Zig Collections

Implementation of some useful data structures in Zig. Inspired by Python's collections module.

Installation

1. In the root directory of your project, run the following command to add zig_collections to your build.zig.zon file (replace 0.0.2 with the latest release number):

   zig fetch --save https://github.com/insolor/zig-collections/archive/refs/tags/0.0.2.zip
   

   Replace main in the URL with the tag you want to use.

2. Add zig_collections as a dependency module in your build.zig file, example:

   const zig_collections = b.dependency("zig_collections", .{});
   exe.root_module.addImport("zig_collections", zig_collections.module("zig_collections"));
   

After that, you'll be able to import zig_collections namespace from your code:

const zig_collections = @import("zig_collections");
const Counter = zig_collections.Counter;
const DefaultHashMap = zig_collections.DefaultHashMap;

Usage examples

Implemented so far:

• ✅ Counter:
  • a minimal functionality is implemented: increment of a value of a key, counting of duplicate values from a slice or an iterator
• ✅ defaultdict (DefaultHashMap)

Counter usage examples

test "add from slice" {
    var counter = Counter(u8).init(allocator);
    defer counter.deinit();

    const array = [_]u8{ 1, 2, 2, 3, 3, 3 };
    try counter.addFromSlice(array[0..]);
    try expectEqual(1, counter.get(1));
    try expectEqual(2, counter.get(2));
    try expectEqual(3, counter.get(3));
}

test "add from iterator" {
    var counter = Counter([]const u8).init(allocator);
    defer counter.deinit();

    const text = "alice bob alice";
    var iterator = std.mem.splitScalar(u8, text, ' ');
    try counter.addFromIterator(&iterator);
    try expectEqual(2, counter.get("alice"));
    try expectEqual(1, counter.get("bob"));
}

DefaultHashMap example

test "DefaultHashMap with list" {
    const EmptyArrayListFactory = struct {
        allocator: std.mem.Allocator,

        fn produce(self: @This()) ArrayList(u8) {
            return ArrayList(u8).init(self.allocator);
        }
    };

    var map = collections.DefaultHashMap(
        u8,
        ArrayList(u8),
        EmptyArrayListFactory{ .allocator = allocator },
        EmptyArrayListFactory.produce,
    ).init(allocator);

    defer map.deinit();

    const array = [_]u8{ 3, 3, 1, 2, 3, 2 };
    for (array, 0..) |item, i| {
        try map.get(item).append(@intCast(i));
    }

    try expectEqualDeep(&[_]u8{2}, map.get(1).items);
    try expectEqualDeep(&[_]u8{ 3, 5 }, map.get(2).items);
    try expectEqualDeep(&[_]u8{ 0, 1, 4 }, map.get(3).items);
}

Corresponding Python code:

from collections import defaultdict

dmap = defaultdict(list)

array = [3, 3, 1, 2, 3, 2]
for i, item in enumerate(array):
    dmap[item].append(i)

assert [2] == dmap[1]
assert [3, 5] == dmap[2]
assert [0, 1, 4] == dmap[3]