91 lines
1.8 KiB
Text
91 lines
1.8 KiB
Text
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#lang scribble/manual
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@(require (for-label racket))
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@title{Pwalk}
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A one-dimensional random walk over a list of values that are embedded@section{related}
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Classes/Pbrown
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@section{categories}
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Streams-Patterns-Events>Patterns>List
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@section{ClassMethods}
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@section{method}
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new
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@section{argument}
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list
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The items to be walked over.
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@section{argument}
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stepPattern
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Returns integers that will be used to increment the index into list.
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@section{argument}
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directionPattern
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Used to determine the behavior at boundaries. When the index crosses a boundary, the next direction is drawn from this stream: 1 means use stepPattern as is, -1 means go in the reverse direction. Common patterns:
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@section{definitionList}
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## 1 || always wrap around to the other boundary.
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## Pseq([1, -1], inf) || go forward first, then backward, then forward again.
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::
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@section{argument}
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startPos
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Where to start in the list.
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@section{Examples}
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@racketblock[
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(
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a = Pwalk(
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Array.series(20, 0, 1), // integers, 0-19
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// steps up to 2 in either direction, weighted toward positive
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Pwrand([-2, -1, 0, 1, 2], [0.05, 0.1, 0.15, 1, 0.1].normalizeSum, inf),
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// reverse direction at boundaries
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Pseq([1, -1], inf),
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10); // start in the middle
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x = a.asStream;
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)
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200.do({ x.next.post; ", ".post });
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b = a.copy.directionPattern_(1); // this one will always wrap around
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x = b.asStream;
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200.do({ x.next.post; ", ".post });
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// non-random walk: easy way to do up-and-down arpeggiation
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s.boot;
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(
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a = Pwalk(
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[60, 64, 67, 72, 76, 79, 84].midicps, // C major
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Pseq([1], inf),
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Pseq([1, -1], inf), // turn around at either end
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0);
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x = a.asStream;
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SynthDef(\help_walk, { arg freq;
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Out.ar(0, Saw.ar([freq, freq+1], 0.5) * EnvGen.kr(Env.perc(0.01, 0.1), doneAction: Done.freeSelf))
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}).add;
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)
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(
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r = Task({
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{
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Synth.new(\help_walk, [\freq, x.next]);
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0.1.wait;
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}.loop;
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}).play(SystemClock);
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)
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r.stop;
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::
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]
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