Compile time function execution...

[Ary Manzana]

Walter Bright escribió:
> ... is now in DMD 1.006. For example:
> 
>> -------------------------------------------
>> import std.stdio;
>>
>> real sqrt(real x)
>> {
>>    real root = x / 2;
>>    for (int ntries = 0; ntries < 5; ntries++)
>>    {
>>        if (root * root - x == 0)
>>            break;
>>        root = (root + x / root) / 2;
>>    }
>>    return root;
>> }
>>
>> void main()
>> {
>>    static x = sqrt(10);   // woo-hoo! set to 3.16228 at compile time!
>>    writefln("%s, %s", x, sqrt(10));  // this sqrt(10) runs at run time
>> }
>> ------------------------------------------
> 
> This should obsolete using templates to compute values at compile time.

This is really great, Walter! Congratulations!

I'm always thinking that D is focused on great runtime performance while 
having great expresiveness, which is awsome. I can't believe computers 
have evolved that much... and still we have to wait 10 o 20 seconds for 
a program to load :-(

A question: is there anyway the compiler can tell the user if a certain 
function can be executed at compile time? Those six rules may be hard to 
memorize and while coding sensitive code it would be great to ask the 
compiler "Is the function I'm writing can be executed at compile time?". 
Otherwise it's just a guess.