Build a list of defined var's

Karger78 has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Build a list of defined var's by CountZero (Bishop) on Oct 20, 2009 at 18:46 UTC
Trying again. The Camel book has the following `for`-loop for enumerating all the variables in a package: `package Test; $testing = 'TEST'; @test_array = (qw/OneTest TwoTest/); %test_hash = ('testkey' => 'testvalue'); foreach $symname (sort keys %Test::) { local sym = $Test::{$symname}; print "\$$symname is defined\n" if defined $sym; print "\@$symname is nonnull\n" if @sym; print "\%$symname is nonnull\n" if %sym; }` [download] Slightly altering the loop content, will `undef` all the package variables. `package Test; $testing = 'TEST'; @test_array = (qw/OneTest TwoTest/); %test_hash = ('testkey' => 'testvalue'); foreach my $symname (sort keys %Test::) { local sym = $Test::{$symname}; if (defined $sym) {$sym = undef; print "\$$symname is cleared\n" } +; if (@sym) {@sym = undef; print "\@$symname is cleared\n" } +; if (%sym) {%sym = undef; print "\%$symname is cleared\n" } +; }` [download] It is not a full solution: it will not work under strict (note: lexical variables are not part of any package) and will be dangerous if used in the `main` package as it will undef also all the special variables CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James	[reply] [d/l] [select]
Re: Build a list of defined var's by ramlight (Friar) on Oct 20, 2009 at 18:26 UTC
It could be easy with a little preparation. You would have to define all of your variables as entries in a hash. Then you could iterate through all of the keys in the hash. `$variable{'a'} = 1; $variable{'b'} = $variable{'a'} + 1; foreach my $k (keys %variable) {$variable{$k} = $reset_value;}` [download] Of course your code would look rather ugly. But sometimes this approach can be useful.	[reply] [d/l]
Re^2: Build a list of defined var's by CountZero (Bishop) on Oct 20, 2009 at 18:48 UTC
Nice try! As a matter of fact, all variables are already in a hash: `%main::` for the main package. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James	[reply] [d/l]
Re: Build a list of defined var's by ikegami (Patriarch) on Oct 20, 2009 at 18:12 UTC
Not really, not perfectly. What are you trying to do.	[reply]
Re^2: Build a list of defined var's by Karger78 (Beadle) on Oct 20, 2009 at 18:15 UTC
Well witin my application, i have a reset button. I would like to undef all my var's that are currently defined. Instead of going though each var and undef them, i though it might be eaiser if there was a way to build a list into an array and just irrate though the array and undef them.	[reply]
Re^3: Build a list of defined var's by merlyn (Sage) on Oct 20, 2009 at 21:40 UTC
Surely you don't want to reset everything, as that would also reset things like `@INC`, making your program a little brain-dead. I mean, that's one of the reasons that `perldoc -f reset` includes the paragraph: `Resetting "A-Z" is not recommended because you'll wipe out + your @ARGV and @INC arrays and your %ENV hash. Resets only pack +age variables--lexical variables are unaffected, but they clea +n themselves up on scope exit anyway, so you'll probably wan +t to use them instead. See "my".` [download] The proper way to go about this is to use proper objects in your program, so that you can have a top level object that is associated with a particular session, and everything else hangs off of that. Then, to reset the session, just generate a new session object. -- Randal L. Schwartz, Perl hacker The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.	[reply] [d/l] [select]
Re^4: Build a list of defined var's by ikegami (Patriarch) on Oct 20, 2009 at 21:50 UTC
Re^3: Build a list of defined var's by ikegami (Patriarch) on Oct 20, 2009 at 18:51 UTC
If you want to start with a fresh slate, it's easy. Assuming you haven't changed the current directory or clobbered @ARGV, `exec $^X, $0, @ARGV` [download] Note: That won't pass to the new interpreter options that were passed to the first (like -p), but I bet that's not an issue for you. Update: Added note.	[reply] [d/l]
Re^3: Build a list of defined var's by zwon (Abbot) on Oct 20, 2009 at 18:41 UTC
Why not just restart application?	[reply]
Re: Build a list of defined var's by CountZero (Bishop) on Oct 20, 2009 at 18:16 UTC
Sorry, I misunderstood your question. This comes close: `use strict; use Data::Dumper; my @array = ('A', 'b', undef, 0, 1, '', 'THE END'); $array[10] = 'The Real End'; my @defined_array = grep {defined} @array; print Dumper(\@array, \@defined_array);` [download] Output: `$VAR1 = [ 'A', 'b', undef, 0, 1, '', 'THE END', undef, undef, undef, 'The Real End' ]; $VAR2 = [ 'A', 'b', 0, 1, '', 'THE END', 'The Real End' ];` [download] CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James	[reply] [d/l] [select]