You can determine whether a type is a class:
is (T : Object)

There's no equivalent for interfaces. You can use the compiles trait:
__traits(compiles, class Something : T {})
Except you can't -- it only takes expressions, not declarations.

There are traits for abstract classes (interfaces aren't) and final classes; how about something for interfaces? Or should I just start using abstract classes instead?

Christopher Wright wrote:
> You can determine whether a type is a class:
> is (T : Object)
> 
> There's no equivalent for interfaces. You can use the compiles trait:
> __traits(compiles, class Something : T {})
> Except you can't -- it only takes expressions, not declarations.
> 
> There are traits for abstract classes (interfaces aren't) and final classes; how about something for interfaces? Or should I just start using abstract classes instead?

Doesn't this work?  It's legal syntax, so I suppose it does what you want.

is(foo == interface)

Christopher Wright wrote:
> You can determine whether a type is a class:
> is (T : Object)
> 
> There's no equivalent for interfaces. You can use the compiles trait:
> __traits(compiles, class Something : T {})
> Except you can't -- it only takes expressions, not declarations.
> 
> There are traits for abstract classes (interfaces aren't) and final classes; how about something for interfaces? Or should I just start using abstract classes instead?

Have you tried is( T == interface ) ?

	-- Daniel

Daniel Keep wrote:
> 
> Christopher Wright wrote:
>> You can determine whether a type is a class:
>> is (T : Object)
>>
>> There's no equivalent for interfaces. You can use the compiles trait:
>> __traits(compiles, class Something : T {})
>> Except you can't -- it only takes expressions, not declarations.
>>
>> There are traits for abstract classes (interfaces aren't) and final
>> classes; how about something for interfaces? Or should I just start
>> using abstract classes instead?
> 
> Have you tried is( T == interface ) ?
> 
> 	-- Daniel

No, I haven't. `interface` isn't a type, so it didn't occur to me to try that. Thank you, and thank torhu.

Reply to Christopher,

> Daniel Keep wrote:
> 
>> Christopher Wright wrote:
>> 
>>> You can determine whether a type is a class:
>>> is (T : Object)
>>> There's no equivalent for interfaces. You can use the compiles
>>> trait:
>>> __traits(compiles, class Something : T {})
>>> Except you can't -- it only takes expressions, not declarations.
>>> There are traits for abstract classes (interfaces aren't) and final
>>> classes; how about something for interfaces? Or should I just start
>>> using abstract classes instead?
>>> 
>> Have you tried is( T == interface ) ?
>> 
>> -- Daniel
>> 
> No, I haven't. `interface` isn't a type, so it didn't occur to me to
> try that. Thank you, and thank torhu.
> 

the full list of things you can do is at:

http://www.digitalmars.com/d/1.0/expression.html#IsExpression