rnd_generators.h

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/* -*- mode: c++; c-indent-level: 4; c++-member-init-indent: 8; comment-column: 35; -*-

  -----------------------------------------------------------------------------
  rnd_generators.h
    Some utility functors for generating random generators:
        uniform_generator : generates uniform floats or doubles
        random_generator  : generates unsigneds, ints etc.
        normal_generator  : normally distributed floats or doubles

 (c) Maarten Keijzer ([e-mail]) and GeNeura Team, 1999, 2000

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library 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
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    Contact: [e-mail], http://geneura.ugr.es
 */

//-----------------------------------------------------------------------------

#ifndef eoRND_GENERATORS_H
#define eoRND_GENERATORS_H

#include "eoRNG.h"
#include <stdexcept>

/**
   The class uniform_generator can be used in the STL generate function
   to easily generate random floats and doubles
   either in [0, _max) if only 1 value (_max) is given
                       (or none, as _max defaults to 1.0)
   or in [_min,_max) if 2 values are given (_min, _max)
*/
template <class T = double> class uniform_generator
{
  // added new ctor with 2 params, and modified the data to minim and range
  // (was maxim only). MS 3/11/2000
  public :
    uniform_generator(T _max = T(1.0), eoRng& _rng = rng) :
      minim(T(0.0)), range(_max), uniform(_rng) {}
    uniform_generator(T _min, T _max, eoRng& _rng = rng) :
      minim(_min), range(_max-_min), uniform(_rng)
  {
    if (_min>_max)
      throw std::logic_error("Min is greater than Max in uniform_generator");
  }

  T operator()(void) { return minim+static_cast<T>(uniform.uniform(range)); }

private :
  T minim;
  T range;
  eoRng& uniform;
};

/**
   The class boolean_generator can be used in the STL generate function
   to easily generate random booleans with a specified bias
*/
class boolean_generator
{
  public :
    boolean_generator(float _bias = 0.5, eoRng& _rng = rng) : bias(_bias), gen(_rng) {}

  bool operator()(void) { return gen.flip(bias); }
  private :
  float bias;
  eoRng& gen;
};

/**
   The class random_generator can be used in the STL generate function
   to easily generate random ints
   either between [0, _max) if only one value (_max) is given to the ctor
   or in [_min,_max) if 2 values are given (_min, _max)
*/
template <class T = uint32_t> class random_generator
{
  public :
  // added new ctor with 2 params, and modified the data to minim and range
  // (was maxim only). MS 3/11/2000
    random_generator(T _max, eoRng& _rng = rng) :
      minim(T(0.0)), range(_max), random(_rng) {}
    random_generator(T _min, T _max, eoRng& _rng = rng) :
      minim(_min), range(_max-_min), random(_rng)
  {
    if (_min>_max)
      throw std::logic_error("Min is greater than Max in random_generator");
  }

  T operator()(void) { return (T) (minim + random.random(range)); }

private :
  T minim;
  T range;
  eoRng& random;
};

/// Specialization for bool
template <>
inline bool random_generator<bool>::operator()(void)
{
    return random.flip(0.5);
}

/**
   Another class random_generator that can be used in the STL random_shuffle
   function (see eoPop::shuffle): its operator() takes an unsigned argument m
   and  must return an unsigned uniformly distributed in [0,m}
*/
template <class T = uint32_t> class UF_random_generator
{
  public :
    UF_random_generator(eoRng& _rng = rng) :
      random(_rng) {}

  T operator()(T _t) { return (T) (random.random(_t)); }

private :
  eoRng& random;
};


/**
   The class normal_generator can be used in the STL generate function
   to easily generate gaussian distributed floats and doubles. The user
   can supply a standard deviation which defaults to 1.
*/
template <class T = double> class normal_generator
{
  public :
    normal_generator(T _stdev = T(1.0), eoRng& _rng = rng) : stdev(_stdev), normal(_rng) {}

  T operator()(void) { return (T) normal.normal(stdev); }

  private :
    T stdev;
  eoRng& normal;
};

/**
   The class negexp_generator can be used in the STL generate function
   to easily generate negative exponential distributed floats and doubles. The user
   can supply a mean.
*/
template <class T = double> class negexp_generator
{
  public :
    negexp_generator(T _mean = 1.0, eoRng& _rng = rng) : mean(_mean), negexp(_rng) {}

  T operator()(void) { return (T) negexp.negexp(mean); }

  private :
    T mean;
  eoRng& negexp;
};

#endif