std::pow, std::powf, std::powl

Parameters

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.

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 exp is a negative odd integer, returns +∞ and raises FE_DIVBYZERO
• pow(-0, exp), where exp is a negative odd integer, returns -∞ and raises FE_DIVBYZERO
• pow(±0, exp), where exp is 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 exp is a positive odd integer, returns +0
• pow(-0, exp), where exp is a positive odd integer, returns -0
• pow(±0, exp), where exp is positive non-integer or a positive even integer, returns +0
• pow(-1, ±∞) returns 1
• pow(+1, exp) returns 1 for any exp, even when exp is NaN
• pow(base, ±0) returns 1 for any base, even when base is NaN
• pow(base, exp) returns NaN and raises FE_INVALID if base is finite and negative and exp is 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 exp is a negative odd integer
• pow(-∞, exp) returns +0 if exp is a negative non-integer or even integer
• pow(-∞, exp) returns -∞ if exp is a positive odd integer
• pow(-∞, exp) returns +∞ if exp is 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

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

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";
}

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

See also