Re: Array wierdness

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Re^2: Array wierdness by lgp (Initiate) on Apr 25, 2022 at 14:30 UTC
Thanks for the explanation. FWIW, assigning the numbers to the arrays in separate lines makes no difference.	[reply]
Re^3: Array wierdness by Animator (Hermit) on Apr 25, 2022 at 15:36 UTC
Just to elaborate a bit more on this, consider the code: `my @PP = ("foo", "bar", "baz"); my @OO = ("AAA", "bar", "CCC"); $PP[1][0] = "foobar";` [download] What happens is that this does not modify the `@PP` array, instead it uses the value of `$PP[1]` as an array reference which points to the global(/package) variable `@bar`. To make this a bit clearer: `#!/usr/bin/perl -l my @PP = ("foo", "bar", "baz"); my @OO = ("AAA", "bar", "CCC"); $PP[1][0] = "foobar"; print "\@PP: " . join(", ", @PP); print "\@OO: " . join(", ", @OO); print "\@bar: " . join(", ", @::bar);` [download] Output: @PP: foo, bar, baz @OO: AAA, bar, CCC @bar: foobar The '@PP' and '@OO' array are unmodified; the '@bar' array however was created. With `use strict;` you get the error: Can't use string ("bar") as an ARRAY ref while "strict refs" in use	[reply] [d/l] [select]
Re^3: Array wierdness by pryrt (Abbot) on Apr 25, 2022 at 15:34 UTC
FWIW, assigning the numbers to the arrays in separate lines makes no difference. This is because your code's comments are wrong: `# fill two 25 x 25 arrays with zeros, then modify a couple of cells my @PP = my @OO = (1..25);` [download] This does not create 25x25 arrays, this creates 1x25 arrays. Below shows a 1x25 (what you have) vs a 2x5: `use strict; use warnings; use Data::Dump; my @one_by_twentyfive = (1..25); my @two_by_five = ([1..5],[1..5]); dd \@one_by_twentyfive; dd \@two_by_five; __END__ [1 .. 25] [[1 .. 5], [1 .. 5]]` [download] or this one populates a 25x25 array, then overrides 3 slots: use strict; use warnings; use Data::Dump; my @pp; push @pp, [1..25] for 1..25; dd \@pp; $pp[1][1] = 1; $pp[2][2] = 2; $pp[3][3] = 3; dd \@pp; __END__ [ [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], ] [ [1 .. 25], [1, 1, 3 .. 25], [1, 2, 2, 4 .. 25], [1, 2, 3, 3, 5 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], [1 .. 25], ] [download]	[reply] [d/l] [select]
Re^4: Array wierdness -- initialize AoA by Discipulus (Canon) on Apr 26, 2022 at 09:04 UTC
Hello, you can also initialize an ArrayOfArrays setting default values using x (repetition operator in list context) like in: `@aoa = ([( 1 ) x 3]) x 3` L* PS I evidently need more coffeine this morning.. see below There are no rules, there are no thumbs.. Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.	[reply] [d/l]
Re^5: Array wierdness -- initialize AoA by hv (Prior) on Apr 26, 2022 at 09:13 UTC
Re^3: Array weirdness by LanX (Saint) on Apr 26, 2022 at 10:25 UTC
short answer print this on a t-shirt: "use `strict` or die!" and wear it at work. ;-) long answer `$PP[1][2]=3` is a shorter notation for `$PP[1]->[2] = 3` so with `$PP[1] == $OO[1] == 1` what you are effectively doing is `1->[2] = 3` which is just populating `@1` debugger-demo `perl -de0` `DB<46> 1->[2] = 3 DB<47> x @1 0 undef 1 undef 2 3 DB<48>` [download] For good reasons that's forbidden under strict `DB<45> use strict; my @PP; $PP[1]=1; $PP[1][2] = 3 Can't use string ("1") as an ARRAY ref while "strict refs" in use at ( +eval 66) ...` [download] > FWIW, assigning the numbers to the arrays in separate lines makes no difference. Well I hope it's now clearer why... Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]

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