Re^2: Hash vs constant vs package vs other for data structure

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Re^3: Hash vs constant vs package vs other for data structure by haukex (Archbishop) on Mar 27, 2017 at 19:09 UTC
What are the advantages of the hash method? Two that I can think of off the top of my head are that you can have sparse property sets (e.g. if one object has `{foo=>1,bar=>2}` and the other has `{quz=>1,baz=>2}`, whereas you'd need four array elements to cover that, a bit of a waste), and that textual serializations of the data would be self-documenting. But if neither of those are a concern to you, then at the moment I can't think of major disadvantages to using constants for the array indicies.	[reply] [d/l] [select]
Re^4: Hash vs constant vs package vs other for data structure by oldtechaa (Beadle) on Mar 27, 2017 at 19:46 UTC
I don't really need either of those, but I also would like to assign to slices, which would be difficult with a hash. I think I'll go with the constant method or uppercase variables probably.	[reply]
Re^5: Hash vs constant vs package vs other for data structure by Anonymous Monk on Mar 27, 2017 at 20:10 UTC
Constants set up with constant are inlined by the compiler (Constant Functions) and should be a little bit faster, and "safer" (no one can accidentally change your variables).	[reply]
Re^5: Hash vs constant vs package vs other for data structure by Anonymous Monk on Mar 27, 2017 at 20:24 UTC
I also would like to assign to slices, which would be difficult with a hash. It works: `$ perl -MData::Dump -e '@{$x[0][0]}{qw/a b/} = qw/c d/; dd \@x' [[{ a => "c", b => "d" }]]` [download]	[reply] [d/l]
Re^6: Hash vs constant vs package vs other for data structure by oldtechaa (Beadle) on Mar 27, 2017 at 20:31 UTC
Re^5: Hash vs constant vs package vs other for data structure by BillKSmith (Monsignor) on Mar 27, 2017 at 21:54 UTC
When faced with a choice which makes little difference, choose one and use it consistently on all future projects. (This restriction may influence your choice.) Bill	[reply]
Re^3: Hash vs constant vs package vs other for data structure by FreeBeerReekingMonk (Deacon) on Mar 27, 2017 at 21:14 UTC
`perl -MData::Dumper -E '$A[3][5][0]="foo"; die Dumper \@A'` output: `$VAR1 = [ undef, undef, undef, [ undef, undef, undef, undef, undef, [ 'foo' ] ] ];` [download] Long? Just try 300 by 500! `perl -MData::Dumper -E '$A{3}{5}{0}="foo"; die Dumper \%A'` output: `$VAR1 = { '3' => { '5' => { '0' => 'foo' } } };` [download] smaller, but slower to iterate through if you have lots of entries. Still you can use an intermediate variable that acts like a pointer: `perl -MData::Dumper -E '$A{3}{5}{0}="foo"; $v = $A{3}{5}; $v->{1}="bar +"; die Dumper \%A'` [download] if you have fixed dimensions... you can also try: $NUM = $x + $y$WIDTH so if you have 300 pixels wide, (x,y)=(3,5) becomes 3+5300 = 1503 but check if you will not run above your maxint: 718414 with that method	[reply] [d/l] [select]


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