diff options
Diffstat (limited to 'exercises/064_builtins.zig')
| -rw-r--r-- | exercises/064_builtins.zig | 40 |
1 files changed, 28 insertions, 12 deletions
diff --git a/exercises/064_builtins.zig b/exercises/064_builtins.zig index 508f8ed..018bf95 100644 --- a/exercises/064_builtins.zig +++ b/exercises/064_builtins.zig @@ -41,22 +41,38 @@ pub fn main() void { var my_result: u4 = undefined; var overflowed: bool = undefined; overflowed = @addWithOverflow(u4, a, b, &my_result); - // + + // Check out our fancy formatting! b:0>4 means, "print + // as a binary number, zero-pad right-aligned four digits." // The print() below will produce: "1101 + 0101 = 0010 (true)". - // Let's make sense of this answer by counting up from 1101: + print("{b:0>4} + {b:0>4} = {b:0>4} ({})", .{ a, b, my_result, overflowed }); + + // Let's make sense of this answer. The value of 'b' in decimal is 5. + // Let's add 5 to 'a' but go one by one and see where it overflows: // - // Overflowed? - // 1101 + 1 = 1110 No. - // 1110 + 1 = 1111 No. - // 1111 + 1 = 0000 Yes! (Real answer is 10000) - // 0000 + 1 = 0001 No. - // 0001 + 1 = 0010 No. + // a | b | result | overflowed? + // ---------------------------------- + // 1101 + 0001 = 1110 | false + // 1110 + 0001 = 1111 | false + // 1111 + 0001 = 0000 | true (the real answer is 10000) + // 0000 + 0001 = 0001 | false + // 0001 + 0001 = 0010 | false // - // Also, check out our fancy formatting! b:0>4 means, "print - // as a binary number, zero-pad right-aligned four digits." - print("{b:0>4} + {b:0>4} = {b:0>4} ({})", .{ a, b, my_result, overflowed }); + // In the last two lines the value of 'a' is corrupted because there was + // an overflow in line 3, but the operations of lines 4 and 5 themselves + // do not overflow. + // There is a difference between + // - a value, that overflowed at some point and is now corrupted + // - a single operation that overflows and maybe causes subsequent errors + // In practise we usually notice the overflowed value first and have to work + // our way backwards to the operation that caused the overflow. + // + // If there was no overflow at all while adding 5 to a, what value would + // 'my_result' hold? Write the answer in into 'expected_result'. + const expected_result: u8 = ???; + print(". Without overflow: {b:0>8}. ", .{expected_result}); - print(". Furthermore, ", .{}); + print("Furthermore, ", .{}); // Here's a fun one: // |