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fix #2892

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2020-01-27 20:59:02 -08:00
parent ca11dc1fc5
commit ee62f83131
3 changed files with 46 additions and 13 deletions
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27
src/smt/theory_seq.cpp
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@ -6490,12 +6490,13 @@ void theory_seq::add_unit_axiom(expr* n) {
}
/**
e1 < e2 => e1 = empty or e1 = xcy
e1 < e2 => e1 = empty or c < d
e1 < e2 => e2 = xdz
!(e1 < e2) => e1 = e2 or e2 = empty or e2 = xdz
!(e1 < e2) => e1 = e2 or e2 = empty or d < c
!(e1 < e2) => e1 = e2 or e1 = xcy
e1 < e2 => prefix(e1, e2) or e1 = xcy
e1 < e2 => prefix(e1, e2) or c < d
e1 < e2 => prefix(e1, e2) or e2 = xdz
e1 < e2 => e1 != e2
!(e1 < e2) => prefix(e2, e1) or e2 = xdz
!(e1 < e2) => prefix(e2, e1) or d < c
!(e1 < e2) => prefix(e2, e1) or e1 = xcy
!(e1 = e2) or !(e1 < e2)
optional:
@ -6521,16 +6522,18 @@ void theory_seq::add_lt_axiom(expr* n) {
literal emp1 = mk_eq(e1, empty_string, false);
literal emp2 = mk_eq(e2, empty_string, false);
literal eq = mk_eq(e1, e2, false);
literal pref21 = mk_literal(m_util.str.mk_prefix(e2, e1));
literal pref12 = mk_literal(m_util.str.mk_prefix(e1, e2));
literal e1xcy = mk_eq(e1, xcy, false);
literal e2xdz = mk_eq(e2, xdz, false);
literal ltcd = mk_literal(m_util.mk_lt(c, d));
literal ltdc = mk_literal(m_util.mk_lt(d, c));
add_axiom(~lt, e2xdz);
add_axiom(~lt, emp1, e1xcy);
add_axiom(~lt, emp1, ltcd);
add_axiom(lt, eq, e1xcy);
add_axiom(lt, eq, emp2, ltdc);
add_axiom(lt, eq, emp2, e2xdz);
add_axiom(~lt, pref12, e2xdz);
add_axiom(~lt, pref12, e1xcy);
add_axiom(~lt, pref12, ltcd);
add_axiom(lt, pref21, e1xcy);
add_axiom(lt, pref21, ltdc);
add_axiom(lt, pref21, e2xdz);
add_axiom(~eq, ~lt);
}