Help/Streams-Patterns-Events/Streams-Patterns-Events2.html

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  28 <p class="p1"><br></p>
  29 <p class="p2"><b>Understanding Streams, Patterns and Events - Part 2</b></p>
  30 <p class="p3"><br></p>
  31 <p class="p4"><b>Patterns</b></p>
  32 <p class="p3"><br></p>
  33 <p class="p4">Often one wants to be able to create multiple streams from a single stream specification. Patterns are just a way to make multiple Streams<span class="Apple-converted-space">  </span>from a single specification, like a cookie cutter. A pattern can be any object that responds to the asStream message by creating a Stream. Once again there is a default implementation in class Object of asStream that simply returns the receiver as its own stream. Thus any object is by default a pattern that returns itself as a stream when sent the asStream message.</p>
  34 <p class="p5"><br></p>
  35 <p class="p6">(</p>
  36 <p class="p6">a = 7.asStream;</p>
  37 <p class="p6">a.postln;</p>
  38 <p class="p6">a.next.postln;</p>
  39 <p class="p6">)</p>
  40 <p class="p3"><br></p>
  41 <p class="p4"><b>Pattern and its subclasses</b></p>
  42 <p class="p3"><br></p>
  43 <p class="p4">There is a class named Pattern that provides more functionality for the concept of a pattern.</p>
  44 <p class="p3"><br></p>
  45 <p class="p4">Pfunc is a Pattern that returns a FuncStream. The same function arguments are supplied as are supplied to FuncStream.</p>
  46 <p class="p3"><br></p>
  47 <p class="p6">(</p>
  48 <p class="p6"><span class="s1">var</span> a, b;</p>
  49 <p class="p6">a = <span class="s1">Pfunc</span>.new({ #[1, 2, 3, 4].choose });</p>
  50 <p class="p7"><span class="s2">b = a.asStream;<span class="Apple-tab-span">     </span></span>// make a stream from the pattern</p>
  51 <p class="p7"><span class="s2">5.do({ b.next.postln; });<span class="Apple-tab-span">   </span><span class="Apple-tab-span">    </span></span>// print 5 values from the stream</p>
  52 <p class="p8"><br></p>
  53 <p class="p6">)</p>
  54 <p class="p3"><br></p>
  55 <p class="p4">Prout is a Pattern that returns a Routine. The same function argument is supplied as is supplied to Routine.</p>
  56 <p class="p3"><br></p>
  57 <p class="p6">(</p>
  58 <p class="p6"><span class="s1">var</span> a, b, c;</p>
  59 <p class="p6">a = <span class="s1">Prout</span>.new({<span class="Apple-converted-space"> </span></p>
  60 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>3.do({ <span class="s1">arg</span> i; 3.rand.yield; })<span class="Apple-converted-space"> </span></p>
  61 <p class="p6"><span class="Apple-tab-span">     </span>});</p>
  62 <p class="p7">// make two streams from the pattern</p>
  63 <p class="p6">b = a.asStream;</p>
  64 <p class="p6">c = a.asStream;</p>
  65 <p class="p7"><span class="s2">4.do({ b.next.postln; });<span class="Apple-tab-span">   </span></span>// print 4 values from first stream</p>
  66 <p class="p7"><span class="s2">4.do({ c.next.postln; });<span class="Apple-tab-span">   </span></span>// print 4 values from second stream</p>
  67 <p class="p6">)</p>
  68 <p class="p3"><br></p>
  69 <p class="p4">Pseries is a Pattern that generates an arithmetic series.</p>
  70 <p class="p5"><br></p>
  71 <p class="p6">(</p>
  72 <p class="p6"><span class="s1">var</span> a, b;</p>
  73 <p class="p7"><span class="s2">a = </span><span class="s1">Pseries</span><span class="s2">.new(10, 3, 8); </span>// stream starts at 10, steps by 3 and has length 8</p>
  74 <p class="p6">b = a.asStream;</p>
  75 <p class="p7"><span class="s2">9.do({ b.next.postln; });<span class="Apple-tab-span">   </span></span>// print 9 values from stream</p>
  76 <p class="p6">)</p>
  77 <p class="p3"><br></p>
  78 <p class="p4">Pgeom is a Pattern that generates a geometric series.</p>
  79 <p class="p3"><br></p>
  80 <p class="p6">(</p>
  81 <p class="p6"><span class="s1">var</span> a, b;</p>
  82 <p class="p7">// stream starts at 10, steps by factor of 3 and has length 8</p>
  83 <p class="p6">a = <span class="s1">Pgeom</span>.new(10, 3, 8);<span class="Apple-converted-space"> </span></p>
  84 <p class="p6">b = a.asStream;</p>
  85 <p class="p7"><span class="s2">9.do({ b.next.postln; });<span class="Apple-tab-span">   </span></span>// print 9 values from stream</p>
  86 <p class="p6">)</p>
  87 <p class="p3"><br></p>
  88 <p class="p4"><b>Math operations on Patterns</b></p>
  89 <p class="p3"><br></p>
  90 <p class="p4">Patterns also respond to math operators by returning patterns that respond to asStream with appropriately modified streams.</p>
  91 <p class="p3"><br></p>
