Collatz conjecture #545

TheRealOwenRees · 2025-07-23T21:41:57Z

Ported the exercise Collatz Conjecture to OCaml.
Added the add-practice-exercise script to generate new practice exercise

Issues:

environment does not build when following the readme file, with package conflicts
https://exercism.org/docs/tracks/ocaml/installation works, but then some exercises do not run tests due to missing packages that require base compiler v5.1.0
in hindsight, using configlet would have been better to create the exercise

BethanyG · 2025-07-23T22:51:33Z

@kahgoh - I triggered the CI and gave a once-over to the files, which look fine to my eye.

But the ocaml code needs a more experienced once-over than I can really give it.

Looks like for PR #539, you were talking about making changes to the test generator. Would that also be something you would want here? If so, I think @TheRealOwenRees is more than willing, but would need some guidance on the details. 😄

kahgoh

Thanks for raising this PR to add collatz conjecture for the OCaml track! I've got some comments below 👇🏻

node_modules/.lsp/debug.log

bin/add-practice-exercise

exercises/practice/collatz-conjecture/test.ml

bin/add-practice-exercise

exercises/practice/collatz-conjecture/test.ml

TheRealOwenRees · 2025-07-24T13:01:40Z

Thanks for raising this PR to add collatz conjecture for the OCaml track! I've got some comments below 👇🏻

Hello and thank you for your comments. I will look into those and resolve those issues.

However I cannot run the commands in the Readme as the OCaml environment does not build. I have a local switch for this and running compiler 5.1.0, as well as trying 5.1.1. I get the following errors:

[ERROR] Package conflict!
  * No agreement on the version of ocaml:
    - (invariant) → ocaml-base-compiler = 5.1.1 → ocaml = 5.1.1
    - getopts → lemonade >= 0.2.1 → mixture < 0.2.1 → ocaml < 5.0.0
    You can temporarily relax the switch invariant with `--update-invariant'
  * No agreement on the version of ocaml-base-compiler:
    - (invariant) → ocaml-base-compiler = 5.1.1
    - getopts → lemonade >= 0.2.1 → mixture < 0.2.1 → ocaml < 5.0.0 → ocaml-base-compiler (= 4.08.1 | = 4.11.1)
  * Incompatible packages:
    - (invariant) → ocaml-base-compiler = 5.1.1
    - getopts → lemonade >= 0.2.1 → mixture < 0.2.1 → ocaml < 5.0.0 → ocaml-system >= 4.02.4
  * Incompatible packages:
    - (invariant) → ocaml-base-compiler = 5.1.1
    - getopts → lemonade >= 0.2.1 → mixture < 0.2.1 → ocaml < 5.0.0 → ocaml-variants (< 4.05.2~ | >= 4.08.1)
  * Missing dependency:
    - getopts → lemonade >= 0.2.1 → mixture < 0.2.1 → ocaml < 5.0.0 → ocaml-variants >= 4.08.1 → ocaml-beta
    unmet availability conditions: 'enable-ocaml-beta-repository'
  * Missing dependency:
    - getopts → lemonade >= 0.2.1 → mixture < 0.2.1 → ocaml < 5.0.0 → ocaml-variants >= 4.08.1 → system-msvc
    unmet availability conditions: 'os = "win32"'

No solution found, exiting

I have also tried with the --update-invariant option.

If you have any pointers to get this working, I am certain I can finalise this PR.

Thanks

TheRealOwenRees · 2025-07-24T19:59:56Z

Thanks for raising this PR to add collatz conjecture for the OCaml track! I've got some comments below 👇🏻

Hello and thank you for your comments. I will look into those and resolve those issues.

However I cannot run the commands in the Readme as the OCaml environment does not build. I have a local switch for this and running compiler 5.1.0, as well as trying 5.1.1. I get the following errors:

[ERROR] Package conflict!
  * No agreement on the version of ocaml:
    - (invariant) → ocaml-base-compiler = 5.1.1 → ocaml = 5.1.1
    - getopts → lemonade >= 0.2.1 → mixture < 0.2.1 → ocaml < 5.0.0
    You can temporarily relax the switch invariant with `--update-invariant'
  * No agreement on the version of ocaml-base-compiler:
    - (invariant) → ocaml-base-compiler = 5.1.1
    - getopts → lemonade >= 0.2.1 → mixture < 0.2.1 → ocaml < 5.0.0 → ocaml-base-compiler (= 4.08.1 | = 4.11.1)
  * Incompatible packages:
    - (invariant) → ocaml-base-compiler = 5.1.1
    - getopts → lemonade >= 0.2.1 → mixture < 0.2.1 → ocaml < 5.0.0 → ocaml-system >= 4.02.4
  * Incompatible packages:
    - (invariant) → ocaml-base-compiler = 5.1.1
    - getopts → lemonade >= 0.2.1 → mixture < 0.2.1 → ocaml < 5.0.0 → ocaml-variants (< 4.05.2~ | >= 4.08.1)
  * Missing dependency:
    - getopts → lemonade >= 0.2.1 → mixture < 0.2.1 → ocaml < 5.0.0 → ocaml-variants >= 4.08.1 → ocaml-beta
    unmet availability conditions: 'enable-ocaml-beta-repository'
  * Missing dependency:
    - getopts → lemonade >= 0.2.1 → mixture < 0.2.1 → ocaml < 5.0.0 → ocaml-variants >= 4.08.1 → system-msvc
    unmet availability conditions: 'os = "win32"'

No solution found, exiting

I have also tried with the --update-invariant option.

If you have any pointers to get this working, I am certain I can finalise this PR.

Thanks

I believe to have fixed this. I will submit a PR for troubleshooting / installation guide updates another time, after finalising this PR.

