Re: how to "rename" a global argument in subroutine?

Parse by reference:

my $red = undef;
my $green = undef;
my $blue = undef;

sub change{
  my($color1, $value1, $color2, $value2, $color3, $value3) = @_;
  ${$color1} = $value1;
  ${$color2} = $value2; # maybe: if defined $value2;
  ${$color3} = $value3;
}

change(\$red, 42, \$green, 255, \$blue, 11);

print "($blue)";
[download]

Alternative:

#!/usr/bin/perl
use strict;
use warnings;

my %COLORS = (
  red => undef,
  green => undef,
  blue => undef,
);

sub change2{
  my($R) = @_;
  my %H = %$R;
  for my $key (keys %H){
    $COLORS{$key} = $H{$key};
  }
}

change2( {red=>5, green=>6, blue=>7} );
print $COLORS{red};
[download]

Comment on Re: how to "rename" a global argument in subroutine? Select or Download Code

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Re^2: how to "rename" a global argument in subroutine? by FreeBeerReekingMonk (Deacon) on Aug 11, 2015 at 18:26 UTC
And if those RGB variables are "static", then why not put them into a nice hash? `#!/usr/bin/perl use strict; use warnings; my %COLORS = ( red => undef, green => undef, blue => undef, ); sub change{ my($R,$G,$B) = @_; $COLORS{red} = $R; $COLORS{green} = $G; $COLORS{blue} = $B; } change(11); print $COLORS{red};` [download]	[reply] [d/l]
Re^3: how to "rename" a global argument in subroutine? by Anonymous Monk on Aug 11, 2015 at 18:48 UTC
I hadn't known about hashing! Thanks for your nice post!	[reply]
Re^2: how to "rename" a global argument in subroutine? by Anonymous Monk on Aug 11, 2015 at 18:42 UTC
Thank you for your answer! ...although I'm now having some other issue related.. Does "parsing by reference" make that a symbolic link? Because later when I try to access $red 's value I get the following error. "Can't use string ("red") as a SCALAR ref while "strict refs" Would you have any other advice on how I could go about resolving this? Much appreciated.	[reply]
Re^3: how to "rename" a global argument in subroutine? by FreeBeerReekingMonk (Deacon) on Aug 11, 2015 at 18:52 UTC
Yes, a reference is a "symbolic link", to point to the value you need to either use the arrow or typecast it. For example: `#!/usr/bin/perl use strict; use warnings; my $red = 23; my $also_red = \$red; ${ $also_red } = 12; # typecast to scalar using ${} print "$red is actually $$also_red"; # this also works` [download]	[reply] [d/l]