77 lines
2 KiB
C++
77 lines
2 KiB
C++
/*
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Copyright (c) 2014 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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*/
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#include "kernel/type_checker.h"
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#include "library/num.h"
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namespace lean {
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static expr g_num(Const("num"));
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static expr g_pos_num(Const("pos_num"));
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static expr g_zero(Const({"num", "zero"}));
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static expr g_pos(Const({"num", "pos"}));
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static expr g_one(Const({"pos_num", "one"}));
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static expr g_bit0(Const({"pos_num", "bit0"}));
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static expr g_bit1(Const({"pos_num", "bit1"}));
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bool has_num_decls(environment const & env) {
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try {
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type_checker tc(env);
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return
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tc.infer(g_zero).first == g_num &&
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tc.infer(g_pos).first == mk_arrow(g_pos_num, g_num) &&
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tc.infer(g_one).first == g_pos_num &&
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tc.infer(g_bit0).first == mk_arrow(g_pos_num, g_pos_num) &&
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tc.infer(g_bit1).first == mk_arrow(g_pos_num, g_pos_num);
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} catch (...) {
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return false;
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}
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}
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expr from_pos_num(mpz const & n) {
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lean_assert(n > 0);
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if (n == 1)
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return g_one;
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if (n % mpz(2) == 1)
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return mk_app(g_bit1, from_pos_num(n / 2));
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else
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return mk_app(g_bit0, from_pos_num(n / 2));
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}
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expr from_num(mpz const & n) {
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expr r;
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lean_assert(n >= 0);
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if (n == 0)
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r = g_zero;
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else
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r = mk_app(g_pos, from_pos_num(n));
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lean_assert(*to_num(r) == n);
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return r;
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}
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optional<mpz> to_pos_num(expr const & e) {
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if (e == g_one) {
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return some(mpz(1));
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} else if (is_app(e)) {
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if (app_fn(e) == g_bit0) {
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if (auto r = to_pos_num(app_arg(e)))
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return some(2*(*r));
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} else if (app_fn(e) == g_bit1) {
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if (auto r = to_pos_num(app_arg(e)))
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return some(2*(*r) + 1);
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}
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}
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return optional<mpz>();
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}
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optional<mpz> to_num(expr const & e) {
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if (e == g_zero)
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return some(mpz(0));
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else if (is_app(e) && app_fn(e) == g_pos)
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return to_pos_num(app_arg(e));
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else
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return optional<mpz>();
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}
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}
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