Merge pull request #127 from SimaDovakin/luhn-exercise

luhn-exercise: added new exercise

config.json

@@ -391,6 +391,14 @@
         "prerequisites": [],
         "difficulty": 4
       },
+      {
+        "slug": "luhn",
+        "name": "Luhn",
+        "uuid": "209e0108-01b7-43e3-bdaa-a3b30ca6b5a2",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "scrabble-score",
         "name": "Scrabble Score",

exercises/practice/luhn/.docs/instructions.md

@@ -0,0 +1,64 @@
+# Instructions
+
+Given a number determine whether or not it is valid per the Luhn formula.
+
+The [Luhn algorithm][luhn] is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers and Canadian Social Insurance Numbers.
+
+The task is to check if a given string is valid.
+
+## Validating a Number
+
+Strings of length 1 or less are not valid.
+Spaces are allowed in the input, but they should be stripped before checking.
+All other non-digit characters are disallowed.
+
+### Example 1: valid credit card number
+
+```text
+4539 3195 0343 6467
+```
+
+The first step of the Luhn algorithm is to double every second digit, starting from the right.
+We will be doubling
+
+```text
+4_3_ 3_9_ 0_4_ 6_6_
+```
+
+If doubling the number results in a number greater than 9 then subtract 9 from the product.
+The results of our doubling:
+
+```text
+8569 6195 0383 3437
+```
+
+Then sum all of the digits:
+
+```text
+8+5+6+9+6+1+9+5+0+3+8+3+3+4+3+7 = 80
+```
+
+If the sum is evenly divisible by 10, then the number is valid.
+This number is valid!
+
+### Example 2: invalid credit card number
+
+```text
+8273 1232 7352 0569
+```
+
+Double the second digits, starting from the right
+
+```text
+7253 2262 5312 0539
+```
+
+Sum the digits
+
+```text
+7+2+5+3+2+2+6+2+5+3+1+2+0+5+3+9 = 57
+```
+
+57 is not evenly divisible by 10, so this number is not valid.
+
+[luhn]: https://en.wikipedia.org/wiki/Luhn_algorithm

exercises/practice/luhn/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "SimaDovakin"
+  ],
+  "files": {
+    "solution": [
+      "luhn.u"
+    ],
+    "test": [
+      "luhn.test.u"
+    ],
+    "example": [
+      ".meta/examples/luhn.example.u"
+    ]
+  },
+  "blurb": "Given a number determine whether or not it is valid per the Luhn formula.",
+  "source": "The Luhn Algorithm on Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Luhn_algorithm"
+}

exercises/practice/luhn/.meta/examples/luhn.example.u

@@ -0,0 +1,43 @@
+luhn.isValid : Text -> Boolean
+luhn.isValid string =
+  charList = toCharList string
+  digitCharList = List.filter (Class.is Class.digit) charList
+  match (charList |> any (not << isValidChar), 1 >= size digitCharList) with
+    (false, false) -> digitCharList
+                        |> map toDigit
+                        |> checkSum
+                        |> (s -> 0 == mod s 10)
+    (_, _) -> false
+
+luhn.checkSum : [Optional Nat] -> Nat
+luhn.checkSum digits =
+  digits
+    |> foldRight accumulateDigits (0, 0)
+    |> at2
+
+luhn.isValidChar : Char -> Boolean
+luhn.isValidChar char =
+  charClass = Class.or Class.digit Class.whitespace
+  Class.is charClass char
+
+luhn.toDigit : Char -> Optional Nat
+luhn.toDigit char =
+  codePoint = toNat char
+  match inRange 48 58 codePoint with
+    true -> Some (codePoint - 48)
+    false -> None
+
+luhn.doubleDigit : Nat -> Nat
+luhn.doubleDigit digit =
+  doubledDigit = digit * 2
+  match doubledDigit > 9 with
+    true -> doubledDigit - 9
+    false -> doubledDigit
+
+luhn.accumulateDigits : Optional Nat -> (Nat, Nat) -> (Nat, Nat)
+luhn.accumulateDigits digit acc =
+  (index, totalSum) = acc
+  match (digit, 1 == mod index 2) with
+    (Some d, true) -> (index + 1, totalSum + doubleDigit d)
+    (Some d, false) -> (index + 1, totalSum + d)
+    (_, _) -> (index, totalSum)

