Hi Johannes,
I thought there was some "more important" reason than convenience, so I asked. :-O)
I put String because I'm currently thinking about error handling, and Left
String is the usual way of reporting failure, and I see Maybe as a type for
reporting errors, failures and similar.
Somehow it looks to me that famous "8 ways to report errors in Haskell" could be
shortened by one if Maybe is replaced with Either (with appropriate synonyms, of
course).
vlatko
-------- Original Message --------
Subject: Re: [Haskell-cafe] Why Maybe exists if there is Either?
From: Johannes Erber
Hi Vlatko,
to keep programs clear, short and simple. What makes you choose String as type to replace Nothing?
Best, Johannes
On 09/01/2014 14:50, Vlatko Basic wrote:
Hello Cafe,
With my current knowledge of Haskell, I do not see why is there Maybe if we have Either.
For example, Functor and Monad instances (and many others) of Maybe and Either are the same (except for fail).
In other words, this should hold:
Maybe a = Either String a -- String or something else Nothing = Left "" Just a = Right a
I'm curious to find out what was the reasoning to make Maybe? What is the added value with introducing it? In which situations the above substitution does not hold?
Best regards,
vlatko
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe