COMPLEXD - Functions to manipulate double-precision complex numbers

dcadd	add two dcomplex numbers
dcsub	subtract two dcomplex numbers
dcmul	multiply two dcomplex numbers
dcdiv	divide two dcomplex numbers
dcmplx	make a dcomplex number from two real numbers
dconjg	dcomplex conjugate of a dcomplex number 
dcneg	negate a dcomplex number
dcinv	invert a dcomplex number
dcsqrt	dcomplex square root of a dcomplex number
dcexp	dcomplex exponential of a dcomplex number
dcrmul	multiply a dcomplex number by a real number 
drcabs	real magnitude of a dcomplex number

Structure:
typedef struct _dcomplexStruct {  dcomplex number
	double r,i;
} dcomplex;

Function Prototypes:
dcomplex dcadd (dcomplex a, dcomplex b);
dcomplex dcsub (dcomplex a, dcomplex b);
dcomplex dcmul (dcomplex a, dcomplex b);
dcomplex dcdiv (dcomplex a, dcomplex b);
double drcabs (dcomplex z);
dcomplex dcmplx (double re, double im);
dcomplex dconjg (dcomplex z);
dcomplex dcneg (dcomplex z);
dcomplex dcinv (dcomplex z);
dcomplex dcsqrt (dcomplex z);
dcomplex dcexp (dcomplex z);
dcomplex dcrmul (dcomplex a, double x);

Notes:
The function "drcabs" was originally called "fcabs". This produced
a collision on some systems so a new name was chosen.

Reference:
Adapted from Press et al, 1988, Numerical Recipes in C (Appendix E).

Author:  Dave Hale, Colorado School of Mines, 06/02/89
Modified:  Dave Hale, Colorado School of Mines, 04/26/90
	Added function dcinv().