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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// UNSUPPORTED: c++03, c++11, c++14
// <numeric>
// template<class _M, class _N>
// constexpr common_type_t<_M,_N> gcd(_M __m, _N __n)
#include <numeric>
#include <cassert>
#include <climits>
#include <cstdint>
#include <limits>
#include <random>
#include <type_traits>
#include "test_macros.h"
constexpr struct {
int x;
int y;
int expect;
} Cases[] = {
{0, 0, 0},
{1, 0, 1},
{0, 1, 1},
{1, 1, 1},
{2, 3, 1},
{2, 4, 2},
{36, 17, 1},
{36, 18, 18}
};
template <typename Input1, typename Input2, typename Output>
constexpr bool test0(int in1, int in2, int out)
{
auto value1 = static_cast<Input1>(in1);
auto value2 = static_cast<Input2>(in2);
static_assert(std::is_same_v<Output, decltype(std::gcd(value1, value2))>, "");
static_assert(std::is_same_v<Output, decltype(std::gcd(value2, value1))>, "");
assert(static_cast<Output>(out) == std::gcd(value1, value2));
return true;
}
template <typename T>
T basic_gcd_(T m, T n) {
return n == 0 ? m : basic_gcd_<T>(n, m % n);
}
template <typename T>
T basic_gcd(T m, T n) {
using Tp = std::make_unsigned_t<T>;
if constexpr (std::is_signed_v<T>) {
if (m < 0 && m != std::numeric_limits<T>::min())
m = -m;
if (n < 0 && n != std::numeric_limits<T>::min())
n = -n;
}
return basic_gcd_(static_cast<Tp>(m), static_cast<Tp>(n));
}
template <typename Input>
void do_fuzzy_tests() {
std::mt19937 gen(1938);
using DistIntType = std::conditional_t<sizeof(Input) == 1, int, Input>; // See N4981 [rand.req.genl]/1.5
constexpr Input max_input = std::numeric_limits<Input>::max();
std::uniform_int_distribution<DistIntType> distrib(0, max_input);
constexpr int nb_rounds = 10000;
for (int i = 0; i < nb_rounds; ++i) {
Input n = static_cast<Input>(distrib(gen));
Input m = static_cast<Input>(distrib(gen));
assert(std::gcd(n, m) == basic_gcd(n, m));
}
}
template <typename Input>
void do_limit_tests() {
Input inputs[] = {
// The behavior of std::gcd is undefined if the absolute value of one of its
// operand is not representable in the result type.
std::numeric_limits<Input>::min() + (std::is_signed<Input>::value ? 3 : 0),
std::numeric_limits<Input>::min() + 1,
std::numeric_limits<Input>::min() + 2,
std::numeric_limits<Input>::max(),
std::numeric_limits<Input>::max() - 1,
std::numeric_limits<Input>::max() - 2,
0,
1,
2,
3,
4,
5,
6,
7,
8,
9,
10,
(Input)-1,
(Input)-2,
(Input)-3,
(Input)-4,
(Input)-5,
(Input)-6,
(Input)-7,
(Input)-8,
(Input)-9,
(Input)-10,
};
for (auto n : inputs) {
for (auto m : inputs) {
assert(std::gcd(n, m) == basic_gcd(n, m));
}
}
}
template <typename Input1, typename Input2 = Input1>
constexpr bool do_test(int = 0)
{
using S1 = std::make_signed_t<Input1>;
using S2 = std::make_signed_t<Input2>;
using U1 = std::make_unsigned_t<Input1>;
using U2 = std::make_unsigned_t<Input2>;
bool accumulate = true;
for (auto TC : Cases) {
{ // Test with two signed types
using Output = std::common_type_t<S1, S2>;
accumulate &= test0<S1, S2, Output>(TC.x, TC.y, TC.expect);
accumulate &= test0<S1, S2, Output>(-TC.x, TC.y, TC.expect);
accumulate &= test0<S1, S2, Output>(TC.x, -TC.y, TC.expect);
accumulate &= test0<S1, S2, Output>(-TC.x, -TC.y, TC.expect);
accumulate &= test0<S2, S1, Output>(TC.x, TC.y, TC.expect);
