Left-Right also good for representing binary trees. 2010/5/27 C. McCann <c...@uptoisomorphism.net>
> On Thu, May 27, 2010 at 10:25 AM, Ionut G. Stan <ionut.g.s...@gmail.com> > wrote: > > 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. > > Because that would confuse matters when using the type for something > other than representing success or failure. > > Either is a generic sum type. That is, "Either A B" only means "either > you have an A, or you have a B". Use of Left to represent failure is > merely a matter of convention. Similarly, the generic product type in > Haskell is the 2-tuple--"(A, B)" only means "you have both an A and a > B". > > Left and Right work well because they don't carry much extra semantic > baggage, and they make it easy to remember which type parameter goes > with which constructor. Other than the mnemonic value, something even > more bland like This and That would work as well. > > Personally, I advocate instead using "Sinister" and "Dexter". Nice and > catchy, don't you think? > > - C. > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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