Επεξεργασία

Κοινή χρήση μέσω

pow, powf, powl

  • Άρθρο

Calculates x raised to the power of y.

Syntax

double pow( double x, double y );
float powf( float x, float y );
long double powl( long double x, long double y );
define pow(X, Y) // Requires C11 or higher

double pow( double x, int y );  // C++ only
float pow( float x, float y );  // C++ only
float pow( float x, int y );  // C++ only
long double pow( long double x, long double y );  // C++ only
long double pow( long double x, int y );  // C++ only

Parameters

x
Base.

y
Exponent.

Return value

Returns the value of xy. No error message is printed on overflow or underflow.

Values of x and y Return value of pow
x != 0.0 and y == 0.0 1
x == 0.0 and y == 0.0 1
x == 0.0 and y < 0 INF

Remarks

pow doesn't recognize integral floating-point values greater than 264 (for example, 1.0E100).

pow has an implementation that uses Streaming SIMD Extensions 2 (SSE2). For information and restrictions about using the SSE2 implementation, see _set_SSE2_enable.

Because C++ allows overloading, you can call any of the various overloads of pow. In a C program, unless you're using the <tgmath.h> macro to call this function, pow always takes two double values and returns a double value.

If you use the pow macro from <tgmath.h>, the type of the argument determines which version of the function is selected. See Type-generic math for details.

The pow(int, int) overload is no longer available. If you use this overload, the compiler may emit C2668. To avoid this problem, cast the first parameter to double, float, or long double.

Originally, the pow(T, int) overloads unrolled the pow call into a sequence of inline multiplication operations. While it was faster, it was also much less accurate. This implementation was removed in Visual Studio 2015 Update 1. For more information, see Conformance improvements in Visual Studio 2015 Update 1.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Requirements

Routine Required header (C) Required header (C++)
pow, powf, powl <math.h> <math.h> or <cmath>
pow macro <tgmath.h>

For more compatibility information, see Compatibility.

Example

// crt_pow.c

#include <math.h>
#include <stdio.h>

int main( void )
{
   double x = 2.0, y = 3.0, z;

   z = pow( x, y );
   printf( "%.1f to the power of %.1f is %.1f\n", x, y, z );
}

2.0 to the power of 3.0 is 8.0

See also

Math and floating-point support
exp, expf, expl
log, logf, log10, log10f
sqrt, sqrtf, sqrtl
_CIpow