Std::sqrt,std::sqrtf,std::sqrtl (3) Linux Manual Page

std::sqrt,std::sqrtf,std::sqrtl – std::sqrt,std::sqrtf,std::sqrtl

Synopsis

Defined in header <cmath>
float sqrt ( float arg );
float sqrtf( float arg ); (since C++11)
double sqrt ( double arg ); (1) (2)
long double sqrt ( long double arg );
long double sqrtl( long double arg ); (3) (since C++11)
double sqrt ( IntegralType arg ); (4) (since C++11)
1-3) Computes the square root of arg.
4) A set of overloads or a function template accepting an argument of any integral_type. Equivalent to 2) (the argument is cast to double).

Parameters

arg – Value of a floating-point or Integral_type

Return value

If no errors occur, square root of arg (
√
arg), is returned.
If a domain error occurs, an implementation-defined value is returned (NaN where supported)
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
Domain error occurs if arg is less than zero.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),

* If the argument is less than -0, FE_INVALID is raised and NaN is returned.
* If the argument is +∞ or ±0, it is returned, unmodified.
* If the argument is NaN, NaN is returned

Notes

std::sqrt is required by the IEEE standard to be exact. The only other operations required to be exact are the arithmetic_operators and the function std::fma. After rounding to the return type (using default rounding mode), the result of std::sqrt is indistinguishable from the infinitely precise result. In other words, the error is less than 0.5 ulp. Other functions, including std::pow, are not so constrained.

Example

// Run this code

#include <iostream>

#include <cmath>

#include <cerrno>

#include <cfenv>

#include <cstring>

#pragma STDC FENV_ACCESS ON

int main()

{
    // normal use
    std::cout << "sqrt(100) = " << std::sqrt(100) << '\n'
              << "sqrt(2) = " << std::sqrt(2) << '\n'
              << "golden ratio = " << (1 + std::sqrt(5)) / 2 << '\n';
    // special values
    std::cout << "sqrt(-0) = " << std::sqrt(-0.0) << '\n';
    // error handling
    errno = 0;
    std::feclearexcept(FE_ALL_EXCEPT);
    std::cout << "sqrt(-1.0) = " << std::sqrt(-1) << '\n';
    if (errno == EDOM)
        std::cout << "    errno = EDOM " << std::strerror(errno) << '\n';
    if (std::fetestexcept(FE_INVALID))
        std::cout << "    FE_INVALID raised\n";
}

Possible output:

  sqrt(100) = 10
  sqrt(2) = 1.41421
  golden ratio = 1.61803
  sqrt(-0) = -0
  sqrt(-1.0) = -nan
      errno = EDOM Numerical argument out of domain
      FE_INVALID raised

std::sqrt,std::sqrtf,std::sqrtl (3) Linux Manual Page