Compile-time calculation

Compile-time calculation is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Some programming languages allow to calculate values at compile time. For this task, calculate 10! at compile time. Print the result when the program is run.

Discuss what limitations apply to compile-time calculations in your language.

Warnings:

• This task is a draft, you can modify it if you find a way to enhance it.

C++

<lang cpp>#include <iostream>

template<int i> struct Fac {

   static const int result = i * Fac<i-1>::result;

};

template<> struct Fac<1> {

   static const int result = 1;

};

int main(int argc, char* argv[]) {

   std::cout << "10! = " << Fac<10>::result << "\n";

}</lang>

Compile-time calculations in C++ look quite different from normal code. We can only use templates, type definitions and a subset of integer arithmetic. It is not possible to use iteration. C++ compile-time programs are similar to programs in pure functional programming languages, albeit with a peculiar syntax.

Oz

<lang oz>functor import

  System Application

prepare

  fun {Fac N}
     {FoldL {List.number 1 N 1} Number.'*' 1}
  end
  Fac10 = {Fac 10}

define

  {System.showInfo "10! = "#Fac10}
  {Application.exit 0}

end</lang>

Code in the prepare section of a functor is executed at compile time. External modules that are used in this code must be imported with a require statement (not shown in this example). Such external functors must have been compiled before the current functor is compiled (ozmake will automatically take care of this).

It is possible to export variables that are defined in the prepare statement. However, such variables must not be stateful entities, e.g. it is not possible to export a cell that was defined at compile time.