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POself made pow() c++
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  1. POself made pow() c++
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    copied!<p>I was reading through <a href="https://stackoverflow.com/questions/2882706/how-can-i-write-a-power-function-myself/2882819#2882819">How can I write a power function myself?</a> and the answer given by dan04 caught my attention mainly because I am not sure about the answer given by fortran, but I took that and implemented this:</p> <pre><code>#include &lt;iostream&gt; using namespace std; float pow(float base, float ex){ // power of 0 if (ex == 0){ return 1; // negative exponenet }else if( ex &lt; 0){ return 1 / pow(base, -ex); // even exponenet }else if ((int)ex % 2 == 0){ float half_pow = pow(base, ex/2); return half_pow * half_pow; //integer exponenet }else{ return base * pow(base, ex - 1); } } int main(){ for (int ii = 0; ii&lt; 10; ii++){\ cout &lt;&lt; "pow(" &lt;&lt; ii &lt;&lt; ".5) = " &lt;&lt; pow(ii, .5) &lt;&lt; endl; cout &lt;&lt; "pow(" &lt;&lt; ii &lt;&lt; ",2) = " &lt;&lt; pow(ii, 2) &lt;&lt; endl; cout &lt;&lt; "pow(" &lt;&lt; ii &lt;&lt; ",3) = " &lt;&lt; pow(ii, 3) &lt;&lt; endl; } } </code></pre> <p>though I am not sure if I translated this right because all of the calls giving .5 as the exponent return 0. In the answer it states that it might need a log2(x) based on <code>a^b = 2^(b * log2(a))</code>, but I am unsure about putting that in as I am unsure where to put it, or if I am even thinking about this right.</p> <p>NOTE: I know that this might be defined in a math library, but I don't need all the added expense of an entire math library for a few functions.</p> <p>EDIT: does anyone know a floating-point implementation for fractional exponents? (I have seen a double implementation, but that was using a trick with registers, and I need floating-point, and adding a library just to do a trick I would be better off just including the math library)</p>
 

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