math.h

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#pragma once
 
#include "mjolnir/core/definitions.h"
#include "mjolnir/core/fundamental_types.h"
#include "mjolnir/core/utility/type.h"
 
#include <concepts>
 
 
// === DECLARATIONS ===================================================================================================
 
namespace mjolnir
{
 
 
template <std::integral T_Type>
[[nodiscard]] constexpr auto is_power_of_2(T_Type value) noexcept -> bool;
 
 
template <std::integral T_Type>
[[nodiscard]] constexpr auto gauss_summation(T_Type n) -> T_Type;
 
 
template <Number T_Type>
[[nodiscard]] constexpr auto power(T_Type base, std::integral auto exponent) noexcept -> T_Type;
 
 
template <Number T_Type = UST>
[[nodiscard]] constexpr auto power_of_2(std::integral auto exponent) noexcept -> T_Type;
 
 
} // namespace mjolnir
 
 
// === DEFINITIONS ====================================================================================================
 
 
#include <cassert>
 
 
namespace mjolnir
{
template <std::integral T_Type>
[[nodiscard]] constexpr auto is_power_of_2(T_Type value) noexcept -> bool
{
    auto u_value = signed_to_unsigned(value);
    return (value > 0) && ! (u_value & (u_value - 1));
}
 
 
// --------------------------------------------------------------------------------------------------------------------
 
template <std::integral T_Type>
[[nodiscard]] constexpr auto gauss_summation(T_Type n) -> T_Type
{
    assert(n >= 0 && "n must be a positive number"); // NOLINT
 
    return (n * n + n) / 2;
}
 
 
// --------------------------------------------------------------------------------------------------------------------
 
template <Number T_Type>
// NOLINTNEXTLINE(misc-no-recursion)
[[nodiscard]] constexpr auto power(T_Type base, std::integral auto exponent) noexcept -> T_Type
{
    assert(exponent >= 0 && "exponent must be a positive number"); // NOLINT
 
    if (exponent == 0)
        return 1;
    if (exponent % 2 == 0)
        return power(base, exponent / 2) * power(base, exponent / 2);
    return base * power(base, (exponent - 1) / 2) * power(base, (exponent - 1) / 2);
}
 
 
// --------------------------------------------------------------------------------------------------------------------
 
template <Number T_Type>
[[nodiscard]] constexpr auto power_of_2(std::integral auto exponent) noexcept -> T_Type
{
    assert(exponent >= 0 && "exponent must be a positive number"); // NOLINT
 
    return static_cast<T_Type>(UST(1) << static_cast<UST>(exponent));
}
 
 
} // namespace mjolnir