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October 14, 2011 10:10
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Bjorklund algorithm in JavaScript
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/* | |
An implementation of the Bjorklund algorithm in JavaScript | |
Inspired by the paper 'The Euclidean Algorithm Generates Traditional Musical Rhythms' | |
by Godfried Toussaint | |
This is a port of the original algorithm by E. Bjorklund which I | |
found in the paper 'The Theory of Rep-Rate Pattern Generation in the SNS Timing Systems' by | |
E. Bjorklund. | |
Jack Rutherford | |
*/ | |
function bjorklund(steps, pulses) { | |
steps = Math.round(steps); | |
pulses = Math.round(pulses); | |
if(pulses > steps || pulses == 0 || steps == 0) { | |
return new Array(); | |
} | |
pattern = []; | |
counts = []; | |
remainders = []; | |
divisor = steps - pulses; | |
remainders.push(pulses); | |
level = 0; | |
while(true) { | |
counts.push(Math.floor(divisor / remainders[level])); | |
remainders.push(divisor % remainders[level]); | |
divisor = remainders[level]; | |
level += 1; | |
if (remainders[level] <= 1) { | |
break; | |
} | |
} | |
counts.push(divisor); | |
var r = 0; | |
var build = function(level) { | |
r++; | |
if (level > -1) { | |
for (var i=0; i < counts[level]; i++) { | |
build(level-1); | |
} | |
if (remainders[level] != 0) { | |
build(level-2); | |
} | |
} else if (level == -1) { | |
pattern.push(0); | |
} else if (level == -2) { | |
pattern.push(1); | |
} | |
}; | |
build(level); | |
return pattern.reverse(); | |
} |
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