302 lines
7.7 KiB
Text
302 lines
7.7 KiB
Text
class:: Stream
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summary:: Stream is the base class for classes that define streams
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related:: Classes/Routine, Classes/FuncStream, Classes/EventStreamPlayer
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categories:: Streams-Patterns-Events
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description::
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Stream is an abstract class that is not used directly. The following attempts to document some aspects of the use of Streams for music generation.
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subsection::Overview
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A Stream represents a sequence of values that are obtained incrementally by repeated strong::next:: messages. A Stream can be restarted with a strong::reset:: message. (Not all streams actually implement reset semantics.)
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The class link::Classes/Object:: defines strong::next:: to return the object itself. Thus every object can be viewed as a stream and most simply stream themselves.
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In SuperCollider, Streams are primarily used for handling text and for generating music.
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subsection::FuncStream(nextFunction, resetFunction)
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A link::Classes/Function:: defines a stream consisting of the Function itself, a link::Classes/FuncStream:: defines a stream that consists of emphasis::evaluations:: of its nextFunction.
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code::
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// Example 1: a Function vs. a FuncStream
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(
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f = { 33.rand };
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x = FuncStream(f);
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10.do({ [f.next, x.next].postln });
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)
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::
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code::
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// Example 2: the reset function
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(
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f = { 33.rand };
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x = FuncStream(f, {thisThread.randSeed_(345)});
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x.reset;
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10.do({ [f.next, x.next].postln });
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x.reset;
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10.do({ [f.next, x.next].postln });
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)
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::
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subsection::Routine(nextFunction, stacksize)
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In a link::Classes/FuncStream::, the nextFunction runs through to completion for each element of the stream. In a link::Classes/Routine::, the nextFunction returns values with strong::yield:: and resumes execution (when it receives a strong::next:: message) at the expression following the yield. This allows a sequence of expressions in the function definition to represent a sequence of distinct events, like a musical score.
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code::
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// example
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(
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x = Routine({
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1.yield;
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2.yield;
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3.yield;
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});
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4.do({ x.next.postln });
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)
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::
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Once the nextFunction completes execution, the Routine simply yields nil repeatedly. Control structures (such as strong::do:: or strong::while::) can be used within the nextFunction in a manner analogous to repeat marks in a score.
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code::
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// example
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(
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x = Routine({
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4.do({
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[1,2,3,4].do({ arg i; i.yield; });
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});
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});
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17.do({ x.next.postln });
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)
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::
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subsection::Playing streams
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Because streams respond like functions to the value message, they can be used as a scheduling task.
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code::
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// compare:
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// a function, returning 0.5
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(
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SystemClock.sched(0.0,
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{ "***".postln; 0.5 }
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);
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)
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// a stream, returning 0.5 and 0.1
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(
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SystemClock.sched(0.0,
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Routine({ loop {
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"***".postln; 0.5.yield;
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"_*_".postln; 0.1.yield;
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} });
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);
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)
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// this is the reason why 'wait' works the same (for numbers) like 'yield'
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(
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SystemClock.sched(0.0,
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Routine({ loop {
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"***".postln; 0.5.wait;
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"_*_".postln; 0.1.wait;
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} });
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);
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)
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::
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Streams that return strong::numbers:: can be played directly with the strong::play:: message.
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code::
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// play at the next beat, with offset 0.4
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(
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Routine({ loop {
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"***".postln; 0.5.wait;
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"_*_".postln; 0.1.wait;
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} }).play(quant:[1, 0.4]);
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)
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::
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Streams that return strong::Events:: need to be wrapped in an link::Classes/EventStreamPlayer::. The Event's strong::delta:: (can also be set by strong::dur::) is used as a scheduling beats value:
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code::
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// play at the next beat, with offset 0.4
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(
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Routine({ loop {
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"///".postln; (delta:0.5).yield;
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"_/_".postln; (delta: 0.1).wait;
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} }).asEventStreamPlayer.play;
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)
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::
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subsection::Iteration
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The method link::#-do:: effectively 'plays' a stream by iterating all of its contents.
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And the following messages create a stream by filtering another stream in some way: link::#-collect::, link::#-reject::, link::#-select::, link::#-dot::, link::#-interlace::, link::#-appendStream::, link::#-embedInStream::, link::#-trace::.
