class specialization for integral types

[Charles Hixson]

On 09/24/2011 02:33 PM, Jonathan M Davis wrote:
> On Saturday, September 24, 2011 14:16:12 Charles Hixson wrote:
>> How would a specialize a parameterized class to only allow integral
>> parameters (i.e., anything that would respond "true" to
>> static if (is (T : long) )
>>
>> (I'd have said "static if (is (T : cent) )" or "static if (is (T :
>> ucent) )", but those are still marked "reserved for future use".)
>>
>> I do want to allow byte, ubyte, etc. to be legal values.
>
> Parameterized? As in templated? Just use a template constraint.
>
> class C(T)
>      if(is(T : long))
> {
> }
>
> T will then be allowed to be anything which is implicitly convertible to long.
> I'd suggest using std.traits.isIntegral instead though.
>
> class C(T)
>      if(isIntegral!T)
> {
> }
>
> It specifically tests for whether the type is a byte, ubyte, short, ushort,
> int, uint, long, or ulong, so it won't included stray structs or classes which
> would be implicitly convertible to long, and if/when eont and ucent come
> along, they'd be added to isIntegral and be automatically supported.
>
> - Jonathan M Davis

Thanks.  isIntegral has given me some error messages that I couldn't 
understand, though, so I'll take your first suggestion.

This is actually a rephrase of the question I first sent, when somehow 
didn't appear on the list:

When checking a template variable, what are the base cases for is?
long will satisfy all integer types.  I.e.
   is (typeof(tst0) : long)  == true
real will satisfy all floating point types.
I think that string will satisfy all arrays of characters (need to check 
that).

But there are lots of other kinds of array.  And while Object will 
satisfy all classes, I don't know anything analogous for structs.  Then 
there's enums (would they be caught by their base type as above, or with 
they be like string and require an immutable corresponding to the base type?

I'd like to create a chunk of code that will handle all possible types 
(for a particular operation) but how to do this isn't obvious.  I can 
handle most common types, but there seem to be LOTS of less frequent types.