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add rewrites for moduli as exercised in example from #2319

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2019-11-24 19:02:28 -08:00
parent fad4356159
commit 84025d5c11
4 changed files with 61 additions and 39 deletions
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10
src/ast/rewriter/arith_rewriter.cpp
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@ -988,6 +988,12 @@ void arith_rewriter::remove_divisor(expr* d, ptr_buffer<expr>& args) {
}
UNREACHABLE();
}
static rational symmod(rational const& a, rational const& b) {
rational r = mod(a, b);
if (2*r > b) r -= b;
return r;
}
br_status arith_rewriter::mk_mod_core(expr * arg1, expr * arg2, expr_ref & result) {
set_curr_sort(m().get_sort(arg1));
@ -1031,6 +1037,10 @@ br_status arith_rewriter::mk_mod_core(expr * arg1, expr * arg2, expr_ref & resul
change = true;
args.push_back(t1);
}
else if (m_util.is_mul(arg, t1, t2) && m_util.is_numeral(t1, arg_v) && symmod(arg_v, v2) != arg_v) {
change = true;
args.push_back(m_util.mk_mul(m_util.mk_numeral(symmod(arg_v, v2), true), t2));
}
else {
args.push_back(arg);
}