crealf, creal, creall

From cppreference.com

Defined in header `<complex.h>`
float crealf ( float complex z ) ;	(1)	(since C99)
double creal ( double complex z ) ;	(2)	(since C99)
long double creall ( long double complex z ) ;	(3)	(since C99)
Defined in header `<tgmath.h>`
#define creal( z )	(4)	(since C99)

1-3) Returns the real part of

4) Type-generic macro: if

has type long double complex , long double imaginary , or long double ,


        creall

is called. If

has type float complex , float imaginary , or float ,


        crealf

is called. If

has type double complex , double imaginary , double , or any integer type,


        creal

is called.

complex argument

The real part of z .

This function is fully specified for all possible inputs and is not subject to any errors described in math_errhandling

For any complex variable z , z == creal ( z ) + I * cimag ( z ) .

Run this code

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

Output:

1.000000+2.000000i

Common mathematical functions
Floating-point environment (C99)
Pseudo-random number generation
Complex number arithmetic (C99)
Type-generic math (C99)

cimag cimagf cimagl (C99) (C99) (C99)	computes the imaginary part a complex number (function)
C++ documentation for real