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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 f431852af9
commit 139f7b49b4
5 changed files with 112 additions and 21 deletions
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3
src/ltltest/reduccmp.test
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@ -364,6 +364,9 @@ for x in ../reduccmp ../reductaustr; do
run 0 $x '{(a;c*;d)|(b;c)}' '(a & X(c W d)) | (b & Xc)'
run 0 $x '!{(a;c*;d)|(b;c)}' '(X(!c M !d) | !a) & (X!c | !b)'
run 0 $x '(Xc R b) & (Xc W 0)' 'b & XGc'
run 0 $x '{{c*|1}[*0..1]}<>-> v' '{{c[+]|1}[*0..1]}<>-> v'
run 0 $x '{{b*;c*}[*3..5]}<>-> v' '{{b*;c*}[*0..5]} <>-> v'
run 0 $x '{{b*&c*}[*3..5]}<>-> v' '{{b[+]|c[+]}[*0..5]} <>-> v'
# not reduced
run 0 $x '{a;(b[*2..4];c*;([*0]+{d;e}))*}!' \