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probabilistic_track.rb
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probabilistic_track.rb
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# A track which fires each event based on the probabality listed, eg.
#
# bass: .5 0 0 0 1 0 0 0 .5 0 0 0 1 0 0 0
#
# has a 1 in 2 chance of playing the first and third drum beat, but
# will always play the second and fourth beat. This is actually
# compiled to a static rhythm with the probabilities being
# worked out beforehand.
class ProbabilisticTrack < Track
def initialize(name, rhythm)
@name = name
self.rhythm = rhythm
end
def self.valid?(rhythm)
# Add a space to make the regexp less complex, otherwise you have to account
# for space at the end!
if (rhythm + ' ') =~ /^((\d+|\.\d|0\.\d|1\.0)\s+|\s*\|\s*)+$/
true
else
false
end
end
def rhythm=(rhythm)
beats = []
beat_length = 0
rhythm.delete(BARLINE).split(' ').map {|i| i.strip }.each do |ch|
prob = Float(ch) rescue raise("Invalid character '#{ch}' in track #{@name}")
test = case ch
when /^1(\.0?)?/ then true # always play
when /^0(\.0?)?/ then false # never play
else
prob >= rand # play if probability is gte to random number
end
if test == true
beats << beat_length
beat_length = 1
else
beat_length += 1
end
end
if beat_length > 0
beats << beat_length
end
counter = 0
indexes = beats.map do |i|
n = counter + i
counter += i
n
end
@rhythm = REST * counter
indexes.each do |i|
@rhythm[i] = BEAT
end
@rhythm.chop!
if beats == []
beats = [0]
end
@beats = beats
end
end