Re^7: Perl list items

in reply to Re^6: Perl list items
in thread Perl list items

my @c = combine(5,@n); # get array of arrays my @A = @$c[0]; # get first sub-array
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Because the 'precedence' (if that's the proper term here) of the @ array dereference sigil is so high, the expression @$c[0] attempts to dereference an array reference held in the $c scalar (not in the @c array) and then access the element at index 0 in the referenced array. (Update: Actually, my first thought was that @$c[0] would look like a 'degenerate' array slice, like @x[0]; not sure why the appropriate warning was not generated.) The expression @{ $c[0] } is what is needed in the given example.

>perl -wMstrict -MData::Dump -le
"my @c = (['x', 'y'], ['a', 'b'], ['c', 'd']);
 my $c = ['foo', 'bar'];
 ;;
 my @A1 = @  $c[0]  ;
 my @A2 = @{ $c[0] };
 dd \@A1;
 dd \@A2;
"
["foo"]

["x", "y"]
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Re^8: Perl list items by Anonymous Monk on Jul 10, 2012 at 08:37 UTC
To clarify `@$c[0]` means the same as `@{$c}[0]` meaning dereference $c, take array slice So `$ perl -e " use Data::Dump; my $c = [qw/ a b c/]; dd @$c[1,2]; " ("b", "c")` [download] While References quick reference lists this item explicitly (item 2), its somewhat documented in perlreftut/perlref but its not recommended	[reply] [d/l] [select]
Re^9: Perl list items by AnomalousMonk (Archbishop) on Jul 10, 2012 at 09:13 UTC
To clarify @$c[0] means the same as @{$c}[0] meaning dereference $c, take array slice Well... I'm not sure it's that much more clear. After all, "I know what I mean, ..." I'm still puzzled by the absence of a "... better written as ..." warning. Maybe the usage is just too far off the beaten track for warnings to stumble over. `>perl -wMstrict -le "my @c = ('foo'); print @c[0]; ;; my $c = ['bar']; print @{$c}[0]; print @ $c [0]; " Scalar value @c[0] better written as $c[0] at -e line 1. foo bar bar` [download]	[reply] [d/l]
Re^10: Perl list items by Anonymous Monk on Jul 10, 2012 at 09:24 UTC
I'm still puzzled by the absence of a "... better written as ..." warning. Because the code is different :) Because @warnme... is different from @$derefNowarn... For verbosity see diagnostics, try `perl -Mdiagnostics -e " @ARGV[0] "`	[reply] [d/l]
Re^11: Perl list items by AnomalousMonk (Archbishop) on Jul 10, 2012 at 10:36 UTC

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