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fix #2061

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2019-01-06 11:49:47 -08:00
parent e770f37f52
commit 71e239c08e
3 changed files with 38 additions and 2 deletions
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35
src/ast/rewriter/seq_rewriter.cpp
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@ -459,6 +459,9 @@ br_status seq_rewriter::mk_app_core(func_decl * f, unsigned num_args, expr * con
case OP_SEQ_AT:
SASSERT(num_args == 2);
return mk_seq_at(args[0], args[1], result);
case OP_SEQ_NTH:
SASSERT(num_args == 2);
return mk_seq_nth(args[0], args[1], result);
case OP_SEQ_PREFIX:
SASSERT(num_args == 2);
return mk_seq_prefix(args[0], args[1], result);
@ -877,6 +880,38 @@ br_status seq_rewriter::mk_seq_at(expr* a, expr* b, expr_ref& result) {
return BR_DONE;
}
br_status seq_rewriter::mk_seq_nth(expr* a, expr* b, expr_ref& result) {
zstring c;
rational r;
if (!m_autil.is_numeral(b, r) || !r.is_unsigned()) {
return BR_FAILED;
}
unsigned len = r.get_unsigned();
expr_ref_vector as(m());
m_util.str.get_concat_units(a, as);
for (unsigned i = 0; i < as.size(); ++i) {
expr* a = as.get(i), *u = nullptr;
if (m_util.str.is_unit(a, u)) {
if (len == i) {
result = u;
return BR_REWRITE1;
}
}
else if (i > 0) {
SASSERT(len >= i);
result = m_util.str.mk_concat(as.size() - i, as.c_ptr() + i);
result = m().mk_app(m_util.get_family_id(), OP_SEQ_NTH, result, m_autil.mk_int(len - i));
return BR_REWRITE2;
}
else {
return BR_FAILED;
}
}
return BR_FAILED;
}
br_status seq_rewriter::mk_seq_index(expr* a, expr* b, expr* c, expr_ref& result) {
zstring s1, s2;
rational r;