Letter.h

#ifndef MCC_PITCH_LETTER_H
#define MCC_PITCH_LETTER_H
 
#include <MCC_BuildSettings.h>
 
#include <stdint.h>
 
#include <Foundation/Math/Arithmetic.h>
 
namespace MCC {

enum class Letter : uint8_t {
    C = 0,
    D = 1,
    E = 2,
    F = 3,
    G = 4,
    A = 5,
    B = 6
};

constexpr uint8_t LetterCount = 7;

namespace Detail {
 
constexpr bool IsLetter(Letter letter) noexcept {
    return static_cast<uint8_t>(letter) < LetterCount;
}
 
} // namespace Detail

constexpr uint8_t DiatonicIndex(Letter letter) noexcept {
    return Detail::IsLetter(letter) ? static_cast<uint8_t>(letter) : 0;
}

MCC_CONSTEXPR14 uint8_t NaturalSemitone(Letter letter) noexcept {
    // Computed rather than tabled so AVR keeps no lookup table in RAM.
    const int32_t index = DiatonicIndex(letter);
    return static_cast<uint8_t>(index * 2 - (index >= 3 ? 1 : 0));
}

constexpr Letter MoveLetter(Letter letter, int32_t steps) noexcept {
    return static_cast<Letter>(Foundation::Math::FloorMod(
        DiatonicIndex(letter) + Foundation::Math::FloorMod(steps, LetterCount),
        LetterCount));
}
 
} // namespace MCC
 
#endif // MCC_PITCH_LETTER_H