Collatz conjecture

.gitignore

@@ -10,3 +10,4 @@ bin/configlet
 .psc-ide-port
 
 .merlin
+_opam

config.json

@@ -590,6 +590,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 2
+      },
+      {
+        "slug": "collatz-conjecture",
+        "name": "Collatz Conjecture",
+        "uuid": "eedc9471-326b-4498-b763-5b1c8eedca88",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
       }
     ]
   },

exercises/practice/anagram/test.ml

@@ -10,8 +10,6 @@ let tests = [
   "no matches" >::
   ae [] (anagrams "diaper" ["hello"; "world"; "zombies"; "pants"]);
   "detects two anagrams" >::
-  ae ["stream"; "maters"] (anagrams "master" ["stream"; "pigeon"; "maters"]);
-  "detects two anagrams" >::
   ae ["lemons"; "melons"] (anagrams "solemn" ["lemons"; "cherry"; "melons"]);
   "does not detect anagram subsets" >::
   ae [] (anagrams "good" ["dog"; "goody"]);
@@ -33,17 +31,13 @@ let tests = [
   ae [] (anagrams "go" ["go Go GO"]);
   "anagrams must use all letters exactly once" >::
   ae [] (anagrams "tapper" ["patter"]);
-  "words are not anagrams of themselves (case-insensitive)" >::
-  ae [] (anagrams "BANANA" ["BANANA"; "Banana"; "banana"]);
   "words are not anagrams of themselves" >::
   ae [] (anagrams "BANANA" ["BANANA"]);
   "words are not anagrams of themselves even if letter case is partially different" >::
   ae [] (anagrams "BANANA" ["Banana"]);
   "words are not anagrams of themselves even if letter case is completely different" >::
   ae [] (anagrams "BANANA" ["banana"]);
   "words other than themselves can be anagrams" >::
-  ae ["Silent"] (anagrams "LISTEN" ["Listen"; "Silent"; "LISTEN"]);
-  "words other than themselves can be anagrams" >::
   ae ["Silent"] (anagrams "LISTEN" ["LISTEN"; "Silent"]);
 ]
 

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

@@ -0,0 +1,3 @@
+# 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/introduction.md

@@ -0,0 +1,28 @@
+# 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/.meta/config.json

@@ -0,0 +1,22 @@
+{
+  "authors": [
+    "therealowenrees"
+  ],
+  "files": {
+    "solution": [
+      "collatz_conjecture.ml"
+    ],
+    "test": [
+      "test.ml"
+    ],
+    "example": [
+      ".meta/example.ml"
+    ],
+    "editor": [
+      "collatz_conjecture.mli"
+    ]
+  },
+  "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/example.ml

@@ -0,0 +1,13 @@
+let collatz_conjecture n =
+    let rec aux n count =
+        match n with
+        | 1 -> Ok count
+        | _ -> 
+            (match n mod 2 with
+                | 0 -> aux (n / 2) (count + 1)
+                | _ -> aux (n * 3 + 1) (count + 1)
+            )
+    in
+    if n < 1 then Error "Only positive integers are allowed"
+    else aux n 0
+

exercises/practice/collatz-conjecture/.meta/tests.toml

@@ -0,0 +1,38 @@
+# 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"

exercises/practice/collatz-conjecture/Makefile

@@ -0,0 +1,9 @@
+default: clean test
+
+test: 
+	dune runtest
+
+clean:
+	dune clean
+
+.PHONY: clean

exercises/practice/collatz-conjecture/collatz_conjecture.ml

@@ -0,0 +1,2 @@
+let collatz_conjecture _ = 
+  failwith "'collatz_conjecture' is missing"

exercises/practice/collatz-conjecture/collatz_conjecture.mli

@@ -0,0 +1 @@
+val collatz_conjecture : int -> (int, string) result

exercises/practice/collatz-conjecture/dune

@@ -0,0 +1,20 @@
+(executable
+ (name test)
+ (libraries base ounit2))
+
+(alias
+ (name runtest)
+ (deps
+  (:x test.exe))
+ (action
+  (run %{x})))
+
+(alias
+ (name buildtest)
+ (deps
+  (:x test.exe)))
+
+(env
+ (dev
+  (flags
+   (:standard -warn-error -A))))

