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imaginary

Defined in header `<complex.h>`
#define imaginary _Imaginary		(since C99)

This macro expands to the keyword _Imaginary.

This is a convenience macro that makes it possible to use float imaginary, double imaginary, and long double imaginary as an alternative way to write the three pure imaginary C types float _Imaginary, double _Imaginary, and long double _Imaginary.

As with any pure imaginary number support in C, this macro is only defined if the imaginary numbers are supported.

A compiler that defines `__STDC_IEC_559_COMPLEX__` is not required to support imaginary numbers. POSIX recommends checking if the macro `_Imaginary_I` is defined to identify imaginary number support.	(since C99) (until C11)
Imaginary numbers are supported if `__STDC_IEC_559_COMPLEX__` is defined.	(since C11)

Notes

Programs are allowed to undefine and perhaps redefine the imaginary macro.

Example

#include <stdio.h>
#include <complex.h>
 
int main(void)
{
    double imaginary i = -2.0*I; // pure imaginary
    double f = 1.0; // pure real
    double complex z = f + i; // complex number
    printf("z = %.1f%+.1fi\n", creal(z), cimag(z));
}

Output:

z = 1.0-2.0i

References

C17 standard (ISO/IEC 9899:2018):

7.3.1/5 imaginary (p: 136)
G.6/1 imaginary (p: 391-392)

C11 standard (ISO/IEC 9899:2011):

7.3.1/5 imaginary (p: 188)
G.6/1 imaginary (p: 537)

C99 standard (ISO/IEC 9899:1999):

7.3.1/3 imaginary (p: 170)
G.6/1 imaginary (p: 472)

imaginary

Notes

Example

References

See also