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TheRealOwenReesTheRealOwenRees
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Add collatz conjecture exercise (#545)
This commit also updates the test generator to honor the "reimplements" key in the canonical data. [no important files changed]
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‎.gitignore

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.psc-ide-port
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.merlin
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_opam

‎config.json

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"practices": [],
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"prerequisites": [],
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"difficulty": 2
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},
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{
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"slug": "collatz-conjecture",
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"name": "Collatz Conjecture",
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"uuid": "eedc9471-326b-4498-b763-5b1c8eedca88",
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"practices": [],
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"prerequisites": [],
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"difficulty": 3
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}
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]
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},

‎exercises/practice/anagram/test.ml

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"no matches" >::
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ae [] (anagrams "diaper" ["hello"; "world"; "zombies"; "pants"]);
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"detects two anagrams" >::
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ae ["stream"; "maters"] (anagrams "master" ["stream"; "pigeon"; "maters"]);
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"detects two anagrams" >::
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ae ["lemons"; "melons"] (anagrams "solemn" ["lemons"; "cherry"; "melons"]);
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"does not detect anagram subsets" >::
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ae [] (anagrams "good" ["dog"; "goody"]);
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ae [] (anagrams "go" ["go Go GO"]);
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"anagrams must use all letters exactly once" >::
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ae [] (anagrams "tapper" ["patter"]);
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"words are not anagrams of themselves (case-insensitive)" >::
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ae [] (anagrams "BANANA" ["BANANA"; "Banana"; "banana"]);
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"words are not anagrams of themselves" >::
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ae [] (anagrams "BANANA" ["BANANA"]);
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"words are not anagrams of themselves even if letter case is partially different" >::
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ae [] (anagrams "BANANA" ["Banana"]);
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"words are not anagrams of themselves even if letter case is completely different" >::
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ae [] (anagrams "BANANA" ["banana"]);
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"words other than themselves can be anagrams" >::
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ae ["Silent"] (anagrams "LISTEN" ["Listen"; "Silent"; "LISTEN"]);
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"words other than themselves can be anagrams" >::
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ae ["Silent"] (anagrams "LISTEN" ["LISTEN"; "Silent"]);
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]
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‎exercises/practice/collatz-conjecture/.docs/instructions.md

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# Instructions
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Given a positive integer, return the number of steps it takes to reach 1 according to the rules of the Collatz Conjecture.

‎exercises/practice/collatz-conjecture/.docs/introduction.md

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# Introduction
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One evening, you stumbled upon an old notebook filled with cryptic scribbles, as though someone had been obsessively chasing an idea.
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On one page, a single question stood out: **Can every number find its way to 1?**
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It was tied to something called the **Collatz Conjecture**, a puzzle that has baffled thinkers for decades.
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The rules were deceptively simple.
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Pick any positive integer.
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- If it's even, divide it by 2.
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- If it's odd, multiply it by 3 and add 1.
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Then, repeat these steps with the result, continuing indefinitely.
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Curious, you picked number 12 to test and began the journey:
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12 ➜ 6 ➜ 3 ➜ 10 ➜ 5 ➜ 16 ➜ 8 ➜ 4 ➜ 2 ➜ 1
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Counting from the second number (6), it took 9 steps to reach 1, and each time the rules repeated, the number kept changing.
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At first, the sequence seemed unpredictable — jumping up, down, and all over.
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Yet, the conjecture claims that no matter the starting number, we'll always end at 1.
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It was fascinating, but also puzzling.
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Why does this always seem to work?
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Could there be a number where the process breaks down, looping forever or escaping into infinity?
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The notebook suggested solving this could reveal something profound — and with it, fame, [fortune][collatz-prize], and a place in history awaits whoever could unlock its secrets.
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[collatz-prize]: https://mathprize.net/posts/collatz-conjecture/

‎exercises/practice/collatz-conjecture/.meta/config.json

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{
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"authors": [
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"therealowenrees"
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],
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"files": {
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"solution": [
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"collatz_conjecture.ml"
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],
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"test": [
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"test.ml"
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],
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"example": [
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".meta/example.ml"
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],
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"editor": [
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"collatz_conjecture.mli"
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]
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},
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"blurb": "Calculate the number of steps to reach 1 using the Collatz conjecture.",
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"source": "Wikipedia",
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"source_url": "https://en.wikipedia.org/wiki/Collatz_conjecture"
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}

‎exercises/practice/collatz-conjecture/.meta/example.ml

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let collatz_conjecture n =
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let rec aux n count =
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match n with
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| 1 -> Ok count
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| _ ->
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(match n mod 2 with
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| 0 -> aux (n / 2) (count + 1)
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| _ -> aux (n * 3 + 1) (count + 1)
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)
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in
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if n < 1 then Error "Only positive integers are allowed"
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else aux n 0
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‎exercises/practice/collatz-conjecture/.meta/tests.toml

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# This is an auto-generated file.
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#
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# Regenerating this file via `configlet sync` will:
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# - Recreate every `description` key/value pair
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# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
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# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
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# - Preserve any other key/value pair
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#
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# As user-added comments (using the # character) will be removed when this file
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# is regenerated, comments can be added via a `comment` key.
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[540a3d51-e7a6-47a5-92a3-4ad1838f0bfd]
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description = "zero steps for one"
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[3d76a0a6-ea84-444a-821a-f7857c2c1859]
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description = "divide if even"
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[754dea81-123c-429e-b8bc-db20b05a87b9]
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description = "even and odd steps"
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[ecfd0210-6f85-44f6-8280-f65534892ff6]
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description = "large number of even and odd steps"
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[7d4750e6-def9-4b86-aec7-9f7eb44f95a3]
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description = "zero is an error"
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include = false
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[2187673d-77d6-4543-975e-66df6c50e2da]
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description = "zero is an error"
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reimplements = "7d4750e6-def9-4b86-aec7-9f7eb44f95a3"
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[c6c795bf-a288-45e9-86a1-841359ad426d]
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description = "negative value is an error"
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include = false
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[ec11f479-56bc-47fd-a434-bcd7a31a7a2e]
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description = "negative value is an error"
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reimplements = "c6c795bf-a288-45e9-86a1-841359ad426d"

‎exercises/practice/collatz-conjecture/Makefile

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default: clean test
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test:
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dune runtest
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clean:
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dune clean
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.PHONY: clean

‎exercises/practice/collatz-conjecture/collatz_conjecture.ml

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let collatz_conjecture _ =
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failwith "'collatz_conjecture' is missing"

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