exercises/practice/collatz-conjecture/dune-project

@@ -0,0 +1 @@
+(lang dune 1.1)

exercises/practice/collatz-conjecture/test.ml

@@ -0,0 +1,26 @@
+open OUnit2
+open Collatz_conjecture
+
+let option_printer = function
+  | Error m  -> Printf.sprintf "Error \"%s\"" m
+  | Ok n -> Printf.sprintf "Ok %d" n
+
+let ae exp got _test_ctxt = assert_equal ~printer:option_printer exp got
+
+let tests = [
+  "zero steps for one" >::
+  ae (Ok 0) (collatz_conjecture (1));
+  "divide if even" >::
+  ae (Ok 4) (collatz_conjecture (16));
+  "even and odd steps" >::
+  ae (Ok 9) (collatz_conjecture (12));
+  "large number of even and odd steps" >::
+  ae (Ok 152) (collatz_conjecture (1000000));
+  "zero is an error" >::
+  ae (Error "Only positive integers are allowed") (collatz_conjecture (0));
+  "negative value is an error" >::
+  ae (Error "Only positive integers are allowed") (collatz_conjecture (-15));
+]
+
+let () =
+  run_test_tt_main ("collatz-conjecture tests" >::: tests)

exercises/practice/etl/dune-project

@@ -1,2 +1,2 @@
 (lang dune 1.1)
-(version 1.0.1)
+(version 1.0)

