Zig: completed ISBN Verifier

zig/isbn-verifier/.exercism/config.json

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+{
+  "authors": [
+    "ee7"
+  ],
+  "files": {
+    "solution": [
+      "isbn_verifier.zig"
+    ],
+    "test": [
+      "test_isbn_verifier.zig"
+    ],
+    "example": [
+      ".meta/example.zig"
+    ]
+  },
+  "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"
+}

zig/isbn-verifier/.exercism/metadata.json

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+{"track":"zig","exercise":"isbn-verifier","id":"6fb4e96621bf4b30a2306e514899179c","url":"https://exercism.org/tracks/zig/exercises/isbn-verifier","handle":"Chomp1295","is_requester":true,"auto_approve":false}

zig/isbn-verifier/HELP.md

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+# Help
+
+## Running the tests
+
+Write your code in `<exercise_name>.zig`.
+
+To run the tests for an exercise, run:
+
+```bash
+zig test test_exercise_name.zig
+```
+
+in the exercise's root directory (replacing `exercise_name` with the name of the exercise).
+
+## Submitting your solution
+
+You can submit your solution using the `exercism submit isbn_verifier.zig` 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 [Zig track's documentation](https://exercism.org/docs/tracks/zig)
+- The [Zig track's programming category on the forum](https://forum.exercism.org/c/programming/zig)
+- [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.
+
+- [The Zig Programming Language Documentation][documentation] is a great overview of all of the language features that Zig provides to those who use it.
+- [Zig Guide][zig-guide] is an excellent primer that explains the language features that Zig has to offer.
+- [Ziglings][ziglings] is highly recommended.
+  Learn Zig by fixing tiny broken programs.
+- [The Zig Programming Language Discord][discord-zig] is the main [Discord][discord].
+  It provides a great way to get in touch with the Zig community at large, and get some quick, direct help for any Zig related problem.
+- [#zig][irc] on irc.freenode.net is the main Zig IRC channel.
+- [/r/Zig][reddit] is the main Zig subreddit.
+- [Stack Overflow][stack-overflow] can be used to discover code snippets and solutions to problems that may have already asked and maybe solved by others.
+
+[discord]: https://discordapp.com
+[discord-zig]: https://discord.com/invite/gxsFFjE
+[documentation]: https://ziglang.org/documentation/master
+[irc]: https://webchat.freenode.net/?channels=%23zig
+[reddit]: https://www.reddit.com/r/Zig
+[stack-overflow]: https://stackoverflow.com/questions/tagged/zig
+[zig-guide]: https://zig.guide/
+[ziglings]: https://codeberg.org/ziglings/exercises

zig/isbn-verifier/README.md

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+# ISBN Verifier
+
+Welcome to ISBN Verifier on Exercism's Zig Track.
+If you need help running the tests or submitting your code, check out `HELP.md`.
+
+## 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
+
+## Source
+
+### Created by
+
+- @ee7
+
+### Based on
+
+Converting a string into a number and some basic processing utilizing a relatable real world example. - https://en.wikipedia.org/wiki/International_Standard_Book_Number#ISBN-10_check_digit_calculation

zig/isbn-verifier/isbn_verifier.zig

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+const std = @import("std");
+
+pub fn isValidIsbn10(s: []const u8) bool {
+    if (s.len < 10) return false;
+
+    var isbn: [10]u8 = undefined;
+    var pos: usize = 0;
+
+    for (s) |c| {
+        if (pos == 10) return false;
+
+        isbn[pos] = switch (c) {
+            '-' => continue,
+            '0'...'9' => blk: {
+                pos += 1;
+                break :blk std.fmt.parseInt(u8, &[_]u8{c}, 10) catch unreachable;
+            },
+            else => blk: {
+                if (c == 'X' and pos == 9) {
+                    pos += 1;
+                    break :blk 10;
+                } else {
+                    return false;
+                }
+            },
+        };
+    }
+
+    var sum: u32 = 0;
+    var factor: usize = 10;
+    var i: usize = 0;
+    while (factor > 0) : ({
+        factor -= 1;
+        i += 1;
+    }) {
+        sum += @intCast(isbn[i] * factor);
+    }
+
+    return sum % 11 == 0;
+}

zig/isbn-verifier/test_isbn_verifier.zig

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+const std = @import("std");
+const testing = std.testing;
+
+const isValidIsbn10 = @import("isbn_verifier.zig").isValidIsbn10;
+
+test "valid ISBN" {
+    try testing.expect(isValidIsbn10("3-598-21508-8"));
+}
+
+test "invalid ISBN check digit" {
+    try testing.expect(!isValidIsbn10("3-598-21508-9"));
+}
+
+test "valid ISBN with a check digit of 10" {
+    try testing.expect(isValidIsbn10("3-598-21507-X"));
+}
+
+test "check digit is a character other than x" {
+    try testing.expect(!isValidIsbn10("3-598-21507-A"));
+}
+
+test "invalid check digit in ISBN is not treated as zero" {
+    try testing.expect(!isValidIsbn10("4-598-21507-B"));
+}
+
+test "invalid character in ISBN is not treated as zero" {
+    try testing.expect(!isValidIsbn10("3-598-P1581-X"));
+}
+
+test "x is only valid as a check digit" {
+    try testing.expect(!isValidIsbn10("3-598-2X507-9"));
+}
+
+test "valid ISBN without separating dashes" {
+    try testing.expect(isValidIsbn10("3598215088"));
+}
+
+test "ISBN without separating dashes and x as check digit" {
+    try testing.expect(isValidIsbn10("359821507X"));
+}
+
+test "ISBN without check digit and dashes" {
+    try testing.expect(!isValidIsbn10("359821507"));
+}
+
+test "too long ISBN and no dashes" {
+    try testing.expect(!isValidIsbn10("3598215078X"));
+}
+
+test "too short ISBN" {
+    try testing.expect(!isValidIsbn10("00"));
+}
+
+test "ISBN without check digit" {
+    try testing.expect(!isValidIsbn10("3-598-21507"));
+}
+
+test "check digit of x should not be used for 0" {
+    try testing.expect(!isValidIsbn10("3-598-21515-X"));
+}
+
+test "empty ISBN" {
+    try testing.expect(!isValidIsbn10(""));
+}
+
+test "input is 9 characters" {
+    try testing.expect(!isValidIsbn10("134456729"));
+}
+
+test "invalid characters are not ignored after checking length" {
+    try testing.expect(!isValidIsbn10("3132P34035"));
+}
+
+test "invalid characters are not ignored before checking length" {
+    try testing.expect(!isValidIsbn10("3598P215088"));
+}
+
+test "input is too long but contains a valid ISBN" {
+    try testing.expect(!isValidIsbn10("98245726788"));
+}