Course of Raku / Regexes and grammars / Grammars / Tokens and rules / Exercises / A spaced rule

Solution: A spaced rule

Here is a possible solution to the task.

Code

grammar Phrase {
    rule TOP   { <word> <word> <word> }
    token word { \w+ }
}

say Phrase.parse('the quick fox').defined;

🦋 You can find the source code in the file spaced-rule.raku.

Output

True

Comments

1. Because TOP is a rule, each space written between the <word> calls requires whitespace in the input.

2. The string 'the quick fox' has spaces between all three words, so it parses. With a token for TOP, the spaces in the pattern would be ignored and the parse would fail.

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