Re^2: Print something when key does not exist

Thanks so much for this insane one-liner. I have learnt so much about awk by writing and reading awk one liners. This will help a great deal as well.

Two questions:

What does the following mean? Is that for handling blank lines?

or !@F;
[download]

How does, index increment for the array in the following to cover every element?

say join ( "^", $_, @{ $h{$_} } {@w} ) for sort keys %h'
[download]

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Re^3: Print something when key does not exist by NetWallah (Canon) on Apr 06, 2014 at 04:51 UTC
++ for asking good questions. Yes the !@F handles blank lines. When split, these will leave the @F array unpopulated, so scalar(@F) will be 0, or false, and the line gets skipped. The %h is a Hash of Hashes. the outer "for sort keys %h" handles the first (outer) hash. Inside that, I use a "hash slice" to get an array of values for keys specified by @w (which is a sorted array). This is pretty much the same thing kcott does in his line: `map { $data{$name}{$_} \|\| '' } @codes;` [download] except - my code does not worry about non-existing keys - since I run without 'warnings', my code does the right thing without complaint. What is the sound of Perl? Is it not the sound of a wall that people have stopped banging their heads against? -Larry Wall, 1992	[reply] [d/l]
Re^4: Print something when key does not exist by jaypal (Beadle) on Apr 06, 2014 at 06:15 UTC
Thanks so much for your prompt response. Hash slice looks really handy. It effectively eliminated the need for two for loops I have in my answer.	[reply]