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table of contents

std::sqrt(std::complex)(3) | C++ Standard Libary | std::sqrt(std::complex)(3) |

# NAME¶

std::sqrt(std::complex) - std::sqrt(std::complex)

# Synopsis¶

Defined in header <complex>

template< class T >

complex<T> sqrt( const complex<T>& z );

Computes the square root of the complex number z with a branch cut along the

negative real axis.

# Parameters¶

z - complex number to take the square root of

# Return value¶

If no errors occur, returns the square root of z, in the range of
the right

half-plane, including the imaginary axis ([0; +∞) along the real axis
and (−∞;

+∞) along the imaginary axis.)

Error handling and special values

Errors are reported consistent with math_errhandling

If the implementation supports IEEE floating-point arithmetic,

* The function is continuous onto the branch cut taking into account the sign
of

imaginary part

* std::sqrt(std::conj(z)) == std::conj(std::sqrt(z))

* If z is (±0,+0), the result is (+0,+0)

* If z is (x,+∞), the result is (+∞,+∞) even if x is NaN

* If z is (x,NaN), the result is (NaN,NaN) (unless x is ±∞) and
FE_INVALID may

be raised

* If z is (-∞,y), the result is (+0,+∞) for finite positive y

* If z is (+∞,y), the result is (+∞,+0) for finite positive y

* If z is (-∞,NaN), the result is (NaN,∞) (sign of imaginary
part unspecified)

* If z is (+∞,NaN), the result is (+∞,NaN)

* If z is (NaN,y), the result is (NaN,NaN) and FE_INVALID may be raised

* If z is (NaN,NaN), the result is (NaN,NaN)

# Notes¶

The semantics of this function are intended to be consistent with
the C function

csqrt.

# Example¶

// Run this code

#include <iostream>

#include <complex>

int main()

{

std::cout << "Square root of -4 is "

<< std::sqrt(std::complex<double>(-4, 0)) << '\n'

<< "Square root of (-4,-0), the other side of the cut, is "

<< std::sqrt(std::complex<double>(-4, -0.0)) << '\n';

}

# Output:¶

Square root of -4 is (0,2)

Square root of (-4,-0), the other side of the cut, is (0,-2)

Defect reports

The following behavior-changing defect reports were applied retroactively to

previously published C++ standards.

DR Applied to Behavior as published Correct behavior

LWG 2597 C++98 specification mishandles signed zero erroneous requirement

imaginary parts removed

# See also¶

pow(std::complex) complex power, one or both arguments may be a
complex number

*(function template)*

sqrt computes square root (\(\small{\sqrt{x} }\)

sqrtf √

sqrtl x)

*(C++11)* *(function)*

*(C++11)*

sqrt(std::valarray) applies the function std::sqrt to each element of
valarray

*(function template)*

2022.07.31 | http://cppreference.com |