Re: Passing hash into sub routines (should i use reference?)

[Jeff Pang]

Hi,

I've copied your codes and format them on my editor and it seems run well for 
me.

use warnings;
use strict;

my %where=(
       Gary => "Dallas",
       Lucy => "Exeter",
       Ian =>  "Reading",
       Samantha => "Oregon"
   );
my $logfile = 'foo.txt';

open FH, '<', $logfile or die "Can't open $logfile!: $!";
while (<FH>){
    my ($person) = /person=(\S+)/;
    my $personstatus = verify(\%where,$person);
    if ($personstatus) {
       print "$person exist\n";
    }
}
close FH;

sub verify {
    my $where = shift @_;
    my $person = shift @_;
    my $personstatus;

    if (exists $where->{$person}){  # use '->' operator for hash's reference
#    if (exists $$where{$person}){  # this line also can work
        $personstatus =1;
    }else {
       $personstatus = 0;
    }

    $personstatus;
}




Jeff Pang
2007-01-18



发件人： Michael Alipio
发送时间： 2007-01-18 14:26:00
收件人： begginers perl.org
抄送： 
主题： Passing hash into sub routines (should i use reference?)

Hi,

Suppose I have this code:

#/usr/local/bin/perl
use warnings;
use strict;
use subs 'verify';

my %where=(
       Gary = > "Dallas",
       Lucy = > "Exeter",
       Ian = >  "Reading",
       Samantha = > "Oregon"
   );

# Then i open a logfile

open FH, ' <', $logfile or die "Can't open $logfile!: $!";

# Now, for every line in the logfile, I will retrive a particular string, let's 
say a person's name and verify if it exists in my hash above:

while ( <FH >){
(my $person) = $_ =~ /person=(\S+)/;
my $personstatus = verify(\%where,$person);

# And do anything if the personstatus is this and that.


# Now,  on my sub "verify", I would like to know if the person exists in my 
hash.

sub verify {
my $where = shift @_;
my $person = shift @_;
my $personstatus;

if (exists $$where{$person}){

$personstatus =1;
}else {
   $personstatus = 0;
     }

$personstatus;
}

Am I thinking as this is how it should be done when passing hashes to a 
subroutine? My program doesn't work and I know it has something to do with the 
"my $personstatus" line as well as "if (exists $$where{$person} line.
Can you show me the right way of passing hashes to subroutines? Thanks.

I also tried declaring %where as 'our' so that I can use "if (exists 
%where{$person}" instead of "if(exists $$where{person}) but i still can't make 
it work.


Do you know if I am making any sense here?

Thanks









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