Static foreach.

[Kirk McDonald]

Walter Bright wrote:
> Nick wrote:
>> Here's a useful example (I think):
>>
>> void rotLeft(X...)()
>> {
>>   typeof(X[0]) tmp = X[0];
>>   foreach(int i, x; X[1..$])
>>     X[i] = x;
>>   X[$-1] = tmp;
>> }
>>
>> void main()
>> {
>>   int a=1, b=2, c=3;
>>   rotLeft!(a,b,c); // Should produce a,b,c = 2,3,1
>> }
>>
>> Compiling gives the error "Integer constant expression expected 
>> instead of i".
>>
>> I'm using this right now, but instead of being generic, the version I 
>> have
>> contains lots statements like
>> ...
>> static if(X.length > 2) X[1] = X[2];
>> static if(X.length > 3) X[2] = X[3];
>> etc.
> 
> Template tuple parameters aren't function parameters that can be 
> modified. You'll need to pass a, b, c as inout parameters to the 
> function, not the template.

Which once again brings up a problem. This doesn't work:

void func(T ...)(inout T t) {
     // ...
}

Similarly, this doesn't work:

void func(T ...)(T t) {
     foreach(inout arg; t) {
         // do something with args
     }
     // call with modified args
     other_func(t);
}

That idiom would be /so useful/.

-- 
Kirk McDonald
Pyd: Wrapping Python with D
http://pyd.dsource.org