array of arrays to hash of hashes

Hi all,

I have a category / subcategory file that looks like this

cereal
cereal:cold:cheerios
cereal:cold:corn flakes
cereal:hotatmeal
cereal:hot:cream of wheat
bread
bread:dakine sweet bread
bread:wheat
bread:white

....... Anyway you get the picture

I read the file in and place into array of arrays

open FILE, "$file";
my @file = (<FILE>);
close FILE;

my @a;
foreach (@file){
my @line = split ':', $_;
push (@a, \@line);
}

I want to put this into a hash of hashes where the last element would be
equal to 1. something like this
$cereal->{cold}->{cheerios} =1;
or $bread->{wheat} = 1;

if later on down the line the file changes so that there is more
subcategories, the 1 would be replaced by a new hash like this

$cereal->{cold}->{cheerios}->{regular} =1;
$cereal->{cold->{cheerios}->{honeynut} = 1;

I'm having trouble writing a function to do this.
Any help or ideas would be appreciated

Jeff wrote:
> Hi all,
>
> I have a category / subcategory file that looks like this
>
> cereal
> cereal:cold:cheerios
> cereal:cold:corn flakes
> cereal:hotatmeal
> cereal:hot:cream of wheat
> bread
> bread:dakine sweet bread
> bread:wheat
> bread:white
>
> ...... Anyway you get the picture
>
> I read the file in and place into array of arrays
>
> open FILE, "$file";
> my @file = (<FILE>);
> close FILE;
>
> my @a;
> foreach (@file){
> my @line = split ':', $_;
> push (@a, \@line);
> }
>
> I want to put this into a hash of hashes where the last element would be
> equal to 1. something like this
> $cereal->{cold}->{cheerios} =1;
> or $bread->{wheat} = 1;
>
> if later on down the line the file changes so that there is more
> subcategories, the 1 would be replaced by a new hash like this
>
> $cereal->{cold}->{cheerios}->{regular} =1;
> $cereal->{cold->{cheerios}->{honeynut} = 1;
>
> I'm having trouble writing a function to do this.
> Any help or ideas would be appreciated
The most obvious way of doing it is to use a recursive function (google
"recursion") to walk the data structure each time a new item is inserted
(ie for each new line). You probably want something a bit like this
(insert_item is the recursive function, if that isn't obvious):

mark@hermes:~$ cat cereal.pl
#!/usr/bin/perl
#
use warnings;
use strict;

use Data:umper;

my $root = {};

while(my $line = <DATA> ){
chomp $line;
my @items = split /:/,$line;

insert_item( $root, @items );
}

print Dumper $root;

sub insert_item {
my $current = shift;
my $nextkey = shift;
my @items = @_;

if(@items){
my $newsubtree;
if(ref $current->{$nextkey}){
$newsubtree = $current->{ $nextkey };
}else{
$newsubtree = {};
$current->{ $nextkey } = $newsubtree;
}
insert_item( $newsubtree, @items );
}else{
$current->{ $nextkey } = 1;
}
}

__END__
cereal
cereal:cold:cheerios
cereal:cold:corn flakes
cereal:hotatmeal
cereal:hot:cream of wheat
bread
bread:dakine sweet bread
bread:wheat
bread:white
mark@hermes:~$ perl cereal.pl
$VAR1 = {
'bread' => {
'white' => 1,
'wheat' => 1,
'dakine sweet bread' => 1
},
'cereal' => {
'cold' => {
'cheerios' => 1,
'corn flakes' => 1
},
'hot' => {
'cream of wheat' => 1,
'oatmeal' => 1
}
}
};


Mark

Thanks a million..

I learned something here and it's great



Mark Clements wrote:
> Jeff wrote:
>> Hi all,
>>
>> I have a category / subcategory file that looks like this
>>
>> cereal
>> cereal:cold:cheerios
>> cereal:cold:corn flakes
>> cereal:hotatmeal
>> cereal:hot:cream of wheat
>> bread
>> bread:dakine sweet bread
>> bread:wheat
>> bread:white
>>
>> ...... Anyway you get the picture
>>
>> I read the file in and place into array of arrays
>>
>> open FILE, "$file";
>> my @file = (<FILE>);
>> close FILE;
>>
>> my @a;
>> foreach (@file){
>> my @line = split ':', $_;
>> push (@a, \@line);
>> }
>>
>> I want to put this into a hash of hashes where the last element would be
>> equal to 1. something like this
>> $cereal->{cold}->{cheerios} =1;
>> or $bread->{wheat} = 1;
>>
>> if later on down the line the file changes so that there is more
>> subcategories, the 1 would be replaced by a new hash like this
>>
>> $cereal->{cold}->{cheerios}->{regular} =1;
>> $cereal->{cold->{cheerios}->{honeynut} = 1;
>>
>> I'm having trouble writing a function to do this.
>> Any help or ideas would be appreciated
> The most obvious way of doing it is to use a recursive function (google
> "recursion") to walk the data structure each time a new item is inserted
> (ie for each new line). You probably want something a bit like this
> (insert_item is the recursive function, if that isn't obvious):
>
> mark@hermes:~$ cat cereal.pl
> #!/usr/bin/perl
> #
> use warnings;
> use strict;
>
> use Data:umper;
>
> my $root = {};
>
> while(my $line = <DATA> ){
> chomp $line;
> my @items = split /:/,$line;
>
> insert_item( $root, @items );
> }
>
> print Dumper $root;
>
> sub insert_item {
> my $current = shift;
> my $nextkey = shift;
> my @items = @_;
>
> if(@items){
> my $newsubtree;
> if(ref $current->{$nextkey}){
> $newsubtree = $current->{ $nextkey };
> }else{
> $newsubtree = {};
> $current->{ $nextkey } = $newsubtree;
> }
> insert_item( $newsubtree, @items );
> }else{
> $current->{ $nextkey } = 1;
> }
> }
>
> __END__
> cereal
> cereal:cold:cheerios
> cereal:cold:corn flakes
> cereal:hotatmeal
> cereal:hot:cream of wheat
> bread
> bread:dakine sweet bread
> bread:wheat
> bread:white
> mark@hermes:~$ perl cereal.pl
> $VAR1 = {
> 'bread' => {
> 'white' => 1,
> 'wheat' => 1,
> 'dakine sweet bread' => 1
> },
> 'cereal' => {
> 'cold' => {
> 'cheerios' => 1,
> 'corn flakes' => 1
> },
> 'hot' => {
> 'cream of wheat' => 1,
> 'oatmeal' => 1
> }
> }
> };
>
>
> Mark
>