src/nmath/d1mach.c

/*
 *  Mathlib - A Mathematical Function Library
 *  Copyright (C) 1998  Ross Ihaka
 *  Copyright (C) 2000-2014 The R Core Team
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, a copy is available at
 *  https://www.R-project.org/Licenses/
 */

/* NaNs propagated correctly */


/*-- FIXME:  Eliminate calls to these
 *   =====   o   from C code when
 *	     o   it is only used to initialize "static" variables (threading)
 *  and use the DBL_... constants instead
 */

#include "nmath.h"

attribute_hidden double Rf_d1mach(int i)
{
    switch(i) {
    case 1: return DBL_MIN;
    case 2: return DBL_MAX;

    case 3: /* = FLT_RADIX  ^ - DBL_MANT_DIG
	      for IEEE:  = 2^-53 = 1.110223e-16 = .5*DBL_EPSILON */
	return 0.5*DBL_EPSILON;

    case 4: /* = FLT_RADIX  ^ (1- DBL_MANT_DIG) =
	      for IEEE:  = 2^-52 = DBL_EPSILON */
	return DBL_EPSILON;

    case 5: return M_LOG10_2;

    default: return 0.0;
    }
}

#ifdef __cplusplus
extern "C" 
#endif

double F77_NAME(d1mach)(int *i)
{
    return Rf_d1mach(*i);
}