imaginary

 

C

Language

headers

Type support

Dynamic memory management

Error handling

Program utilities

Variadic function support

Date and time utilities

Strings library

Algorithms

Numerics

Input/output support

Localization support

Thread support (C11)

Atomic operations (C11)

Technical Specifications

 

Numerics

Common mathematical functions

Floating-point environment

Complex number arithmetics

Random number generation

Type-generic math

 

Complex number arithmetic

Types and the imaginary constant
complex _Complex_I CMPLX	imaginary _Imaginary_I I
Manipulation
cimag creal carg	cabs 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 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

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

• 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 (macro constant)