imaginary

 

C

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Variadic function support

Error handling

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Strings library

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Date and time utilities

Input/output support

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Concurrency support (C11)

Technical Specifications

Symbol index

 

Numerics

Common mathematical functions

Floating-point environment (C99)

Pseudo-random number generation

Complex number arithmetic (C99)

Type-generic math (C99)

Bit manipulation (C23)

Checked integer arithmetic (C23)

 

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)
Trigonometric functions
ccos (C99) csin (C99) ctan (C99)	cacos (C99) casin (C99) catan (C99)
Hyperbolic functions
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)

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