SAbs stack, wnf)
| _ => raise (Run "internal error in strong: weak failed")
end handle InterruptedExecution state => raise InterruptedExecution (stack, resolve state))
| strong_reduce (false, prog, stack, clos as (CApp (u, v))) = Continue (false, prog, SAppL (v, stack), u)
| strong_reduce (false, prog, stack, clos) = Continue (true, prog, stack, clos)
| strong_reduce (true, prog, SAbs stack, m) = Continue (false, prog, stack, CAbs m)
| strong_reduce (true, prog, SAppL (b, stack), a) = Continue (false, prog, SAppR (a, stack), b)
| strong_reduce (true, prog, SAppR (a, stack), b) = Continue (true, prog, stack, CApp (a, b))
| strong_reduce (true, prog, stack, clos) = Stop (stack, clos)
and simp prog t =
(let
val (stack, wnf) = do_reduction weak_reduce (false, prog, SEmpty, t)
in
case stack of
SEmpty => (case do_reduction strong_reduce (false, prog, SEmpty, wnf) of
(SEmpty, snf) => snf
| _ => raise (Run "internal error in run: strong failed"))
| _ => raise (Run "internal error in run: weak failed")
end handle InterruptedExecution state => resolve state)
fun run prog t =
(let
val (stack, wnf) = do_reduction weak_reduce (false, prog, SEmpty, Closure ([], clos_of_term t))
in
case stack of
SEmpty => (case do_reduction strong_reduce (false, 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 handle InterruptedExecution state => term_of_clos (resolve state))
fun discard p = ()
end