Putting an array into a hash

Theo has asked for the wisdom of the Perl Monks concerning the following question:

I have some alumni data from which I need to extract useful info. To that end I'm trying to go from the native (pseudo)XML file to a key/value hash.
Before stripping out the excess XML tags the @info array has the full record of one person, a sample of which is in Listing 1. Listing 2 is printed by the code segment shown and the error message is below that.
I've preloaded %data hash just to be sure I can see if there are any changes in the hash.
I'd like to know what the error means, but the real question is how to transform an array into a hash.
The nature of this data is that the keys will all be unique.
(code being tested on a Win98 PC using Active State version 5.005_03)

########### Code Segment ##############
my %data = (one => 1, two => 2, three => 3);
:
# XML stripped off here
:
print @info;                # Prints Listing 2
print %data;                # bottom of listing 2
%data = @info =~ /(\w+)\s*(\w+)/g;    # Line that gives error
print %data;                # Prints nothing
#######################################

### Listing 1 ###
<Position>      Stdnt</Position>
<GradYear>      1987</GradYear>
<WebPage>       http://</WebPage>
<E-mail>        SomeAddr@abc.com</E-mail>
<Comments>      Needs highschool yearbooks</Comments>

### Listing 2 ###
Position    Stdnt
GradYear    1987
WebPage    http://
Email        SomeAddr@abc.com
Comments    Needs highschool yearbooks
three3two2one1

### Error message ###
Applying pattern match to @array will act on scalar(@array) at e.pl li
+ne 29
[download]

Due to the embedded spaces in some of the data, a better approach might be to strip the XML and create the hash in the same step, but not till I can get through this problem.

Update: Thank you Zaxo, saintmike and ysth. I'm still recovering from the first bout of flu I've had in 20 years and not thinking clearly. I'll put this to use in a few days. Again, thanks!

-Theo- (so many nodes and so little time ... )

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Re: Putting an array into a hash by Zaxo (Archbishop) on Dec 10, 2004 at 06:09 UTC
This should do the job, `%data = map {/(\w+)\s*(\w+)/} @info;` That will key the hash with the first word and place the next word as value. You may want to replace that with `split ' ', $_, 2`, so that punctuation in the data or multi-word values don't give mangled results. For instance, in your data, your regex will cut off the email address at the @ sign. `%data = map {split ' ', $_, 2} @info;` After Compline, Zaxo	[reply] [d/l] [select]
Re: Putting an array into a hash by saintmike (Vicar) on Dec 10, 2004 at 06:09 UTC
You don't want to apply the pattern match to an array -- you want to apply it to every element: `%data = map { /(\w+)\s*(\w+)/; ($1, $2) } @info;` [download]	[reply] [d/l]
Re^2: Putting an array into a hash by Theo (Priest) on Dec 13, 2004 at 06:31 UTC
Thanks to the observations of Zaxo and you, I've gotten through some errors, misunderstandings and typos, but there is one error message I don't understand (even with use diagnostics). The whole program follows with the error listed first. The line giving the error is the one with the `map` command. It looks like the variables `$1, $2` are somehow not being set. Perhaps the oddest aspect is that the program seems to work anyway. The error message is repeated 3 times. Error: Use of uninitialized value at e.pl line 13, <DATA> chunk 5. Code: `#!/usr/bin/perl -w my $file; my @info; my $line; my %data = (one => 1, two => 2, three => 3); foreach $file (<BXML=Tr>) { open (DATA, $file); @info = <DATA>; # @info contains the whole xml record foreach $line (@info) { chomp $line; $line =~ s\|E-mail\|Email\|g; # make email tags match all other + tags %data = map { /<(\w+)>\s(.?)<\/\w+>/; ($1, $2) } @info; } print "\n",$data{"Position"},"\t",$data{"GradYear"},"\t",$data{"Em +ail"},"\n"; } close (DATA);` [download] OutPut:* Stdnt 1987 SomeAddr@abc.com So, can I safely ignore the error since the code does what I expect? Or is that asking for trouble? -Theo- (so many nodes and so little time ... )	[reply] [d/l] [select]
Re: Putting an array into a hash by ysth (Canon) on Dec 10, 2004 at 12:54 UTC
I'd like to know what the error means, but the real question is how to transform an array into a hash. ... `%data = @info =~ /(\w+)\s*(\w+)/g; # Line that gives error` ... `Applying pattern match to @array will act on scalar(@array) at e.pl line 29` You can get more information on any error by putting "use diagnostics;" in your script (or looking up the error via perldoc perldiag or the splain utility). $ echo 'Applying pattern match to @array will act on scalar(@array) at + e.pl lin e 29'\|splain\|fmt Applying pattern match to @array will act on scalar(@array) at e.pl li +ne 29 (#1) (W misc) The pattern match (//), substitution (s///), and transliteration (tr///) operators work on scalar values. If you apply one of them to an array or a hash, it will convert th +e array or hash to a scalar value -- the length of an array, or the population info of a hash -- and then work on that scalar value. This is probably not what you meant to do. See perlfunc/grep and perlfunc/map for alternatives. [download]	[reply] [d/l] [select]


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