Templates array detection

[Cube]

On Wednesday, 12 December 2012 at 12:34:34 UTC, bearophile wrote:
> Cube:
>
>> I'm having a problem getting templates to work correctly.
>> I want to handle arrays differently, but when I try to compile 
>> the following example code it says it matches more than 1 
>> template. What is the correct way to do this?
>>
>>
>> --
>> void main()
>> {
>>    foo(1);
>>    foo([1,1]);
>> }
>>
>> void foo(T)(T t)
>> {
>>    writeln(t);
>> }
>>
>> void foo(T)(T[] t)
>> {
>>    for(int i = 0; i < t.length; i++)
>>        writeln(t[i]);
>> }
>> --
>
> In general D templates refuse ambiguity. So to fix your 
> situation you have to state that the T in your first foo 
> overload is not an array:
>
> import std.stdio, std.traits;
>
> void main()
> {
>     foo(1);
>     foo([1, 1]);
> }
>
> void foo(T)(T t) if (!isArray!T)
> {
>     writeln(t);
> }
>
> void foo(T)(T[] t)
> {
>     foreach (ti; t)
>         writeln(ti);
> }
>
>
> Bye,
> bearophile

Hi,

I eventually modified my code to:
--
void main()
{
     foo(1);
     foo([1,1]);
}

void foo(T)(T t)
{
	bar!(T)(t);
}

void bar(T)(T t)
{
     writeln(t+1);
}

void bar(T: T[])(T[] t)
{
     for(int i = 0; i < t.length; i++)
         writeln(t[i]);
}
--
Essentially I added a helper function that added !(T).
What, if any, is the benefit of either approach?


And a similar issue, what if I have a struct:
--
struct Data(T)
{
	int elem = 3;
}

void main()
{
     foo(1);
     foo([1,1]);

     foo(new Data!(int));
     foo(new Data!(float));
}

void foo(T)(T t)
{
	bar!(T)(t);
}

void bar(T)(T t)
{
     writeln(t+1);
}

void bar(T: T[])(T[] t)
{
     for(int i = 0; i < t.length; i++)
         writeln(t[i]);
}
--

And I want to add this to the rest of the program. Where/how can 
I direct the Data's to separate functions?

Thanks :)