gistfile1.txt

fn List(comptime T: type) type {
    return struct {
        const List_t = this;
        buf: []T,

        pub fn init(buf: []T) List_t {
            return List_t {
                .buf= buf
            };
        }

        // intentional isize instead of usize -> if negative, return error
        pub fn at(self: *List_t, i: isize) !T {
            if (i < 0) return error.NegativeValue;
            return self.buf[usize(i)];
        }
    };
}

const Item = struct {
    name: []const u8
};


fn NumberOrError() !i32 {
    return error.SomethingWentWrong;
}

pub fn main() void {
    const warn = @import("std").debug.warn;

    var buf: [10]Item = undefined;
    var i: usize = 0;
    while (i < buf.len) {
        buf[i] = Item {
            .name = "Whatever"
        };
    }

    var item_list = List(Item).init(&buf);
    var some_item = item_list.at(4);

    // // Uncomment here and build -- Can't unwrap error from `!Item`
    // if (some_item) |item| {
    //     warn("{}", item);
    // }

    if (NumberOrError()) |val| {
        warn("It worked!");
    } else |err| {
        warn("Error: {}", @errorName(err));
    }
}