template specialization for arrays

[Timon Gehr]

On 10/29/2011 11:32 PM, Timon Gehr wrote:
> On 10/29/2011 05:24 PM, J Arrizza wrote:
>> I have a template that I'd like to have a specialization for arrays.
>> Initiall I need it to work for byte arrays, but I'd like to make it
>> eventually work for all arrays. The page
>> http://d-programming-language.org/template says to use
>>
>> template TFoo(T : T[]) { ... } // #2
>>
>>
>> but when I try it, it doesn't quite work:
>>
>> template abc(T)
>> {
>> void abc(T parm1)
>> {
>> writeln("simpleparm: ", parm1);
>> }
>> }
>>
>> template abc(T: T[])
>> {
>> void abc(T parm1)
>> {
>> writeln("array : ", parm1);
>> }
>> }
>>
>>
>> void main(string[] args)
>> {
>> abc(1);
>> abc("str");
>> int[] arr = [1, 2];
>> abc(arr);
>> }
>>
>>
>> The output is:
>>
>> simpleparm: 1
>> simpleparm: str
>> simpleparm: [1, 2]
>>
>>
>> Which is not what I want, it needs to be the specialized template for
>> arrays. Note, this doesn't work either:
>>
>> template abc(T: T[])
>> {
>> void abc(T[] parm1)
>> {
>> writeln("array : ", parm1);
>> }
>> }
>>
>>
>> John
>
> Fixed:
>
> template abc(T) {
> void abc(T parm1) {
> writeln("simpleparm: ", parm1);
> }
> }
>
> void abc(T:T[])(T[] parm1) {
> writeln("array : ", parm1);
> }
>
>
> void main(string[] args) {
> abc(1);
> abc!(typeof("str"))("str");
> int[] arr = [1, 2];
> abc!(int[])(arr);
> }
>
>
> The important thing to note is that when pattern matching on T[] is
> done, then T is the element type of the array, not the array type.
>
>

When using pattern matching, explicit template arguments are necessary. 
You probably don't want that, the following code does not need them:

void abc(T)(T parm1) if(!isDynamicArray!T)
{
     writeln("simpleparm: ", parm1);
}

void abc(T)(T parm1) if(isDynamicArray!T){
     writeln("array : ", parm1);
}


void main(string[] args)
{
     abc(1);
     abc("str");
     int[] arr = [1, 2];
     abc(arr);
}