Chain two different struct specialization

[Era Scarecrow]

On Friday, 1 March 2013 at 14:32:12 UTC, Andrea Fontana wrote:
>> struct MyStruct(WEIGHTS)
>> {
>>   string ...
>>   string ...
>>
>>   alias WEIGHTS weights;
>> }
>>

>> enum FirstWeights : double
>> {
>>
>> }
>
> enum SecondWeights : double
> {
>     double foo = 0.3,
>     double bar = 0.4
> }
>
> so:
> auto s1 = MyStruct!FirstWeights ...
> auto s2 = MyStruct!SecondWeights ...

  With templates there's a few different ways you can consider 
handling it; I'm not recommending any of them but. Keeping it 
simple, clean & easy to read is probably the best solution; 
Although most of these won't help with any algorithms that need 
them to be identical (unless cast or they are not templates).

  1) If structs are the same size: You can forcibly cast it so one 
will work with the other, however enums (or anything related 
that's static or not stored with the struct) doesn't transfer 
over and is lost.

  I've tried this in my experimental polymorphic struct; Where the 
methods differed slightly but data the structure is guaranteed to 
be identical.

  2) Conversion/Accessing differences: You can include a flag 
specifying it's of a certain type or qualification, this can let 
them interact if they are basically the same thing with something 
minor under the hood different but that doesn't matter (or will 
get in the way); Although unqual (or related in std.traits) might 
be a better option for it, not sure myself.

   struct MyStruct(WEIGHTS) {
     enum isMyStruct = true;
   }

   void test(T1, T2)(T1 lhs, T2 rhs)
     if (hasMember!(T1, "isMyStruct") && hasMember!(T2, 
"isMyStruct")) {}

  3) non-Template: As mentioned you can avoid templates & 
different enums and instead use variables as appropriate.

  I'm sure there's other ideas but I'm drawing a blank right now...