/*Translated by FOR_C, v3.4.2 (-), on 07/09/115 at 08:30:06 */
/*FOR_C Options SET: ftn=u io=c no=p op=aimnv s=dbov str=l x=f - prototypes */
#include <math.h>
#include "fcrt.h"
#include "drotg.h"
#include <stdlib.h>
void /*FUNCTION*/ drotg(
double *a,
double *b,
double *c,
double *s)
{
	double r, u, v;
 
	/* Copyright (c) 1996 California Institute of Technology, Pasadena, CA.
	 * ALL RIGHTS RESERVED.
	 * Based on Government Sponsored Research NAS7-03001.
	 *>> 1994-10-20 DROTG  Krogh  Changes to use M77CON
	 *>> 1994-04-19 DROTG  Krogh   Changed to use generic intrinsics.
	 *>> 1985-08-02 DROTG  Lawson  Initial code.
	 *--D replaces "?": ?ROTG, ?ROT
	 *
	 *     DESIGNED BY C.L.LAWSON, JPL, 1977 SEPT 08
	 *
	 *
	 *     CONSTRUCT THE GIVENS TRANSFORMATION
	 *
	 *         ( C  S )
	 *     G = (      ) ,    C**2 + S**2 = 1 ,
	 *         (-S  C )
	 *
	 *     WHICH ZEROS THE SECOND ENTRY OF THE 2-VECTOR  (A,B)**T .
	 *
	 *     THE QUANTITY R = (+/-)SQRT(A**2 + B**2) OVERWRITES A IN
	 *     STORAGE.  THE VALUE OF B IS OVERWRITTEN BY A VALUE Z WHICH
	 *     ALLOWS C AND S TO BE RECOVERED BY THE FOLLOWING ALGORITHM:
	 *           IF Z=1  SET  C=0.D0  AND  S=1.D0
	 *           IF ABS(Z) .LT. 1  SET  C=SQRT(1-Z**2)  AND  S=Z
	 *           IF ABS(Z) .GT. 1  SET  C=1/Z  AND  S=SQRT(1-C**2)
	 *
	 *     NORMALLY, THE SUBPROGRAM DROT(N,X,INCX,Y,INCY,C,S) WILL
	 *     NEXT BE CALLED TO APPLY THE TRANSFORMATION TO A 2 BY N MATRIX.
	 *
	 * ------------------------------------------------------------------
	 * */
	if (fabs( *a ) <= fabs( *b ))
		goto L_10;
 
	/* *** HERE ABS(A) .GT. ABS(B) ***
	 * */
	u = *a + *a;
	v = *b/u;
 
	/*     NOTE THAT U AND R HAVE THE SIGN OF A
	 * */
	r = sqrt( .25e0 + SQ(v) )*u;
 
	/*     NOTE THAT C IS POSITIVE
	 * */
	*c = *a/r;
	*s = v*(*c + *c);
	*b = *s;
	*a = r;
	return;
 
	/* *** HERE ABS(A) .LE. ABS(B) ***
	 * */
L_10:
	if (*b == 0.e0)
		goto L_20;
	u = *b + *b;
	v = *a/u;
 
	/*     NOTE THAT U AND R HAVE THE SIGN OF B
	 *     (R IS IMMEDIATELY STORED IN A)
	 * */
	*a = sqrt( .25e0 + SQ(v) )*u;
 
	/*     NOTE THAT S IS POSITIVE
	 * */
	*s = *b/ *a;
	*c = v*(*s + *s);
	if (*c == 0.e0)
		goto L_15;
	*b = 1.e0/ *c;
	return;
L_15:
	*b = 1.e0;
	return;
 
	/* *** HERE A = B = 0.D0 ***
	 * */
L_20:
	*c = 1.e0;
	*s = 0.e0;
	return;
 
} /* end of function */