static code generation

[js.mdnq]

On Sunday, 16 December 2012 at 15:34:34 UTC, Philippe Sigaud 
wrote:
>> One could also think of it as an algebra of structs.
>>
>> It would be nice to be able to do stuff like
>>
>> A + B, A - B(possibly useless), A*B(possibly useless), etc...
>>
>> A + B would just combine the members, A - B could remove the 
>> members that
>> overlap, A*B could qualify overlapping members.
>>
>
> Usually, given types A and B, A+B means `A or B` (in D,
> std.typecons.Algebraic!(A,B) ) and A*B means the tuple 
> containing A and B
> (in D, std.typecons.Tuple!(A,B) ).
>
>
> What you're trying to do is doable in D, but you'd have to 
> define it a bit
> more:
>
> if we have
>
> struct A { int a; int b}
> struct B { int b; int a} // just a and b swapped.
>
> What is `A+B`? `A-B`?



(Thanks for the typeof(this) works great!)


Yes, A+B = A or B. Or is inclusive though.. and "overlap" and 
order is immaterial.

So `A+B` is equivalent to

struct ApB { int a; int b; }

Since order ultimately matters(the layout of the struct in 
memory) we could define

`B+A` =
struct BpA { int b; int a; }

`A-B` = `B-A` = (only in this case)
struct AmB { } = struct BmA { }


So A*B = std.typecons.Algebraic!(A,B) which is what I initially 
said * should be. That should take care of that operation. How do 
you do the other ops?