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Merge pull request #938 from mtrberzi/str-at-semantics

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alternate str.at semantics check in seq_rewriter
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Nikolaj Bjorner 2017-03-13 19:50:02 +01:00 • committed by GitHub
commit 5cff42bbfa
1 changed files with 15 additions and 4 deletions
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19
src/ast/rewriter/seq_rewriter.cpp
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@ -598,14 +598,25 @@ br_status seq_rewriter::mk_seq_contains(expr* a, expr* b, expr_ref& result) {
return BR_FAILED;
}
/*
* (str.at s i), constants s/i, i < 0 or i >= |s| ==> (str.at s i) = ""
*/
br_status seq_rewriter::mk_seq_at(expr* a, expr* b, expr_ref& result) {
zstring c;
rational r;
if (m_util.str.is_string(a, c) && m_autil.is_numeral(b, r) && r.is_unsigned()) {
unsigned j = r.get_unsigned();
if (j < c.length()) {
result = m_util.str.mk_string(c.extract(j, 1));
if (m_util.str.is_string(a, c) && m_autil.is_numeral(b, r)) {
if (r.is_neg()) {
result = m_util.str.mk_string(symbol(""));
return BR_DONE;
} else if (r.is_unsigned()) {
unsigned j = r.get_unsigned();
if (j < c.length()) {
result = m_util.str.mk_string(c.extract(j, 1));
return BR_DONE;
} else {
result = m_util.str.mk_string(symbol(""));
return BR_DONE;
}
}
}
return BR_FAILED;