imaginary

 

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Complex number arithmetic

Types and the imaginary constant
complex (C99) _Complex_I (C99)     CMPLX (C11)	imaginary (C99) _Imaginary_I (C99) I (C99)
Manipulation
cimag (C99) creal (C99) carg (C99)	cabs (C99) conj (C99) cproj (C99)
Power and exponential functions
cexp (C99) clog (C99)	cpow (C99) csqrt (C99)
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ccos (C99) csin (C99) ctan (C99)	cacos (C99) casin (C99) catan (C99)
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ccosh (C99) csinh (C99) ctanh (C99)	cacosh (C99) casinh (C99) catanh (C99)

 

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.

To date, only Oracle C compiler is known to have implemented imaginary types.

Example

Run this code

#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)

See also

complex (C99)

complex type macro (keyword macro)