cmp_less.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2024 Tobias Hienzsch
 
#ifndef TETL_UTILITY_CMP_LESS_HPP
#define TETL_UTILITY_CMP_LESS_HPP
 
#include <etl/_concepts/builtin_integer.hpp>
#include <etl/_type_traits/is_signed.hpp>
#include <etl/_type_traits/make_unsigned.hpp>
 
namespace etl {
 
/// Compare the values of two integers t and u. Unlike builtin comparison
/// operators, negative signed integers always compare less than (and not equal
/// to) unsigned integers: the comparison is safe against lossy integer
/// conversion.
///
/// https://en.cppreference.com/w/cpp/utility/intcmp
///
/// \ingroup utility
template <builtin_integer T, builtin_integer U>
[[nodiscard]] constexpr auto cmp_less(T t, U u) noexcept -> bool
{
    using UT = etl::make_unsigned_t<T>;
    using UU = etl::make_unsigned_t<U>;
    if constexpr (etl::is_signed_v<T> == etl::is_signed_v<U>) {
        return t < u;
    } else if constexpr (etl::is_signed_v<T>) {
        return t < 0 ? true : UT(t) < u;
    } else {
        return u < 0 ? false : t < UU(u);
    }
}
 
} // namespace etl
 
#endif // TETL_UTILITY_CMP_LESS_HPP