Passing hashes into subroutines

[dooley28]

Hi,

I'm trying to pass a hash into a subroutine a few times.
When I pass the hash in I use
$ref_to_wf=\%wordswithfreq;
then pass the $ref_to_wf to the subroutine.

In the subroutine I set the reference to $answerarray.
When I want to modify a value in the hash, say

$answerarray->{$temp}++;


It works fine, but when I want to add a new value in the hash it will add the value, but not what its equal to.
For example:
$temp="NewVal"
$answerarray{$temp}=1;

When the subroutine is called again it will see
$answerarray{"NewVal"} as being 0.

Can anyone tell me what I'm doing wrong?

Thanks

 

[Kirsle]

For one:

$answerarray->{$temp}++;
$answerarray{$temp}=1;

These aren't the same. The first one is a hash reference and the other one is just a hash.

i.e.

my $hashref = {}; # curly brackets
my %hash = (); # parenthesis

Make sure your syntax is consistent with what kind of hash you're working with.

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Project Fearless | My web blog

 

[dooley28]

I see what you mean but, when I pass an empty
hash reference into the subroutine and set it to
$answerarray, when I use:

$answerarray->{$temp}=1;

the hash its referencing is never set.


When I use this

$answerarray{$temp}=1;

the key is at least set, the value isn't however.

 

[KevinADC]

Can we see some actual code. A small sample of the data would be good too.

------------------------------------------
- Kevin, perl coder unexceptional!

 

[dooley28]

%wordswithfreq;

while($record = $sth2->FetchRow) {

$ref_to_wf=\%wordswithfreq;
wordsandfreq($ref_to_wf,\@myArray,\$totalqwords);

}

sub wordsandfreq{
my ($answerarray, $records, $totalqw ) = @_;
@temprecs = @$records;
foreach $temp (@temprecs){
$found=0;
$$totalqw++;
while(($word,$freq) = each(%answerarray)){
if($temp eq $word){
$found=1;
$answerarray->{$temp}++;
}
}
if($found == 0){
$answerarray->{$temp}=1;
print "Adding $temp to hash<br />";
}

}
}

The hash keys are basically words and the data is the frequency at which they occur.

So: Hi -> 7
Bye -> 8

 

[KevinADC]

Well, this line is certainly wrong:

while(($word,$freq) = each(%answerarray)){

if you had 'strict' and 'warnings' on you would have gotten an error alerting you to that problem. This is a bit odd, you pass a reference to a scalar:

\$totalqwords

just pass the scalar, there is no need to pass a reference unless maybe the string is gigantic.

Maybe I am missing something but this makes no sense to me:

while($record = $sth2->FetchRow) {

    $ref_to_wf=\%wordswithfreq;
    wordsandfreq($ref_to_wf,\@myArray,\$totalqwords);

}

You aren't doing anything with $record, whats the point of the loop?



------------------------------------------
- Kevin, perl coder unexceptional!

 

[dooley28]

Kevin,

I'm not sure what you find wrong with this line.

while(($word,$freq) = each(%answerarray)){

But it works for me.


When I pass in the scalar $totalqwords, not a reference the value stays at 0 when I increment it in the subroutine.


while($record = $sth2->FetchRow) {

$ref_to_wf=\%wordswithfreq;
wordsandfreq($ref_to_wf,\@myArray,\$totalqwords);

}

This while loop is doing more than whats written here, it gets certain values, I only wrote this part as the rest really isn't needed for my problem, that I can't add values to my hash reference.

$answerarray->{$temp}=1;

 

[KevinADC]

it should be:

while(($word,$freq) = each([b]%{$answerarray}[/b])){


that way you are processing the hash you passed as a reference to the function. I'm a bit surprised your code does anything, is there another hash named %answerarray? There has to be something in the hash for the "while/each" construct to loop through.

------------------------------------------
- Kevin, perl coder unexceptional! [wiggle]

 

[KevinADC]

It can't be said enough times: start using "strict" and "warnings". Your code could eventually "melt" and you may not be able to find the bugs unless you are using "strict".

------------------------------------------
- Kevin, perl coder unexceptional!

 

[dooley28]

Yeah I really should have gone with strict, but the script wasn't going to be that long, so I was a bit lazy. Regretting it now.

Cheers for spotting that, never noticed I wasn't processing a reference, probably because for some reason the code was cycling through a working hash and I never saw the problem.
I can't honestly tell you why that code worked?? Could have been because I was adding to the hash using:
$answerarray{$temp}=1;

But shouldn't this have only created a local copy?
When I called the subroutine again,
while(($word,$freq) = each(%answerarray)){
might have been accessing this local copy.

Anyway not to worry changing the while loop condition seems to have worked perfectly. Thanks for that Kevin.

 

[KevinADC]

I think I see whats going on:

sub wordsandfreq{
    my ($answerarray, $records, $totalqw ) = @_;
    @temprecs = @$records;
        foreach $temp (@temprecs){
        $found=0;[red]<--- $found equals 0[/red]
                $$totalqw++;
        while(($word,$freq) = each(%answerarray)){
            if($temp eq $word){[red]<--- this returns false[/red]
                $found=1;[red]<--- this never gets done[/red]
                $answerarray->{$temp}++;[red]<--- this never gets done[/red]
            }
        }
        if($found == 0){[red]<--- $found is still 0[/red] 
            $answerarray->{$temp}=1;[red]<--- here you add $temp to the hash[/red]
            print "Adding $temp to hash<br />";
        }
        
    }
}

------------------------------------------
- Kevin, perl coder unexceptional!