exercises/practice/pangram/test.ml

@@ -22,8 +22,6 @@ let tests = [
   ae false (is_pangram "7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog");
   "mixed case and punctuation" >::
   ae true (is_pangram "\"Five quacking Zephyrs jolt my wax bed.\"");
-  "case insensitive" >::
-  ae false (is_pangram "the quick brown fox jumps over with lazy FX");
   "a-m and A-M are 26 different characters but not a pangram" >::
   ae false (is_pangram "abcdefghijklm ABCDEFGHIJKLM");
   "empty sentence" >::
@@ -44,8 +42,6 @@ let tests = [
   ae false (is_pangram "7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog");
   "mixed case and punctuation" >::
   ae true (is_pangram "\"Five quacking Zephyrs jolt my wax bed.\"");
-  "case insensitive" >::
-  ae false (is_pangram "the quick brown fox jumps over with lazy FX");
   "a-m and A-M are 26 different characters but not a pangram" >::
   ae false (is_pangram "abcdefghijklm ABCDEFGHIJKLM");
   "empty sentence" >::
@@ -66,8 +62,6 @@ let tests = [
   ae false (is_pangram "7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog");
   "mixed case and punctuation" >::
   ae true (is_pangram "\"Five quacking Zephyrs jolt my wax bed.\"");
-  "case insensitive" >::
-  ae false (is_pangram "the quick brown fox jumps over with lazy FX");
   "a-m and A-M are 26 different characters but not a pangram" >::
   ae false (is_pangram "abcdefghijklm ABCDEFGHIJKLM");
   "empty sentence" >::
@@ -88,8 +82,6 @@ let tests = [
   ae false (is_pangram "7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog");
   "mixed case and punctuation" >::
   ae true (is_pangram "\"Five quacking Zephyrs jolt my wax bed.\"");
-  "case insensitive" >::
-  ae false (is_pangram "the quick brown fox jumps over with lazy FX");
   "a-m and A-M are 26 different characters but not a pangram" >::
   ae false (is_pangram "abcdefghijklm ABCDEFGHIJKLM");
   "empty sentence" >::
@@ -110,8 +102,6 @@ let tests = [
   ae false (is_pangram "7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog");
   "mixed case and punctuation" >::
   ae true (is_pangram "\"Five quacking Zephyrs jolt my wax bed.\"");
-  "case insensitive" >::
-  ae false (is_pangram "the quick brown fox jumps over with lazy FX");
   "a-m and A-M are 26 different characters but not a pangram" >::
   ae false (is_pangram "abcdefghijklm ABCDEFGHIJKLM");
   "empty sentence" >::
@@ -132,8 +122,6 @@ let tests = [
   ae false (is_pangram "7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog");
   "mixed case and punctuation" >::
   ae true (is_pangram "\"Five quacking Zephyrs jolt my wax bed.\"");
-  "case insensitive" >::
-  ae false (is_pangram "the quick brown fox jumps over with lazy FX");
   "a-m and A-M are 26 different characters but not a pangram" >::
   ae false (is_pangram "abcdefghijklm ABCDEFGHIJKLM");
   "empty sentence" >::
@@ -154,8 +142,6 @@ let tests = [
   ae false (is_pangram "7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog");
   "mixed case and punctuation" >::
   ae true (is_pangram "\"Five quacking Zephyrs jolt my wax bed.\"");
-  "case insensitive" >::
-  ae false (is_pangram "the quick brown fox jumps over with lazy FX");
   "a-m and A-M are 26 different characters but not a pangram" >::
   ae false (is_pangram "abcdefghijklm ABCDEFGHIJKLM");
   "empty sentence" >::
@@ -176,8 +162,6 @@ let tests = [
   ae false (is_pangram "7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog");
   "mixed case and punctuation" >::
   ae true (is_pangram "\"Five quacking Zephyrs jolt my wax bed.\"");
-  "case insensitive" >::
-  ae false (is_pangram "the quick brown fox jumps over with lazy FX");
   "a-m and A-M are 26 different characters but not a pangram" >::
   ae false (is_pangram "abcdefghijklm ABCDEFGHIJKLM");
   "empty sentence" >::
@@ -198,8 +182,6 @@ let tests = [
   ae false (is_pangram "7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog");
   "mixed case and punctuation" >::
   ae true (is_pangram "\"Five quacking Zephyrs jolt my wax bed.\"");
-  "case insensitive" >::
-  ae false (is_pangram "the quick brown fox jumps over with lazy FX");
   "a-m and A-M are 26 different characters but not a pangram" >::
   ae false (is_pangram "abcdefghijklm ABCDEFGHIJKLM");
   "empty sentence" >::
@@ -220,30 +202,6 @@ let tests = [
   ae false (is_pangram "7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog");
   "mixed case and punctuation" >::
   ae true (is_pangram "\"Five quacking Zephyrs jolt my wax bed.\"");
-  "case insensitive" >::
-  ae false (is_pangram "the quick brown fox jumps over with lazy FX");
-  "a-m and A-M are 26 different characters but not a pangram" >::
-  ae false (is_pangram "abcdefghijklm ABCDEFGHIJKLM");
-  "empty sentence" >::
-  ae false (is_pangram "");
-  "perfect lower case" >::
-  ae true (is_pangram "abcdefghijklmnopqrstuvwxyz");
-  "only lower case" >::
-  ae true (is_pangram "the quick brown fox jumps over the lazy dog");
-  "missing the letter 'x'" >::
-  ae false (is_pangram "a quick movement of the enemy will jeopardize five gunboats");
-  "missing the letter 'h'" >::
-  ae false (is_pangram "five boxing wizards jump quickly at it");
-  "with underscores" >::
-  ae true (is_pangram "the_quick_brown_fox_jumps_over_the_lazy_dog");
-  "with numbers" >::
-  ae true (is_pangram "the 1 quick brown fox jumps over the 2 lazy dogs");
-  "missing letters replaced by numbers" >::
-  ae false (is_pangram "7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog");
-  "mixed case and punctuation" >::
-  ae true (is_pangram "\"Five quacking Zephyrs jolt my wax bed.\"");
-  "case insensitive" >::
-  ae false (is_pangram "the quick brown fox jumps over with lazy FX");
   "a-m and A-M are 26 different characters but not a pangram" >::
   ae false (is_pangram "abcdefghijklm ABCDEFGHIJKLM");
 ]