  92 <p class="p4">Applying a unary operator to a pattern</p>
  93 <p class="p3"><br></p>
  94 <p class="p6">(</p>
  95 <p class="p6"><span class="s1">var</span> a, b, c;</p>
  96 <p class="p7">// a is a pattern whose stream counts from 0 to 9</p>
  97 <p class="p6">a = <span class="s1">Pseries</span>.new(0,1,10);</p>
  98 <p class="p7"><span class="s2">b = a.squared;<span class="Apple-tab-span">      </span></span>// pattern b is a square of the pattern a</p>
  99 <p class="p6">c = b.asStream;</p>
 100 <p class="p6">12.do({ c.next.postln; });</p>
 101 <p class="p6">)</p>
 102 <p class="p3"><br></p>
 103 <p class="p4">Using a binary operator on a pattern</p>
 104 <p class="p5"><br></p>
 105 <p class="p6">(</p>
 106 <p class="p6"><span class="s1">var</span> a, b, c;</p>
 107 <p class="p7">// a is a pattern whose stream counts from 0 to 9</p>
 108 <p class="p6">a = <span class="s1">Pseries</span>.new(0,1,10);</p>
 109 <p class="p7"><span class="s2">b = a + 100;<span class="Apple-tab-span">        </span></span>// add a constant value to pattern a</p>
 110 <p class="p6">c = b.asStream;</p>
 111 <p class="p6">12.do({ c.next.postln; });</p>
 112 <p class="p6">)</p>
 113 <p class="p3"><br></p>
 114 <p class="p4"><b>Filtering operations on patterns</b></p>
 115 <p class="p3"><br></p>
 116 <p class="p4">Patterns also respond to the messages collect, select, and reject by returning a new Pattern.</p>
 117 <p class="p3"><br></p>
 118 <p class="p4">The collect message returns a Pattern whose Stream is modified by a function in the same way as the collect message sent to a Collection returns a modified Collection.</p>
 119 <p class="p5"><br></p>
 120 <p class="p6">(</p>
 121 <p class="p6"><span class="s1">var</span> a, b, c;</p>
 122 <p class="p7">// a is a pattern whose stream counts from 0 to 9</p>
 123 <p class="p6">a = <span class="s1">Pseries</span>.new(0,1,10);</p>
 124 <p class="p7">// b is a pattern whose stream adds 100 to even values</p>
 125 <p class="p6">b = a.collect({ <span class="s1">arg</span> item; if (item.even, { item + 100 },{ item }); });</p>
 126 <p class="p6">c = b.asStream;</p>
 127 <p class="p6">6.do({ c.next.postln; });</p>
 128 <p class="p6">)</p>
 129 <p class="p3"><br></p>
 130 <p class="p4">The select message creates a pattern whose stream passes only items that return true from a user supplied function.</p>
 131 <p class="p5"><br></p>
 132 <p class="p6">(</p>
 133 <p class="p6"><span class="s1">var</span> a, b, c;</p>
 134 <p class="p7">// a is a pattern whose stream counts from 0 to 9</p>
 135 <p class="p6">a = <span class="s1">Pseries</span>.new(0,1,10);</p>
 136 <p class="p7">// b is a pattern whose stream only returns the odd values</p>
 137 <p class="p6">b = a.select({ <span class="s1">arg</span> item; item.odd; });</p>
 138 <p class="p6">c = b.asStream;</p>
 139 <p class="p6">6.do({ c.next.postln; });</p>
 140 <p class="p6">)</p>
 141 <p class="p3"><br></p>
 142 <p class="p4">The reject message creates a pattern whose stream passes only items that return false from a<span class="Apple-converted-space"> </span></p>
 143 <p class="p4">user supplied function.</p>
 144 <p class="p3"><br></p>
 145 <p class="p6">(</p>
 146 <p class="p6"><span class="s1">var</span> a, b, c;</p>
 147 <p class="p7">// a is a pattern whose stream counts from 0 to 9</p>
 148 <p class="p6">a = <span class="s1">Pseries</span>.new(0,1,10);</p>
 149 <p class="p7">// b is a pattern whose stream that only returns the non-odd values</p>
 150 <p class="p6">b = a.reject({ <span class="s1">arg</span> item; item.odd; });</p>
 151 <p class="p6">c = b.asStream;</p>
 152 <p class="p6">6.do({ c.next.postln; });</p>
 153 <p class="p6">)</p>
 154 <p class="p5"><br></p>
 155 <p class="p3"><br></p>
 156 <p class="p4"><b>Making Music with Patterns</b></p>
 157 <p class="p3"><br></p>
 158 <p class="p4">Here is a variation of the example given in part 1 that uses a Pattern to create two instances of the random melody stream.</p>
 159 <p class="p3"><br></p>
 160 <p class="p6">(</p>
 161 <p class="p6"><span class="Apple-tab-span">     </span>s = <span class="s1">Server</span>.local;</p>
 162 <p class="p6"><span class="Apple-tab-span">     </span><span class="s1">SynthDef</span>(<span class="s3">\help_SPE2</span>, { <span class="s1">arg</span> i_out=0, sustain=1, freq;</p>
 163 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="s1">var</span> out;</p>
 164 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>out = <span class="s1">RLPF</span>.ar(</p>
 165 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="s1">LFSaw</span>.ar( freq ),</p>
