Hello perlynewby,

Since the input data will “later be scrambled,” there doesn’t seem to be much point in pursuing the strategy of Experiment 1. I have therefore looked only at Experiment 2, using a hash for lookup. The resulting code is far from perfect, but it produces the desired output:

Some notes:

• I have moved the file open and close statements to reflect the actual usage of the filehandles. It is generally a good idea to minimise a variable’s effective scope.

• I have added tests such as:

  if ($ita)
  [download]

  to exclude undefs and null strings from the hash. These tests should really be more explicit:

  if (defined $ita && $ita ne '')
  [download]

  but the shortcut is OK since neither 0 nor '0' is going to occur in the data as a valid value.

• In the line

  join(',', map { $_ // () } @{ $hash{$ita} }),
  [download]

  the map removes undef fields which otherwise produce warnings such as this:

  Use of uninitialized value in join or string at ... line ...
  [download]

• The hash keys are sorted using a special-purpose sub, which in turn uses a hash that maps each Italian number name to its corresponding numerical value. See sort for other syntax options.

• The two chomps are not needed as each is effectively performed by the immediately-following split on whitespace (\s).

Hope that helps,

Updates: Made minor improvements to code and text; added final note.

thank you...I will follow the FH open and close within their scope...I liked that and clear to me now and looks elegant.also, I like your way of IF structures...mine still looks too childish

I have a few question on somethings you did here, please help me understand. I am reading on this now too.

what is the ? do here?

my    $fh = defined $hash{$ita}[0] &&
                    defined $hash{$ita}[1] ? $out : $out1;
[download]

hmm, what is in the sort_italian() at start? and why () and not square brackets?

confused on hash_ref which uses square and now parenthesis

for my $ita (sort { sort_italian() } keys %hash)
[download]

map...nice function, I'm geeking out on map right now. but what is the () mean? is this NOT a hash_ref then??as per your comment, $_ is the value of the keys being check for UNDEF values , I understand that but not ()

print $fh "$ita => ",
                   join(',', map { $_ // () } @{ $hash{$ita} }),
                  "\n";
[download]

I have problems following the error checking. what is this statement saying here?         return $numbers{$a} <=> $numbers{$b};

Hello again perlynewby,

It seems that, between aaron_baugher’s excellent replies and your own further reading, you already have answers to most of your questions. I will just comment on this part of my code:

my    $fh = defined $hash{$ita}[0] &&
            defined $hash{$ita}[1] ? $out : $out1;

print $fh "$ita => ",
           join(',', map { $_ // () } @{ $hash{$ita} }),
          "\n";
[download]

The ... ? ... : ... construct is the conditional, or ternary, operator, which is documented here. I use it to select which of two filehandles will be written to by the following print statement. This is an example of applying the DRY (“don’t repeat yourself”) principle by changing the original two parallel print statements into a single statement. The advantage here is that if the statement is later changed (see below!), there is no danger of updating one statement and overlooking the other in the process.

The expression { $_ // () } uses the Logical Defined-Or operator to select the empty parentheses — () — only if the current value ($_) is undefined. Empty parentheses are used because they represent an empty list, and interpolating an empty list into a second list has no effect on that second list. Any other value here — e.g. undef, "" (the empty string), [] (which is a reference to an empty anonymous array) — would add something unwanted to the second list, because in each case the value is a scalar which is added as a new list element. The following should make this a little clearer:

17:42 >perl -MData::Dump -wE "my @c = qw(a e i o u); @c = map { $_ eq 
+'i' ? undef : $_ } @c; dd \@c;"
["a", "e", undef, "o", "u"]

17:44 >perl -MData::Dump -wE "my @c = qw(a e i o u); @c = map { $_ eq 
+'i' ? () : $_ } @c; dd \@c;"
["a", "e", "o", "u"]

17:44 >
[download]

map...nice function, I'm geeking out on map right now.

Yor’re right! Unfortunately, map was the wrong function to use here. :-( I should have used grep:

print $fh "$ita => ",
           join(',', grep { defined } @{ $hash{$ita} }),
          "\n";
[download]

— much more straightforward. D’oh!

Hope that helps,

Athanasius <°(((>< contra mundum

Iustus alius egestas vitae, eros Piratica,

ok, I read about most of my questions and I think I understand them some but I still have an issue with understanding the error check portion here. don't know what this does

return $numbers{$a} <=> $numbers{$b}; #I guess it's checking against e
+achother...but how? is this a subroutine somewhere in a library/modul
+e??
[download]

after reading, this is still a little vague. I have issues understanding when to use the [] vs (). any clarification will be appreciated.

$hash{$ita}[0]=$spa; #here we assign has_ref $span value address to fi
+rst position in array

for my $ita (sort { sort_italian() } keys %hash) #here ?? adding value
+ to array? am I right? not sure...
[download]