Add armstrong numbers (#12)

* Clarify message in case of Grapheme.split error

* Add armstrong-numbers exercise and add to_roc_bool filter

bin/generate_tests.py

@@ -132,6 +132,10 @@ def to_camel(string: str) -> str:
 del i
 
 
+def to_roc_bool(b: bool) -> str:
+    return "Bool.true" if b else "Bool.false"
+
+
 def to_roc_string(string: str) -> str:
     """
     Return a Roc representation of a Python string
@@ -483,6 +487,7 @@ def generate(
     env.filters["to_snake"] = to_snake
     env.filters["to_pascal"] = to_pascal
     env.filters["to_camel"] = to_camel
+    env.filters["to_roc_bool"] = to_roc_bool
     env.filters["to_roc_string"] = to_roc_string
     env.filters["wrap_overlong"] = wrap_overlong
     env.filters["regex_replace"] = regex_replace

config.json

@@ -83,6 +83,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 1
+      },
+      {
+        "slug": "armstrong-numbers",
+        "name": "Armstrong Numbers",
+        "uuid": "da8055c2-c2f0-43ad-85f2-dd55f10e84be",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 1
       }
     ]
   },

exercises/practice/armstrong-numbers/.docs/instructions.md

@@ -0,0 +1,14 @@
+# Instructions
+
+An [Armstrong number][armstrong-number] is a number that is the sum of its own digits each raised to the power of the number of digits.
+
+For example:
+
+- 9 is an Armstrong number, because `9 = 9^1 = 9`
+- 10 is _not_ an Armstrong number, because `10 != 1^2 + 0^2 = 1`
+- 153 is an Armstrong number, because: `153 = 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153`
+- 154 is _not_ an Armstrong number, because: `154 != 1^3 + 5^3 + 4^3 = 1 + 125 + 64 = 190`
+
+Write some code to determine whether a number is an Armstrong number.
+
+[armstrong-number]: https://en.wikipedia.org/wiki/Narcissistic_number

exercises/practice/armstrong-numbers/.meta/Example.roc

@@ -0,0 +1,16 @@
+module [isArmstrongNumber]
+
+listDigits = \number ->
+    if number < 10 then
+        [number]
+    else
+        (listDigits (number // 10)) |> List.append (number % 10)
+
+isArmstrongNumber = \number ->
+    digits = listDigits number
+    len = List.len digits
+    candidate =
+        digits
+        |> List.map (\digit -> digit |> Num.powInt len)
+        |> List.sum
+    candidate == number

exercises/practice/armstrong-numbers/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "ageron"
+  ],
+  "files": {
+    "solution": [
+      "ArmstrongNumbers.roc"
+    ],
+    "test": [
+      "armstrong-numbers-test.roc"
+    ],
+    "example": [
+      ".meta/Example.roc"
+    ]
+  },
+  "blurb": "Determine if a number is an Armstrong number.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Narcissistic_number"
+}

exercises/practice/armstrong-numbers/.meta/template.j2

@@ -0,0 +1,11 @@
+{%- import "generator_macros.j2" as macros with context -%}
+{{ macros.canonical_ref() }}
+{{ macros.header() }}
+
+import {{ exercise | to_pascal }} exposing [isArmstrongNumber]
+
+{% for case in cases -%}
+# {{ case["description"] }}
+expect {{ case["property"] | to_camel }} {{ case["input"]["number"] }} == {{ case["expected"] | to_roc_bool }}
+
+{% endfor %}

