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<section id="using-the-conditional-function">
<h1>Using the conditional function<a class="headerlink" href="#using-the-conditional-function" title="Permalink to this heading">¶</a></h1>
<p><strong>07-condition.py</strong></p>
<p>The <cite>if</cite> function let the user set different processing branches
according to the result of a condition. The syntax is:</p>
<div class="highlight-scheme notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nf">condition</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="nf">then</span><span class="p">)</span><span class="w"> </span><span class="p">(</span><span class="k">else</span><span class="p">))</span><span class="w"></span>
</pre></div>
</div>
<p>The example below uses two conditional statements. The first one
adjusts the duty cycle of a pulse-width-modulation waveform and
the second one split the positive and negative parts of the wave.
A slider, controlling a user variable, sets the gain of the
negative part.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <a class="sphinx-codeautolink-a" href="../../api/alphabetical.html#module-pyo" title="pyo"><span class="nn">pyo</span></a> <span class="kn">import</span> <span class="o">*</span>
<span class="n">s</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/server.html#pyo.Server" title="pyo.lib.server.Server"><span class="n">Server</span></a><span class="p">()</span><span class="o">.</span><span class="n">boot</span><span class="p">()</span>
<span class="n">expression</span> <span class="o">=</span> <span class="s2">"""</span>
<span class="s2">// Width of the duty cycle.</span>
<span class="s2">(var #thresh 0.5)</span>
<span class="s2">// Gain of the negative part of the waveform.</span>
<span class="s2">(var #gain 1)</span>
<span class="s2">// Running phase.</span>
<span class="s2">(let #sig (~ 172))</span>
<span class="s2">// If running phase is below threshold,</span>
<span class="s2">// then 1.0, else -1.0</span>
<span class="s2">(let #rect (</span>
<span class="s2"> if (<= #sig #thresh) (1.0) (-1.0)</span>
<span class="s2"> )</span>
<span class="s2">)</span>
<span class="s2">// If positive, pass through, else,</span>
<span class="s2">// modulated by #gain variable.</span>
<span class="s2">(if (>= #rect 0)</span>
<span class="s2"> (#rect)</span>
<span class="s2"> (* #gain #rect)</span>
<span class="s2">)</span>
<span class="s2">"""</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/expression.html#pyo.Expr" title="pyo.lib.expression.Expr"><span class="n">expr</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/expression.html#pyo.Expr" title="pyo.lib.expression.Expr"><span class="n">Expr</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">Sig</span></a><span class="p">(</span><span class="mi">0</span><span class="p">),</span> <span class="n">expression</span><span class="p">,</span> <span class="n">mul</span><span class="o">=</span><span class="mf">0.5</span><span class="p">)</span>
<span class="n">expr</span><span class="o">.</span><span class="n">editor</span><span class="p">()</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">threshold</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">Sig</span></a><span class="p">(</span><span class="mf">0.5</span><span class="p">)</span>
<span class="n">threshold</span><span class="o">.</span><span class="n">ctrl</span><span class="p">([</span><a class="sphinx-codeautolink-a" href="../../api/classes/map.html#pyo.SLMap" title="pyo.lib._maps.SLMap"><span class="n">SLMap</span></a><span class="p">(</span><span class="mf">0.01</span><span class="p">,</span> <span class="mf">0.5</span><span class="p">,</span> <span class="s2">"lin"</span><span class="p">,</span> <span class="s2">"value"</span><span class="p">,</span> <span class="mf">0.5</span><span class="p">)],</span> <span class="n">title</span><span class="o">=</span><span class="s2">"Duty Cycle"</span><span class="p">)</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">rectifier</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">Sig</span></a><span class="p">(</span><span class="mf">1.0</span><span class="p">)</span>
<span class="n">rectifier</span><span class="o">.</span><span class="n">ctrl</span><span class="p">([</span><a class="sphinx-codeautolink-a" href="../../api/classes/map.html#pyo.SLMap" title="pyo.lib._maps.SLMap"><span class="n">SLMap</span></a><span class="p">(</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">,</span> <span class="s2">"lin"</span><span class="p">,</span> <span class="s2">"value"</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">)],</span> <span class="n">title</span><span class="o">=</span><span class="s2">"Rectifier"</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">change</span><span class="p">():</span>
<span class="s2">"Sends new values to user variables in the expression."</span>
<span class="n">expr</span><span class="o">.</span><span class="n">setVar</span><span class="p">([</span><span class="s2">"#thresh"</span><span class="p">,</span> <span class="s2">"#gain"</span><span class="p">],</span> <span class="p">[</span><span class="n">threshold</span><span class="o">.</span><span class="n">get</span><span class="p">(),</span> <span class="n">rectifier</span><span class="o">.</span><span class="n">get</span><span class="p">()])</span>
<span class="c1"># Calls the change() function every 20 ms to update the user variables.</span>
<span class="n">pat</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/pattern.html#pyo.Pattern" title="pyo.lib.pattern.Pattern"><span class="n">Pattern</span></a><span class="p">(</span><span class="n">change</span><span class="p">,</span> <span class="mf">0.025</span><span class="p">)</span><span class="o">.</span><span class="n">play</span><span class="p">()</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/analysis.html#pyo.Scope" title="pyo.lib.analysis.Scope"><span class="n">sc</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/analysis.html#pyo.Scope" title="pyo.lib.analysis.Scope"><span class="n">Scope</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/expression.html#pyo.Expr" title="pyo.lib.expression.Expr"><span class="n">expr</span></a><span class="p">)</span>
<span class="n">pan</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/pan.html#pyo.Pan" title="pyo.lib.pan.Pan"><span class="n">Pan</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/expression.html#pyo.Expr" title="pyo.lib.expression.Expr"><span class="n">expr</span></a><span class="p">)</span><span class="o">.</span><span class="n">out</span><span class="p">()</span>
<span class="n">s</span><span class="o">.</span><span class="n">gui</span><span class="p">(</span><span class="nb">locals</span><span class="p">())</span>
</pre></div>
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