Monads in D

[deadalnix via Digitalmars-d]

On Saturday, 11 June 2016 at 14:26:20 UTC, Atila Neves wrote:
> I give you a facsimile of a Haskell do block:
>
>     with(Maybe!int) {
>         return_(5).bind!(a => return_(a + 
> 1)).shouldEqual(just(6));
>         nothing.bind!(a => return_(a + 1)).shouldEqual(nothing);
>         return_(8).bind!(a => nothing).bind!(a => return_(a + 
> 1)).shouldEqual(nothing);
>     }
>
>     with(Maybe!string) {
>         return_("foo").bind!(a => return_(a ~ 
> "bar")).shouldEqual(just("foobar"));
>         nothing.bind!(a => return_(a ~ 
> "bar")).shouldEqual(nothing);
>         return_("foo").bind!(a => return_(a ~ "bar")).bind!(a 
> => nothing).shouldEqual(nothing);
>     }
>
>
> Why? Because I could, I don't plan on using this for anything 
> serious. I think "with" is my favourite D feature right now. I 
> also wrote the Writer and State monads (not that D needs them):
>
> https://github.com/atilaneves/felix
>
> I tried overloading `>>>` for bind (closest overloadable 
> operator to `>>=`) but it went horribly wrong. I always get 
> problems when I try to pass lambdas as runtime values instead 
> of template parameters.
>
>
> Atila

Honestly, the whole bind/return is just a giant NIH. >>> and >>= 
are its symptoms. There is a reason why nobody understands jack 
shit about monad even after 10s of tutorial when they aren't even 
hard in any way: because haskell and alike have made all that is 
in their power to obfuscate what is a monad.

I could go on, but this guy already did it way better that I can:
https://www.infoq.com/presentations/functional-pros-cons

The part about monad starts 25mins in.