Course of Raku / Advanced / Subroutines / Multiple dispatch / Exercises / Classify the size

Solution: Classify the size

Here is a possible solution to the task.

Code

multi sub size(Int $n where $n.abs < 10)  { 'small' }
multi sub size(Int $n where $n.abs < 100) { 'medium' }
multi sub size(Int $n)                    { 'large' }

say size(7);
say size(30);
say size(-250);

🦋 You can find the source code in the file classify-sign.raku.

Output

small
medium
large

Comments

1. All three candidates take a single Int, so without the where clauses they would clash. The conditions on the first two make them distinct, and the third is the catch-all.

2. The where clauses test $n.abs, so the magnitude alone decides the result and the sign is ignored. size(7) matches the first candidate (small), while size(-250) has an absolute value of 250, which fails both conditions and falls through to the catch-all (large).

3. The candidates are tested from the most specific to the most general — exactly the order in which they are written here.

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