[gleam] complete luhn

gleam/luhn/.gitignore

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+*.beam
+*.ez
+build
+erl_crash.dump

gleam/luhn/HELP.md

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+# Help
+
+## Running the tests
+
+To run the tests, run the command `gleam test` from within the exercise directory.
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit src/luhn.gleam` command.
+This command will upload your solution to the Exercism website and print the solution page's URL.
+
+It's possible to submit an incomplete solution which allows you to:
+
+- See how others have completed the exercise
+- Request help from a mentor
+
+## Need to get help?
+
+If you'd like help solving the exercise, check the following pages:
+
+- The [Gleam track's documentation](https://exercism.org/docs/tracks/gleam)
+- The [Gleam track's programming category on the forum](https://forum.exercism.org/c/programming/gleam)
+- [Exercism's programming category on the forum](https://forum.exercism.org/c/programming/5)
+- The [Frequently Asked Questions](https://exercism.org/docs/using/faqs)
+
+Should those resources not suffice, you could submit your (incomplete) solution to request mentoring.
+
+To get help if you're having trouble, you can use one of the following resources:
+
+- [gleam.run](https://gleam.run/documentation/) is the gleam official documentation.
+- [Discord](https://discord.gg/Fm8Pwmy) is the discord channel.
+- [StackOverflow](https://stackoverflow.com/questions/tagged/gleam) can be used to search for your problem and see if it has been answered already. You can also ask and answer questions.

gleam/luhn/README.md

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+# Luhn
+
+Welcome to Luhn on Exercism's Gleam Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## 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
+
+## Source
+
+### Created by
+
+- @natanaelsirqueira
+
+### Based on
+
+The Luhn Algorithm on Wikipedia - https://en.wikipedia.org/wiki/Luhn_algorithm

gleam/luhn/gleam.toml

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+name = "luhn"
+version = "0.1.0"
+
+[dependencies]
+gleam_bitwise = "~> 1.2"
+gleam_otp = "~> 0.7 or ~> 1.0"
+gleam_stdlib = "~> 0.32 or ~> 1.0"
+simplifile = "~> 1.0"
+gleam_erlang = ">= 0.25.0 and < 1.0.0"
+
+[dev-dependencies]
+exercism_test_runner = "~> 1.4"

gleam/luhn/manifest.toml

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+# This file was generated by Gleam
+# You typically do not need to edit this file
+
+packages = [
+  { name = "argv", version = "1.0.1", build_tools = ["gleam"], requirements = [], otp_app = "argv", source = "hex", outer_checksum = "A6E9009E50BBE863EB37D963E4315398D41A3D87D0075480FC244125808F964A" },
+  { name = "exercism_test_runner", version = "1.7.0", build_tools = ["gleam"], requirements = ["argv", "gap", "glance", "gleam_community_ansi", "gleam_erlang", "gleam_json", "gleam_stdlib", "simplifile"], otp_app = "exercism_test_runner", source = "hex", outer_checksum = "2FC1BADB19BEC2AE77BFD2D3A606A014C85412A7B874CAFC4BA8CF04B0B257CD" },
+  { name = "gap", version = "1.1.0", build_tools = ["gleam"], requirements = ["gleam_community_ansi", "gleam_stdlib"], otp_app = "gap", source = "hex", outer_checksum = "2EE1B0A17E85CF73A0C1D29DA315A2699117A8F549C8E8D89FA8261BE41EDEB1" },
+  { name = "glance", version = "0.8.2", build_tools = ["gleam"], requirements = ["gleam_stdlib", "glexer"], otp_app = "glance", source = "hex", outer_checksum = "ACF09457E8B564AD7A0D823DAFDD326F58263C01ACB0D432A9BEFDEDD1DA8E73" },
+  { name = "gleam_bitwise", version = "1.3.1", build_tools = ["gleam"], requirements = [], otp_app = "gleam_bitwise", source = "hex", outer_checksum = "B36E1D3188D7F594C7FD4F43D0D2CE17561DE896202017548578B16FE1FE9EFC" },
+  { name = "gleam_community_ansi", version = "1.4.0", build_tools = ["gleam"], requirements = ["gleam_community_colour", "gleam_stdlib"], otp_app = "gleam_community_ansi", source = "hex", outer_checksum = "FE79E08BF97009729259B6357EC058315B6FBB916FAD1C2FF9355115FEB0D3A4" },
+  { name = "gleam_community_colour", version = "1.3.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_community_colour", source = "hex", outer_checksum = "A49A5E3AE8B637A5ACBA80ECB9B1AFE89FD3D5351FF6410A42B84F666D40D7D5" },
+  { name = "gleam_erlang", version = "0.25.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "gleam_erlang", source = "hex", outer_checksum = "054D571A7092D2A9727B3E5D183B7507DAB0DA41556EC9133606F09C15497373" },
+  { name = "gleam_json", version = "1.0.0", build_tools = ["gleam"], requirements = ["gleam_stdlib", "thoas"], otp_app = "gleam_json", source = "hex", outer_checksum = "8B197DD5D578EA6AC2C0D4BDC634C71A5BCA8E7DB5F47091C263ECB411A60DF3" },
+  { name = "gleam_otp", version = "0.10.0", build_tools = ["gleam"], requirements = ["gleam_erlang", "gleam_stdlib"], otp_app = "gleam_otp", source = "hex", outer_checksum = "0B04FE915ACECE539B317F9652CAADBBC0F000184D586AAAF2D94C100945D72B" },
+  { name = "gleam_stdlib", version = "0.36.0", build_tools = ["gleam"], requirements = [], otp_app = "gleam_stdlib", source = "hex", outer_checksum = "C0D14D807FEC6F8A08A7C9EF8DFDE6AE5C10E40E21325B2B29365965D82EB3D4" },
+  { name = "glexer", version = "0.7.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "glexer", source = "hex", outer_checksum = "4484942A465482A0A100936E1E5F12314DB4B5AC0D87575A7B9E9062090B96BE" },
+  { name = "simplifile", version = "1.5.0", build_tools = ["gleam"], requirements = ["gleam_stdlib"], otp_app = "simplifile", source = "hex", outer_checksum = "EB9AA8E65E5C1E3E0FDCFC81BC363FD433CB122D7D062750FFDF24DE4AC40116" },
+  { name = "thoas", version = "0.4.1", build_tools = ["rebar3"], requirements = [], otp_app = "thoas", source = "hex", outer_checksum = "4918D50026C073C4AB1388437132C77A6F6F7C8AC43C60C13758CC0ADCE2134E" },
+]
+
+[requirements]
+exercism_test_runner = { version = "~> 1.4" }
+gleam_bitwise = { version = "~> 1.2" }
+gleam_erlang = { version = ">= 0.25.0 and < 1.0.0"}
+gleam_otp = { version = "~> 0.7 or ~> 1.0" }
+gleam_stdlib = { version = "~> 0.32 or ~> 1.0" }
+simplifile = { version = "~> 1.0" }

