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Add trivial identity {b}=b and !{b}=!b for any Boolean formula b.

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* src/ltlast/unop.cc: Perform the simplification.
* src/ltlast/unop.hh, doc/tl/tl.tex: Document it.
* src/ltltest/equals.test: Adjust test cases.
This commit is contained in:
Alexandre Duret-Lutz 2011-11-07 11:30:27 +01:00
parent 98f67973eb
commit 77d704ea9e
4 changed files with 28 additions and 18 deletions
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14
src/ltlast/unop.cc
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@ -295,19 +295,25 @@ namespace spot
break;
case Closure:
if (child == constant::true_instance()
|| child == constant::empty_word_instance())
return constant::true_instance();
if (child == constant::false_instance())
// {0} = 0, {1} = 1, {b} = b
if (child->is_boolean())
return child;
// {[*0]} = 1
if (child == constant::empty_word_instance())
return constant::true_instance();
break;
case NegClosure:
// {1} = 0, {[*0]} = 0
if (child == constant::true_instance()
|| child == constant::empty_word_instance())
return constant::false_instance();
// {0} = 1
if (child == constant::false_instance())
return constant::true_instance();
// {b} = !b
if (child->is_boolean())
return unop::instance(Not, child);
break;
}