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