[Haskell-cafe] Why Either = Left | Right instead of something like Result = Success | Failure

[Vo Minh Thu]

2010/5/27 Ionut G. Stan <ionut.g.stan at gmail.com>:
> Hi,
>
> I was just wondering if there's any particular reason for which the two
> constructors of the Either data type are named Left and Right. I'm thinking
> that something like Success | Failure or Right | Wrong would have been a
> little better.
>
> I've recently seen that Scala uses a similar convention for some error
> notifications so I'm starting to believe there's more background behind it
> than just an unfortunate naming.

Hi,

Either *can* be used to represent success and failures, but not
necessarily. It is a convention, when using Either to model
success/failure, to use Right for success and Left for failure. Even
if Left as a word does not match with the meaning of failure, it is
easy to get it Right :)

Cheers,
Thu