CODEWITHSUNDEEP
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Jim Bollinger
Jim Bollinger

Reputation: 1815

How can I terminate a loop started in a BEGIN block?

I would like to show a progress bar while the application is loading/initializing.

This code doesn't work, but should give you an idea of what I'm trying to accomplish.

my Bool $done-compiling = False;
BEGIN {
    start repeat {
        print '*';
        sleep 0.33;
    } until $done-compiling;
};

INIT {
    $done-compiling = True;
};

Is there an event triggered that I could respond to in the BEGIN block?

Upvotes: 9

Views: 165

Answers (3)

codesections
codesections

Reputation: 9600

You've already gotten two answers that work. But both of them rely on using variables across different threads, which always makes me a bit nervous. Given that we need multiple threads here, I'd probably turn to one of Raku's helpful concurrency primitives. Here's a very minor change to the accepted answer that uses a Promise:

my Promise $done-compiling;
BEGIN {
    $done-compiling .= new;
    start repeat {
        print '*';
        sleep 0.33;
    } until $done-compiling ~~ Kept;
}

BEGIN sleep 3; # simulate compilation / loading

INIT $done-compiling.keep;

Upvotes: 2

raiph
raiph

Reputation: 32404

Liz has provided a solution in terms of the code you'd written, fixing the bug that was in your original.

Here's a simpler version:

BEGIN start repeat { print '*'; sleep 0.33 } until INIT True

(You might be thinking INIT True is some special feature but it just falls out naturally from how phasers that return a value work.)

Upvotes: 7

Elizabeth Mattijsen
Elizabeth Mattijsen

Reputation: 26924

I think the code is ok. And if you simulate loading, you'll see a progress bar of *'s:

my Bool $done-compiling;
BEGIN {
    start repeat {
        print '*';
        sleep 0.33;
    } until $done-compiling;
}

BEGIN sleep 3; # simulate compilation / loading

INIT $done-compiling = True;

Setting the flag in the INIT block should be enough! I guess you could consider execution of the INIT block to be the event you're looking for?

Upvotes: 6

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