maybe: change type of S.Nothing from ‘-> Maybe a’ to ‘Maybe a’ #225
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| }; | ||
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| //# Maybe.empty :: -> Maybe a | ||
| //. | ||
| //. Returns a Nothing. | ||
| //. Returns Nothing. |
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I ❤️ getting to remove “a” here: conceptually there's a single Nothing value.
davidchambers
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LGTM. |
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Initially,
S.Nothingexisted both to create theNothingvalue and to supportR.is(S.Nothing).S.Nothingis no longer a constructor function, and we now haveS.isNothingto answer the question of whether a given value of typeMaybe aisNothing. This meansS.Nothingcan now be theNothingvalue, improving Haskell correspondence:S.Nothing()S.Just(42)S.NothingS.Just(42)NothingJust 42Can anyone think of a problem with this change?
This evening I realized for the first time that “nothing” is comprised of “no” and “thing”. I now think Haskell should have gone with
data Maybe a = Thing a | Nothing. ;)