Course of Raku / Functional, concurrent, reactive, and web programming / Reactive programming / react and whenever / The react block

Quiz — react

What does the following program print?

my @got;

react {
    whenever Supply.from-list(1, 2, 3, 4, 5) {
        @got.push($_);
        done if $_ == 3;
    }
}

say @got;
1[1 2 3]
0[1 2 3 4 5]
0[3]
0[4 5]

The whenever body collects each value, but calls done as soon as it sees 3. done closes the react block, so the supply is abandoned and 4 and 5 are never processed, leaving [1 2 3].

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