collatz-conjecture (#7)

Author: glennj

.gitignore

@@ -1,7 +1,3 @@
-*.swp
-.DS_Store
-bin/configlet
 bin/configlet.exe
-bin/latest-configlet.tar.gz
-bin/latest-configlet.zip
-bin/configlet.zip
+bin/configlet
+canonical-data/

canonical-data/armstrong-numbers.json

@@ -46,6 +46,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 2
+      },
+      {
+        "slug": "collatz-conjecture",
+        "name": "Collatz Conjecture",
+        "uuid": "0c6713d7-d0d8-4724-8c41-cbec5202689f",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
       }
     ]
   },

config.json

@@ -0,0 +1,5 @@
+return {
+  default = {
+    ROOT = { '.' }
+  }
+}

exercises/practice/collatz-conjecture/.busted

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+# Instructions
+
+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/instructions.md

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

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

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

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

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+collatz_steps = (n) ->
+  assert n > 0, 'Only positive integers are allowed'
+
+  steps = 0
+  while n > 1
+    if n & 1 == 0
+      n >>= 1
+    else
+      n = 3 * n + 1
+    steps += 1
+
+  steps
+
+{ steps: collatz_steps }

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

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+{
+  module_name: 'CollatzConjecture',
+  generate_test: (case, level) ->
+    local lines
+    if type(case.expected) == 'number'
+      lines = {
+        "result = CollatzConjecture.steps #{case.input.number}",
+        "assert.are.equal #{case.expected}, result"
+      }
+    else
+      lines = {
+        "f = -> CollatzConjecture.steps #{case.input.number}",
+        "assert.has.errors f, '#{case.expected.error}'"
+      }
+
+    table.concat [indent line, level for line in *lines], '\n'
+}

exercises/practice/collatz-conjecture/.meta/spec_generator.moon

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