Re^2: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop)

That's a way to avoid the undocumented feature, but it is also nonstandard. I'll experiment with a variation though:

sort { $obj->_compare }
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which also passes $obj as first parameter and see if I still get $a and $b for free, which IS documented magic. Many thanks for the suggestion.

One world, one people

Comment on Re^2: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop) Download Code

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Re^3: Sort mechanics problems... (updated) by haukex (Archbishop) on Jun 01, 2016 at 16:05 UTC
and see if I still get $a and $b for free You can get at them: `use warnings; use strict; { package Bar; my $obj = Foo->new; print join ", ", sort {$obj->mysort($a,$b,"bar")} qw/x a o/; } { package Foo; sub new { bless {}, shift } use Data::Dump 'pp'; sub mysort { pp \@_; $_[0] cmp $_[1]; } } __END__ [bless({}, "Foo"), "x", "a", "bar"] [bless({}, "Foo"), "x", "o", "bar"] [bless({}, "Foo"), "o", "a", "bar"] x, o, a` [download] Updated example: Previously I had `mysort` reaching into the `main` package via `$::a`, which is obviously not the best solution, now I'm passing `$a` and `$b` as parameters. (I see the AM made the same suggestion.) Update 2: There are other solutions possible as well. Hope this helps, -- Hauke D	[reply] [d/l] [select]
Re^3: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop) by ikegami (Patriarch) on Jun 01, 2016 at 16:52 UTC
That makes things far more complicated. Because `_compare` is likely to be in a package other than the `sort`, `_compare` would have to use `${ caller.'::a' }` and `${ caller.'::b' }` instead of `$_[0]` and `$_[1]`. Best to pass `$a` and `$b` are arguments.	[reply] [d/l] [select]
Re^3: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop) by Anonymous Monk on Jun 01, 2016 at 16:06 UTC
If you pass $a and $b explicitly, you might be able to reuse that sub outside of sort. The "efficiency" of the implicit $a and $b is not really a big deal. `$obj->_compare($a,$b)`	[reply] [d/l]
Re^4: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop) by anonymized user 468275 (Curate) on Jun 01, 2016 at 16:21 UTC
It's not about efficiency. If $a and $b can't be relied on, any such use of the sort mechanism becomes definitively non-standard and the sort keyword would have to be avoided. One world, one people	[reply]
Re^5: Sort mechanics problems with objects and potentially contradicting comparisons (would cause infinite loop) by Anonymous Monk on Jun 01, 2016 at 16:26 UTC
They can be relied on, but they have scoping problems and can be confusing when your program spans multiple packages (see hakuex's edit).	[reply]