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Fix infinite recursion when translating E* and E accepts [*0].

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* src/tgbaalgos/ltl2tgba_fm.cc (ratexp_trad_visitor::visit):
Use a different translating rule for E* if E accepts [*0].
* src/tgbatest/ltl2tgba.test: Add test case.
This commit is contained in:
Alexandre Duret-Lutz 2011-02-14 10:09:17 +01:00
parent cce6dd34f8
commit a29c87b2ed
2 changed files with 57 additions and 3 deletions
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57
src/tgbaalgos/ltl2tgba_fm.cc
View file

@ -432,10 +432,61 @@ namespace spot
if (to_concat_)
f = multop::instance(multop::Concat, f, to_concat_->clone());
res_ = recurse(bo->child(), f);
if (min == 0)
res_ |= now_to_concat();
if (!bo->child()->accepts_eword())
{
// f*;g -> f;f*;g | g
//
// If f does not accept the empty word, we can easily
// add "f*;g" as to_concat_ when translating f.
res_ = recurse(bo->child(), f);
if (min == 0)
res_ |= now_to_concat();
}
else
{
// if "f" accepts the empty words, doing the above would
// lead to an infinite loop:
// f*;g -> f;f*;g | g
// f;f*;g -> f*;g | ...
//
// So we do in two steps:
// 1. translate f,
// 2. append f*;g to all destinations
// 3. add |g
res_ = recurse(bo->child());
// f*;g -> f;f*;g
minato_isop isop(res_);
bdd cube;
res_ = bddfalse;
while ((cube = isop.next()) != bddfalse)
{
bdd label = bdd_exist(cube, dict_.next_set);
bdd dest_bdd = bdd_existcomp(cube, dict_.next_set);
formula* dest =
dict_.conj_bdd_to_formula(dest_bdd);
formula* dest2;
int x;
if (dest == constant::empty_word_instance())
{
x = dict_.register_next_variable(f);
res_ |= label & bdd_ithvar(x);
}
else
{
dest2 = multop::instance(multop::Concat, dest,
f->clone());
if (dest2 != constant::false_instance())
{
x = dict_.register_next_variable(dest2);
dest2->destroy();
res_ |= label & bdd_ithvar(x);
}
}
}
f->destroy();
res_ |= now_to_concat();
}
return;
case bunop::Equal:
case bunop::Goto:

3
src/tgbatest/ltl2tgba.test
View file

@ -85,6 +85,9 @@ check_psl '{[*2];a[*2..4]}|->b'
check_psl '{a[*2..5] && b[*..3]}|->c'
check_psl '{{[+];a;[+]} && {[+];b;[+]}}<>->c'
check_psl '{(a[->3]) & {[+];b}}<>->c'
# This formula (built by a random formula generator), exhibited an
# infinite recursion in the translation:
check_psl '{(a|[*0])[*];1}'
# Example from "Beyond Hardware Verification" by Glazberg, Moulin, Orni,
# Ruah, Zarpas (2007).
check_psl '{[*];req;ack}|=>{start;busy[*];done}'