std::pow
| Defined in header <cmath>
|
||
| float pow( float base, float exp ); |
(1) | |
| double pow( double base, double exp ); |
(2) | |
| long double pow( long double base, long double exp ); |
(3) | |
| float pow( float base, int iexp ); |
(4) | (until C++11) |
| double pow( double base, int iexp ); |
(5) | (until C++11) |
| long double pow( long double base, int iexp ); |
(6) | (until C++11) |
| Promoted pow( Arithmetic1 base, Arithmetic2 exp ); |
(7) | (since C++11) |
base raised to the power exp or iexp.Promoted is also long double, otherwise the return type is always double.Contents |
[edit] Parameters
| base | - | base as a value of floating-point or integral type |
| exp | - | exponent as a value of floating-point or integral type |
| iexp | - | exponent as integer value |
[edit] Return value
If no errors occur, base raised to the power of exp (or iexp) (baseexp
), is returned.
If a domain error occurs, an implementation-defined value is returned (NaN where supported)
If a pole error or a range error due to overflow occurs, ±HUGE_VAL, ±HUGE_VALF, or ±HUGE_VALL is returned.
If a range error occurs due to underflow, the correct result (after rounding) is returned.
[edit] Error handling
Errors are reported as specified in math_errhandling
If base is finite and negative and exp is finite and non-integer, a domain error occurs and a range error may occur.
If base is zero and exp is zero, a domain error may occur.
If base is zero and exp is negative, a domain error or a pole error may occur.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
- pow(+0, exp), where
expis a negative odd integer, returns +∞ and raises FE_DIVBYZERO - pow(-0, exp), where
expis a negative odd integer, returns -∞ and raises FE_DIVBYZERO - pow(±0, exp), where
expis negative, finite, and is an even integer or a non-integer, returns +∞ and raises FE_DIVBYZERO - pow(±0, -∞) returns +∞ and may raise FE_DIVBYZERO
- pow(+0, exp), where
expis a positive odd integer, returns +0 - pow(-0, exp), where
expis a positive odd integer, returns -0 - pow(±0, exp), where
expis positive non-integer or a positive even integer, returns +0 - pow(-1, ±∞) returns
1 - pow(+1, exp) returns
1for anyexp, even whenexpisNaN - pow(base, ±0) returns
1for anybase, even whenbaseisNaN - pow(base, exp) returns
NaNand raises FE_INVALID ifbaseis finite and negative andexpis finite and non-integer. - pow(base, -∞) returns +∞ for any
|base|<1 - pow(base, -∞) returns +0 for any
|base|>1 - pow(base, +∞) returns +0 for any
|base|<1 - pow(base, +∞) returns +∞ for any
|base|>1 - pow(-∞, exp) returns -0 if
expis a negative odd integer - pow(-∞, exp) returns +0 if
expis a negative non-integer or even integer - pow(-∞, exp) returns -∞ if
expis a positive odd integer - pow(-∞, exp) returns +∞ if
expis a positive non-integer or even integer - pow(+∞, exp) returns +0 for any negative
exp - pow(+∞, exp) returns +∞ for any positive
exp - except where specified above, if any argument is NaN, NaN is returned
[edit] Notes
pow(float, int) returns float until C++11 (per overload 4) but returns double since C++11 (per overload 7)
Although std::pow cannot be used to obtain a root of a negative number, std::cbrt is provided for the common case where exp is 1/3
[edit] Example
#include <iostream> #include <cmath> #include <cerrno> #include <cfenv> #include <cstring> #pragma STDC FENV_ACCESS ON int main() { // typical usage std::cout << "pow(2, 10) = " << std::pow(2,10) << '\n' << "pow(2, 0.5) = " << std::pow(2,0.5) << '\n' << "pow(-2, -3) = " << std::pow(-2,-3) << '\n'; // special values std::cout << "pow(-1, NAN) = " << std::pow(-1,NAN) << '\n' << "pow(+1, NAN) = " << std::pow(+1,NAN) << '\n' << "pow(INFINITY, 2) = " << std::pow(INFINITY, 2) << '\n' << "pow(INFINITY, -1) = " << std::pow(INFINITY, -1) << '\n'; // error handling errno = 0; std::feclearexcept(FE_ALL_EXCEPT); std::cout << "pow(-1, 1/3) = " << std::pow(-1, 1.0/3) << '\n'; if(errno == EDOM) std::cout << " errno == EDOM " << std::strerror(errno) << '\n'; if(std::fetestexcept(FE_INVALID)) std::cout << " FE_INVALID raised\n"; std::feclearexcept(FE_ALL_EXCEPT); std::cout << "pow(-0, -3) = " << std::pow(-0.0, -3) << '\n'; if(std::fetestexcept(FE_DIVBYZERO)) std::cout << " FE_DIVBYZERO raised\n"; }
Possible output:
pow(2, 10) = 1024
pow(2, 0.5) = 1.41421
pow(-2, -3) = -0.125
pow(-1, NAN) = nan
pow(+1, NAN) = 1
pow(INFINITY, 2) = inf
pow(INFINITY, -1) = 0
pow(-1, 1/3) = -nan
errno == EDOM Numerical argument out of domain
FE_INVALID raised
pow(-0, -3) = -inf
FE_DIVBYZERO raised[edit] See also
| computes square root (√x) (function) | |
| (C++11) |
computes cubic root (3√x) (function) |
| (C++11) |
computes square root of the sum of the squares of two given numbers (√x2 +y2 ) (function) |
| complex power, one or both arguments may be a complex number (function template) | |
| applies the function std::pow to two valarrays or a valarray and a value (function template) | |
| C documentation for pow
| |