implement linked-list exercise #372
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Hi @voila, and thanks for your PR on this one, too.
The reason I haven't responded is that I am torn on it:
In a pure functional language, a doubly-linked list is not that interesting. The idea of a doubly linked list is to be able to grab a node and go in either direction, or to be able to splice into the middle of a list. In a pure functionaly language you probably are better off with one of these two data structures:
A singly linked list with a pointer in the middle, from which you can go either left or right (a variant of Huet's "Zipper")
A finger tree, which is a mind-blowing data structure invented by Ralf Hinze and Ross Paterson.
I'm a big fan of the zipper; it's useful in a lot of situations.
Note that there is already a zipper exercise. We currently don't have any exercises that address finger trees; do you think this could be more interesting, perhaps?
https://www.youtube.com/watch?v=UXdr_K0Lwg4
https://en.wikipedia.org/wiki/Finger_tree
OCaml is not a purely functional language. I think it's interesting to see imperative stuff done with it too. |
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Alright, then. Let's add the exercise.
The following comment relates to the problem-specifications repo and not this exercise. I'm noting that the following property of the exercise is rather unnecessary:
To keep your implementation simple, the tests will not cover error
conditions. Specifically: `pop` or `shift` will never be called on an
empty list.
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Hi @voila, and sorry for post-poning this review for so long. I'll look at it tomorrow morning! |
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OK, so I felt bad about having neglected this PR until now and made an assessment now instead.
Besides the individual comments made, I have one observation: It seems that the tests are manually made, which is fine by me. But it also happens that @marionebl made a pretty significant (but perhaps still somewhat undocumented--yet to be confirmed by a third party) contribution to the track's test generator.
Perhaps, rather than prolong this PR further, we can create an issue on the subject of converting the tests to a generator.
| "topics": [ | ||
| "data_structures", | ||
| "lists", | ||
| "recursion" |
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This is a syntax error. Our CI should definitely have caught this.
| "recursion" | |
| "recursion" | |
| ] |
| } | ||
| } |
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This change is unnecessary to the subject of the PR.
(Also, a CI check should probably have failed here. Considering how CI didn't catch a syntax error, perhaps configlet fmt . isn't run at all. I'll open an issue to investigate.)
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| (flags (:standard -warn-error -A)))) |
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I notice that most (but not all of) the files you generate don't have line termination and the files generated by configlet do.
I don't have my development computer at hand, so I can't say if we are consistent about this across the track.
The easiest consistency we could aim for is across single exercises, which I think we should aim for either way.
Since README.md is forced to have line endings, I think this and other files should have, too.
Feel free to object and argue otherwise.
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