Class: HeadMusic::Rudiment::Pitch::NaturalStep

Inherits:
Object
  • Object
show all
Defined in:
lib/head_music/rudiment/pitch/natural_step.rb

Overview

Computes where a signed number of diatonic (letter-name) steps lands relative to a starting letter name: the destination letter and how many octaves the move crosses. The computation is register-agnostic, working purely from the letter name’s position in the scale, so #applied_to takes the pitch that supplies the register.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(letter_name, num_steps) ⇒ NaturalStep

Returns a new instance of NaturalStep.



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# File 'lib/head_music/rudiment/pitch/natural_step.rb', line 10

def initialize(letter_name, num_steps)
  @letter_name = letter_name
  @num_steps = num_steps
end

Instance Attribute Details

#letter_name ⇒ Object (readonly)

Returns the value of attribute letter_name.



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# File 'lib/head_music/rudiment/pitch/natural_step.rb', line 8

def letter_name
  @letter_name
end

#num_steps ⇒ Object (readonly)

Returns the value of attribute num_steps.



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# File 'lib/head_music/rudiment/pitch/natural_step.rb', line 8

def num_steps
  @num_steps
end

Instance Method Details

#applied_to(pitch) ⇒ Object 



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# File 'lib/head_music/rudiment/pitch/natural_step.rb', line 27

def applied_to(pitch)
  HeadMusic::Rudiment::Pitch.get([target_letter_name, pitch.register + octaves_delta].join)
end

#octaves_delta ⇒ Object 



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# File 'lib/head_music/rudiment/pitch/natural_step.rb', line 19

def octaves_delta
  whole_octaves = (num_steps.abs / 7) * (num_steps.negative? ? -1 : 1)
  return whole_octaves - 1 if wrapped_down?
  return whole_octaves + 1 if wrapped_up?

  whole_octaves
end

#target_letter_name ⇒ Object 



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# File 'lib/head_music/rudiment/pitch/natural_step.rb', line 15

def target_letter_name
  @target_letter_name ||= letter_name.steps_up(num_steps)
end

#wrapped_down? ⇒ Boolean (private)

Returns:

  • (Boolean) 


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# File 'lib/head_music/rudiment/pitch/natural_step.rb', line 33

def wrapped_down?
  num_steps.negative? && target_letter_name.position > letter_name.position
end

#wrapped_up? ⇒ Boolean (private)

Returns:

  • (Boolean) 


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# File 'lib/head_music/rudiment/pitch/natural_step.rb', line 37

def wrapped_up?
  num_steps.positive? && target_letter_name.position < letter_name.position
end