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<h3 class="section">7.27 Power Function</h3>
<p><a name="index-power-function-756"></a><a name="index-integer-powers-757"></a>
The following functions are equivalent to the function <code>gsl_pow_int</code>
(see <a href="Small-integer-powers.html">Small integer powers</a>) with an error estimate. These functions are
declared in the header file <samp><span class="file">gsl_sf_pow_int.h</span></samp>.
<div class="defun">
— Function: double <b>gsl_sf_pow_int</b> (<var>double x, int n</var>)<var><a name="index-gsl_005fsf_005fpow_005fint-758"></a></var><br>
— Function: int <b>gsl_sf_pow_int_e</b> (<var>double x, int n, gsl_sf_result * result</var>)<var><a name="index-gsl_005fsf_005fpow_005fint_005fe-759"></a></var><br>
<blockquote><p>These routines compute the power x^n for integer <var>n</var>. The
power is computed using the minimum number of multiplications. For
example, x^8 is computed as ((x^2)^2)^2, requiring only 3
multiplications. For reasons of efficiency, these functions do not
check for overflow or underflow conditions.
</p></blockquote></div>
<pre class="example"> #include <gsl/gsl_sf_pow_int.h>
/* compute 3.0**12 */
double y = gsl_sf_pow_int(3.0, 12);
</pre>
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