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Contents
class HeadMusic::LetterName
NAMES = %w[C D E F G A B]
NATURAL_PITCH_CLASS_NUMBERS = {
'C' => 0,
'D' => 2,
'E' => 4,
'F' => 5,
'G' => 7,
'A' => 9,
'B' => 11,
}
def self.all
NAMES.map { |letter_name| get(letter_name)}
end
def self.get(identifier)
from_name(identifier) || from_pitch_class(identifier)
end
def self.from_name(name)
@letter_names ||= {}
name = name.to_s.first.upcase
@letter_names[name] ||= new(name) if NAMES.include?(name)
end
def self.from_pitch_class(pitch_class)
@letter_names ||= {}
return nil if pitch_class.to_s == pitch_class
pitch_class = pitch_class.to_i % 12
name = NAMES.detect { |candidate| pitch_class == NATURAL_PITCH_CLASS_NUMBERS[candidate] }
name ||= HeadMusic::PitchClass::SHARP_SPELLINGS[pitch_class].first
@letter_names[name] ||= new(name) if NAMES.include?(name)
end
attr_reader :name
delegate :to_s, to: :name
delegate :to_sym, to: :name
delegate :to_i, to: :pitch_class
def initialize(name)
@name = name
end
def pitch_class
HeadMusic::PitchClass.get(NATURAL_PITCH_CLASS_NUMBERS[name])
end
def ==(value)
to_s == value.to_s
end
def position
NAMES.index(self.to_s) + 1
end
def steps(num)
HeadMusic::LetterName.get(cycle[num % NAMES.length])
end
def steps_to(other, direction = :ascending)
other = HeadMusic::LetterName.get(other)
other_position = other.position
if direction == :descending
other_position -= NAMES.length if other_position > position
position - other_position
else
other_position += NAMES.length if other_position < position
other_position - position
end
end
def cycle
cycle = NAMES
while cycle.first != self.to_s
cycle = cycle.rotate
end
cycle
end
private_class_method :new
end
Version data entries
19 entries across 19 versions & 1 rubygems