Compile-time function execution: Difference between revisions

Revision as of 21:22, 27 September 2008

Revision as of 06:39, 22 March 2009

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This example code is in the [[D programming language]]:

<source lang="D">

int square(int x)

{

return x * x;

}

const int y = square(3); // y is set to 9 at compile time

</source>

===Example 2===

Line 18 ⟶ 20:

In [[C++]], [[template metaprogramming]] is often used to compute values at compile time, such as:

<source lang="CPP">

<pre>

template <int N>

struct Factorial

Line 38 ⟶ 40:

int y = Factorial<0>::value; // == 1

}

</presource>

With compile time function evaluation, the code used to generate the factorial would be exactly the same as what one would write for run time evaluation (example is in D):

<source lang="D">

<pre>

int factorial(int n)

{

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static const int y = factorial(0); // == 0! == 1

}

</presource>

The use of static const tells the compiler that the initializer for the variables must be computed at compile time.