template parameters

[BCS]

Hello Ellery,

> BCS wrote:
> 
>> Hello Ellery,
>> 
>>> Hello.
>>> 
>>> Today I was looking at the grammar for template value parameters and
>>> realized I didn't know what the conditional expression is for in
>>> 
>>> TemplateValueParameter => BasicType Declarator :
>>> ConditionalExpression
>>> 
>>> So what does it do?
>>> 
>>> (I assume = ConditionalExpression is the default value for the
>>> parameter)
>>> 
>> That is correct. it would seem that expression should be used, but
>> that includes an assignment expression so the next things down is
>> used.
>> 
>> http://www.digitalmars.com/d/1.0/expression.html#AssignExpression
>> 
> Okay, let me rephrase that:
> 
> When you have a <something> preceded by a colon in a template value
> parameter, what are its semantics? Is it the same as a default
> parameter value? Is it some sort of constraining expression? Is it a
> vestige?
>
 
You should check me on this but I think it's explicit instantiation: "This 
is the special case for when given some value".