Class: HeadMusic::Notation::LilyPond::MusicItemReader

Inherits:
Object
  • Object
show all
Defined in:
lib/head_music/notation/lily_pond/music_item_reader.rb

Overview

Reads the items a sequence of music is made of — notes, rests, chords, ties, bar checks, and the \key, \time, and \clef commands that appear among them — into the stream of the context that holds them. Everything that opens a level of its own belongs to the MusicReader that calls this one.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(cursor, readers) ⇒ MusicItemReader

Returns a new instance of MusicItemReader.



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 9

def initialize(cursor, readers)
  @cursor = cursor
  @readers = readers
  @duration_reader = DurationReader.new
end

Instance Attribute Details

#cursor ⇒ Object (readonly, private)

Returns the value of attribute cursor.



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 78

def cursor
  @cursor
end

#duration_reader ⇒ Object (readonly, private)

Returns the value of attribute duration_reader.



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 78

def duration_reader
  @duration_reader
end

#readers ⇒ Object (readonly, private)

Returns the value of attribute readers.



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 78

def readers
  @readers
end

Instance Method Details

#chord_note ⇒ Object (private) 



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 80

def chord_note
  token = cursor.advance
  raise cursor.unsupported_token(token) if token.type == :unsupported
  raise cursor.error(%(Unexpected token "#{token.lexeme}" inside a chord), token) unless token.type == :note
  raise cursor.error("Chord notes cannot carry durations", token) if token.duration

  reject_multiplier(token)
  token
end

#located(command) ⇒ Object (private)

A key or meter reader rejects a token without knowing where in the document it came from, so an error that carries no line is given the line of the command that introduced it.



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 99

def located(command)
  yield
rescue ParseError => parse_error
  raise parse_error if parse_error.line_number

  raise cursor.error(parse_error.message, command)
end

#read_bar_check(context) ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 49

def read_bar_check(context)
  context.stream.bar_check(cursor.advance.line)
end

#read_chord(context) ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 33

def read_chord(context)
  opener = cursor.advance
  notes = []
  notes << chord_note until cursor.peek.type == :close_chord
  closer = cursor.advance
  raise cursor.error("Empty chord", opener) if notes.empty?

  reject_multiplier(closer)
  pitches = readers.current.chord_pitches(notes)
  context.stream.add_note(pitches, duration_reader.rhythmic_value(closer), opener.line)
end

#read_clef ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 68

def read_clef
  command = cursor.advance
  token = cursor.advance
  return if token && (%i[word string].include?(token.type) || (token.type == :note && token.duration.nil?))

  raise cursor.error("\\clef expects a clef name", token || command)
end

#read_key(context) ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 53

def read_key(context)
  command = cursor.advance
  pitch_token = cursor.advance
  mode_token = cursor.advance
  located(command) do
    context.stream.change_key_signature(KeyReader.key_signature(pitch_token, mode_token), command.line)
  end
end

#read_note(context) ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 15

def read_note(context)
  token = cursor.advance
  reject_multiplier(token)
  pitch = readers.current.pitch(token)
  context.stream.add_note([pitch], duration_reader.rhythmic_value(token), token.line)
end

#read_rest(context) ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 22

def read_rest(context)
  token = cursor.advance
  reject_multiplier(token)
  context.stream.add_rest(duration_reader.rhythmic_value(token), token.line)
end

#read_tie(context) ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 45

def read_tie(context)
  context.stream.open_tie(cursor.advance.line)
end

#read_time(context) ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 62

def read_time(context)
  command = cursor.advance
  meter_token = cursor.advance
  located(command) { context.stream.change_meter(MeterReader.meter(meter_token), command.line) }
end

#read_whole_bar_rest(context) ⇒ Object 



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 28

def read_whole_bar_rest(context)
  token = cursor.advance
  context.stream.add_whole_bar_rest(duration_reader.whole_bar_fraction(token), token.line)
end

#reject_multiplier(token) ⇒ Object (private) 



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# File 'lib/head_music/notation/lily_pond/music_item_reader.rb', line 90

def reject_multiplier(token)
  return unless token.multiplier

  raise cursor.unsupported("Duration multipliers on notes and rests are not supported", token)
end