std.AutoHashMap.zig

// from https://zig.guide/standard-library/hashmaps
// license https://github.com/sobeston/zig.guide?tab=MIT-1-ov-file#readme

const std = @import("std");
const test_allocator = std.testing.allocator;

test "hashing" {
    const Point = struct { x: i32, y: i32 };

    var map = std.AutoHashMap(u32, Point).init(
        test_allocator,
    );
    defer map.deinit();

    try map.put(1525, .{ .x = 1, .y = -4 });
    try map.put(1550, .{ .x = 2, .y = -3 });
    try map.put(1575, .{ .x = 3, .y = -2 });
    try map.put(1600, .{ .x = 4, .y = -1 });

    try std.testing.expect(map.count() == 4);

    var sum = Point{ .x = 0, .y = 0 };
    var iterator = map.iterator();

    while (iterator.next()) |entry| {
        sum.x += entry.value_ptr.x;
        sum.y += entry.value_ptr.y;
    }

    try std.testing.expect(sum.x == 10);
    try std.testing.expect(sum.y == -10);
}

test "fetchPut" {
    var map = std.AutoHashMap(u8, f32).init(
        test_allocator,
    );
    defer map.deinit();

    try map.put(255, 10);
    const old = try map.fetchPut(255, 100);

    try std.testing.expect(old.?.value == 10);
    try std.testing.expect(map.get(255).? == 100);
}