isJust/isNothing without instanceof check #88
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| @@ -11,9 +11,15 @@ function _Just(x) { | |||
| } | |||
| util.extend(_Just, Maybe); | |||
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| _Just.prototype.isJust = R.T; | |||
| _Just.prototype.isNothing = R.F; | |||
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Why not the following?
_Just.prototype.isJust = true;
_Just.prototype.isNothing = false;There was a problem hiding this comment.
Would work as well. But I think it's more intuitive when isJust, isNothing, isLeft and isRight are functions.
But I could live with both.
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I think I'd prefer them both to have static properties on their prototypes rather than functions too (apologies for my earlier suggestion in #86 for using R.T/R.F). We still have the functions available on Maybe/Either for people to use where a function is more appropriate.
stoeffel
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I changed |
| @@ -29,11 +35,19 @@ Maybe.of = Maybe.Just; | |||
| Maybe.prototype.of = Maybe.Just; | |||
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| Maybe.isJust = function(x) { | |||
| return x instanceof _Just; | |||
| if (typeof x.isJust !== 'boolean') { | |||
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I think the typeof test is no longer necessary here (or in isNothing) and we can just return x.isJust === true;
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Then we need to change the signature to Maybe.isJust :: Any -> boolean
see #86 your comment:
I wasn't initially going to suggest the use of typeof x.isLeft === 'function', but if Maybe.isJust is to be implemented the same way then it would also change from Any -> Boolean to Maybe a -> Boolean due to its current use of instanceof. I'd prefer Maybe a -> Boolean, but it would be a potentially breaking change.
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We can still keep the types signature to specify that only Maybe instances are accepted. It's just a matter of whether we throw in the implementation if something other than a Maybe instance is given.
If we're to add type checking to functions, we will need to approach it more holistically such as the suggestion in #89.
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convinced. will drop it.
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Would you mind doing the same in the Either PR #86? Then I think we're in a good position for both of them. :)
- throwing an exception if not a Maybe is passed
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Thanks again, @stoeffel 🍄 |
isJust/isNothing without instanceof check
refs #86