NAME¶

std::sqrt,std::sqrtf,std::sqrtl - std::sqrt,std::sqrtf,std::sqrtl

Synopsis¶

Defined in header <cmath>
float sqrt ( float num );

double sqrt ( double num ); (until C++23)

long double sqrt ( long double num );
/* floating-point-type */ (since C++23)
sqrt ( /* floating-point-type */ num ); (constexpr since C++26)
float sqrtf( float num ); (1) (2) (since C++11)
(constexpr since C++26)
long double sqrtl( long double num ); (3) (since C++11)
(constexpr since C++26)
Additional overloads (since C++11)
Defined in header <cmath>
template< class Integer > (A) (constexpr since C++26)
double sqrt ( Integer num );

1-3) Computes the square root of num.
The library provides overloads of std::sqrt for all cv-unqualified floating-point
types as the type of the parameter.
(since C++23)

A) Additional overloads are provided for all integer types, which are (since C++11)
treated as double.

Parameters¶

num - floating-point or integer value

Return value¶

If no errors occur, square root of num (\({\small \sqrt{num} }\)
√
num), 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 num 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 correctly rounded from the
infinitely precise result. In particular, the exact result is produced if it can be
represented in the floating-point type. The only other operations which require this
are the arithmetic operators and the function std::fma. Other functions, including
std::pow, are not so constrained.

The additional overloads are not required to be provided exactly as (A). They only
need to be sufficient to ensure that for their argument num of integer type,
std::sqrt(num) has the same effect as std::sqrt(static_cast<double>(num)).

Example¶

// Run this code

#include <cerrno>
#include <cfenv>
#include <cmath>
#include <cstring>
#include <iostream>
// #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 cube 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
(since C++17) given numbers (\(\scriptsize{\sqrt{x^2+y^2}}\)
√
hypot x2
hypotf +y2
hypotl )
(C++11) , (\(\scriptsize{\sqrt{x^2+y^2+z^2}}\)
(C++11) √
(C++11) x2
+y2
+z2
)
(since C++17)
(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)
C documentation for
sqrt