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update epsilon encoding

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Nikolaj Bjorner 2026-07-02 15:19:11 -07:00
parent 2a8f66f22b
commit f15584cdae
1 changed files with 22 additions and 2 deletions
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24
src/cmd_context/tptp_frontend.cpp
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@ -1467,8 +1467,28 @@ class tptp_parser {
m_bound.push_back(scope);
expr_ref body = parse_formula(is_boolean);
m_bound.pop_back();
// Approximate choice as existential quantification
return mk_quantifier(false, vars, body);
// Choice/description operator. @+ is Hilbert's choice (indefinite
// description) and @- is definite description. Both denote an ELEMENT of
// the bound sort T — a witness selected from those satisfying the predicate
// — NOT a Boolean. Encode as Z3's array OP_CHOICE applied to the predicate
// lambda (λX:T. body), which yields a term of sort T (cf. smt2parser).
if (vars.empty())
return body;
expr_ref pred = ensure_bool(body);
// OP_CHOICE is single-arity. With several binders choose over the first
// variable and existentially bind the remainder inside the predicate.
if (vars.size() > 1) {
ptr_vector<app> rest;
for (unsigned i = 1; i < vars.size(); ++i) rest.push_back(vars[i]);
pred = expr_ref(::mk_exists(m, rest.size(), rest.data(), pred.get()), m);
}
app* xvar = vars[0];
expr_ref abs_body(m);
expr_abstract(m, 0, 1, (expr* const*)&xvar, pred, abs_body);
sort* xs = xvar->get_sort();
symbol xnm = xvar->get_decl()->get_name();
expr_ref lam(m.mk_lambda(1, &xs, &xnm, abs_body), m);
return expr_ref(m_array.mk_choice(lam), m);
}
expr_ref_vector args(m);