source/util/math.cpp

   1 /**********************************************************************
   2  * $Id$
   3  *
   4  * GEOS - Geometry Engine Open Source
   5  * http://geos.refractions.net
   6  *
   7  * Copyright (C) 2006 Refractions Research
   8  *
   9  * This is free software; you can redistribute and/or modify it under
  10  * the terms of the GNU Lesser General Public Licence as published
  11  * by the Free Software Foundation.
  12  * See the COPYING file for more information.
  13  *
  14  **********************************************************************/
  15
  16 #include "geos/util.h"
  17 #include <cmath>
  18
  19 namespace geos {
  20 namespace util { // geos.util
  21
  22 /*
  23  * Symmetric Rounding Algorithm  - equivalent to C99 round()
  24  */
  25 double
  26 sym_round(double val)
  27 {
  28         double n;
  29         double f = std::fabs(std::modf(val, &n));
  30         if (val >= 0) {
  31                 if (f < 0.5) {
  32                         return std::floor(val);
  33                 } else if (f > 0.5) {
  34                         return std::ceil(val);
  35                 } else {
  36                         return (n + 1.0);
  37                 }
  38         } else {
  39                 if (f < 0.5) {
  40                         return std::ceil(val);
  41                 } else if (f > 0.5) {
  42                         return std::floor(val);
  43                 } else {
  44                         return (n - 1.0);
  45                 }
  46         }
  47 }
  48
  49 /*
  50  * Asymmetric Rounding Algorithm  - equivalent to Java Math.round()
  51  */
  52 double java_math_round(double val)
  53 {
  54         double n;
  55         double f = std::fabs(std::modf(val, &n));
  56
  57         if (val >= 0)
  58         {
  59                 if (f < 0.5) {
  60                         return std::floor(val);
  61                 } else if (f > 0.5) {
  62                         return std::ceil(val);
  63                 } else {
  64                         return (n + 1.0);
  65                 }
  66         } else {
  67                 if (f < 0.5) {
  68                         return std::ceil(val);
  69                 } else if (f > 0.5) {
  70                         return std::floor(val);
  71                 } else {
  72                         return n;
  73                 }
  74         }
  75 } // java_math_round
  76
  77 /*
  78  * Implementation of rint()
  79  */
  80 double
  81 rint_vc(double val)
  82 {
  83         double n;
  84         double f=std::fabs(std::modf(val,&n));
  85         if (val>=0) {
  86                 if (f<0.5) {
  87                         return std::floor(val);
  88                 } else if (f>0.5) {
  89                         return std::ceil(val);
  90                 } else {
  91                         return(std::floor(n/2)==n/2)?n:n+1.0;
  92                 }
  93         } else {
  94                 if (f<0.5) {
  95                         return std::ceil(val);
  96                 } else if (f>0.5) {
  97                         return std::floor(val);
  98                 } else {
  99                         return(std::floor(n/2)==n/2)?n:n-1.0;
 100                 }
 101         }
 102 }
 103
 104 } // namespace geos.util
 105 } // namespace geos
 106