random.hxx

// random.hxx: this file is part of the Vaucanson project.
//
// Vaucanson, a generic library for finite state machines.
//
// Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006 The Vaucanson Group.
//
// 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.
//
// The complete GNU General Public Licence Notice can be found as the
// `COPYING' file in the root directory.
//
// The Vaucanson Group consists of people listed in the `AUTHORS' file.
//
#ifndef VCSN_MISC_RANDOM_HXX
# define VCSN_MISC_RANDOM_HXX

# include <vaucanson/misc/random.hh>
# include <vaucanson/misc/limits.hh>

# include <cmath>
# include <cstdlib>
# include <vector>

namespace vcsn {
  namespace misc {
    namespace random {

      template<>
      inline char generate<char> ()
      {
        // We do not want any 0, because it could generate errors in strings.
        return char (1 + unsigned (rand ()) % ( (1 << (sizeof (char) * 8)) - 1));
      }

      template<>
      inline char generate<char> (char min, char max)
      {
        unsigned range = unsigned (max - min) + 1;
        return char (min + rand () % range);
      }

      inline char generate_letter ()
      {
        return generate<char> ('a', 'z');
      }

      inline char generate_digit ()
      {
        return generate<char> ('0', '9');
      }

      template<>
      inline bool generate<bool> ()
      {
        return static_cast<bool> (rand () & 1);
      }

      template<>
      inline int generate<int> ()
      {
        int res = rand () % vcsn::misc::limits<int>::max ();
        return generate<bool> () ? res : res * -1;
      }

      template<>
      inline int generate<int> (int min, int max)
      {
        unsigned range = unsigned (max - min) + 1;
        return min + rand () % range;
      }

      template<>
      inline unsigned generate<unsigned> ()
      {
        return rand () % vcsn::misc::limits<unsigned>::max ();
      }

      template<>
      inline unsigned generate<unsigned> (unsigned min, unsigned max)
      {
        unsigned range = unsigned (max - min) + 1;
        return min + rand () % range;
      }

      template<>
      inline float generate<float> ()
      {
        // This formula comes from the caml stdlib. It generates numbers
        // between -2 and 2 (values that can be starable or not).
        return ( ((static_cast<float> (rand ()) / RAND_MAX +
                   static_cast<float> (rand ())) / RAND_MAX +
                  static_cast<float> (rand ())) / RAND_MAX) * 4 - 2;
      }

      template<>
      inline float generate<float> (float min, float max)
      {
        float range = float (max - min);
        float generate_one = ( (static_cast<float> (rand ()) / RAND_MAX +
                                static_cast<float> (rand ())) / RAND_MAX +
                               static_cast<float> (rand ())) / RAND_MAX;

        return min + generate_one * range;
      }

      template<>
      inline double generate<double> ()
      {
        // This formula comes from the caml stdlib. It generates numbers
        // between -2 and 2 (values that can be starable or not).
        return ( ((static_cast<double> (rand ()) / RAND_MAX +
                   static_cast<double> (rand ())) / RAND_MAX +
                  static_cast<double> (rand ())) / RAND_MAX) * 4 - 2;
      }

      template<>
      inline double generate<double> (double min, double max)
      {
        double range = double (max - min);
        double generate_one = ( (static_cast<double> (rand ()) / RAND_MAX +
                                 static_cast<double> (rand ())) / RAND_MAX +
                                static_cast<double> (rand ())) / RAND_MAX;

        return min + generate_one * range;
      }

      template <class Iterator, class OutputIterator>
      void sample_n (Iterator first, Iterator end,
                     OutputIterator out, unsigned n)
      {
        std::vector<int> from;
        for (Iterator i = first; i != end; ++i)
          from.push_back (*i);

        while ( (from.size () > 0) && (n > 0))
        {
          int  c = generate<int> (0, from.size () - 1);
          *out = from[c];
          ++out;
          from.erase (from.begin () + c);
          --n;
        }
      }

      template<>
      inline
      vcsn::algebra::RationalNumber
      generate<vcsn::algebra::RationalNumber> ()
      {
        const int num = generate<int> ();
        const unsigned denom =
          generate<unsigned> (1, vcsn::misc::limits<unsigned>::max ());
        return vcsn::algebra::RationalNumber (num, denom);
      }

      template<>
      inline
      vcsn::algebra::RationalNumber
      generate<vcsn::algebra::RationalNumber>
      (const vcsn::algebra::RationalNumber min,
       const vcsn::algebra::RationalNumber max)
      {
        const int denom = vcsn::algebra::lcm (min.denom (), max.denom ());
        const int num1 = min.num ()*denom/min.denom ();
        const int num2 = max.num ()*denom/max.denom ();
        const int maxi = std::max (std::max (abs (num1), abs (num2)),denom);
        const int ratio = (vcsn::misc::limits<int>::max ()-1)/maxi;
        return
          vcsn::algebra::RationalNumber (generate<int> (num1*ratio, num2*ratio),
                                         denom * ratio);
      }

      template <>
      inline
      std::pair<char, int> generate<std::pair<char, int> > ()
      {
        return std::make_pair (generate<char> (), generate<int> ());
      }

      template <>
      inline
      small_alpha_letter_t
      generate<small_alpha_letter_t> ()
      {
        return generate<char> (small_alpha_interval_t::from_value,
                               small_alpha_interval_t::to_value);
      }

    } // Random
  } // misc
} // vcsn

#endif // ! VCSN_MISC_RANDOM_HXX

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