Course of Raku / Regexes and grammars / Grammars / The parse tree, make and made / Exercises / Extract the number

Solution: Extract the number

Here is a possible solution to the task.

Code

grammar Weight {
    token TOP    { <number> 'kg' { make $<number>.Int } }
    token number { \d+ }
}

say Weight.parse('5kg').made;

🦋 You can find the source code in the file extract-the-number.raku.

Output

5

Comments

1. The pattern matches the digits and the literal kg, but the inline block stores only $<number>.Int — the integer, without the unit.

2. made reads that value back: a real 5, ready to compute with, rather than the text 5kg. This is the typical job of make — turning a match into the clean value you actually want.

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