Boost generic programming

From:
Hans Mull <deyringer@googlemail.com>
Newsgroups:
comp.lang.c++
Date:
Fri, 08 Feb 2008 14:42:59 +0100
Message-ID:
<fohm94$dns$1@online.de>
Hi!
I'm working on a random number generator which makes use of
Boost::random. I have to write a function that gets 2 int-parameters
from the GUI. One is a number that indicates which algorithm to use and
the other shows which distribution we have to use. Boost uses templates
so I cannot use polymorphism (Or is there a way to use polymorphism even
if the classes aren't derivated from a base class?). I tried to use a
template function, but I don't know the types when I call the fuction
(xxParam are static variables):

template<class boostEngine, class boostDistribution>
void GenRandBoost()
{
    ///Cache parameters
    ulong amount = amountParam;
    ulong ulSeed = seedParam;
    string filename = filenameParam;
    double ulDouble = ulDoubleParam;
    double llDouble = llDoubleParam;
    int distributionSelection = distributionSelectionParam;
    int algorithmSelection = algorithmSelectionParam;
    ulong bits = bitsParam;

    ///Initialize template pointers
    boostEngine *algorithm;
    boostDistribution *distribution;

    ///Open fstream
    fstream f(filename.c_str(), fstream::out);
    //Initialize counter
    ulong i;

    ///Switch distribution
    switch(algorithmSelection)
        {
            case 0: ///MT 19937
                {
                    mt19937 mersenne(ulSeed);
                    algorithm = &mersenne;
                    break;
                }
            case 1: ///Linear congruential
                {
                    minstd_rand0 linCongr(ulSeed);
                    algorithm = &linCongr;
                    break;
                }
            case 2: ///Additive combine
                {
                    ecuyer1988 addComb(ulSeed);
                    algorithm = &addComb;
                    break;
                }
            case 3: ///Inverse congruential
                {
                    hellekalek1995 invCongr(ulSeed);
                    algorithm = &invCongr;
                    break;
                }
            case 4: ///Shuffle output
                {
                    kreutzer1986 shOut(ulSeed);
                    algorithm = &shOut;
                    break;
                }
// case 5: ///Lagged Fibonacci
// {
// lagged_fibonacci lagFib(ulSeed);
// algorithm = &lagFib;
// break;
// }
            default: break;
        }
    ///Switch distribution
    switch(distributionSelection)
        {
            case 0: ///Uniform small int
                {
                    uniform_smallint<double> smallInt(llDouble, ulDouble);
                    distribution = &smallInt;
                }
            case 1: ///Uniform integer
                {
                    uniform_int<double> uniInt(llDouble, ulDouble);
                    distribution = &uniInt;
                }
            case 2: ///Uniform 01
                {
                    //uniform_01<double, double> uni01(llDouble, ulDouble);
                    //distribution = &uni01;
                }
            case 3: ///Uniform real
                {
                    uniform_real<double> uniReal(llDouble, ulDouble);
                    distribution = &uniReal;

                }
            case 4: ///Triangle
                {
                    triangle_distribution<double> triangle(llDouble,
ulDouble);
                    distribution = &triangle;
                }
            case 5: ///Bernoulli
                {
                    bernoulli_distribution<double> bernoulli(llDouble,
ulDouble);
                    distribution = &bernoulli;
                }
            case 6: ///Cauchy
                {
                    cauchy_distribution<double> cauchy(llDouble, ulDouble);
                    distribution = &cauchy;
                }
            case 7: ///Exponential
                {
                    exponential_distribution<double>
exponential(llDouble, ulDouble);
                    distribution = &exponential;
                }
            case 8: ///Geometric
                {
                    geometric_distribution<double> geometric(llDouble,
ulDouble);
                    distribution = &geometric;
                }
            case 9: ///Normal
                {
                    normal_distribution<double> normal(llDouble, ulDouble);
                    distribution = &normal;
                }
            case 10: ///Lognormal
                {
                    lognormal_distribution<double> lognormal(llDouble,
ulDouble);
                    distribution = &lognormal;
                }
            case 11: ///Uniform on Sphere
                {
                    uniform_on_sphere<double> uniSphere(llDouble, ulDouble);
                    distribution = &uniSphere;
                }
            default: {break;}
        }
        ///Variate Generator
        variate_generator<boostEngine, boostDistribution>
generator(algorithm, distribution);
        ///TODO: Main loop
        for(;i < amount;i++)
        {
            f << generator() << endl;
        }
}

I don't want to have a distributionSelection switch in each
algorithmSelection case statement.

Do you have any ideas?

Thanks in advance, Hans

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