Complex_I

 

C

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Numerics

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Complex number arithmetic

Types and the imaginary constant
complex Complex_I CMPLX	imaginary Imaginary_I I
Manipulation
cimag creal carg	conj cproj
Power and exponential functions
cexp clog	cpow csqrt
Trigonometric functions
ccos csin ctan	cacos casin catan
Hyperbolic functions
ccosh csinh ctanh	cacosh casinh catanh

 

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.

Example

Run this code

#include <stdio.h>
#include <complex.h>
 
int main(void)
{
    #ifdef __STDC_NO_COMPLEX__
            printf("__STDC_NO_COMPLEX__ is defined.\n");
    #else
        printf("__STDC_NO_COMPLEX__ is undefined.\n");
    #endif
 
    #ifdef __STDC_IEC_559_COMPLEX__
        printf("__STDC_IEC_559_COMPLEX__ is defined.\n");
    #else
        printf("__STDC_IEC_559_COMPLEX__ is undefined.\n");
    #endif
 
    printf("_Complex_I = %.1f%+.1fi\n", creal(_Complex_I), cimag(_Complex_I));
    printf("sizeof(_Complex_I) = %zu\n", sizeof(_Complex_I));
 
    double complex z = 1.0 + 2.0*_Complex_I;
    printf("z = %.1f%+.1fi\n", creal(z), cimag(z));
 
    return 0;
}

Output:

__STDC_NO_COMPLEX__ is undefined.
__STDC_IEC_559_COMPLEX__ is defined.
_Complex_I = 0.0+1.0i
sizeof(_Complex_I) = 8
z = 1.0+2.0i

See also

Imaginary_I (C99)	the imaginary unit constant i (macro constant)
I (C99)	the complex or imaginary unit constant i (macro constant)