so i'm reading through tom christiansen's perl style guide the other day, since i'm going to release a couple of projects into the community soon and it's just possible that people will, you know, look at them.

I get to slide 18, and encounter this:

Consider finding the union and intersection of two unique arrays @a an
+d @b:

    foreach $e (@a) { $union{$e} = 1 }
    foreach $e (@b) {
        if ( $union{$e} ) { $isect{$e} = 1 }
        $union{$e} = 1;
    }
    @union = keys %union;
    @isect = keys %isect;

This would be more idiomatically written as:

    foreach $e (@a, @b) { $union{$e}++ && $isect{$e}++ }
    @union = keys %union;
    @isect = keys %isect;

[download]

Idiomatic yes, working no. As far as i can see, but i can't quite bring myself to contradict the great man. %isect and %union are going to be the same, surely? the last line needs to be something like:

$isect{$_} > 1 && push(@isect,$_) for keys %isect;

[download]

but more stylish. Please would someone correct me if i've misunderstood?

In reply to mistake in style guide? by thpfft

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