gleam/luhn/src/luhn.gleam

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+import gleam/int
+import gleam/list
+import gleam/string
+
+pub fn valid(value: String) -> Bool {
+  let digits =
+    value
+    |> string.replace(" ", "")
+    |> string.to_graphemes()
+    |> list.try_map(int.parse)
+
+  case digits {
+    Ok(digits) -> list.length(digits) > 1 && luhn_sum(digits) % 10 == 0
+    _ -> False
+  }
+}
+
+fn luhn_sum(digits: List(Int)) -> Int {
+  list.index_fold(list.reverse(digits), 0, fn(sum, n, index) {
+    case int.is_odd(index), n * 2 {
+      False, _ -> sum + n
+      True, double if double <= 9 -> sum + double
+      True, double -> sum + double - 9
+    }
+  })
+}

gleam/luhn/test/luhn_test.gleam

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+import exercism/test_runner
+import luhn
+
+pub fn main() {
+  test_runner.main()
+}
+
+pub fn single_digit_strings_can_not_be_valid_test() {
+  let assert False = luhn.valid("1")
+}
+
+pub fn a_single_zero_is_invalid_test() {
+  let assert False = luhn.valid("0")
+}
+
+pub fn a_simple_valid_sin_that_remains_valid_if_reversed_test() {
+  let assert True = luhn.valid("059")
+}
+
+pub fn a_simple_valid_sin_that_becomes_invalid_if_reversed_test() {
+  let assert True = luhn.valid("59")
+}
+
+pub fn a_valid_canadian_sin_test() {
+  let assert True = luhn.valid("055 444 285")
+}
+
+pub fn invalid_canadian_sin_test() {
+  let assert False = luhn.valid("055 444 286")
+}
+
+pub fn invalid_credit_card_test() {
+  let assert False = luhn.valid("8273 1232 7352 0569")
+}
+
+pub fn invalid_long_number_with_an_even_remainder_test() {
+  let assert False = luhn.valid("1 2345 6789 1234 5678 9012")
+}
+
+pub fn invalid_long_number_with_a_remainder_divisible_by_5_test() {
+  let assert False = luhn.valid("1 2345 6789 1234 5678 9013")
+}
+
+pub fn valid_number_with_an_even_number_of_digits_test() {
+  let assert True = luhn.valid("095 245 88")
+}
+
+pub fn valid_number_with_an_odd_number_of_spaces_test() {
+  let assert True = luhn.valid("234 567 891 234")
+}
+
+pub fn valid_strings_with_a_non_digit_added_at_the_end_become_invalid_test() {
+  let assert False = luhn.valid("059a")
+}
+
+pub fn valid_strings_with_punctuation_included_become_invalid_test() {
+  let assert False = luhn.valid("055-444-285")
+}
+
+pub fn valid_strings_with_symbols_included_become_invalid_test() {
+  let assert False = luhn.valid("055# 444$ 285")
+}
+
+pub fn single_zero_with_space_is_invalid_test() {
+  let assert False = luhn.valid(" 0")
+}
+
+pub fn more_than_a_single_zero_is_valid_test() {
+  let assert True = luhn.valid("0000 0")
+}
+
+pub fn input_digit_9_is_correctly_converted_to_output_digit_9_test() {
+  let assert True = luhn.valid("091")
+}
+
+pub fn very_long_input_is_valid_test() {
+  let assert True = luhn.valid("9999999999 9999999999 9999999999 9999999999")
+}
+
+pub fn valid_luhn_with_an_odd_number_of_digits_and_non_zero_first_digit_test() {
+  let assert True = luhn.valid("109")
+}
+
+pub fn using_ascii_value_for_non_doubled_non_digit_isn_t_allowed_test() {
+  let assert False = luhn.valid("055b 444 285")
+}
+
+pub fn using_ascii_value_for_doubled_non_digit_isn_t_allowed_test() {
+  let assert False = luhn.valid(":9")
+}
+
+pub fn non_numeric_non_space_char_in_the_middle_with_a_sum_that_s_divisible_by_10_isn_t_allowed_test() {
+  let assert False = luhn.valid("59%59")
+}