/* derived from /netlib/fdlibm */ /* @(#)s_scalbn.c 1.3 95/01/18 *//* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunSoft, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice  * is preserved. * ==================================================== */ /*  * scalbn (double x, int n) * scalbn(x,n) returns x* 2**n  computed by  exponent   * manipulation rather than by actually performing an  * exponentiation or a multiplication. */ #include "fdlibm.h" static const doubletwo54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */Huge   = 1.0e+300,tiny   = 1.0e-300; 	double scalbn (double x, int n){	int  k,hx,lx;	hx = __HI(x);	lx = __LO(x);        k = (hx&0x7ff00000)>>20;		/* extract exponent */        if (k==0) {				/* 0 or subnormal x */            if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */	    x *= two54; 	    hx = __HI(x);	    k = ((hx&0x7ff00000)>>20) - 54;             if (n< -50000) return tiny*x; 	/*underflow*/	    }        if (k==0x7ff) return x+x;		/* NaN or Inf */        k = k+n;         if (k >  0x7fe) return Huge*copysign(Huge,x); /* overflow  */        if (k > 0) 				/* normal result */	    {__HI(x) = (hx&0x800fffff)|(k<<20); return x;}        if (k <= -54)            if (n > 50000) 	/* in case integer overflow in n+k */		return Huge*copysign(Huge,x);	/*overflow*/	    else return tiny*copysign(tiny,x); 	/*underflow*/        k += 54;				/* subnormal result */        __HI(x) = (hx&0x800fffff)|(k<<20);        return x*twom54;}