«

Hi!

I have a problem with a file. It looks like this
;r;information;more_info;1;key1;value1;
;s;more;more;2;key1;value1;key2;value2;
;t;info;and;4;key1;value1;key2;value1;key1;value3; key2;value4

I have to extract the information in key and value of each line and
compare it to some information in another file.
I would like to read the file and store the key;value pairs into a hash
and then compare it later on with the other information I have.
As you can see (hopefully) in my example (i.e. line 3) I have some keys
that are used twice (or more often). My suggestion would be an hash of
arrays.
I think in the end it should "look" like this: (for line 3)
%name_of_hash = (
key1 => ["value1"], ["value3"],
key2 => ["value1"], ["value4"]
);
The file uses ";" as a delimiter and in field 4 you have information
about how many key;value-pairs there will be.

I hope I could make myself clear about the problem. I want to read a
file line by line and compare it with some other file. But at the
moment I don't know how to store the information in a hash!
If someone had an idea that would be great!

Greetings
Chris

christrier wrote:
> I don't know how to store the information in a hash!

Chapter 5. of the Perl Cookbook has some recipes on Hashes and storing
multiple values per key.

Otherwise a google for `Perl "hash of hash"' will turn up plenty of
examples and tutorials.

I guess you missunderstood me!
I know how to store information in a hash but at the moment I don't
know how to get the information that is written in the line!

christrier <> wrote in comp.lang.perl.misc:
> I guess you missunderstood me!
> I know how to store information in a hash but at the moment I don't
> know how to get the information that is written in the line!

So what have you tried, and how does it fail? For a start, see
perldoc -f split.

Anno
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"christrier" <> wrote:
> Hi!
>
> I have a problem with a file. It looks like this
> ;r;information;more_info;1;key1;value1;
> ;s;more;more;2;key1;value1;key2;value2;
> ;t;info;and;4;key1;value1;key2;value1;key1;value3; key2;value4
>
> I have to extract the information in key and value of each line and
> compare it to some information in another file.
> I would like to read the file and store the key;value pairs into a hash
> and then compare it later on with the other information I have.
> As you can see (hopefully) in my example (i.e. line 3) I have some keys
> that are used twice (or more often). My suggestion would be an hash of
> arrays.
> I think in the end it should "look" like this: (for line 3)
> %name_of_hash = (
> key1 => ["value1"], ["value3"],
> key2 => ["value1"], ["value4"]
> );
> The file uses ";" as a delimiter and in field 4 you have information
> about how many key;value-pairs there will be.

How about:

my (undef,undef,undef,undef,undef,@pairs)=split/;/, $line;
die "Odd number!" if @pairs%2;
while (my ($k,$v)=splice @pairs,0,2) {
push @{$some_hash{$k}},$v;
};

Xho

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I am sorry, but I am quite a Newbie to Perl and I don't really get what
you mean!
> my (undef,undef,undef,undef,undef,@pairs)=split/;/, $line;
what exactly does this line do? I think it reads the first five
statements into the undef-variable and then it reads the rest into the
@pairs-array - if i am wrong please correct me!
Why do you use 5 undef-variables?

> die "Odd number!" if @pairs%2;

> while (my ($k,$v)=splice @pairs,0,2) {
> push @{$some_hash{$k}},$v;
> };
>
this loop reads from position 0 to position 2 and writes everything
into the hash and "deletes entry 0 and 1 - so you can repeat the same
operation until the array is empty?
Again, if i am wrong please correct me.

> my (undef,undef,undef,undef,undef,@pairs)=split/;/, $line;
> die "Odd number!" if @pairs%2;
> while (my ($k,$v)=splice @pairs,0,2) {
> push @{$some_hash{$k}},$v;
> };

I already said that I am a Newbie.
I have another question: is this an array of hashes what you used or
and hash of arrays? I am not quite sure which one you used.

Best regards
Chris

christrier <> wrote:

> I don't really get what
> you mean!
>> my (undef,undef,undef,undef,undef,@pairs)=split/;/, $line;

> what exactly does this line do?


It discards the 1st 5 elements of the list returned from the split().

This use of undef is documented in the "List value constructors" section in:

perldoc perldata

An exception to this is that you may assign to C<undef> in a list.
This is useful for throwing away some of the return values of a
function


> Why do you use 5 undef-variables?


To discard the 1st 5 elements of the list returned from the split().


--
Tad McClellan SGML consulting
Perl programming
Fort Worth, Texas

christrier <> wrote:

>> push @{$some_hash{$k}},$v;


> I already said that I am a Newbie.


You don't need to repeat it in each post.


> I have another question: is this an array of hashes what you used or
> and hash of arrays? I am not quite sure which one you used.


You can answer this question yourself by using the Data:umper module:


use Data:umper;

# ... code that loads %some_hash

print Dumper \%some_hash;


--
Tad McClellan SGML consulting
Perl programming
Fort Worth, Texas

"christrier" <> wrote:
> I am sorry, but I am quite a Newbie to Perl and I don't really get what
> you mean!

I only included code. I didn't "mean" anything by it, it was just code!

> > my (undef,undef,undef,undef,undef,@pairs)=split/;/, $line;

> what exactly does this line do? I think it reads the first five
> statements into the undef-variable and then it reads the rest into the
> @pairs-array - if i am wrong please correct me!

Well, undef isn't a variable, it is just a place holder. And split doesn't
return statements, it returns strings. Statements are code, strings are
data.

> Why do you use 5 undef-variables?

Because your data lines start with 5 fields that are not interesting.

>
> > die "Odd number!" if @pairs%2;
>
> > while (my ($k,$v)=splice @pairs,0,2) {
> > push @{$some_hash{$k}},$v;
> > };
> >

> this loop reads from position 0 to position 2

It is a length of 2 starting from 0, so that means position 0 to
position *1*. And I wouldn't call it "reading", but rather "assigning".

> and writes everything
> into the hash and "deletes entry 0 and 1 - so you can repeat the same
> operation until the array is empty?

Pretty much, yes.

Xho

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