CMPLXF, CMPLX, CMPLXL
From cppreference.com
Defined in header <complex.h>


float complex CMPLXF( float real, float imag ); 
(since C11)  
double complex CMPLX( double real, double imag ); 
(since C11)  
long double complex CMPLXL( long double real, long double imag ); 
(since C11)  
Each of these macros expands to an expression that evaluates to the value of the specified complex type, with the real part having the value of real
(converted to the specified argument type) and the imaginary part having the value of imag
(converted to the specified argument type)
The expressions are suitable for use as initializers for objects with static or thread storage duration, as long as the expressions real
and imag
are also suitable.
Parameters
real    the real part of the complex number to return 
imag    the imaginary part of the complex number to return 
Return value
A complex number composed of real
and imag
as the real and imaginary parts.
Notes
These macros are implemented as if the imaginary types are supported (even if they are otherwise not supported and _Imaginary_I is actually undefined) and as if defined as follows:
#define CMPLX(x, y) ((double complex)((double)(x) + _Imaginary_I * (double)(y))) #define CMPLXF(x, y) ((float complex)((float)(x) + _Imaginary_I * (float)(y))) #define CMPLXL(x, y) ((long double complex)((long double)(x) + \ _Imaginary_I * (long double)(y)))
Example
Run this code
Output:
z = 0.00.0i
References
 C11 standard (ISO/IEC 9899:2011):
 7.3.9.3 The CMPLX macros (p: 197)
See also
(C99) 
the imaginary unit constant i (macro constant) 
C++ documentation for complex
