Re: Consise way to filter out keys with undef values from a hash slice?

This

> grep { $args{$_ } } keys %ta;

Will also delete all false values like 0 or "" . You rather want to test on definedness and not truth

This keys on a slice

> keys %args{'profile', 'user', 'password'};

Is over complicated and doesn't make sense.

You obviously just want the list of keys directly

'profile', 'user', 'password'

But I concur with choroba that using exists right from the beginning is the cleanest way, since undef could be a legal value.

There is - unfortunately - no "slice when exists" operator in Perl.

Otherwise (ab)using hashes for set operations like intersections would be trivial.

Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery}

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Re^2: Consise way to filter out keys with undef values from a hash slice? by LanX (Saint) on Jun 01, 2020 at 22:00 UTC
On a side note, I was surprised that the following is even legal syntax. I only knew slicing lists with @ > `%args{'profile', 'user', 'password'};` Turns out it was introduced with 5.20 and returns a list of key/value pairs. Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l]
Re^2: Consise way to filter out keys with undef values from a hash slice? by jo37 (Deacon) on Jun 02, 2020 at 19:05 UTC
Otherwise (ab)using hashes for set operations like intersections would be trivial. Though off-topic here: Is there a common idiom for an intersection of two hash-sets? The first thing that comes to my mind is something like: `%a_b = map {exists $b{$_} ? ($_ => $b{$_}) : ()} keys %a;` [download] Greetings, -jo `$gryYup$d0ylprbpriprrYpkJl2xyl~rzg??P~5lp2hyl0p$`	[reply] [d/l]
Re^3: Consise way to filter out keys with undef values from a hash slice? by LanX (Saint) on Jun 02, 2020 at 22:54 UTC
Hi You might be interested in this older thread Using hashes for set operations... and this particular post Re: Using hashes for set operations... Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply]


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