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by chriswarbo 1820 days ago
I have the same feeling after spending a few years with Haskell, StandardML, Agda, Idris, Coq, etc.

One trick I've found very useful is to realise that Maybe (AKA Option) can be though of as "a list with at most one element". Dynamic languages usually have some notion of list/array, which we can use as if it were a Maybe/Option type; e.g. we can follow a 'parse, don't validate' approach by wrapping a "parsed" result in a list, and returning an empty list otherwise. This allows us to use their existing 'map', 'filter', etc. too ;)

(This is explored in more detail, including links to logic programming, in https://link.springer.com/chapter/10.1007%2F3-540-15975-4_33 )

If we want to keep track of useful error messages, I've found Scala's "Try" type to be useful ('Try[T]' is isomorphic to 'Either Throwable T'). Annoyingly, built-in sum type; the closest thing is usually a tagged pair like '[true, myFoo]'/'[false, myException]', which is pretty naff.
2 comments
np_tedious 1820 days ago
> a list with at most one element

I've found scala or even LINQ to really hammer down this point, even to those who aren't into FP very much. Doing that map/flatmap makes it click for just about anyone

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specialist 1820 days ago
Ya, having 'foreach( null )' be a no-op is my #1 language feature request.

Not being a big fan of method chaining, a null saavy foreach would probably eliminate most of my null checks, need for Optional.

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