$a and strict

mce has asked for the wisdom of the Perl Monks concerning the following question:

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Re (tilly) 1: $a and strict by tilly (Archbishop) on Jul 18, 2001 at 18:02 UTC
$a and $b are special because they are used by sort, so there is an exception for them. You should never use those as variable names. Among other problems, if you declare them with my, you will be unable to write custom sort functions afterwards. Oops.	[reply]
Re: Re (tilly) 1: $a and strict by John M. Dlugosz (Monsignor) on Jul 18, 2001 at 19:12 UTC
Only within the scope of the my, or anywhere after? What about having the sort function qualify the names, eg. $main::a, to avoid that issue?	[reply]
Re (tilly) 3: $a and strict by tilly (Archbishop) on Jul 18, 2001 at 19:15 UTC
There is only an issue with sort if you are not using the fully qualified package name and you are within the scope of a my declaration. (Or an our declaration from a different package.) Of course your co-workers may still want a clearer variable name...	[reply]
Re: Re (tilly) 3: $a and strict by danger (Priest) on Jul 19, 2001 at 00:29 UTC
Re: Re: Re (tilly) 3: $a and strict by Anonymous Monk on Jul 19, 2001 at 16:09 UTC
Some notes below your chosen depth have not been shown here
Re: Re (tilly) 3: $a and strict by John M. Dlugosz (Monsignor) on Jul 18, 2001 at 19:23 UTC
Re (tilly) 5: $a and strict by tilly (Archbishop) on Jul 18, 2001 at 21:22 UTC
Re: $a and strict by Masem (Monsignor) on Jul 18, 2001 at 18:00 UTC
$a and $b are special in that they are automagically defined in the main:: scope due to their use in the sort function. In other words, with regards to strictness, they're considered in the same class as @_, $_, etc. Dr. Michael K. Neylon - mneylon-pm@masemware.com \|\| "You've left the lens cap of your mind on again, Pinky" - The Brain	[reply]
Re (tilly) 2: $a and strict by tilly (Archbishop) on Jul 18, 2001 at 18:13 UTC
Not true. Unlike _, ENV, etc, $a and $b are in the current package. They are just~~, like @INC,~~ only exempt from strict. Beware! Should you wish to write a sort subroutine that will be called from another package, you must go out of your way to use $a and $b from their package, and not your own. (Similarly if they try to pass a sort subroutine into your function, it won't work as expected.) UPDATE Thanks tye for spotting my obvious thinko.	[reply]
Re: $a and strict by davorg (Chancellor) on Jul 18, 2001 at 18:02 UTC
`$a` and `$b` are special cases that are immune from `use strict 'vars'`. This is because of their use as the comparison variables in `sort`. -- <http://www.dave.org.uk> Perl Training in the UK <http://www.iterative-software.com>	[reply]
(kudra: $a used in sorting) Re: $a and strict by kudra (Vicar) on Jul 18, 2001 at 18:04 UTC
When you use strict, you need to explicitly declare your variables. That is why $c doesn't work. $a and $b are used for sorting and already belong to a package, so they do not require declaration.	[reply]
Re: $a and strict by Hofmator (Curate) on Jul 19, 2001 at 14:40 UTC
I searched perldoc , deja, O'Reilly books, strict.pm but no luck. You got your answer, but just a small comment - I don't think this information was so well hidden. From `perldoc strict` Because of their special use by sort(), the variables $a and $b are exempted from this check. The camel (3rd edition) has it in the index and this points to the section about the special variables. Furthermore you can find it in 'Pragmatic Modules'->use strict 'vars' -- Hofmator	[reply] [d/l]