 166 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="s1">LFNoise1</span>.kr(1, 36, 110).midicps,</p>
 167 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>0.1</p>
 168 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>) * <span class="s1">EnvGen</span>.kr( <span class="s1">Env</span>.perc, levelScale: 0.3,<span class="Apple-converted-space"> </span></p>
 169 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>timeScale: sustain, doneAction: 2 );</p>
 170 <p class="p7"><span class="s2"><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span></span>//out = [out, DelayN.ar(out, 0.04, 0.04) ];</p>
 171 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>4.do({ out = <span class="s1">AllpassN</span>.ar(out, 0.05, [0.05.rand, 0.05.rand], 4) });</p>
 172 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="s1">Out</span>.ar( i_out, out );</p>
 173 <p class="p6"><span class="Apple-tab-span">     </span>}).send(s);</p>
 174 <p class="p6">)</p>
 175 <p class="p6">(</p>
 176 <p class="p7">// streams as a sequence of pitches</p>
 177 <p class="p6"><span class="Apple-tab-span">     </span><span class="s1">var</span> pattern, streams, dur, durDiff;</p>
 178 <p class="p6"><span class="Apple-tab-span">     </span>dur = 1/7;</p>
 179 <p class="p6"><span class="Apple-tab-span">     </span>durDiff = 3;</p>
 180 <p class="p6"><span class="Apple-tab-span">     </span>pattern = <span class="s1">Prout</span>.new({</p>
 181 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>loop({</p>
 182 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>if (0.5.coin, {</p>
 183 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>#[ 24,31,36,43,48,55 ].do({ <span class="s1">arg</span> fifth; fifth.yield });</p>
 184 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>});</p>
 185 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>rrand(2,5).do({</p>
 186 <p class="p7"><span class="s2"><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span></span>// varying arpeggio</p>
 187 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>60.yield;</p>
 188 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>#[63,65].choose.yield;</p>
 189 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>67.yield;</p>
 190 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>#[70,72,74].choose.yield;</p>
 191 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>});</p>
 192 <p class="p7"><span class="s2"><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span></span>// random high melody</p>
 193 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>rrand(3,9).do({<span class="Apple-converted-space">  </span>#[74,75,77,79,81].choose.yield });</p>
 194 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>});</p>
 195 <p class="p6"><span class="Apple-tab-span">     </span>});</p>
 196 <p class="p6"><span class="Apple-tab-span">     </span>streams = [ <span class="Apple-converted-space"> </span></p>
 197 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>(pattern - <span class="s1">Pfunc</span>.new({ #[12, 7, 7, 0].choose })).midicps.asStream,</p>
 198 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>pattern.midicps.asStream</p>
 199 <p class="p6"><span class="Apple-tab-span">     </span>];</p>
 200 <p class="p9"><span class="s2"><span class="Apple-tab-span">    </span></span>Routine<span class="s2">({</span></p>
 201 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>loop({</p>
 202 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="s1">Synth</span>( <span class="s3">\help_SPE2</span>, [ <span class="s3">\freq</span>, streams.at(0).next, <span class="s3">\sustain</span>, dur * durDiff<span class="Apple-converted-space">  </span>] );</p>
 203 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>durDiff.do({</p>
 204 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="s1">Synth</span>( <span class="s3">\help_SPE2</span>, [ <span class="s3">\freq</span>, streams.at(1).next, <span class="s3">\sustain</span>, dur<span class="Apple-converted-space">  </span>] );</p>
 205 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>dur.wait;</p>
 206 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>});</p>
 207 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>})</p>
 208 <p class="p6"><span class="Apple-tab-span">     </span>}).play</p>
 209 <p class="p6">)</p>
 210 <p class="p3"><br></p>
 211 <p class="p4">To go to the next file:</p>
 212 <p class="p10"><span class="s4"><a href="Streams-Patterns-Events3.html">Streams-Patterns-Events3</a></span></p>
 213 <p class="p3"><br></p>
 214 <p class="p3"><br></p>
 215 </body>
 216 </html>