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(C++) Template metaprogram

Technique to perform programs during compiling

There is no semantic difference between class and typename in a template-parameter [0] .

Example: calculate the factorial of an ( unsigned) integer during compile-time

#include <iostream>

template <unsigned int N>

struct Factorial

{

static unsigned int const value = N * Factorial<N-1>::value;

};

template <>

struct Factorial<0>

{

static unsigned int const value = 1;

};

int main()

{

std::cout

<< Factorial<0>::value << '\n'

<< Factorial<1>::value << '\n'

<< Factorial<2>::value << '\n'

<< Factorial<3>::value << '\n'

<< Factorial<4>::value << '\n'

<< Factorial<5>::value << '\n'

<< Factorial<6>::value << '\n'

<< Factorial<7>::value << '\n'

<< Factorial<8>::value << '\n'

<< Factorial<9>::value << '\n'

<< Factorial<10>::value << '\n'

<< Factorial<11>::value << '\n'

<< Factorial<12>::value << '\n';

}

Note that before the program starts to run, all factorials are already calculated.

References