Re: Can @ARGV work within Perl functions or is it just for script input?

Normally, as MidLifeXis states, @_ is the argument list for a sub and @ARGV is the argument list for a script, altho' you could, if you were sufficiently perverse, do this (without affecting @ARGV in the calling context)...

sub foo {
    local @ARGV = @_;
    .
    .
    .
}
[download]

Note, also, that the context of the my $argument_size = scalar(@ARGV); statement is unclear (the closing brace for either sub doesn't appear to be present), but

sub verify_function_params
{
 
   my $num = $_[0];
   my $function_name = $_[1];
   my $input =  $_[2];
   my $type = $_[3];
 
 
   my $argument_size = scalar(@_);
 
   print "argument_size is $argument_size\n";
   .
   .
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may well produce the results you (seem to have) expected.

Now, understanding the above, you will probably be able to see why...

sub verify_function_params
{
 
   my $num = $_[0];
   my $function_name = $_[1];
   my $input =  $_[2];
   my $type = $_[3];
   .
   .
[download]

is usually written as...

sub verify_function_params
{
   my ($num, $function_name, $input, $type) = @_;
   .
   .
[download]

A user level that continues to overstate my experience :-))

Comment on Re: Can @ARGV work within Perl functions or is it just for script input? Select or Download Code

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Re^2: Can @ARGV work within Perl functions or is it just for script input? by jdporter (Paladin) on Feb 09, 2009 at 20:30 UTC
Note, of course, that code can be made to work with either `@_` or `@ARGV` depending on whether it's inside or outside a sub: just use `shift`: `my $arg1 = shift;` [download] :-) `local @ARGV = @_;` [download] Normally there's no need to do this, of course, and is contra-idiomatic. But there is one situation when it is called for: when you are going to be calling some other function which expects its inputs in `@ARGV`. Example: Getopt::Long. `use Getopt::Long; sub do_awesome_things { local @ARGV = @_; GetOptions( 'files=s' => \my @files, 'verbose!' => \my $verbose, ); warn "Going to process files @files. " . "Verbose is ".( $verbose ? 'ON' : 'OFF' ).".\n"; } do_awesome_things -v => -file => 'foo.txt', -file => 'bar.txt';` [download] Between the mind which plans and the hands which build, there must be a mediator... and this mediator must be the heart.	[reply] [d/l] [select]
Re^3: Can @ARGV work within Perl functions or is it just for script input? by jasonk (Parson) on Feb 10, 2009 at 16:46 UTC
Even in those cases, there are usually clearer solutions... `use Getopt::Long qw( GetOptionsFromArray ); sub do_awesome_things { GetOptionsFromArray( \@_, 'files=s' => \my @files, 'verbose!' => \my $verbose, ); warn "Going to process files @files. " . "Verbose is ".( $verbose ? 'ON' : 'OFF' ).".\n"; } do_awesome_things -v => -file => 'foo.txt', -file => 'bar.txt';` [download] www.jasonkohles.com We're not surrounded, we're in a target-rich environment!	[reply] [d/l]
Re^2: Can @ARGV work within Perl functions or is it just for script input? by johngg (Canon) on Feb 09, 2009 at 20:39 UTC
you could, if you were sufficiently perverse, do this (without affecting @ARGV in the calling context)... One thing to bear in mind doing that is that shift inside the subroutine will still act on `@_`, and will not magically transfer it's allegiance to `@ARGV`. `$ perl -le ' > sub x > { > local @ARGV = @_; > print while $_ = shift; > print qq{->@ARGV<-}; > print qq{->@_<-}; > } > > x( qw{ 1 2 3 } ); > print while $_ = shift;' a b c 1 2 3 ->1 2 3<- -><- a b c $` [download] I hope this is of interest. Cheers, JohnGG	[reply] [d/l] [select]