This is a bit confusingly written.

The question was about checking if a hash is empty, and %h in scalar context can be used to do this portably (though the relative recent change makes it more efficient).

That said,

%h in scalar context can't be used to get the number of keys portably.

keys(%h) in scalar context can be used to get the number of keys portably and efficiently.

That's not true. You could aways use There was a relatively recent change thatefficiency of hash in boolean context

This is a bit confusingly written. That's not true. You could aways use There was a relatively recent change thatefficiency of hash in boolean context

> to portably get the number of keys in a hash, use keys in scalar context; scalar(%hash) is not backwards compatible

nitpick for the sake of fun, b/c of the magic of the string_to_number conversion using it as a number will portably work.

(tho I'd also prefer using keys here :)

  DB<1> p $]
5.024001

  DB<2> %h=(a=>0)

  DB<3> p scalar %h
1/8

  DB<4> p 0+ %h
1

  DB<5>
[download]

nitpick for the sake of fun, b/c of the magic of the string_to_number conversion using it as a number will portably work.

Sorry, no, it doesn't:

$ perlbrew exec perl -e '%h="a".."z";warn"$] ".keys%h," ".%h," ",0+%h,
+"\n"' >/dev/null
5.034000 13 13 13
5.032001 13 13 13
5.030003 13 13 13
5.028003 13 13 13
5.026003 13 13 13
5.024004 13 8/16 8
5.022004 13 10/16 10
5.020003 13 7/16 7
5.018004 13 11/16 11
5.016003 13 9/16 9
5.014004 13 9/16 9
5.012005 13 9/16 9
5.010001 13 9/16 9
5.010000 13 9/16 9
5.008009 13 9/16 9
5.008001 13 12/16 12
5.006002 13 4/8 4
[download]

Minor edits to shorten output.

damn you're right...

... of course #buckets <= #keys because of collisions.

Thanks for the correction! :)

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery}