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POErlang function with number for parameter
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copied!<p>Hi I'm learning Erlang via Learn You Some Erlang by Fred Hebert.</p> <p>And I've come across a code that I'm confuse about:</p> <pre><code>sword(1) -> throw(slice); sword(2) -> erlang:error(cut_arm); sword(3) -> exit(cut_leg); sword(4) -> throw(punch); sword(5) -> exit(cross_bridge). talk() -> "blah blah". black_knight(Attack) when is_function(Attack, 0) -> try Attack() of _ -> "None shall pass." catch throw:slice -> "It is but a scratch."; error:cut_arm -> "I've had worse."; exit:cut_leg -> "Come on you pansy!"; _:_ -> "Just a flesh wound." end. </code></pre> <p>So here's the confusion. I don't understand <code>sword(#)</code> function. Why are there number as parameter? The function <code>is_function</code> actually check if these function are of arity 0 and apparently all the <code>sword(#)</code> functions are of arity 0. </p> <p>Also the way to pass in the <code>sword(#)</code> function to the <code>black_knight</code> function is different compare to the <code>talk</code> function.</p> <p>Here's how the book pass a <code>sword</code> function and the <code>talk</code> function.</p> <pre><code>exceptions:black_knight(fun exceptions:talk/0). </code></pre> <p>vs</p> <pre><code>exceptions:black_knight(fun() -> exceptions:sword(1) end). </code></pre> <p>The <code>talk</code> function we just pass the function where as the <code>sword(1)</code> function we have to wrap it with a anonymous function. I don't get it.</p> <p>So the questions are:</p> <ol> <li>Why is passing these <code>sword(#)</code> different from <code>talk</code> function.</li> <li>Why <code>sword(#)</code> have a number as a parameter?</li> <li>Why <code>sword(#)</code> have 0 arity when it seems like it have an arity of 1 (I'm counting the number parameter as a parameter)?</li> </ol> <p><a href="http://learnyousomeerlang.com/errors-and-exceptions#dealing-with-exceptions" rel="nofollow">The chapter of the book I'm at.</a></p> <p>Thank you for your time.</p>

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