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<p>Click the play icon next to each programme to test it. Note that all programmes will auto-run and some, highlighted in red with a circle, may freeze or crash the tab they're running in so proceed with cautiond.</p><p class="link"><a href="https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=WHZVfWFATWdYKzE&input=MTM" target="_blank"><svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Try it</title><path d="M8,5.14V19.14L19,12.14L8,5.14Z"/></svg></a></p><pre><code>XvU}a@MgX+1</code></pre><p>Without the first <code>@</code> to open the left function the, now unmatched, closing <code>}</code> causes the programme to throw an error.</p><p class="link"><a href="https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=QHZVfWFATWdYKzE&input=MTM" target="_blank"><svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Try it</title><path d="M8,5.14V19.14L19,12.14L8,5.14Z"/></svg></a></p><pre><code>@vU}a@MgX+1</code></pre><p>Removing the first <code>X</code> results in <code>U</code> being auto-inserted between the <code>@</code> and the <code>v</code> and, therefore, the left function instead testing whether <code>U</code> is divisible by itself, which, of course, it is. So, no matter the input, the programme will exit after the first iteration and always return <code>1</code>.</p><p class="link"><a href="https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=QFhVfWFATWdYKzE&input=MTM" target="_blank"><svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Try it</title><path d="M8,5.14V19.14L19,12.14L8,5.14Z"/></svg></a></p><pre><code>@XU}a@MgX+1</code></pre><p>If the <code>v</code> is removed then the <code>X</code> is ignored and the left function now tests whether <code>U</code> is truthy, which, for all non-zero inputs, it always will be. So, as above, the programme will exit after the first iteration and always return <code>1</code>.</p><p class="link"><a href="https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=QFh2fWFATWdYKzE&input=MTM" target="_blank"><svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Try it</title><path d="M8,5.14V19.14L19,12.14L8,5.14Z"/></svg></a></p><pre><code>@Xv}a@MgX+1</code></pre><p>The default agrument for the <code>v</code> method when applied to an integer is <code>2</code> so, by checking if <code>X</code> is divisible by 2, this version will always return the first even Fibonacci number: <code>2</code>.<p class="link"><a href="https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=QFh2VWFATWdYKzE&input=MTM" target="_blank"><svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Try it</title><path d="M8,5.14V19.14L19,12.14L8,5.14Z"/></svg></a></p><pre><code>@XvUa@MgX+1</code></pre><p class="link"><a href="https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=QFh2VX1ATWdYKzE&input=MTM" target="_blank"><svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Try it</title><path d="M8,5.14V19.14L19,12.14L8,5.14Z"/></svg></a></p><pre><code>@XvU}@MgX+1</code></pre><p class="link"><a href="https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=QFh2VX1hTWdYKzE&input=MTM" target="_blank"><svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Try it</title><path d="M8,5.14V19.14L19,12.14L8,5.14Z"/></svg></a></p><pre><code>@XvU}aMgX+1</code></pre><p class="link"><a href="https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=QFh2VX1hQGdYKzE&input=MTM" target="_blank"><svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Try it</title><path d="M8,5.14V19.14L19,12.14L8,5.14Z"/></svg></a></p><pre><code>@XvU}a@gX+1</code></pre><p class="link"><a href="https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=QFh2VX1hQE1YKzE&input=MTM" target="_blank"><svg class="warning" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Try it</title><path d="M12,20C7.59,20 4,16.41 4,12C4,7.59 7.59,4 12,4C16.41,4 20,7.59 20,12C20,16.41 16.41,20 12,20M12,2A10,10 0 0,0 2,12A10,10 0 0,0 12,22A10,10 0 0,0 22,12A10,10 0 0,0 12,2M10,16.5L16,12L10,7.5V16.5Z"/></svg></a></p><pre><code>@XvU}a@MX+1</code></pre><p class="link"><a href="https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=QFh2VX1hQE1nKzE&input=MTM" target="_blank"><svg class="warning" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Try it</title><path d="M12,20C7.59,20 4,16.41 4,12C4,7.59 7.59,4 12,4C16.41,4 20,7.59 20,12C20,16.41 16.41,20 12,20M12,2A10,10 0 0,0 2,12A10,10 0 0,0 12,22A10,10 0 0,0 22,12A10,10 0 0,0 12,2M10,16.5L16,12L10,7.5V16.5Z"/></svg></a></p><pre><code>@XvU}a@Mg+1</code></pre><p class="link"><a href="https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=QFh2VX1hQE1nWDE&input=MTM" target="_blank"><svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Try it</title><path d="M8,5.14V19.14L19,12.14L8,5.14Z"/></svg></a></p><pre><code>@XvU}a@MgX1</code></pre><p class="link"><a href="https://petershaggynoble.github.io/Japt-Interpreter/?v=1.4.6&code=QFh2VX1hQE1nWCs&input=MTM" target="_blank"><svg viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Try it</title><path d="M8,5.14V19.14L19,12.14L8,5.14Z"/></svg></a></p><pre><code>@XvU}a@MgX+</code></pre>