On 21 December 2012 06:30, Greg Aiken <gai...@visioninfosoft.com> wrote:
> #if one desires to pass a scalar reference into a sub-routine,
> #the easiest way to assign a local scalar to the contents of the scalar
> reference is...
> subroutine(\$scalar);
> sub subroutine {
> my $subroutine_scalar = ${$_[0]}; #note you need the {} brackets, or
> this doesn't work!
> print "$subroutine_scalar\n";
> }
>
> #if one desires to pass an array reference into a sub-routine,
> #the easiest way to assign a local array to the contents of the array
> reference is...
> subroutine(\@array);
> sub subroutine {
> my @subroutine_array = @{$_[0]}; #note you need the {} brackets, or
> this doesn't work!
> print "in subroutine: " . join(' ', @subroutine_array) . "\n";
> }
>
> #if one desires to pass a hash reference into a sub-routine,
> #the easiest way to assign a local hash to the contents of the hash
> reference is...
> subroutine(\%hash);
> sub subroutine {
> my %subroutine_hash = %{$_[0]}; #note you need the {} brackets, or
> this doesn't work!
> print "in subroutine: " . join(' ', keys (%subroutine_hash)) . "\n";
> }
>
> all above works fine and is easy for me to understand. its below that im
> having difficulty with...
>
> #seeing the 'pattern' of behavior for $, @, % variable types...
> #i, not knowing any better, assumed the same should also be able to be
> done for & (subroutines)
> #i therefore tried a test to see if i could assign a new subroutine to
> equal a de-referenced subroutine reference
> #i literally copied the same code as used above, but used the & operator
> instead of ($, @, %)
> #this did not give the expected result... perl reported:
> #hello CODE(0x237dbc)
> #Can't modify non-lvalue subroutine call at D:\_junk\TEST.PL line 6.
>
> sub subroutine {
> print "hello @_\n"
> }
> sub2(\&subroutine);
> sub sub2 {
> &sub3 = &{$_[0]}; #problem is obviously here with this line, seems its
> not being dereference
> sub3('world');
> }
>
It's more like:
use strict;
use warnings;
sub subroutine
{
print "hello @_\n";
}
sub2( \&subroutine );
sub sub2
{
my $sub3 = shift;
$sub3->('world');
}
Typically you assign from subroutine parameters straight away rather than
use @_ implicitly.
Anyway, if you're on this path a recommended read is
http://hop.perl.plover.com/
A definite cure for the seasonal hangovers . . .
Just in
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