TheRealOwenRees · 2025-07-25T18:40:25Z

removed mistakenly added files
added template to test generator

I will need to write a special case for the test, where result is a return type with Ok and Error? I think that might be a little beyond me at this stage. I will attempt it and submit again.

TheRealOwenRees · 2025-07-26T10:30:21Z

Test template added.

However it is generating multiple tests for 0 and -15 according to what is in the canonical data:

 {
      "uuid": "7d4750e6-def9-4b86-aec7-9f7eb44f95a3",
      "description": "zero is an error",
      "property": "steps",
      "input": {
        "number": 0
      },
      "expected": {
        "error": "Only positive numbers are allowed"
      }
    },
    {
      "uuid": "2187673d-77d6-4543-975e-66df6c50e2da",
      "reimplements": "7d4750e6-def9-4b86-aec7-9f7eb44f95a3",
      "description": "zero is an error",
      "comments": ["Collatz Conjecture holds only for positive integers"],
      "property": "steps",
      "input": {
        "number": 0
      },
      "expected": {
        "error": "Only positive integers are allowed"
      }
    },
    ```
    
 If someone can point me in the direction to fix that, I believe I may have finally cracked it.
 
 Thanks

kahgoh · 2025-07-27T00:41:00Z

The test generator doesn't handle the reimplements 😅. Admittedly, this is also causing some of the broken test generation issues.

If you're up fixing this limitation that would be greatly appreciated 😁. You'll probably need to dive into the test-generator code. I think the points of interest are:

bin_test_gen/test_gen.ml - the generator's starting point
lib_generator/controller.ml - the controller used by test_gen to apply the templates
lib_generator/exercism.ml - the of_candidate function is where the canonical data for the exercise is read

If not, that's okay too 😉 . In this case, let's just mark the test generation broken by adding a templates/collatz-conjecture/.broken file. Contents can be empty or a note about not handling the reimplements key.

kahgoh · 2025-07-27T00:44:46Z

Also, Github is reporting a merge conflict on config.json. Would you mind merging and resolving?

…n canonical_data.json

TheRealOwenRees · 2025-07-27T18:19:57Z

filter added to remove any UUID tests cases that are referenced by reimplements
the above filter affected two other exercises - anagram and pangram
resolved config.json conflict

kahgoh

It is looking good! A couple of minor comments.

kahgoh · 2025-07-28T03:43:00Z

.gitignore

+_opam
+
+node_modules


I think you've accidentally added node_modules? Could you please remove.

kahgoh · 2025-07-28T03:55:06Z

test-generator/lib_generator/canonical_data.ml

+
+  (* filter original cases whose UUID is referenced in "reimplements" *)
+  let reimplemented_uuids = get_reimplemented_uuids cases in
+let filtered_cases =


The alignment seems a little off. Should this be indented?

kahgoh · 2025-07-28T07:19:24Z

node_modules/.lsp/debug.log

This file has been accidentally added again 😅.

Oh dear, this is why I added that line to the .gitignore. My environment likes to add a debug file for some reason. I will delete and resubmit. Apologies for the inconvenience!

Actually, I was kinda curious what might be causing it be generated and added .... At least in my environment, I haven't seen node_modules get generated, although my OCaml version is 4.14.2...

I am running a 5.1.1 global switch for this as the Readme stipulates OCaml 5.1 is needed. Perhaps this is the cause of the issue!

Readme stipulates OCaml 5.1 is needed

Oh that's interesting! I had my environment set up a long time ago based on the track docs which says 4.08.0 😅. We should fix that - I'll add that as a separate issue later.

I was actually going to submit a PR for this later in the week! I would be interested to see if you have any dependency issues when installing this according to the readme. I had the compiler version errors listed in an earlier comment here, but have a fix. I just need to make sure it is not just me with the error !

Thanks! I've just created #546 to note this version discrepancy.

kahgoh

Thanks, this looks good!

TheRealOwenRees added 4 commits July 23, 2025 22:26

add collatz-conjecture slug via newly added add-practice-exercise script

3341abe

project files setup

6d4753e

added exercise with tests

5473b7e

exercise uuid added

894e080

BethanyG requested a review from kahgoh July 23, 2025 22:47

kahgoh reviewed Jul 24, 2025

View reviewed changes

TheRealOwenRees added 4 commits July 25, 2025 19:52

delete mistakenly added files

44b02cd

remove commented out code in test

1beea81

ignore node_modules that appear from time to time

26df8af

test generator template added

5250a96

test template added

0f5265b

TheRealOwenRees added 3 commits July 27, 2025 20:06

filter original test cases whose UUID is referenced in reimplements i…

aa31c68

…n canonical_data.json

original test cases referenced by reimplements are deleted

1bee45a

Merge branch 'main' into collatz-conjecture

e4a1a9f

does not need a set for filtering UUIDs

d47631e

kahgoh reviewed Jul 28, 2025

View reviewed changes

formatting fixes

9e2cb7f

kahgoh reviewed Jul 28, 2025

View reviewed changes

redelete node modules debug file

9918b00

kahgoh approved these changes Jul 28, 2025

View reviewed changes

kahgoh added the x:rep/large Large amount of reputation label Jul 28, 2025

kahgoh merged commit 20c62f0 into exercism:main Jul 28, 2025
2 checks passed

TheRealOwenRees deleted the collatz-conjecture branch July 28, 2025 12:23

TheRealOwenRees mentioned this pull request Jul 28, 2025

Update version in track docs #546

Open

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Collatz conjecture #545

Collatz conjecture #545

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TheRealOwenRees commented Jul 23, 2025 •

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