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Fraction.cpp

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00001 /*
00002     Copyright (c) 2005, Quentin Lequy and Romain Gaucher
00003     All rights reserved.
00004 
00005     Redistribution and use in source and binary forms, with or 
00006     without modification, are permitted provided that the following 
00007     conditions are met:
00008 
00009         * Redistributions of source code must retain the above copyright 
00010           notice, this list of conditions and the following disclaimer.
00011 
00012         * Redistributions in binary form must reproduce the above copyright 
00013           notice, this list of conditions and the following disclaimer in the 
00014           documentation and/or other materials provided with the distribution.
00015 
00016         * Neither the name of Quentin Lequy or Romain Gaucher nor the names 
00017           of its contributors may be used to endorse or promote products 
00018           derived from this software without specific prior written permission.
00019 
00020     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
00021     AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
00022     IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
00023     ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
00024     LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 
00025     DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
00026     SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 
00027     AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
00028     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 
00029     SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00030 */
00031 
00032 #include "Fraction.h"
00033 #include <map>
00034 #include <iostream>
00035 
00036 namespace Modelib {
00037 
00038 using namespace std;
00039 
00044 FractionConvert::FractionConvert(unsigned _n)
00045 {
00046  map<float,Fraction> tmp;
00047  map<float,Fraction>::iterator trouve;
00048  for(unsigned i = 0; i <_n; ++i)
00049  {
00050    for(unsigned j = 0; j <i; ++j)
00051    {
00052     trouve = tmp.find(float(j)/float(i));
00053     if( trouve == tmp.end() )
00054       tmp[float(j)/float(i)] = Fraction(j,i);
00055     else if( trouve->second.num > i )
00056       trouve->second = Fraction(j,i);
00057    }
00058  }
00059  nfrac = tmp.size();
00060  frac = new Fraction[nfrac];
00061  reel = new float[nfrac];
00062 
00063  unsigned i =0;  
00064  for(trouve = tmp.begin(); trouve != tmp.end(); ++trouve)
00065  {
00066    reel[i] = trouve->first;
00067    frac[i] = trouve->second;
00068    ++i;
00069  }
00070 }
00071 
00075 FractionConvert::~FractionConvert()
00076 {
00077   delete [] frac;
00078   delete [] reel; 
00079 }
00080 
00081 
00090 bool FractionConvert::Approx(float nb, int & num, unsigned  & den) const
00091 {
00092    unsigned a = 0,b=nfrac-1;
00093    if(nb==0.0)
00094    {
00095        num = 0;
00096        den = 1;
00097        return false;
00098    }
00099 
00100    while(a<b)
00101    {
00102      unsigned mil = (a+b)/2;
00103      if(reel[mil] < nb)
00104         a = mil + 1;
00105      else
00106         b = mil;
00107    }
00108    if(a < nfrac)
00109    {
00110      if( reel[a]-nb >= nb - reel[a-1] )
00111        a--;
00112      num = frac[a].num;
00113      den = frac[a].den;
00114      return true;
00115    }
00116    else
00117      return false;
00118 }
00119 
00120 }

Généré le Sun Oct 2 19:13:12 2005 pour Modelib par  doxygen 1.4.4