Slangify-Tutorial

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02. Your First Schema

In Slangify, the DSL schema is a Raku Grammar. Each named token is a field; the TOP rule defines the canonical DSL line the LLM must produce.

The booking grammar

grammar Slangify::Tutorial::Grammar {
    token TOP {
        <.ws>
        name        <.ws> <name>       <.ws>
        party       <.ws> <party>      <.ws>
        time        <.ws> <time>       <.ws>
        restaurant  <.ws> <restaurant> <.ws>
        date        <.ws> <date>       <.ws>?
        $
    }

    token name       { '"' <( <-["]>+ )> '"' }
    token party      { \d+                   }
    token time       { \d+ ':' \d\d          }
    token restaurant { '"' <( <-["]>+ )> '"' }
    token date       { \S+                   }
    token ws         { \h*                   }
}

Field types

name / restaurant

Quoted string — any characters except ". The <( )> markers strip the surrounding quotes from the capture.

party

One or more digits — coerced to Int by the Booking class.

time

24-hour HH:MM — e.g. 19:30 for 7:30 pm.

date

Any non-whitespace token: today, tomorrow, a weekday, or 2026-06-01.

Required vs optional

Every field in TOP is required by default. To make a field optional, add **{0..1} or ? after its subrule call, and handle the missing case in Booking.

Testing the grammar standalone

The grammar parses the canonical DSL line without any LLM, keeping the schema that defines your DSL distinct and concrete to maximize clarity, effectiveness and ease of test:

my $m = Slangify::Tutorial::Grammar.parse(
    'name "Jane" party 4 time 19:30 restaurant "Bistro Verde" date tomorrow'
);
say $m<name>;        # Jane
say $m<party>;       # 4
say $m<restaurant>;  # Bistro Verde

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