Re^5: enumerating values for slopes

The error occurs in the module, but the coding error is actually located in your calling program. When you do this:

my @vector = (4.3125, 0.4375);
push @AoA, @vector;
@vector = (4.375, 0.375);
push @AoA, @vector;
[download]

you are not creating an array of arrays (AoA), but a simple array whose 4 elements are:

(4.3125, 0.4375, 4.375, 0.375)
[download]

You need to push on @AoA a reference to @vector:
my @vector = (4.3125, 0.4375); push @AoA, \@vector; @vector = (4.375, 0.375); push @AoA, \@vector;
[download]
or build directly an array reference:

push @AoA, [4.3125, 0.4375];
push @AoA, [4.375, 0.375];
[download]

I guess this should solve your issue.

As I said earlier, you should avoid using the $a and $b variables, they are special variables used among other things for sorting, they behave differently from other variables, and using as you do them might lead to difficult-to-track bugs. You may use $c or $d, if you like, this will not be a problem, but I would personally put a more meaningful name helping comprehension of what they represent.

Update: As pointed below by farang the first method above for building an AoA is actually buggy. Use the second one. Thanks to farang for picking that.

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Re^6: enumerating values for slopes by farang (Chaplain) on Sep 24, 2014 at 02:07 UTC
You need to push on @AoA a reference to @vector: `my @vector = (4.3125, 0.4375); push @AoA, \@vector; @vector = (4.375, 0.375); push @AoA, \@vector;` [download] That way is buggy, though, as the redefinition of `@vector` will clobber the first `push`ed array element. This is explained under COMMON MISTAKES in `perldsc`, "taking a reference to the same memory location repeatedly". So both lines above should instead use a square bracket reference. `push @AoA, [ @vector ];` [download]	[reply] [d/l] [select]
Re^7: enumerating values for slopes by Laurent_R (Canon) on Sep 24, 2014 at 06:59 UTC
You are right, it's a mistake to push references to the same array without declaring it anew. I have been bitten by that a couple of times, I should know better. That's why I am actually almost always using the second method using the `[]` anonymous array reference constructor.	[reply] [d/l]
Re^6: enumerating values for slopes by Aldebaran (Curate) on Sep 24, 2014 at 06:30 UTC
$ perl sill2.pl elt 0 0 is 0.4375 elt 0 1 is 4.3125 elt 0 2 is bath-left elt 1 0 is 0.375 elt 1 1 is 4.375 elt 1 2 is bath-middle elt 2 0 is 0.375 elt 2 1 is 4.4375 elt 2 2 is bath-right bath-left has slope 5.82263230478133 bath-middle has slope 4.91710033552881 bath-right has slope 4.84767847916148 $ cat sill2.pl #!/usr/bin/perl -w use strict; use 5.010; use Math::Trig; BEGIN { push @INC, ".."; } use utils1; my @AoA; my $aoa_ref = \@AoA; my $vector_ref = [0.4375, 4.3125, "bath-left"]; push @AoA, $vector_ref; $vector_ref = [0.375, 4.375, "bath-middle"]; push @AoA, $vector_ref; $vector_ref = [0.375,4.4375, "bath-right"]; push @AoA, $vector_ref; print_aoa($aoa_ref); for my $i ( 0 .. $#AoA ) { my $ratio = $AoA[$i][0]/$AoA[$i][1]; my $rad = asin($ratio); my $degrees = rad2deg($rad); my $name = $AoA[$i][2]; say "$name has slope $degrees"; } __END__ $ [download] This might be the most robust version of this material.	[reply] [d/l]


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