accumulate &= test0<S2, S1, Output>(-TC.x, TC.y, TC.expect);
accumulate &= test0<S2, S1, Output>(TC.x, -TC.y, TC.expect);
accumulate &= test0<S2, S1, Output>(-TC.x, -TC.y, TC.expect);
}
{ // test with two unsigned types
using Output = std::common_type_t<U1, U2>;
accumulate &= test0<U1, U2, Output>(TC.x, TC.y, TC.expect);
accumulate &= test0<U2, U1, Output>(TC.x, TC.y, TC.expect);
}
{ // Test with mixed signs
using Output = std::common_type_t<S1, U2>;
accumulate &= test0<S1, U2, Output>(TC.x, TC.y, TC.expect);
accumulate &= test0<U2, S1, Output>(TC.x, TC.y, TC.expect);
accumulate &= test0<S1, U2, Output>(-TC.x, TC.y, TC.expect);
accumulate &= test0<U2, S1, Output>(TC.x, -TC.y, TC.expect);
}
{ // Test with mixed signs
using Output = std::common_type_t<S2, U1>;
accumulate &= test0<S2, U1, Output>(TC.x, TC.y, TC.expect);
accumulate &= test0<U1, S2, Output>(TC.x, TC.y, TC.expect);
accumulate &= test0<S2, U1, Output>(-TC.x, TC.y, TC.expect);
accumulate &= test0<U1, S2, Output>(TC.x, -TC.y, TC.expect);
}
}
return accumulate;
}
int main(int argc, char**)
{
int non_cce = argc; // a value that can't possibly be constexpr
static_assert(do_test<signed char>(), "");
static_assert(do_test<short>(), "");
static_assert(do_test<int>(), "");
static_assert(do_test<long>(), "");
static_assert(do_test<long long>(), "");
assert(do_test<signed char>(non_cce));
assert(do_test<short>(non_cce));
assert(do_test<int>(non_cce));
assert(do_test<long>(non_cce));
assert(do_test<long long>(non_cce));
static_assert(do_test<std::int8_t>(), "");
static_assert(do_test<std::int16_t>(), "");
static_assert(do_test<std::int32_t>(), "");
static_assert(do_test<std::int64_t>(), "");
assert(do_test<std::int8_t>(non_cce));
assert(do_test<std::int16_t>(non_cce));
assert(do_test<std::int32_t>(non_cce));
assert(do_test<std::int64_t>(non_cce));
static_assert(do_test<signed char, int>(), "");
static_assert(do_test<int, signed char>(), "");
static_assert(do_test<short, int>(), "");
static_assert(do_test<int, short>(), "");
static_assert(do_test<int, long>(), "");
static_assert(do_test<long, int>(), "");
static_assert(do_test<int, long long>(), "");
static_assert(do_test<long long, int>(), "");
assert((do_test<signed char, int>(non_cce)));
assert((do_test<int, signed char>(non_cce)));
assert((do_test<short, int>(non_cce)));
assert((do_test<int, short>(non_cce)));
assert((do_test<int, long>(non_cce)));
assert((do_test<long, int>(non_cce)));
assert((do_test<int, long long>(non_cce)));
assert((do_test<long long, int>(non_cce)));
// LWG#2837
{
auto res = std::gcd(static_cast<std::int64_t>(1234), INT32_MIN);
static_assert(std::is_same_v<decltype(res), std::int64_t>, "");
assert(res == 2);
}
do_fuzzy_tests<std::int8_t>();
do_fuzzy_tests<std::int16_t>();
do_fuzzy_tests<std::int32_t>();
do_fuzzy_tests<std::int64_t>();
do_fuzzy_tests<std::uint8_t>();
do_fuzzy_tests<std::uint16_t>();
do_fuzzy_tests<std::uint32_t>();
do_fuzzy_tests<std::uint64_t>();
do_limit_tests<std::int8_t>();
do_limit_tests<std::int16_t>();
do_limit_tests<std::int32_t>();
do_limit_tests<std::int64_t>();
do_limit_tests<std::uint8_t>();
do_limit_tests<std::uint16_t>();
do_limit_tests<std::uint32_t>();
do_limit_tests<std::uint64_t>();
return 0;
}
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