Add hamming exercise

config.json

@@ -251,6 +251,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 1
+      },
+      {
+        "slug": "hamming",
+        "name": "Hamming",
+        "uuid": "3ea9f608-75a0-49c9-bb62-28a8df533c26",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 1
       }
     ]
   },

exercises/practice/hamming/.docs/instructions.md

@@ -0,0 +1,27 @@
+# Instructions
+
+Calculate the Hamming distance between two DNA strands.
+
+Your body is made up of cells that contain DNA.
+Those cells regularly wear out and need replacing, which they achieve by dividing into daughter cells.
+In fact, the average human body experiences about 10 quadrillion cell divisions in a lifetime!
+
+When cells divide, their DNA replicates too.
+Sometimes during this process mistakes happen and single pieces of DNA get encoded with the incorrect information.
+If we compare two strands of DNA and count the differences between them we can see how many mistakes occurred.
+This is known as the "Hamming distance".
+
+We read DNA using the letters C, A, G and T.
+Two strands might look like this:
+
+    GAGCCTACTAACGGGAT
+    CATCGTAATGACGGCCT
+    ^ ^ ^  ^ ^    ^^
+
+They have 7 differences, and therefore the Hamming distance is 7.
+
+The Hamming distance is useful for lots of things in science, not just biology, so it's a nice phrase to be familiar with :)
+
+## Implementation notes
+
+The Hamming distance is only defined for sequences of equal length, so an attempt to calculate it between sequences of different lengths should not work.

exercises/practice/hamming/.meta/Example.roc

@@ -0,0 +1,13 @@
+module [distance]
+
+distance : Str, Str -> Result (Num *) [StrandsMustBeOfEqualLength]
+distance = \strand1, strand2 ->
+    nucleotides1 = strand1 |> Str.toUtf8
+    nucleotides2 = strand2 |> Str.toUtf8
+    if List.len nucleotides1 == List.len nucleotides2 then
+        List.map2 nucleotides1 nucleotides2 \n1, n2 ->
+            if n1 == n2 then 0 else 1
+        |> List.sum
+        |> Ok
+    else
+        Err StrandsMustBeOfEqualLength

exercises/practice/hamming/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "ageron"
+  ],
+  "files": {
+    "solution": [
+      "Hamming.roc"
+    ],
+    "test": [
+      "hamming-test.roc"
+    ],
+    "example": [
+      ".meta/Example.roc"
+    ]
+  },
+  "blurb": "Calculate the Hamming difference between two DNA strands.",
+  "source": "The Calculating Point Mutations problem at Rosalind",
+  "source_url": "https://rosalind.info/problems/hamm/"
+}

exercises/practice/hamming/.meta/template.j2

@@ -0,0 +1,17 @@
+{%- import "generator_macros.j2" as macros with context -%}
+{{ macros.canonical_ref() }}
+{{ macros.header() }}
+
+import {{ exercise | to_pascal }} exposing [{{ cases[0]["property"] | to_camel }}]
+
+{% for case in cases -%}
+# {{ case["description"] }}
+expect
+    result = {{ case["property"] | to_camel }} {{ case["input"]["strand1"] | to_roc }} {{ case["input"]["strand2"] | to_roc }}
+{%- if case["expected"]["error"] %}
+    result == Err {{ case["expected"]["error"] | to_pascal }}
+{%- else %}
+    result == Ok {{ case["expected"] }}
+{%- endif %}
+
+{% endfor %}