exercises/practice/armstrong-numbers/.meta/tests.toml

@@ -0,0 +1,45 @@
+# 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.
+
+[c1ed103c-258d-45b2-be73-d8c6d9580c7b]
+description = "Zero is an Armstrong number"
+
+[579e8f03-9659-4b85-a1a2-d64350f6b17a]
+description = "Single-digit numbers are Armstrong numbers"
+
+[2d6db9dc-5bf8-4976-a90b-b2c2b9feba60]
+description = "There are no two-digit Armstrong numbers"
+
+[509c087f-e327-4113-a7d2-26a4e9d18283]
+description = "Three-digit number that is an Armstrong number"
+
+[7154547d-c2ce-468d-b214-4cb953b870cf]
+description = "Three-digit number that is not an Armstrong number"
+
+[6bac5b7b-42e9-4ecb-a8b0-4832229aa103]
+description = "Four-digit number that is an Armstrong number"
+
+[eed4b331-af80-45b5-a80b-19c9ea444b2e]
+description = "Four-digit number that is not an Armstrong number"
+
+[f971ced7-8d68-4758-aea1-d4194900b864]
+description = "Seven-digit number that is an Armstrong number"
+
+[7ee45d52-5d35-4fbd-b6f1-5c8cd8a67f18]
+description = "Seven-digit number that is not an Armstrong number"
+
+[5ee2fdf8-334e-4a46-bb8d-e5c19c02c148]
+description = "Armstrong number containing seven zeroes"
+include = false
+
+[12ffbf10-307a-434e-b4ad-c925680e1dd4]
+description = "The largest and last Armstrong number"
+include = false

exercises/practice/armstrong-numbers/ArmstrongNumbers.roc

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

exercises/practice/armstrong-numbers/armstrong-numbers-test.roc

@@ -0,0 +1,41 @@
+# These tests are auto-generated with test data from:
+# https://github.com/exercism/problem-specifications/tree/main/exercises/armstrong-numbers/canonical-data.json
+# File last updated on 2024-08-25
+app [main] {
+    pf: platform "https://github.com/roc-lang/basic-cli/releases/download/0.12.0/Lb8EgiejTUzbggO2HVVuPJFkwvvsfW6LojkLR20kTVE.tar.br",
+}
+
+import pf.Task exposing [Task]
+
+main =
+    Task.ok {}
+
+import ArmstrongNumbers exposing [isArmstrongNumber]
+
+# Zero is an Armstrong number
+expect isArmstrongNumber 0 == Bool.true
+
+# Single-digit numbers are Armstrong numbers
+expect isArmstrongNumber 5 == Bool.true
+
+# There are no two-digit Armstrong numbers
+expect isArmstrongNumber 10 == Bool.false
+
+# Three-digit number that is an Armstrong number
+expect isArmstrongNumber 153 == Bool.true
+
+# Three-digit number that is not an Armstrong number
+expect isArmstrongNumber 100 == Bool.false
+
+# Four-digit number that is an Armstrong number
+expect isArmstrongNumber 9474 == Bool.true
+
+# Four-digit number that is not an Armstrong number
+expect isArmstrongNumber 9475 == Bool.false
+
+# Seven-digit number that is an Armstrong number
+expect isArmstrongNumber 9926315 == Bool.true
+
+# Seven-digit number that is not an Armstrong number
+expect isArmstrongNumber 9926314 == Bool.false
+

exercises/practice/leap/.meta/template.j2

@@ -7,6 +7,6 @@ import Leap exposing [isLeapYear]
 
 {% for case in cases -%}
 # {{ case["description"] }}
-expect (isLeapYear {{ case["input"]["year"] }}) == Bool.{{- case ["expected"] | lower }}
+expect (isLeapYear {{ case["input"]["year"] }}) == {{ case ["expected"] | to_roc_bool }}
 
 {% endfor %}

exercises/practice/reverse-string/.meta/Example.roc

@@ -18,7 +18,7 @@ reverse = \string ->
         graphemes = string |> Grapheme.split
         when graphemes is
             Ok gs -> gs |> List.reverse |> Str.joinWith ""
-            Err _ -> "Ooops"
+            Err _ -> "Unexpected error: could not split the string into graphemes"
 
 
 ## This function reverses the input string, e.g., "hello" -> "olleh". It is