NAME¶

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 (\({\small \sqrt{arg} }\)
√
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

See also¶

pow
powf raises a number to the given power (\(\small{x^y}\)x^y)
powl (function)
(C++11)
(C++11)
cbrt computes cubic root (\(\small{\sqrt[3]{x} }\)
cbrtf 3
cbrtl √
(C++11) x)
(C++11) (function)
(C++11)
computes square root of the sum of the squares of two or three
(C++17) given numbers (\(\scriptsize{\sqrt{x^2+y^2} }\)
√
hypot x2
hypotf +y2
hypotl ), (\(\scriptsize{\sqrt{x^2+y^2+z^2} }\)
(C++11) √
(C++11) x2
(C++11) +y2
+z2
)
(function)
sqrt(std::complex) complex square root in the range of the right half-plane
(function template)
sqrt(std::valarray) applies the function std::sqrt to each element of valarray
(function template)