csqrtf, csqrt, csqrtl

Parameters

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
• csqrt ( conj ( z ) ) == conj ( csqrt ( z ) )
• If z is ±0+0i , the result is +0+0i
• If z is x+∞i , the result is +∞+∞i even if x is NaN
• If z is x+NaNi , the result is NaN+NaNi (unless x is ±∞) and FE_INVALID may be raised
• If z is -∞+yi , the result is +0+∞i for finite positive y
• If z is +∞+yi , the result is +∞+0i) for finite positive y
• If z is -∞+NaNi , the result is NaN±∞i (sign of imaginary part unspecified)
• If z is +∞+NaNi , the result is +∞+NaNi
• If z is NaN+yi , the result is NaN+NaNi and FE_INVALID may be raised
• If z is NaN+NaNi , the result is NaN+NaNi

Example

#include <stdio.h>
#include <complex.h>
 
int main(void)
{
    double complex z1 = csqrt(-4);
    printf("Square root of -4 is %.1f%+.1fi\n", creal(z1), cimag(z1));
 
    double complex z2 = csqrt(conj(-4)); // or, in C11, CMPLX(-4, -0.0)
    printf("Square root of -4-0i, the other side of the cut, is "
           "%.1f%+.1fi\n", creal(z2), cimag(z2));
}

Square root of -4 is 0.0+2.0i
Square root of -4-0i, the other side of the cut, is 0.0-2.0i

References