On 08/14/2013 12:42 AM, Daniel Trstenjak wrote:
On Tue, Aug 13, 2013 at 06:57:22PM -0400, Edward A Kmett wrote:
I look forward to finding out the new name for MaybeT then. ;) That's a bit unfair, because the Maybe data type has a clear meaning which also holds for its Monad instance.
What is the distinction? For me, `Maybe` is as language-neutral as `Either`. It simply augments a value with an additional state with no connotation of error handling. If you were really trying to be consistent, you would rename `MaybeT` to `FailableT` and remove the `Monad` instance from `Maybe`.
That's not the case for Either. The Either data type doesn't propose a special meaning to the 'Left' or 'Right' case, but the Monad instance of Either does.
No, it does not have a special meaning. Bot the `Either` and `Maybe` monads are also used for short-circuiting. See here: http://www.haskellforall.com/2012/07/breaking-from-loop.html This isn't hypothetical: I do this all the time in my programming. By your logic, I should remove the `Monad` instance for `Maybe` because it's unclear in my code whether I'm using it in its capacity for error handling or for general-purpose short-circuiting.