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A common complaint about the standard C library is its lack of a
function for calculating (small) integer powers. GSL provides a simple
functions to fill this gap. For reasons of efficiency, these functions
do not check for overflow or underflow conditions.
- Function: double gsl_pow_int (double x, int n)
-
This routine computes the power @math{x^n} for integer n. The
power is computed using the minimum number of multiplications. For
example, @math{x^8} is computed as @math{((x^2)^2)^2}, requiring only 3
multiplications. A version of this function which also computes the
numerical error in the result is available as
gsl_sf_pow_int_e
.
- Function: double gsl_pow_2 (const double x)
-
- Function: double gsl_pow_3 (const double x)
-
- Function: double gsl_pow_4 (const double x)
-
- Function: double gsl_pow_5 (const double x)
-
- Function: double gsl_pow_6 (const double x)
-
- Function: double gsl_pow_7 (const double x)
-
- Function: double gsl_pow_8 (const double x)
-
- Function: double gsl_pow_9 (const double x)
-
These functions can be used to compute small integer powers @math{x^2},
@math{x^3}, etc. efficiently. The functions will be inlined when
possible so that use of these functions should be as efficient as
explicitly writing the corresponding product expression.
#include <gsl/gsl_math.h>
double y = gsl_pow_4 (3.141) /* compute 3.141**4 */
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