feat(test): port isbn-verifier to vlang (resolves #145)

config.json

@@ -121,6 +121,14 @@
         "prerequisites": [],
         "difficulty": 6
       },
+      {
+        "uuid": "c0a26fda-7ce7-43f0-8da1-cb5b5d5e434f",
+        "slug": "isbn-verifier",
+        "name": "ISBN Verifier",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "uuid": "e9a9d0d1-1756-4be5-8fc8-bd2d2d52611c",
         "slug": "grains",

exercises/practice/isbn-verifier/.docs/instructions.md

@@ -0,0 +1,42 @@
+# Instructions
+
+The [ISBN-10 verification process][isbn-verification] is used to validate book identification numbers.
+These normally contain dashes and look like: `3-598-21508-8`
+
+## ISBN
+
+The ISBN-10 format is 9 digits (0 to 9) plus one check character (either a digit or an X only).
+In the case the check character is an X, this represents the value '10'.
+These may be communicated with or without hyphens, and can be checked for their validity by the following formula:
+
+```text
+(d₁ * 10 + d₂ * 9 + d₃ * 8 + d₄ * 7 + d₅ * 6 + d₆ * 5 + d₇ * 4 + d₈ * 3 + d₉ * 2 + d₁₀ * 1) mod 11 == 0
+```
+
+If the result is 0, then it is a valid ISBN-10, otherwise it is invalid.
+
+## Example
+
+Let's take the ISBN-10 `3-598-21508-8`.
+We plug it in to the formula, and get:
+
+```text
+(3 * 10 + 5 * 9 + 9 * 8 + 8 * 7 + 2 * 6 + 1 * 5 + 5 * 4 + 0 * 3 + 8 * 2 + 8 * 1) mod 11 == 0
+```
+
+Since the result is 0, this proves that our ISBN is valid.
+
+## Task
+
+Given a string the program should check if the provided string is a valid ISBN-10.
+Putting this into place requires some thinking about preprocessing/parsing of the string prior to calculating the check digit for the ISBN.
+
+The program should be able to verify ISBN-10 both with and without separating dashes.
+
+## Caveats
+
+Converting from strings to numbers can be tricky in certain languages.
+Now, it's even trickier since the check digit of an ISBN-10 may be 'X' (representing '10').
+For instance `3-598-21507-X` is a valid ISBN-10.
+
+[isbn-verification]: https://en.wikipedia.org/wiki/International_Standard_Book_Number

exercises/practice/isbn-verifier/.meta/config.json

@@ -0,0 +1,11 @@
+{
+  "authors": ["m-charlton"],
+  "files": {
+    "solution": ["isbn-verifier.v"],
+    "test": ["run_test.v"],
+    "example": [".meta/example.v"]
+  },
+  "blurb": "Check if a given string is a valid ISBN-10 number.",
+  "source": "Converting a string into a number and some basic processing utilizing a relatable real world example.",
+  "source_url": "https://en.wikipedia.org/wiki/International_Standard_Book_Number#ISBN-10_check_digit_calculation"
+}

exercises/practice/isbn-verifier/.meta/example.v

@@ -0,0 +1,54 @@
+module main
+
+import arrays { group, sum }
+import regex { regex_opt }
+
+const (
+	isbn_len = 10
+
+	/*
+	Using a regular expression, I now have two problems:
+
+	https://blog.codinghorror.com/regular-expressions-now-you-have-two-problems/
+
+	however, it solves two problems:
+	- length check
+	- character validation
+	*/
+	isbn_re  = regex_opt(r'^\d{9}(\d|X)$') or { panic('Invalid ISBN-10 regular expression') }
+	weights  = []int{len: isbn_len, init: isbn_len - index} // [10, 9, 8, ..., 1]
+	zero     = int(`0`)
+)
+
+// convert single digit (`0`...`9`) to its integer equivalent.
+fn digit_to_int(d u8) int {
+	assert d.is_digit(), '<${d}> is not a valid digit'
+	return int(d) - zero
+}
+
+// is 'isbn_10' a valid ISBN-10 code?
+pub fn is_valid(isbn_10 string) bool {
+	norm_isbn := isbn_10.replace('-', '').trim_space()
+
+	if !isbn_re.matches_string(norm_isbn) {
+		return false
+	}
+
+	check_idx := isbn_len - 1
+	mut numbers := norm_isbn[..check_idx].bytes().map(digit_to_int(it))
+	check_num := norm_isbn[check_idx]
+
+	numbers << match check_num {
+		`X` { 10 }
+		else { digit_to_int(check_num) }
+	}
+
+	if total := sum(group[int](numbers, weights).map(fn (pair []int) int {
+		return pair[0] * pair[1]
+	}))
+	{
+		return total % 11 == 0
+	}
+
+	return false
+}

