🚀 go-pugleaf

gcato@st6000.sct.edu (Vaughn Cato) wrote:
>I am curious as to the reasoning behind disallowing the use of a template
>name as a synonym for a template id with no template parameters:
>
>template <class T = int> class A;
>
>void f()
>{
>  A<> *p1; // The legal way to default the argument
>  A *p2;   // Syntax error
>}

If the latter was allowed, it would be ambiguous if a non-templated class A 
existed.

If we allowed it anyway and just told the compiler to complain about 
ambiguities, then the above code would break the moment an unrelated class A 
visible to this function was created... bad side effect.

>This parallels with
>the function call syntax, which requires ()'s to be used even when no
>actual parameters are passed.

Exactly, for similar reasons: it would be odd if your code suddenly broke 
(became ambiguous and uncompilable) if someone added a variable that happened 
to have the same name as a function you're using... without (), it wouldn't be 
possible to differentiate the two.


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