ziglings/exercises/23_errors3.zig

//
// One way to deal with error unions is to "catch" any error and
// replace it with a default value.
//
//     foo = canFail() catch 6;
//
// If canFail() fails, foo will equal 6.
//
const std = @import("std");

const MyNumberError = error{ TooSmall };

pub fn main() void {
    var a: u32 = addTwenty(44) catch 22;
    var b: u32 = addTwenty(4)  ???   22;

    std.debug.print("a={}, b={}", .{a,b});
}

// Please provide the return type from this function.
// Hint: it'll be an error union.
fn addTwenty(n: u32) ??? {
    if (n < 5) {
        return MyNumberError.TooSmall;
    } else {
        return n + 20;
    }
}