[Issue 9065] Please consider adding these std.traits

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http://d.puremagic.com/issues/show_bug.cgi?id=9065



--- Comment #7 from Manu <turkeyman at gmail.com> 2012-11-24 14:35:53 PST ---
(In reply to comment #6)
> is(T == function) actually tests whether T is the type of a function, not
> whether it's a function pointer. This stackoverflow question discusses the
> differences between is(T == function), isFunctionPointer!T, isDelegate!T, and
> isSomeFunction!T:
> 
> http://stackoverflow.com/questions/11067972/functions-versus-function-pointers-whats-the-difference

Looking at that link, what's with all the typeof(bar) stuff? Do those tempaltes
not work by alias? Surely I should be able to say isSomeFunction!bar, not
requiring isSomeFunction!(typeof(bar)) ?

Using typeof() like that makes generic code harder, because 'bar' could be
anything, and if it doesn't have a typeof, then it is a different compile error
and I have to produce even more logic prior to eliminate that case. Surely that
could be encapsulated?

> A related issue is issue# 4427
> 
> We may want to add more of these to std.traits, but we should probably think
> carefully about exactly what we should add, especially because is expressions
> do most (all?) of it already, and often fairly cleanly. It's just that they're
> complicated enough in general and not understood well enough, that many people
> don't have a clue what they can do. It still may be worth adding stuff like
> isVariable to std.traits though.

In my experience, code to the effect of isVariable is actually rather
non-trivial. It would be very useful. Ideally, written by someone who knows
what they're doing ;) (I clearly don't)

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