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snf: Fix the handling of bounded repetition.

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star_normal_form() used to be called under bounded
repetitions like [*0..4], but some of these rewritings
are only correct for [*0..].  For instance
     (a*|1)[*]      can be rewritten to    1[*]
but  (a*|1)[*0..1]  cannot be rewritten to 1[*0..1]
it would be correct to rewrite the latter as (a[+]|1)[*0..1],
canceling the empty word in a*.

Also (a*;b*)[*]     can be rewritten to    (a|b)[*]
but  (a*;b*)[*0..1]  cannot be rewritten to (a|b)[*0..1]
and it cannot either be rewritten to (a[+]|b[+])[*0..1].

This patch introduces a new function to implement
rewritings under bounded repetition.

* src/ltlvisit/snf.hh, src/ltlvisit/snf.cc (star_normal_form_unbounded):
New function.
* src/ltlvisit/simplify.cc: Use it.
* src/ltltest/reduccmp.test: Add tests.
* doc/tl/tl.tex: Document the rewritings implemented.
This commit is contained in:
Alexandre Duret-Lutz 2014-05-15 20:06:43 +02:00
parent 53de8fc3a4
commit 05ed3def00
5 changed files with 112 additions and 21 deletions
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23
src/ltlvisit/simplify.cc
View file

@ -106,6 +106,16 @@ namespace spot
old->first->destroy();
}
}
{
snf_cache::iterator i = snfb_cache_.begin();
snf_cache::iterator end = snfb_cache_.end();
while (i != end)
{
snf_cache::iterator old = i++;
old->second->destroy();
old->first->destroy();
}
}
{
f2f_map::iterator i = bool_isop_.begin();
f2f_map::iterator end = bool_isop_.end();
@ -387,6 +397,13 @@ namespace spot
return ltl::star_normal_form(f, &snf_cache_);
}
const formula*
star_normal_form_bounded(const formula* f)
{
return ltl::star_normal_form_bounded(f, &snfb_cache_);
}
const formula*
boolean_to_isop(const formula* f)
{
@ -406,6 +423,7 @@ namespace spot
f2f_map nenoform_;
syntimpl_cache_t syntimpl_;
snf_cache snf_cache_;
snf_cache snfb_cache_;
f2f_map bool_isop_;
};
@ -1080,7 +1098,10 @@ namespace spot
min = 0;
if (min == 0)
{
const formula* s = c_->star_normal_form(h);
const formula* s =
bo->max() == bunop::unbounded ?
c_->star_normal_form(h) :
c_->star_normal_form_bounded(h);
h->destroy();
h = s;
}