Course of Raku / Advanced / More about built-in types / Native types 🆕 / Exercises / Wrapping around

Solution: Wrapping around

Here is a possible solution to the task.

Code

my uint8 $u = 250;
$u += 10;
say $u;

my uint8 $v = 0;
$v--;
say $v;

🦋 You can find the source code in the file wrap-around.raku.

Output

4
255

Comments

1. A uint8 ranges from 0 to 255, which is 256 distinct values. Arithmetic on it is effectively done modulo 256.

2. 250 + 10 would be 260, which does not fit. It wraps around, landing 260 - 256 = 4 past the bottom. So overflow is not limited to stepping over the top by one — any result outside the range is folded back in.

3. Going the other way overflows too: decrementing 0 cannot give -1 in an unsigned type, so it wraps to the maximum, 255.

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