exercises/practice/hamming/.meta/tests.toml

@@ -0,0 +1,67 @@
+# 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.
+
+[f6dcb64f-03b0-4b60-81b1-3c9dbf47e887]
+description = "empty strands"
+
+[54681314-eee2-439a-9db0-b0636c656156]
+description = "single letter identical strands"
+
+[294479a3-a4c8-478f-8d63-6209815a827b]
+description = "single letter different strands"
+
+[9aed5f34-5693-4344-9b31-40c692fb5592]
+description = "long identical strands"
+
+[cd2273a5-c576-46c8-a52b-dee251c3e6e5]
+description = "long different strands"
+
+[919f8ef0-b767-4d1b-8516-6379d07fcb28]
+description = "disallow first strand longer"
+include = false
+
+[b9228bb1-465f-4141-b40f-1f99812de5a8]
+description = "disallow first strand longer"
+reimplements = "919f8ef0-b767-4d1b-8516-6379d07fcb28"
+
+[8a2d4ed0-ead5-4fdd-924d-27c4cf56e60e]
+description = "disallow second strand longer"
+include = false
+
+[dab38838-26bb-4fff-acbe-3b0a9bfeba2d]
+description = "disallow second strand longer"
+reimplements = "8a2d4ed0-ead5-4fdd-924d-27c4cf56e60e"
+
+[5dce058b-28d4-4ca7-aa64-adfe4e17784c]
+description = "disallow left empty strand"
+include = false
+
+[db92e77e-7c72-499d-8fe6-9354d2bfd504]
+description = "disallow left empty strand"
+include = false
+reimplements = "5dce058b-28d4-4ca7-aa64-adfe4e17784c"
+
+[b764d47c-83ff-4de2-ab10-6cfe4b15c0f3]
+description = "disallow empty first strand"
+reimplements = "db92e77e-7c72-499d-8fe6-9354d2bfd504"
+
+[38826d4b-16fb-4639-ac3e-ba027dec8b5f]
+description = "disallow right empty strand"
+include = false
+
+[920cd6e3-18f4-4143-b6b8-74270bb8f8a3]
+description = "disallow right empty strand"
+include = false
+reimplements = "38826d4b-16fb-4639-ac3e-ba027dec8b5f"
+
+[9ab9262f-3521-4191-81f5-0ed184a5aa89]
+description = "disallow empty second strand"
+reimplements = "920cd6e3-18f4-4143-b6b8-74270bb8f8a3"

exercises/practice/hamming/Hamming.roc

@@ -0,0 +1,4 @@
+module [distance]
+
+distance = \strand1, strand2 ->
+    crash "Please implement the 'distance' function"

exercises/practice/hamming/hamming-test.roc

@@ -0,0 +1,59 @@
+# These tests are auto-generated with test data from:
+# https://github.com/exercism/problem-specifications/tree/main/exercises/hamming/canonical-data.json
+# File last updated on 2024-08-28
+app [main] {
+    pf: platform "https://github.com/roc-lang/basic-cli/releases/download/0.14.0/dC5ceT962N_4jmoyoffVdphJ_4GlW3YMhAPyGPr-nU0.tar.br",
+}
+
+import pf.Task exposing [Task]
+
+main =
+    Task.ok {}
+
+import Hamming exposing [distance]
+
+# empty strands
+expect
+    result = distance "" ""
+    result == Ok 0
+
+# single letter identical strands
+expect
+    result = distance "A" "A"
+    result == Ok 0
+
+# single letter different strands
+expect
+    result = distance "G" "T"
+    result == Ok 1
+
+# long identical strands
+expect
+    result = distance "GGACTGAAATCTG" "GGACTGAAATCTG"
+    result == Ok 0
+
+# long different strands
+expect
+    result = distance "GGACGGATTCTG" "AGGACGGATTCT"
+    result == Ok 9
+
+# disallow first strand longer
+expect
+    result = distance "AATG" "AAA"
+    result == Err StrandsMustBeOfEqualLength
+
+# disallow second strand longer
+expect
+    result = distance "ATA" "AGTG"
+    result == Err StrandsMustBeOfEqualLength
+
+# disallow empty first strand
+expect
+    result = distance "" "G"
+    result == Err StrandsMustBeOfEqualLength
+
+# disallow empty second strand
+expect
+    result = distance "G" ""
+    result == Err StrandsMustBeOfEqualLength
+