Computes the square root of the complex numberz with a branch cut along the negative real axis.

[edit]Parameters

[edit]Return value

If no errors occur, returns the square root ofz, in the range of the right half-plane, including the imaginary axis ([0; +∞) along the real axis and(−∞; +∞) along the imaginary axis).

[edit]Error handling and special values

Errors are reported consistent withmath_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))
• Ifz is(±0,+0), the result is(+0,+0)
• Ifz is(x,+∞), the result is(+∞,+∞) even if x is NaN
• Ifz is(x,NaN), the result is(NaN,NaN) (unless x is ±∞) andFE_INVALID may be raised
• Ifz is(-∞,y), the result is(+0,+∞) for finite positive y
• Ifz is(+∞,y), the result is(+∞,+0) for finite positive y
• Ifz is(-∞,NaN), the result is(NaN,∞) (sign of imaginary part unspecified)
• Ifz is(+∞,NaN), the result is(+∞,NaN)
• Ifz is(NaN,y), the result is(NaN,NaN) andFE_INVALID may be raised
• Ifz is(NaN,NaN), the result is(NaN,NaN)

[edit]Notes

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

[edit]Example

#include <complex>#include <iostream> int main(){std::cout<<"Square root of -4 is "<<std::sqrt(std::complex<double>(-4.0,0.0))<<'\n'<<"Square root of (-4,-0) is "<<std::sqrt(std::complex<double>(-4.0,-0.0))<<" (the other side of the cut)\n";}

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

[edit]Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit]See also

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