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Tail-rec version of sform in tseitin.

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Guillaume Bury 2014-11-12 18:56:56 +01:00
parent e2d4f4fdc5
commit 752fcbe2ba
1 changed files with 26 additions and 23 deletions
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49
sat/tseitin.ml
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@ -56,36 +56,39 @@ module Make (F : Formula_intf.S) = struct
let make_not f = make Not [f]
let make_and l = make And (flatten And [] l)
let make_imply f1 f2 = make Imp [f1; f2]
let make_equiv f1 f2 = make And [ make_imply f1 f2; make_imply f2 f1]
let make_xor f1 f2 = make Or [ make And [ make Not [f1]; f2 ];
make And [ f1; make Not [f2] ] ]
let make_or = function
| [] -> raise Empty_Or
| [a] -> a
| l -> Comb (Or, flatten Or [] l)
let make_imply f1 f2 = make Imp [f1; f2]
let make_equiv f1 f2 = make_and [ make_imply f1 f2; make_imply f2 f1]
let make_xor f1 f2 = make_or [ make_and [ make Not [f1]; f2 ];
make_and [ f1; make Not [f2] ] ]
(* simplify formula *)
let rec sform = function
| Comb (Not, [Lit a]) -> Lit (F.neg a)
| Comb (Not, [Comb (Not, [f])]) -> sform f
| Comb (Not, [Comb (Or, l)]) ->
let nl = List.rev_map (fun a -> sform (Comb (Not, [a]))) l in
Comb (And, nl)
| Comb (Not, [Comb (And, l)]) ->
let nl = List.rev_map (fun a -> sform (Comb (Not, [a]))) l in
Comb (Or, nl)
| Comb (Not, [Comb (Imp, [f1; f2])]) ->
Comb (And, [sform f1; sform (Comb (Not, [f2]))])
| Comb (And, l) ->
Comb (And, List.rev_map sform l)
| Comb (Or, l) ->
Comb (Or, List.rev_map sform l)
let (%%) f g x = f (g x)
let rec sform f k = match f with
| Comb (Not, [Lit a]) -> k (Lit (F.neg a))
| Comb (Not, [Comb (Not, [f])]) -> sform f k
| Comb (Not, [Comb (Or, l)]) -> sform_list_not [] l (k %% make_and)
| Comb (Not, [Comb (And, l)]) -> sform_list_not [] l (k %% make_or)
| Comb (And, l) -> sform_list [] l (k %% make_and)
| Comb (Or, l) -> sform_list [] l (k %% make_or)
| Comb (Imp, [f1; f2]) ->
Comb (Or, [sform (Comb (Not, [f1])); sform f2])
sform (make_not f1) (fun f1' -> sform f2 (fun f2' -> k (make_or [f1'; f2'])))
| Comb (Not, [Comb (Imp, [f1; f2])]) ->
sform f1 (fun f1' -> sform (make_not f2) (fun f2' -> k (make_and [f1';f2'])))
| Comb ((Imp | Not), _) -> assert false
| Lit _ as f -> f
| Lit _ -> k f
and sform_list acc l k = match l with
| [] -> k acc
| f :: tail ->
sform f (fun f' -> sform_list (f'::acc) tail k)
and sform_list_not acc l k = match l with
| [] -> k acc
| f :: tail ->
sform (make_not f) (fun f' -> sform_list_not (f'::acc) tail k)
let rec simplify_clause acc = function
| [] -> Some acc
@ -294,7 +297,7 @@ module Make (F : Formula_intf.S) = struct
let make_cnf f =
acc_or := [];
acc_and := [];
cnf (sform f)
cnf (sform f (fun f' -> f'))
(* Naive CNF XXX remove???
let make_cnf f = mk_cnf (sform f)