Compile time function execution...

[Bill Baxter]

Walter Bright wrote:
> ... 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.

Any chance that concatenation onto a variable will be supported?

I'd like to write this:

char[] NReps(char[] x, int n)
{
     char[] ret = "";
     for(int i=0; i<n; i++) { ret ~= x; }
     return ret;
}

But that doesn't work.  The recursive version does, though:

char[]  NReps2(char[] x, int n, char[] acc="")
{
     if (n<=0) return acc;
     return NReps2(x, n-1, acc~x);
}

--bb