Merge pull request #124 from keiravillekode/luhn

Add luhn exercise

config.json

@@ -71,6 +71,14 @@
         "prerequisites": [],
         "difficulty": 5
       },
+      {
+        "slug": "luhn",
+        "name": "Luhn",
+        "uuid": "ea924bf8-a870-47a3-8f26-a35cf62ed7eb",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 5
+      },
       {
         "slug": "difference-of-squares",
         "name": "Difference of Squares",

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

@@ -0,0 +1,5 @@
+# Instruction append
+
+## Reserved Memory
+
+The buffer for the input string uses bytes 64-319 of linear memory.

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/.eslintrc

@@ -0,0 +1,18 @@
+{
+  "root": true,
+  "extends": "@exercism/eslint-config-javascript",
+  "env": {
+    "jest": true
+  },
+  "overrides": [
+    {
+      "files": [
+        "*.spec.js"
+      ],
+      "excludedFiles": [
+        "custom.spec.js"
+      ],
+      "extends": "@exercism/eslint-config-javascript/maintainers"
+    }
+  ]
+}

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

@@ -0,0 +1,28 @@
+{
+  "authors": [
+    "keiravillekode"
+  ],
+  "files": {
+    "solution": [
+      "luhn.wat"
+    ],
+    "test": [
+      "luhn.spec.js"
+    ],
+    "example": [
+      ".meta/proof.ci.wat"
+    ],
+    "invalidator": [
+      "package.json"
+    ]
+  },
+  "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",
+  "custom": {
+    "version.tests.compatibility": "jest-27",
+    "flag.tests.task-per-describe": false,
+    "flag.tests.may-run-long": false,
+    "flag.tests.includes-optional": false
+  }
+}

exercises/practice/luhn/.meta/proof.ci.wat

@@ -0,0 +1,56 @@
+(module
+  (memory (export "mem") 1)
+
+  (global $SPACE i32 (i32.const 32))
+
+  (global $ZERO i32 (i32.const 48))
+
+  ;;
+  ;; Checks if a string is valid per the Luhn formula.
+  ;;
+  ;; @param {i32} offset - offset of string in linear memory
+  ;; @param {i32} length - length of string in linear memory
+  ;;
+  ;; @returns {i32} 1 if valid per Luhn formula, 0 otherwise
+  ;;
+  (func (export "valid") (param $offset i32) (param $length i32) (result i32)
+    (local $count i32)
+    (local $total i32)
+    (local $index i32)
+    (local $digit i32)
+
+    (local.set $count (i32.const 0))
+    (local.set $total (i32.const 0))
+
+    ;; We traverse the string once, starting from the end.
+    (local.set $index (i32.add (local.get $offset) (local.get $length)))
+    (loop
+      (if (i32.eq (local.get $index) (local.get $offset)) (then
+        (return (i32.and (i32.gt_u (local.get $count) (i32.const 1))
+                         (i32.eqz (i32.rem_u (local.get $total) (i32.const 10)))))
+      ))
+
+      (local.set $index (i32.sub (local.get $index) (i32.const 1)))
+      (local.set $digit (i32.load8_u (local.get $index)))
+      (br_if 0 (i32.eq (local.get $digit) (global.get $SPACE)))
+
+      (local.set $digit (i32.sub (local.get $digit) (global.get $ZERO)))
+      (if (i32.gt_u (local.get $digit) (i32.const 9)) (then
+        ;; $digit is not a valid digit.
+        (return (i32.const 0))
+      ))
+      (local.set $count (i32.add (local.get $count) (i32.const 1)))
+
+      (if (i32.eqz (i32.rem_u (local.get $count) (i32.const 2))) (then
+        (local.set $digit (i32.add (local.get $digit) (local.get $digit)))
+        (if (i32.gt_u (local.get $digit) (i32.const 9)) (then
+          (local.set $digit (i32.sub (local.get $digit) (i32.const 9)))
+        ))
+      ))
+
+      (local.set $total (i32.add (local.get $total) (local.get $digit)))
+      (br 0)
+    )
+    (unreachable)
+  )
+)

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"

exercises/practice/luhn/.npmrc

@@ -0,0 +1 @@
+audit=false

exercises/practice/luhn/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2021 Exercism
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

exercises/practice/luhn/babel.config.js

@@ -0,0 +1,4 @@
+export default {
+  presets: ["@exercism/babel-preset-javascript"],
+  plugins: [],
+};