Re^4: Why doesn't exist work with hash slices?

Delete returns the deleted value*s* (plural) of a slice and you didn't test a slice. š

Exists returns an (informal) Boolean (1 or dualvar ""/0) for a hash entry, and logically should also return a list of booleans in case of a slice.

Cheers Rolf

_{(addicted to the Perl Programming Language :)

see Wikisyntax for the Monastery}

Edit

š) From the docs of delete I already linked to

my %hash = (foo => 11, bar => 22, baz => 33);
my $scalar = delete $hash{foo};         # $scalar is 11
$scalar = delete @hash{qw(foo bar)}; # $scalar is 22
my @array  = delete @hash{qw(foo baz)}; # @array  is (undef,33) <--- H
+ERE
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Re^5: Why doesn't exist work with hash slices? by ysth (Canon) on Sep 21, 2025 at 20:15 UTC
And if given a key value slice, delete returns a list of key value pairs of what was deleted from the hash. Not clear what a corresponding exists feature would do.	[reply]
Re^6: Why doesn't exist work with hash slices? by LanX (Saint) on Sep 22, 2025 at 09:17 UTC
> delete returns a list of key value pairs of what was deleted Yes and no. `delete` returns also key value pairs that are in the slice but didn't exist before, now with an undef value. `DB<1> @h{a..c}=1..3 DB<2> x delete %h{c,d} 0 'c' 1 3 2 'd' 3 undef DB<4> x delete @h{a,d} 0 1 1 undef DB<5>` [download] This means you can't use delete to calculate the intersection of two sets of keys. (Well you can, but only with detours). This is a missed opportunity with `delete %h{LIST}` we could have implemented sets via hashes. > Not clear what a corresponding exists feature would do Probably exactly the same thing like with a classic slice. But `exists SLICE` in scalar context could return the number of existing elements. This could be equally used to calculate `any` or `all` . Well this kind of would break the symmetry to delete SLICE with only returns the last element in the list. But this is a pretty useless feature anyway IMHO Cheers Rolf _{(addicted to the Perl Programming Language :) see Wikisyntax for the Monastery}	[reply] [d/l] [select]