Monad.unit method purpose

[ValentinTrinque]

Hi,

I was studying the library API and ends up on Monad.unit method.

I have some thought about the purpose of this method but I am not sure.

Can you enlighten me?

Thanks.

[cbowdon]

It wraps a value in the monad. It's there for completeness more than anything else, since the static constructors are more useful.

[ValentinTrinque]

I had a look to the of function in fantasy land, but I have to say that it's fairly obscure to me. Then I also had a look to issues dealing with it, but it still looks obscure; whence my question.

What's I don't understand is, why isn't it a static function ? What did I miss ?

[cbowdon]

IIRC my reasoning was this: it could work as a static function, but all things considered it was slightly better to have it as an instance method (compatible with Fantasy Land) and use the more readable static constructors.

If it was static, you unfortunately wouldn't get the ad-hoc polymorphism of Haskell. It would still be necessary to explicitly say which monad's unit implementation you wanted, e.g. Maybe<T>.unit(1234) rather than simply being able to say unit(1234) and let the type system figure it out. So if you have to be explicit, you might as well say Maybe.just(1234) as it's slightly more readable.

[ValentinTrinque]

Ok, I got it. Thanks a lot.