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ambrus has asked for the wisdom of the Perl Monks concerning the following question: ⭐ (data structures)

How to check whether a hash is empty (has no keys)?

Originally posted as a Categorized Question.

  • Comment on How to check whether a hash is empty (has no keys)?

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Re: How to check whether a hash is empty (has no keys)?⭐
by ambrus (Abbot) on Sep 05, 2011 at 10:32 UTC

    Just use the name of the hash in scalar context, such as 

    if (%foo) {
    # %foo has at least one key
} else {
    # %foo has no keys
}

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    If you want to be very explicit, you can also write 

    if (!!%foo) { ... }

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    or 
    if (scalar %foo) { ... }

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    or 
    if (0+%foo) { ... }

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Re: How to check whether a hash is empty (has no keys)?⭐
by davido (Cardinal) on Sep 06, 2011 at 02:13 UTC
    keys, in scalar context returns the number of keys in the hash. 
    if( keys %hash ) {
    # There are keys
} else {
    # There are no keys
}

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