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    <p>Everything in Clojure is fully dynamic, but you have to take note of when you're working with a <em>Var</em> and when you're working with the <em>Function</em> which is the current <em>value</em> of that Var.</p> <p>In your first example:</p> <pre><code>(defn factorial [n] (if (&lt; n 2) n (* n (factorial (dec n))))) </code></pre> <p>The <code>factorial</code> symbol is resolved to the Var <code>#'user/factorial</code>, which is then evaluated by the compiler to get its current value, a compiled function. This evaluation happens only once, when the function is compiled. The <code>factorial</code> in this first example is the <em>value</em> of the Var <code>#'user/factorial</code> at the moment the function was defined.</p> <p>In the second example:</p> <pre><code>(defn factorial [n] (if (&lt; n 2) n (* n (#'factorial (dec n))))) </code></pre> <p>You have explicitly asked for the Var <code>#'user/factorial</code>. Invoking a Var has the same effect as dereferencing the Var and invoking its (function) value. This example could be written more explicitly as:</p> <pre><code>(defn factorial [n] (if (&lt; n 2) n (* n ((deref (var factorial)) (dec n))))) </code></pre> <p>The <code>clojure.contrib.trace/dotrace</code> macro (which I wrote, ages ago) uses <code>binding</code> to temporarily rebind a Var to a different value. It does not change the definition of any functions. Instead, it creates a new function which calls the original function and prints the trace lines, then it binds that function to the Var.</p> <p>In your first example, since the original function was compiled with the <em>value</em> of the <code>factorial</code> function, <code>dotrace</code> has no effect. In the second example, each invocation of the <code>factorial</code> function looks up the current value of the <code>#'user/factorial</code> Var, so each invocation sees the alternate binding created by <code>dotrace</code>. </p>
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    1. POCan clojure be made fully dynamic?
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    1. USStuart Sierra
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    1. COyou miss the point again. the real issue is not about vars vs. functions. problem here is a change between clojure pre 1.2 and 1.2 that lexically scopes a functions own name within the function, so self calls no longer go through the var.
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    2. COThanks! Is there any way to always make calls go through the var, or any way of predicting when they will and when they won't? I keep finding that things won't change when I want them to, and to fix it I have to keep sticking in #'. It's not just with self-calls.
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      1. USJohn Lawrence Aspden
 

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