exercises/practice/luhn/.meta/testAnnotation.json

@@ -0,0 +1,90 @@
+[
+  {
+    "name": "luhn.isValid.tests.ex1",
+    "test_code": "expect (false == luhn.isValid \"1\")\n    |> Test.label \"single digit strings can not be valid\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex2",
+    "test_code": "expect (false == luhn.isValid \"0\")\n    |> Test.label \"a single zero is invalid\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex3",
+    "test_code": "expect (true == luhn.isValid \"059\")\n    |> Test.label \"a simple valid SIN that remains valid if reversed\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex4",
+    "test_code": "expect (true == luhn.isValid \"59\")\n    |> Test.label \"a simple valid SIN that becomes invalid if reversed\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex5",
+    "test_code": "expect (true == luhn.isValid \"055 444 285\")\n    |> Test.label \"a valid Canadian SIN\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex6",
+    "test_code": "expect (false == luhn.isValid \"055 444 286\")\n    |> Test.label \"invalid Canadian SIN\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex7",
+    "test_code": "expect (false == luhn.isValid \"8273 1232 7352 0569\")\n    |> Test.label \"invalid credit card\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex8",
+    "test_code": "expect (false == luhn.isValid \"1 2345 6789 1234 5678 9012\")\n    |> Test.label \"invalid long number with an even remainder\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex9",
+    "test_code": "expect (false == luhn.isValid \"1 2345 6789 1234 5678 9013\")\n    |> Test.label \"invalid long number with a remainder divisible by 5\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex10",
+    "test_code": "expect (true == luhn.isValid \"095 245 88\")\n    |> Test.label \"valid number with an even number of digits\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex11",
+    "test_code": "expect (true == luhn.isValid \"234 567 891 234\")\n    |> Test.label \"valid number with an odd number of spaces\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex12",
+    "test_code": "expect (false == luhn.isValid \"059a\")\n    |> Test.label \"valid strings with a non-digit added at the end become invalid\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex13",
+    "test_code": "expect (false == luhn.isValid \"055-444-285\")\n    |> Test.label \"valid strings with punctuation included become invalid\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex14",
+    "test_code": "expect (false == luhn.isValid \"055# 444$ 285\")\n    |> Test.label \"valid strings with symbols included become invalid\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex15",
+    "test_code": "expect (false == luhn.isValid \" 0\")\n    |> Test.label \"single zero with space is invalid\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex16",
+    "test_code": "expect (true == luhn.isValid \"0000 0\")\n    |> Test.label \"more than a single zero is valid\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex17",
+    "test_code": "expect (true == luhn.isValid \"091\")\n    |> Test.label \"input digit 9 is correctly converted to output digit 9\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex18",
+    "test_code": "expect (true == luhn.isValid \"9999999999 9999999999 9999999999 9999999999\")\n    |> Test.label \"very long input is valid\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex19",
+    "test_code": "expect (true == luhn.isValid \"109\")\n    |> Test.label \"valid luhn with an odd number of digits and non zero first digit\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex20",
+    "test_code": "expect (false == luhn.isValid \"055b 444 285\")\n    |> Test.label \"using ascii value for non-doubled non-digit isn't allowed\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex21",
+    "test_code": "expect (false == luhn.isValid \":9\")\n    |> Test.label \"using ascii value for doubled non-digit isn't allowed\""
+  },
+  {
+    "name": "luhn.isValid.tests.ex22",
+    "test_code": "expect (false == luhn.isValid \"59%59\")\n    |> Test.label \"non-numeric, non-space char in the middle with a sum that's divisible by 10 isn't allowed\""
+  }
+]

exercises/practice/luhn/.meta/testLoader.md

@@ -0,0 +1,9 @@
+# Testing transcript for luhn exercise
+
+```ucm
+.> load ./luhn.u
+.> add
+.> load ./luhn.test.u
+.> add
+.> move.term luhn.tests tests
+```

exercises/practice/luhn/.meta/tests.toml

@@ -0,0 +1,76 @@
+# 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.
+
+[792a7082-feb7-48c7-b88b-bbfec160865e]
+description = "single digit strings can not be valid"
+
+[698a7924-64d4-4d89-8daa-32e1aadc271e]
+description = "a single zero is invalid"
+
+[73c2f62b-9b10-4c9f-9a04-83cee7367965]
+description = "a simple valid SIN that remains valid if reversed"
+
+[9369092e-b095-439f-948d-498bd076be11]
+description = "a simple valid SIN that becomes invalid if reversed"
+
+[8f9f2350-1faf-4008-ba84-85cbb93ffeca]
+description = "a valid Canadian SIN"
+
+[1cdcf269-6560-44fc-91f6-5819a7548737]
+description = "invalid Canadian SIN"
+
+[656c48c1-34e8-4e60-9a5a-aad8a367810a]
+description = "invalid credit card"
+
+[20e67fad-2121-43ed-99a8-14b5b856adb9]
+description = "invalid long number with an even remainder"
+
+[7e7c9fc1-d994-457c-811e-d390d52fba5e]
+description = "invalid long number with a remainder divisible by 5"
+
+[ad2a0c5f-84ed-4e5b-95da-6011d6f4f0aa]
+description = "valid number with an even number of digits"
+
+[ef081c06-a41f-4761-8492-385e13c8202d]
+description = "valid number with an odd number of spaces"
+
+[bef66f64-6100-4cbb-8f94-4c9713c5e5b2]
+description = "valid strings with a non-digit added at the end become invalid"
+
+[2177e225-9ce7-40f6-b55d-fa420e62938e]
+description = "valid strings with punctuation included become invalid"
+
+[ebf04f27-9698-45e1-9afe-7e0851d0fe8d]
+description = "valid strings with symbols included become invalid"
+
+[08195c5e-ce7f-422c-a5eb-3e45fece68ba]
+description = "single zero with space is invalid"
+
+[12e63a3c-f866-4a79-8c14-b359fc386091]
+description = "more than a single zero is valid"
+
+[ab56fa80-5de8-4735-8a4a-14dae588663e]
+description = "input digit 9 is correctly converted to output digit 9"
+
+[b9887ee8-8337-46c5-bc45-3bcab51bc36f]
+description = "very long input is valid"
+
+[8a7c0e24-85ea-4154-9cf1-c2db90eabc08]
+description = "valid luhn with an odd number of digits and non zero first digit"
+
+[39a06a5a-5bad-4e0f-b215-b042d46209b1]
+description = "using ascii value for non-doubled non-digit isn't allowed"
+
+[f94cf191-a62f-4868-bc72-7253114aa157]
+description = "using ascii value for doubled non-digit isn't allowed"
+
+[8b72ad26-c8be-49a2-b99c-bcc3bf631b33]
+description = "non-numeric, non-space char in the middle with a sum that's divisible by 10 isn't allowed"