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Merge pull request #127 from SimaDovakin/luhn-exercise
luhn-exercise: added new exercise
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‎config.json

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

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

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

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

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

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

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

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

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

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

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# Testing transcript for luhn exercise
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```ucm
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.> load ./luhn.u
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.> add
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.> load ./luhn.test.u
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.> add
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.> move.term luhn.tests tests
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```

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

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

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