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Add imitation step for equalities.

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Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
This commit is contained in:
Leonardo de Moura 2013-09-19 16:04:34 -07:00
parent b3aa8b37f3
commit 4afeb1a400
1 changed files with 35 additions and 21 deletions
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54
src/library/ho_unifier.cpp
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@ -38,7 +38,6 @@ class ho_unifier::imp {
state_stack m_state_stack;
unsigned m_delayed;
unsigned m_next_state_id;
bool m_ho; // true if used higher-order
volatile bool m_interrupted;
static metavar_env & subst_of(state & s) { return s.m_subst; }
@ -77,7 +76,6 @@ class ho_unifier::imp {
void init(context const & ctx, expr const & l, expr const & r, metavar_env const & menv) {
m_next_state_id = 0;
m_ho = false;
m_state_stack.clear();
m_state_stack.push_back(mk_state(menv, cqueue()));
add_constraint(ctx, l, r);
@ -233,6 +231,20 @@ class ho_unifier::imp {
return r;
}
/**
\brief Return (f x_{num_vars - 1} ... x_0)
*/
expr mk_app_vars(expr const & f, unsigned num_vars) {
buffer<expr> args;
args.push_back(f);
unsigned i = num_vars;
while (i > 0) {
--i;
args.push_back(mk_var(i));
}
return mk_app(args.size(), args.data());
}
/**
\brief Process a constraint <tt>ctx |- a = b</tt> where \c a is of the form <tt>(?m ...)</tt>.
We perform a "case split" using "projection" or "imitation". See Huet&Lang's paper on higher order matching
@ -241,7 +253,6 @@ class ho_unifier::imp {
bool process_meta_app(context const & ctx, expr const & a, expr const & b) {
lean_assert(is_meta_app(a));
lean_assert(!is_meta_app(b));
m_ho = true; // using higher-order matching
expr f_a = arg(a, 0);
lean_assert(is_metavar(f_a));
state top_state = m_state_stack.back();
@ -254,13 +265,14 @@ class ho_unifier::imp {
for (unsigned i = 1; i < num_a; i++) {
arg_types.push_back(m_type_infer(arg(a, i), ctx, &s, &upw));
}
// clear the cache since we don't want a reference to s inside of m_type_infer
// Clear m_type_infer cache since we don't want a reference to s inside of m_type_infer
m_type_infer.clear();
if (upw.failed())
return false;
m_state_stack.pop_back();
// add projections
// Add projections
for (unsigned i = 1; i < num_a; i++) {
// Assign f_a <- fun (x_1 : T_0) ... (x_{num_a-1} : T_{num_a-1}), x_i
cqueue new_q = q;
new_q.push_front(constraint(ctx, arg(a, i), b));
metavar_env new_s = s;
@ -268,37 +280,39 @@ class ho_unifier::imp {
new_s.assign(midx, proj);
m_state_stack.push_back(mk_state(new_s, new_q));
}
// add imitation
// Add imitation
metavar_env new_s = s;
cqueue new_q = q;
if (is_app(b)) {
// Imitation for applications
expr f_b = arg(b, 0);
unsigned num_b = num_args(b);
// Assign f_a <- fun (x_1 : T_0) ... (x_{num_a-1} : T_{num_a-1}), f_b (h_1 x_1 ... x_{num_a-1}) ... (h_{num_b-1} x_1 ... x_{num_a-1})
buffer<expr> imitation_args; // arguments for the imitation
imitation_args.push_back(f_b);
for (unsigned i = 1; i < num_b; i++) {
expr h_i = new_s.mk_metavar(ctx);
buffer<expr> h_app_var_args;
buffer<expr> h_app_subst_args;
h_app_var_args.push_back(h_i);
h_app_subst_args.push_back(h_i);
for (unsigned j = 1; j < num_a; j++) {
h_app_var_args.push_back(mk_var(num_a - j - 1));
h_app_subst_args.push_back(arg(a, j));
}
imitation_args.push_back(mk_app(h_app_var_args.size(), h_app_var_args.data()));
new_q.push_front(constraint(ctx, mk_app(h_app_subst_args.size(), h_app_subst_args.data()), arg(b, i)));
imitation_args.push_back(mk_app_vars(h_i, num_a - 1));
new_q.push_front(constraint(ctx, update_app(a, 0, h_i), arg(b, i)));
}
expr imitation = mk_lambda(arg_types, mk_app(imitation_args.size(), imitation_args.data()));
new_s.assign(midx, imitation);
m_state_stack.push_back(mk_state(new_s, new_q));
} else if (is_eq(b)) {
// Imitation for equality
// Assign f_a <- fun (x_1 : T_0) ... (x_{num_a-1} : T_{num_a-1}), (h_1 x_1 ... x_{num_a-1}) = (h_2 x_1 ... x_{num_a-1})
expr h_1 = new_s.mk_metavar(ctx);
expr h_2 = new_s.mk_metavar(ctx);
expr imitation = mk_lambda(arg_types, mk_eq(mk_app_vars(h_1, num_a - 1), mk_app_vars(h_2, num_a - 1)));
new_s.assign(midx, imitation);
new_q.push_front(constraint(ctx, update_app(a, 0, h_1), eq_lhs(b)));
new_q.push_front(constraint(ctx, update_app(a, 0, h_2), eq_rhs(b)));
} else {
// TODO(Leo) handle eq like we handle applications
// make f_a the constant function
// "Dump imitation" aka the constant function
// Assign f_a <- fun (x_1 : T_0) ... (x_{num_a-1} : T_{num_a-1}), b
expr imitation = mk_lambda(arg_types, lift_free_vars(b, 0, num_a - 1));
new_s.assign(midx, imitation);
m_state_stack.push_back(mk_state(new_s, new_q));
}
m_state_stack.push_back(mk_state(new_s, new_q));
reset_delayed();
return true;
}