_Complex_I
From cppreference.com
The
_Complex_I macro expands to a value of type const float _Complex with the value of the imaginary unit.
[edit] Notes
This macro may be used when I is not available, such as when it has been undefined by the application.
Unlike _Imaginary_I and CMPLX, use of this macro to construct a complex number may lose the sign of zero on the imaginary component.
[edit] Example
Run this code
#include <stdio.h> #include <complex.h> #undef I #define J _Complex_I // can be used to redefine I int main(void) { // can be used to construct a complex number double complex z = 1.0 + 2.0 * _Complex_I; printf("1.0 + 2.0 * _Complex_I = %.1f%+.1fi\n", creal(z), cimag(z)); // sign of zero may not be preserved double complex z2 = 0.0 + -0.0 * _Complex_I; printf("0.0 + -0.0 * _Complex_I = %.1f%+.1fi\n", creal(z2), cimag(z2)); }
Possible output:
1.0 + 2.0 * _Complex_I = 1.0+2.0i 0.0 + -0.0 * _Complex_I = 0.0+0.0i