exercises/practice/isbn-verifier/.meta/tests.toml

@@ -0,0 +1,67 @@
+# 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.
+
+[0caa3eac-d2e3-4c29-8df8-b188bc8c9292]
+description = "valid isbn"
+
+[19f76b53-7c24-45f8-87b8-4604d0ccd248]
+description = "invalid isbn check digit"
+
+[4164bfee-fb0a-4a1c-9f70-64c6a1903dcd]
+description = "valid isbn with a check digit of 10"
+
+[3ed50db1-8982-4423-a993-93174a20825c]
+description = "check digit is a character other than X"
+
+[9416f4a5-fe01-4b61-a07b-eb75892ef562]
+description = "invalid check digit in isbn is not treated as zero"
+
+[c19ba0c4-014f-4dc3-a63f-ff9aefc9b5ec]
+description = "invalid character in isbn is not treated as zero"
+
+[28025280-2c39-4092-9719-f3234b89c627]
+description = "X is only valid as a check digit"
+
+[f6294e61-7e79-46b3-977b-f48789a4945b]
+description = "valid isbn without separating dashes"
+
+[185ab99b-3a1b-45f3-aeec-b80d80b07f0b]
+description = "isbn without separating dashes and X as check digit"
+
+[7725a837-ec8e-4528-a92a-d981dd8cf3e2]
+description = "isbn without check digit and dashes"
+
+[47e4dfba-9c20-46ed-9958-4d3190630bdf]
+description = "too long isbn and no dashes"
+
+[737f4e91-cbba-4175-95bf-ae630b41fb60]
+description = "too short isbn"
+
+[5458a128-a9b6-4ff8-8afb-674e74567cef]
+description = "isbn without check digit"
+
+[70b6ad83-d0a2-4ca7-a4d5-a9ab731800f7]
+description = "check digit of X should not be used for 0"
+
+[94610459-55ab-4c35-9b93-ff6ea1a8e562]
+description = "empty isbn"
+
+[7bff28d4-d770-48cc-80d6-b20b3a0fb46c]
+description = "input is 9 characters"
+
+[ed6e8d1b-382c-4081-8326-8b772c581fec]
+description = "invalid characters are not ignored after checking length"
+
+[daad3e58-ce00-4395-8a8e-e3eded1cdc86]
+description = "invalid characters are not ignored before checking length"
+
+[fb5e48d8-7c03-4bfb-a088-b101df16fdc3]
+description = "input is too long but contains a valid isbn"

exercises/practice/isbn-verifier/isbn-verifier.v

@@ -0,0 +1,4 @@
+module main
+
+pub fn is_valid(isbn_10 string) bool {
+}

exercises/practice/isbn-verifier/run_test.v

@@ -0,0 +1,77 @@
+module main
+
+fn test_a_valid_isbn() {
+	assert is_valid('3-598-21508-8')
+}
+
+fn test_invalid_isbn_check_digit() {
+	assert !is_valid('3-598-21508-9')
+}
+
+fn test_valid_isbn_with_a_check_digit_of_10() {
+	assert is_valid('3-598-21507-X')
+}
+
+fn test_check_digit_is_a_character_other_than_x() {
+	assert !is_valid('3-598-21507-A')
+}
+
+fn test_invalid_check_digit_in_isbn_is_not_treated_as_zero() {
+	assert !is_valid('4-598-21507-B')
+}
+
+fn test_invalid_character_in_isbn_is_not_treated_as_zero() {
+	assert !is_valid('3-598-P1581-X')
+}
+
+fn test_x_is_only_valid_as_a_check_digit() {
+	assert !is_valid('3-598-2X507-9')
+}
+
+fn test_valid_isbn_without_separating_dashes() {
+	assert is_valid('3598215088')
+}
+
+fn test_isbn_without_separating_dashes_and_x_as_check_digit() {
+	assert is_valid('359821507X')
+}
+
+fn test_isbn_without_check_digit_and_dashes() {
+	assert !is_valid('359821507')
+}
+
+fn test_too_long_isbn_and_no_dashes() {
+	assert !is_valid('3598215078X')
+}
+
+fn test_too_short_isbn() {
+	assert !is_valid('00')
+}
+
+fn test_isbn_without_check_digit() {
+	assert !is_valid('3-598-21507')
+}
+
+fn test_check_digit_of_x_should_not_be_used_for_0() {
+	assert !is_valid('3-598-21515-X')
+}
+
+fn test_empty_isbn() {
+	assert !is_valid('')
+}
+
+fn test_input_is_9_characters() {
+	assert !is_valid('134456729')
+}
+
+fn test_invalid_characters_are_not_ignored_after_checking_length() {
+	assert !is_valid('3132P34035')
+}
+
+fn test_invalid_characters_are_not_ignored_before_checking_length() {
+	assert !is_valid('3598P215088')
+}
+
+fn test_input_is_too_long_but_contains_a_valid_isbn() {
+	assert !is_valid('98245726788')
+}