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feat(library/type_context): add eta-expansion to type_context

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This commit is contained in:
Leonardo de Moura 2015-12-15 17:24:53 -08:00
parent 10273bf176
commit 1387cdfa0f
2 changed files with 22 additions and 7 deletions
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21
src/library/type_context.cpp
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@ -688,16 +688,27 @@ bool type_context::is_def_eq_args(expr const & e1, expr const & e2) {
return true;
}
/** \brief Try to solve e1 := (lambda x : A, t) =?= e2 by eta-expanding e2.
\remark eta-reduction is not a good alternative (even in a system without cumulativity like Lean).
Example:
(lambda x : A, f ?M) =?= f
The lhs cannot be eta-reduced because ?M is a meta-variable. */
bool type_context::is_def_eq_eta(expr const & e1, expr const & e2) {
expr new_e1 = try_eta(e1);
expr new_e2 = try_eta(e2);
if (e1 != new_e1 || e2 != new_e2) {
if (is_lambda(e1) && !is_lambda(e2)) {
expr e2_type = relaxed_whnf(infer(e2));
if (is_pi(e2_type)) {
// e2_type may not be a Pi because it is a stuck term.
// We are ignoring this case and just failing.
expr new_e2 = mk_lambda(binding_name(e2_type), binding_domain(e2_type),
mk_app(e2, Var(0)), binding_info(e2_type));
scope s(*this);
if (is_def_eq_core(new_e1, new_e2)) {
if (is_def_eq_core(e1, new_e2)) {
s.commit();
return true;
}
}
}
return false;
}
@ -974,6 +985,8 @@ bool type_context::is_def_eq_core(expr const & t, expr const & s) {
if (is_def_eq_eta(t_n, s_n))
return true;
if (is_def_eq_eta(s_n, t_n))
return true;
if (is_def_eq_proof_irrel(t_n, s_n))
return true;

2
tests/lean/run/blast_simp_sum.lean
View file

@ -14,6 +14,8 @@ sorry
attribute add.assoc add.comm add.left_comm mul_one add_zero zero_add one_mul mul.comm mul.assoc mul.left_comm [simp]
exit -- There is a bug in how local constants are handled in blast, disable tests for now.
example (f : nat → nat) (n : nat) : (Σ x < n, f x + 1) = (Σ x < n, f x) + n :=
by simp