DGtal  0.9.4.1
Functions
approximation.cpp File Reference
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <iomanip>
#include "DGtal/arithmetic/LighterSternBrocot.h"
#include "DGtal/base/StdRebinders.h"
Include dependency graph for approximation.cpp:

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Functions

void usage (int, char **argv)
 
int main (int argc, char **argv)
 

Detailed Description

Author
Jacques-Olivier Lachaud (jacqu.nosp@m.es-o.nosp@m.livie.nosp@m.r.la.nosp@m.chaud.nosp@m.@uni.nosp@m.v-sav.nosp@m.oie..nosp@m.fr ) Laboratory of Mathematics (CNRS, UMR 5127), University of Savoie, France
Date
2012/02/06

An example file named approximation.

This file is part of the DGtal library.

Definition in file approximation.cpp.

Function Documentation

◆ main()

int main ( int  argc,
char **  argv 
)

Main.

[approximation-types]

[approximation-types]

[approximation-process]

[approximation-process]

Definition at line 73 of file approximation.cpp.

References DGtal::NumberTraits< T >::castToInt64_t(), and usage().

74 {
75  if ( argc < 2 )
76  {
77  usage( argc, argv );
78  return 1;
79  }
80 
82  typedef DGtal::int64_t Integer;
83  typedef DGtal::int64_t Quotient;
84  typedef LighterSternBrocot<Integer, Quotient, StdMapRebinder> SB; // the type of the Stern-Brocot tree
85  typedef SB::Fraction Fraction; // the type for fractions
86  typedef std::back_insert_iterator< Fraction > OutputIterator;
88 
90  long double epsilon = 1e-14;
91  long double number0 = strtold( argv[ 1 ], 0 );
92  long double number = number0;
93  ASSERT( number >= 0.0 );
94  Fraction f;
95  OutputIterator itback = std::back_inserter( f );
96  Quotient i = 0;
97  while ( true )
98  {
99  long double int_part = floorl( number );
100  Quotient u = NumberTraits<long double>::castToInt64_t( int_part );
101  *itback++ = std::make_pair( u, i++ );
102  long double approx =
103  ( (long double) NumberTraits<Integer>::castToDouble( f.p() ) )
104  / ( (long double) NumberTraits<Integer>::castToDouble( f.q() ) );
105  std::cout << "z = " << f.p() << " / " << f.q()
106  << " =~ " << std::setprecision( 16 ) << approx << std::endl;
107  number -= int_part;
108  if ( ( (number0 - epsilon ) < approx )
109  && ( approx < (number0 + epsilon ) ) ) break;
110  number = 1.0 / number;
111  }
112  std::cout << "z = " << f.p() << " / " << f.q() << std::endl;
114  return 0;
115 }
DGtal::int32_t Integer
Definition: StdDefs.h:74
void usage(int, char **argv)
Aim: The traits class for all models of Cinteger.
Definition: NumberTraits.h:69
Aim: The Stern-Brocot tree is the tree of irreducible fractions. This class allows to construct it pr...
boost::int64_t int64_t
signed 94-bit integer.
Definition: BasicTypes.h:74

◆ usage()

void usage ( int  ,
char **  argv 
)