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Z3str3: correct str.replace semantics

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This commit is contained in:
Murphy Berzish 2018-11-28 14:42:19 -05:00
parent 4686429318
commit e76e501216
1 changed files with 27 additions and 14 deletions
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41
src/smt/theory_str.cpp
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@ -1661,53 +1661,66 @@ namespace smt {
}
}
// (str.replace s t t') is the string obtained by replacing the first occurrence
// of t in s, if any, by t'. Note that if t is empty, the result is to prepend
// t' to s; also, if t does not occur in s then the result is s.
void theory_str::instantiate_axiom_Replace(enode * e) {
context & ctx = get_context();
ast_manager & m = get_manager();
app * expr = e->get_owner();
if (axiomatized_terms.contains(expr)) {
TRACE("str", tout << "already set up Replace axiom for " << mk_pp(expr, m) << std::endl;);
app * ex = e->get_owner();
if (axiomatized_terms.contains(ex)) {
TRACE("str", tout << "already set up Replace axiom for " << mk_pp(ex, m) << std::endl;);
return;
}
axiomatized_terms.insert(expr);
axiomatized_terms.insert(ex);
TRACE("str", tout << "instantiate Replace axiom for " << mk_pp(expr, m) << std::endl;);
TRACE("str", tout << "instantiate Replace axiom for " << mk_pp(ex, m) << std::endl;);
expr_ref x1(mk_str_var("x1"), m);
expr_ref x2(mk_str_var("x2"), m);
expr_ref i1(mk_int_var("i1"), m);
expr_ref result(mk_str_var("result"), m);
expr * replaceS;
expr * replaceT;
expr * replaceTPrime;
u.str.is_replace(ex, replaceS, replaceT, replaceTPrime);
// t empty => result = (str.++ t' s)
expr_ref emptySrcAst(ctx.mk_eq_atom(replaceT, mk_string("")), m);
expr_ref prependTPrimeToS(ctx.mk_eq_atom(result, mk_concat(replaceTPrime, replaceS)), m);
// condAst = Contains(args[0], args[1])
expr_ref condAst(mk_contains(expr->get_arg(0), expr->get_arg(1)), m);
expr_ref condAst(mk_contains(ex->get_arg(0), ex->get_arg(1)), m);
// -----------------------
// true branch
expr_ref_vector thenItems(m);
// args[0] = x1 . args[1] . x2
thenItems.push_back(ctx.mk_eq_atom(expr->get_arg(0), mk_concat(x1, mk_concat(expr->get_arg(1), x2))));
thenItems.push_back(ctx.mk_eq_atom(ex->get_arg(0), mk_concat(x1, mk_concat(ex->get_arg(1), x2))));
// i1 = |x1|
thenItems.push_back(ctx.mk_eq_atom(i1, mk_strlen(x1)));
// args[0] = x3 . x4 /\ |x3| = |x1| + |args[1]| - 1 /\ ! contains(x3, args[1])
expr_ref x3(mk_str_var("x3"), m);
expr_ref x4(mk_str_var("x4"), m);
expr_ref tmpLen(m_autil.mk_add(i1, mk_strlen(expr->get_arg(1)), mk_int(-1)), m);
thenItems.push_back(ctx.mk_eq_atom(expr->get_arg(0), mk_concat(x3, x4)));
expr_ref tmpLen(m_autil.mk_add(i1, mk_strlen(ex->get_arg(1)), mk_int(-1)), m);
thenItems.push_back(ctx.mk_eq_atom(ex->get_arg(0), mk_concat(x3, x4)));
thenItems.push_back(ctx.mk_eq_atom(mk_strlen(x3), tmpLen));
thenItems.push_back(mk_not(m, mk_contains(x3, expr->get_arg(1))));
thenItems.push_back(ctx.mk_eq_atom(result, mk_concat(x1, mk_concat(expr->get_arg(2), x2))));
thenItems.push_back(mk_not(m, mk_contains(x3, ex->get_arg(1))));
thenItems.push_back(ctx.mk_eq_atom(result, mk_concat(x1, mk_concat(ex->get_arg(2), x2))));
// -----------------------
// false branch
expr_ref elseBranch(ctx.mk_eq_atom(result, expr->get_arg(0)), m);
expr_ref elseBranch(ctx.mk_eq_atom(result, ex->get_arg(0)), m);
th_rewriter rw(m);
expr_ref breakdownAssert(m.mk_ite(condAst, m.mk_and(thenItems.size(), thenItems.c_ptr()), elseBranch), m);
expr_ref breakdownAssert(m.mk_ite(emptySrcAst, prependTPrimeToS,
m.mk_ite(condAst, mk_and(thenItems), elseBranch)), m);
expr_ref breakdownAssert_rw(breakdownAssert, m);
rw(breakdownAssert_rw);
assert_axiom(breakdownAssert_rw);
expr_ref reduceToResult(ctx.mk_eq_atom(expr, result), m);
expr_ref reduceToResult(ctx.mk_eq_atom(ex, result), m);
expr_ref reduceToResult_rw(reduceToResult, m);
rw(reduceToResult_rw);
assert_axiom(reduceToResult_rw);