Monads compared to InputRanges?

[Max Klyga]

On Wednesday, 4 December 2013 at 08:24:03 UTC, qznc wrote:
> On Wednesday, 4 December 2013 at 01:53:39 UTC, Shammah 
> Chancellor wrote:
>> Or is D syntax not generic enough to define monads?
>
> I started to port monads to D [0]. You can do it, but it looks 
> ugly. The trick is to implement (Haskell) type classes via 
> template specialization. I came to the conclusion that it is 
> not worth it.
>
> What D kind of lacks is a way to define a general type class 
> aka the interface. Of course, you could use the "interface" 
> keyword, but then you cannot apply it to structs. Haskell has 
> no structs (value type records), so they do not have this 
> problem. Look at how isInputRange is implemented [1]. The 
> traits in Rust [2] provide this interface mechanisms as a 
> language feature. D uses static-if instead.

D uses static if and template constraints for typeclass/concept 
checking because one cannot add specializations to templates 
defined in other modules. Using template specialization for 
defining type class instances would render them not extensible 
for users