hash sorting problems

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

Dear Monks I have written a program which extracts details from a text file (works fine)and stores in a hash, which prints out the results (works fine) but I am having difficulties sorting that hash so that the result is sorted into ascending numerical order. Why won't the sort work on my hash??; see code below.

foreach $word(@words){
$Counter = $Counter+1;
#print("$word\n");
}
$sentence_count{($Counter)} = $sentence_count{($Counter)}sort by_num (
+keys (%sentence_count));
while (($sentence_count,$word_count) = 
each(%sentence_count)) {  
print ("\nThere are $word_count sentences of $sentence_count words\n")
+; 
}

sub by_num {
    if ($b < $a) {
        return -1;
    } elsif ($a == $b){
        return 0;
    } elsif ($b > $a){
        return 1;
    }
}
[download]

Comment on hash sorting problems Download Code

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(jeffa) Re: hash sorting problems by jeffa (Bishop) on Apr 20, 2001 at 22:06 UTC
EEK! `foreach $word(@words){ $Counter = $Counter+1; #print("$word\n"); }` [download] don't do that - if you want to know how many elements are in an array, just get it's value in SCALAR context: `my $count = scalar @words; # style pointer: it is a $count not a $Counter` [download] If you want to know what the index of the last element is, you can subtract 1 from `$count` or better yet: `# not very useful my $last = $#words; # very useful for(0..$#words) { ... }` [download] </code> Jeff R-R-R--R-R-R--R-R-R--R-R-R--R-R-R-- L-L--L-L--L-L--L-L--L-L--L-L--L-L--	[reply] [d/l] [select]
Re: hash sorting problems by satchboost (Scribe) on Apr 20, 2001 at 21:42 UTC
Ok..... First off, your sort should be something along the lines of `sort {$a <=> $b} (keys %sentence_count)`. (This is known as the spaceship operator.) My main question, though, is where are you putting the result of the sort?? You have the line (as I read it): `$sentence_count{($Counter)} = $sentence_count{($Counter)}sort by_num (keys (%sentence_count));` This line doesn't make much sense to me. Update your node with the code reformatted, please.	[reply] [d/l] [select]
Re: Re: hash sorting problems by little (Curate) on Apr 20, 2001 at 22:20 UTC
ok, look up perlfunc:sort and read about user defined sorting criteria. Have a nice day All decision is left to your taste	[reply]
Re: hash sorting problems by Sprad (Hermit) on Apr 20, 2001 at 21:54 UTC
Is there some reason why you're rolling your own sort instead of using the built-in sort function? The Perl FAQ has a nice section on hashes, and there's even a question that gives sample code for sorting a hash. --- I'm too sexy for my .sig.	[reply]
Re: hash sorting problems by Beatnik (Parson) on Apr 21, 2001 at 02:40 UTC
Hashes have both keys and values; they arent stored by indices (like arrays). Perl stores the hash elements internally by calcing some values... As already described above, try something similar to `@sorted_keys = sort { $a <=> $b } keys %hash; #use { $a <=> $b } for numerical sorting #use { $a cmp $b } for string sorting foreach(@sorted_keys) { print $hash{$_}; }` [download] Greetz Beatnik ... Quidquid perl dictum sit, altum viditur.	[reply] [d/l]