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subsection::Composite Streams
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Routines can be strong::embedded:: in each other, using link::#-embedInStream:: :
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code::
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// example
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(
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x = Routine({
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2.do({
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[1,2,3,4].do({ arg i; i.yield; });
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});
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});
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y = Routine({
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100.yield;
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30.yield;
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x.embedInStream;
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440.yield;
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1910.yield;
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});
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17.do({ y.next.postln });
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)
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::
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Routines can be strong::concatenated:: just like Streams:
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code::
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(
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x = Routine({
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2.do({
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[1,2,3,4].do({ arg i; i.yield; });
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});
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});
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y = Routine({
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100.yield;
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30.yield;
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});
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z = x ++ y;
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17.do({ z.next.postln });
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)
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::
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Routines can be strong::combined:: with the composition operator <>
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code::
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(
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x = Routine({ arg inval;
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2.do({
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[1,2,3,4].do({ arg i;
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if(inval.isNil) { nil.alwaysYield };
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inval = (i * inval).yield;
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});
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});
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});
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y = Routine({
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100.yield;
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30.yield;
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4.do { 1.0.rand.yield };
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});
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z = x <> y;
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17.do({ z.value.postln }); // call .value here, as this is a function.
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)
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::
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Composite Streams can be defined as combinations of Streams using the unary and binary messages.
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subsection::Unary messages
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Streams support most of the unary messages defined in link::Classes/AbstractFunction:: :
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code::
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(
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a = Routine({ 20.do({ 33.rand.yield }) });
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b = Routine({ [-100,00,300,400].do({ arg v; v.yield}) });
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c = b.neg; // define a composite stream
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// enumerate and perform all of the unary messages:
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[
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\neg, \reciprocal, \bitNot, \abs, \asFloat, \asInteger, \ceil,
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\floor, \frac, \sign, \squared, \cubed, \sqrt, \exp, \midicps,
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\cpsmidi, \midiratio, \ratiomidi, \ampdb, \dbamp, \octcps,
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\cpsoct, \log, \log2, \log10, \sin, \cos, \tan, \asin, \acos, \atan,
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\sinh, \cosh, \tanh, \rand, \rand2, \linrand, \bilinrand, \sum3rand,
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\distort, \softclip, \coin, \even, \odd, \isPositive, \isNegative,
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\isStrictlyPositive
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]
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.do({ arg msg;
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postf("\n msg: % \n", msg);
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b.reset.perform(msg).do({arg v; v.post; " ".post;});
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});
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nil;
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)
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::
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subsection::Binary messages
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Streams support the following binary messages defined in link::Classes/AbstractFunction:: :
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code::
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(
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a = Routine({ 20.do({ 33.rand.yield }) });
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b = Routine({ [-100,00,300,400].do({ arg v; v.yield}) });
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[
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'+' , '-' , '*', '/', \div, '%', '**', \min, \max, '<', '<=', '>', '>=', '&', '|',
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\bitXor, \lcm, \gcd, \round, \trunc, \atan2,
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\hypot, '>>', '+>>', \ring1, \ring2, \ring3, \ring4,
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\difsqr, \sumsqr, \sqrdif, \absdif, \amclip,
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\scaleneg, \clip2, \excess, '<!', \rrand, \exprand
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]
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.do({ arg msg;
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postf("\n msg: % \n", msg);
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b.reset.perform(msg).do({ arg v; v.post; " ".post; });
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});
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nil;
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)
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::
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InstanceMethods::
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method::play
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Streams that return strong::numbers:: can be played directly with the strong::play:: message. Streams that return strong::events:: need to be wrapped in an link::Classes/EventStreamPlayer::. See link::#-asEventStreamPlayer::.
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argument::clock
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a clock. link::Classes/TempoClock:: by default.
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argument::quant
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either a number strong::n:: (quantize to strong::n:: beats), or an array strong::[n, m]:: (quantize to n beats, with offset m).
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method::do
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iterate until a nil is encountered.
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warning::
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Applying do to an endless stream will lock up the interpreter!
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::
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method::collect
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iterate indefinitely.
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method::reject
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return only those elements for which function.value(element) is false.
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method::select
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return only those elements for which function.value(element) is true.
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method::dot
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return function.value(this.next, stream.next) for each element.
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method::interlace
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iterate all of stream for each element of this. Combine the values using function.
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method::appendStream
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append stream after this returns nil. The same like ++
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method::embedInStream
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iterate all of this from within whatever Stream definition it is called.
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method::trace
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print out the results of a stream while returning the original values.
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argument::key
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when streaming events, post only this key.
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argument::printStream
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printOn this stream (default: link::Classes/Post::).
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argument::prefix
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string added to the printout to separate different streams.
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