DCMPLX — Double complex conversion function ¶DCMPLX(X [,Y]) returns a double complex number where X is
converted to the real component.  If Y is present it is converted to the
imaginary component.  If Y is not present then the imaginary component is
set to 0.0.  If X is complex then Y must not be present.
GNU extension
Elemental function
RESULT = DCMPLX(X [, Y])
| X | The type may be INTEGER,REAL,
orCOMPLEX. | 
| Y | (Optional if X is not COMPLEX.) May beINTEGERorREAL. | 
The return value is of type COMPLEX(8)
program test_dcmplx
    integer :: i = 42
    real :: x = 3.14
    complex :: z
    z = cmplx(i, x)
    print *, dcmplx(i)
    print *, dcmplx(x)
    print *, dcmplx(z)
    print *, dcmplx(x,i)
end program test_dcmplx