mirror of
https://github.com/mpusz/mp-units.git
synced 2026-07-05 08:01:01 +02:00
Mateusz Pusz
fc7eb739e7
`double_width_int` was previously missing a number of operators that generic numerical code
expects from a 128-bit integer. On platforms with native `__int128` this was harmless, but on
MSVC (where `int128_t` / `uint128_t` alias `double_width_int<(u)int64_t>`) the recent
`UsesIntegerScaling` change wired the synthetic dwint into concept checks, and `compare_quantities`
+ magnitude folding into runtime paths, exposing every gap.
This change rounds out the operator set so `double_width_int` truly behaves as an integer type:
* binary `+`, `-`, `*`, `/` between two `double_width_int`s (alongside the existing narrow-rhs
overloads).
* unary `~` and binary `&`, `|`, `^`.
* compound assignment for arithmetic, bitwise, and shift operations.
* pre/post `++` and `--`.
* `static_cast<long double>` (and `double`/`float`) with sign-preserving conversion that avoids
catastrophic cancellation on platforms where `long double == double`.
* `std::numeric_limits<double_width_int<T>>` specialization so generic code probing `::max()`,
`::min()`, `::digits`, `::is_signed`, etc. gets correct answers (needed by
`checked_int_pow`, `compute_base_power`, `safe_int::operator-`).
* fields `hi_` / `lo_` and the `(hi, lo)` ctor are public so cross-instance inline friend
operators can access each other without further friend declarations.
While here, also:
* extract `double_width_int` (and its `std::numeric_limits` specialization) into a dedicated
header `bits/double_width_int.h`; `fixed_point.h` now just includes it and keeps the
`int128_t` aliases, `min_width_uint_t` / `double_width_int_for_t` / `wide_product_of`
helpers, and the `fixed_point` class itself.
* rename a local variable `m` in `wide_product_of` to `mid` to avoid shadowing
`si::unit_symbols::m` (MSVC C4459).
* rewrite the `lo_ > 0 ? -1 : 0` unary-minus body to use `Tl{0} - lo_` instead of `-lo_`,
silencing MSVC C4146 about unary minus on an unsigned operand.
Tests:
* new `test/static/double_width_int_test.cpp` pins down each new operator at compile time
(carry/borrow edges, schoolbook multiplication, narrow/wide division paths, bitwise
identities, numeric_limits values, long-double round-trips).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
93 lines
4.2 KiB
C++
93 lines
4.2 KiB
C++
// The MIT License (MIT)
|
|
//
|
|
// Copyright (c) 2018 Mateusz Pusz
|
|
//
|
|
// Permission is hereby granted, free of charge, to any person obtaining a copy
|
|
// of this software and associated documentation files (the "Software"), to deal
|
|
// in the Software without restriction, including without limitation the rights
|
|
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
|
// copies of the Software, and to permit persons to whom the Software is
|
|
// furnished to do so, subject to the following conditions:
|
|
//
|
|
// The above copyright notice and this permission notice shall be included in all
|
|
// copies or substantial portions of the Software.
|
|
//
|
|
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
|
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
|
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
|
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
|
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
|
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
|
|
// SOFTWARE.
|
|
|
|
#include <mp-units/bits/fixed_point.h>
|
|
#include <mp-units/compat_macros.h>
|
|
#include <mp-units/framework.h>
|
|
#include <mp-units/systems/angular.h>
|
|
#ifdef MP_UNITS_IMPORT_STD
|
|
import std;
|
|
#else
|
|
#include <cstdint>
|
|
#include <type_traits>
|
|
#endif
|
|
|
|
using namespace mp_units;
|
|
|
|
namespace {
|
|
|
|
// min_width_uint_t selects the narrowest standard unsigned type that holds N bits
|
|
static_assert(std::is_same_v<detail::min_width_uint_t<1>, std::uint8_t>);
|
|
static_assert(std::is_same_v<detail::min_width_uint_t<7>, std::uint8_t>);
|
|
static_assert(std::is_same_v<detail::min_width_uint_t<8>, std::uint8_t>);
|
|
static_assert(std::is_same_v<detail::min_width_uint_t<9>, std::uint16_t>);
|
|
static_assert(std::is_same_v<detail::min_width_uint_t<31>, std::uint32_t>);
|
|
static_assert(std::is_same_v<detail::min_width_uint_t<32>, std::uint32_t>);
|
|
static_assert(std::is_same_v<detail::min_width_uint_t<33>, std::uint64_t>);
|
|
|
|
// scale<To>(M{}, value) — integer-to-integer path (exact arithmetic, no floating point)
|
|
|
|
// integral factor: exact integer multiply
|
|
static_assert(scale<int>(mag<1000>, 5) == 5000);
|
|
static_assert(scale<long>(mag<60>, 2l) == 120l);
|
|
|
|
// integral inverse: exact integer divide
|
|
static_assert(scale<int>(mag_ratio<1, 1000>, 5000) == 5);
|
|
static_assert(scale<int>(mag_ratio<1, 60>, 120) == 2);
|
|
|
|
// rational M (3/2 * 4 == 6): exact widened integer arithmetic (int64_t for int)
|
|
static_assert(scale<int>(mag_ratio<3, 2>, 4) == 6);
|
|
// (1/3 * 9 == 3)
|
|
static_assert(scale<int>(mag_ratio<1, 3>, 9) == 3);
|
|
|
|
// identity
|
|
static_assert(scale<int>(mag<1>, 42) == 42);
|
|
|
|
// floating-point path
|
|
static_assert(scale<double>(mag_ratio<1, 2>, 1.0) == 0.5);
|
|
static_assert(scale<float>(mag<3>, 1.0f) == 3.0f);
|
|
|
|
// MagnitudeScalable concept
|
|
static_assert(detail::MagnitudeScalable<int>);
|
|
static_assert(detail::MagnitudeScalable<long>);
|
|
static_assert(detail::MagnitudeScalable<double>);
|
|
static_assert(detail::MagnitudeScalable<float>);
|
|
|
|
// Irrational magnitude conversions with integer representation require explicit value_cast.
|
|
// deg = (π/180) rad — the conversion factor is irrational, so every integer result is approximate.
|
|
//
|
|
// Positive: value_cast compiles and produces the expected truncated integer result.
|
|
static_assert(value_cast<angular::degree>(1 * angular::radian).numerical_value_in(angular::degree) == 57);
|
|
static_assert(value_cast<angular::radian>(180 * angular::degree).numerical_value_in(angular::radian) == 3);
|
|
|
|
// Negative: implicit conversion is blocked at compile time to prevent accidental precision loss.
|
|
static_assert(!std::is_convertible_v<quantity<angular::radian, int>, quantity<angular::degree, int>>);
|
|
static_assert(!std::is_convertible_v<quantity<angular::degree, int>, quantity<angular::radian, int>>);
|
|
|
|
// Large-value safety: deg -> grad uses factor 10/9. Being a pure rational, the
|
|
// computation uses exact 128-bit integer arithmetic — correct on all platforms,
|
|
// including ARM / Apple Silicon where long double == double (64-bit mantissa).
|
|
static_assert(value_cast<angular::gradian>(std::int64_t{1'000'000'000'000'000'000} * angular::degree)
|
|
.numerical_value_in(angular::gradian) == std::int64_t{1'111'111'111'111'111'111});
|
|
|
|
} // namespace
|