Namespaces
Variants
Views
Actions

_Complex_I

From cppreference.com
< c‎ | numeric‎ | complex
Defined in header <complex.h>
#define _Complex_I /* unspecified */
(since C99)

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

#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

[edit] See also

the imaginary unit constant i
(macro constant) [edit]
(C99)
the complex or imaginary unit constant i
(macro constant) [edit]