/* Copyright (C) 1996 by Thomas Glen Smith.  All Rights Reserved. */
/* powerpx APL2 V1.0.0  ************************************************
* Called from powerp when *left is negative, and the denominator of the*
* fraction representing *rite (the exponent) is even.  The result can  *
* be expressed by ((|*left)**rite)X-1**rite.                           *
***********************************************************************/
#define INCLUDES MATH
#include "includes.h"
#define ABS(v) ((v) > 0e0 ? (v) : -(v))
void powerpx(left,rite,pret,ret,num,den)
double	*left, /* Real number to be taken to the power in *rite. */
		*rite, /* Exponent, or power, to which *left is taken. */
		*pret, /* Place to store the answer. */
		*ret;  /* *ret == (|*left)**rite, *(ret+1) == 0e0. */
double num,den; /* Numerator and denominator of exponent. */
{
	Timesx;
	extern double fuzz;
	double angle,wrka[2],wrkb[2];

	for (;;) { /* Lets me use break. */
		if (fmod(num,2.0) < fuzz) break; /* Num. even, -1**rite == 1. */
		num = 1e0; /* Numerator might as well be 1. */
		den /= 2e0; /* Make it for (-1*.5)*1%den. */
		angle = PI / 2 * den;
		*wrka = cos(angle);
		*(wrka+1) = sin(angle);
		*wrkb = *ret;
		*(wrkb+1) = *(ret+1);
		timesx(wrka,wrkb,ret);
		break; /* Final break from for(;;) */
	}
	*pret = *ret;
	*(pret+1) = *(ret+1);
}