*	'double' and 'mp_int' types.
 *
 * Copyright (c) 2005 by Kevin B. Kenny. All rights reserved.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclStrToD.c,v 1.4.2.26 2010/03/06 03:40:56 dgp Exp $
 * RCS: @(#) $Id: tclStrToD.c,v 1.4.2.27 2010/04/02 23:48:14 dgp Exp $
 *
 *----------------------------------------------------------------------
 */

#include <tclInt.h>
#include <stdio.h>
#include <stdlib.h>

				 * represented exactly in a 'double'. */
static int log10_DIGIT_MAX;	/* The number of decimal digits that fit in an
				 * mp_digit. */
static int log2FLT_RADIX;	/* Logarithm of the floating point radix. */
static int mantBits;		/* Number of bits in a double's significand */
static mp_int pow5[9];		/* Table of powers of 5**(2**n), up to
				 * 5**256 */
static double tiny;		/* The smallest representable double */
static int maxDigits;		/* The maximum number of digits to the left of
				 * the decimal point of a double. */
static int minDigits;		/* The maximum number of digits to the right
				 * of the decimal point in a double. */
static int mantDIGIT;		/* Number of mp_digit's needed to hold the
				 * significand of a double. */
static const double pow_10_2_n[] = {	/* Inexact higher powers of ten. */

    retval = BignumToBiasedFrExp(significand, &machexp);
    retval = Pow10TimesFrExp(exponent, retval, &machexp);
    if (machexp > DBL_MAX_EXP*log2FLT_RADIX) {
	retval = HUGE_VAL;
	goto returnValue;
    }
    retval = SafeLdExp(retval, machexp);
    if (retval < tiny) {
	retval = tiny;
    if (retval <= 0.0) {
	retval = SafeLdExp(1.0, DBL_MIN_EXP * log2FLT_RADIX - mantBits);
    }

    /*
     * Refine the result twice. (The second refinement should be necessary
     * only if the best approximation is a power of 2 minus 1/2 ulp).
     */

    /*
     * Determine the number of decimal digits to the left and right of the
     * decimal point in the largest and smallest double, the smallest double
     * that differs from zero, and the number of mp_digits needed to represent
     * the significand of a double.
     */

    tiny = SafeLdExp(1.0, DBL_MIN_EXP * log2FLT_RADIX - mantBits);
    maxDigits = (int) ((DBL_MAX_EXP * log((double) FLT_RADIX)
	    + 0.5 * log(10.)) / log(10.));
    minDigits = (int) floor((DBL_MIN_EXP - DBL_MANT_DIG)
	    * log((double) FLT_RADIX) / log(10.));
    mantDIGIT = (mantBits + DIGIT_BIT-1) / DIGIT_BIT;
    log10_DIGIT_MAX = (int) floor(DIGIT_BIT * log(2.) / log(10.));