9.10 Random Number Generator Example

FILENAME: example9.cpp

#include <rw/math/funcobj.h>
#include <rw/histo.h>      
#include <rw/rstream.h>
#include <rw/rand.h>
#include "myrand.h"


//**********************************************************

// Class MyRand demonstrates how to convert a function into a 
// function object, which can then be used as the template
// parameter to the random number generator classes in Math.h++.
// The function motherRNG is George Marsaglia's "Mother of all
// Random Number Generators" and is defined in mrng.cpp.
//**********************************************************

class MyRand
{
public:
  // RandFtn is a typedef for a pointer to a 
  // function that takes an unsigned long* and returns a double:
  typedef double (*RandFtn)( unsigned long * );

  // Function call operator returns the random number 
  // by calling the function:
  double operator()() { return (*randFunction_)(&randInt_); }

  // Default constructor:
  MyRand(unsigned long seed = 123455):randFunction_(motherRNG),
                                      randInt_(seed) {;}

private:
  unsigned long randInt_;
  RandFtn randFunction_;
};

int main()
{
// Create a binomial random number generator 
// using the class MyRand to generate the 
// underlying uniform (0,1) deviates:
  RWTRandBinomial<MyRand> randBino( 23 );

// Create a thousand random numbers and store them in a vector. 
  RWMathVec<double> randomNumbers( 1000, rwUninitialized );

RWMathVec<double>::iterator first = randomNumbers.begin();
RWMathVec<double>::iterator last = randomNumbers.end();

while (first != last)
  *first++ = randBino();

// Put the random numbers in a histogram and print them.
  Histogram h( 10U, randomNumbers );
  cout << h << endl;

  return 0;
}

Sample Input:

None required.

Sample Output:

HISTOGRAM:

Total number of Counts  =        1000
Total number of bins    =          10
Number of larger values =           0
Number of smaller values =          0

 Bin number    -- Bin boundaries --    Counts

       0          2         3.2          54
       1          3.2       4.4          89
       2          4.4       5.6         123
       3          5.6       6.8         163
       4          6.8       8           368
       5          8         9.2          97
       6          9.2      10.4          53
       7         10.4      11.6          35
       8         11.6      12.8          10
       9         12.8      14             8