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Merge pull request #942 from mtrberzi/str-extract-semantics

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alternate str.extract semantics in seq_rewriter
This commit is contained in:
Nikolaj Bjorner 2017-03-21 10:48:06 -07:00 • committed by GitHub
commit e342b87921
1 changed files with 30 additions and 5 deletions
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35
src/ast/rewriter/seq_rewriter.cpp
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@ -509,15 +509,40 @@ br_status seq_rewriter::mk_seq_length(expr* a, expr_ref& result) {
br_status seq_rewriter::mk_seq_extract(expr* a, expr* b, expr* c, expr_ref& result) {
zstring s;
rational pos, len;
if (m_util.str.is_string(a, s) && m_autil.is_numeral(b, pos) && m_autil.is_numeral(c, len) &&
pos.is_unsigned() && len.is_unsigned() && pos.get_unsigned() + len.get_unsigned() <= s.length()) {
unsigned _pos = pos.get_unsigned();
unsigned _len = len.get_unsigned();
result = m_util.str.mk_string(s.extract(_pos, _len));
bool constantBase = m_util.str.is_string(a, s);
bool constantPos = m_autil.is_numeral(b, pos);
bool constantLen = m_autil.is_numeral(c, len);
// case 1: pos<0 or len<0
// rewrite to ""
if ( (constantPos && pos.is_neg()) || (constantLen && len.is_neg()) ) {
result = m_util.str.mk_empty(m().get_sort(a));
return BR_DONE;
}
// case 1.1: pos >= length(base)
// rewrite to ""
if (constantBase && constantPos && pos.get_unsigned() >= s.length()) {
result = m_util.str.mk_empty(m().get_sort(a));
return BR_DONE;
}
if (constantBase && constantPos && constantLen) {
if (pos.get_unsigned() + len.get_unsigned() >= s.length()) {
// case 2: pos+len goes past the end of the string
unsigned _len = s.length() - pos.get_unsigned() + 1;
result = m_util.str.mk_string(s.extract(pos.get_unsigned(), _len));
return BR_DONE;
} else {
// case 3: pos+len still within string
result = m_util.str.mk_string(s.extract(pos.get_unsigned(), len.get_unsigned()));
return BR_DONE;
}
}
return BR_FAILED;
}
br_status seq_rewriter::mk_seq_contains(expr* a, expr* b, expr_ref& result) {
zstring c, d;
if (m_util.str.is_string(a, c) && m_util.str.is_string(b, d)) {