expr copy(expr const & a) {
switch (a.kind()) {
case expr_kind::Var: return mk_var(var_idx(a));
case expr_kind::Constant: return mk_constant(const_name(a));
case expr_kind::Type: return mk_type(ty_level(a));
case expr_kind::Value: return mk_value(static_cast<expr_value*>(a.raw())->m_val);
case expr_kind::App: return mk_app(num_args(a), begin_args(a));
case expr_kind::Eq: return mk_eq(eq_lhs(a), eq_rhs(a));
case expr_kind::Lambda: return mk_lambda(abst_name(a), abst_domain(a), abst_body(a));
case expr_kind::Pi: return mk_pi(abst_name(a), abst_domain(a), abst_body(a));
case expr_kind::Let: return mk_let(let_name(a), let_type(a), let_value(a), let_body(a));
case expr_kind::MetaVar: return mk_metavar(metavar_idx(a), metavar_ctx(a));
}
lean_unreachable();
}
optional<substitution> fo_unify(expr e1, expr e2) {
substitution s;
unsigned i1, i2;
buffer<expr_pair> todo;
todo.emplace_back(e1, e2);
while (!todo.empty()) {
auto p = todo.back();
todo.pop_back();
e1 = find(s, p.first);
e2 = find(s, p.second);
if (e1 != e2) {
if (is_metavar_wo_local_context(e1)) {
assign(s, e1, e2);
} else if (is_metavar_wo_local_context(e2)) {
assign(s, e2, e1);
} else if (is_equality(e1) && is_equality(e2)) {
expr_pair p1 = get_equality_args(e1);
expr_pair p2 = get_equality_args(e2);
todo.emplace_back(p1.second, p2.second);
todo.emplace_back(p1.first, p2.first);
} else {
if (e1.kind() != e2.kind())
return optional<substitution>();
switch (e1.kind()) {
case expr_kind::Var: case expr_kind::Constant: case expr_kind::Type: case expr_kind::Value: case expr_kind::MetaVar:
return optional<substitution>();
case expr_kind::App:
i1 = num_args(e1);
i2 = num_args(e2);
while (i1 > 0 && i2 > 0) {
--i1;
--i2;
if (i1 == 0 && i2 > 0) {
todo.emplace_back(arg(e1, i1), mk_app(i2+1, begin_args(e2)));
} else if (i2 == 0 && i1 > 0) {
todo.emplace_back(mk_app(i1+1, begin_args(e1)), arg(e2, i2));
} else {
todo.emplace_back(arg(e1, i1), arg(e2, i2));
}
}
break;
case expr_kind::Lambda: case expr_kind::Pi:
todo.emplace_back(abst_body(e1), abst_body(e2));
todo.emplace_back(abst_domain(e1), abst_domain(e2));
break;
case expr_kind::Let:
todo.emplace_back(let_body(e1), let_body(e2));
todo.emplace_back(let_value(e1), let_value(e2));
if (static_cast<bool>(let_type(e1)) != static_cast<bool>(let_type(e2)))
return optional<substitution>();
if (let_type(e1)) {
lean_assert(let_type(e2));
todo.emplace_back(*let_type(e1), *let_type(e2));
}
break;
}
}
}
}
return optional<substitution>(s);
}
