uninitialized value in split

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

...is the error I am receiving with this in the first and second subroutine:

use strict;

# finds the words in $otherfile that are not in $wordfile;

my $wordfile = shift;
my $otherfile = shift;

sub dict_line{
  our %dict;
  my $line = shift;
  print $line;
  my @words = split $line;
  #print"@words";
  foreach my $word (@words){
    $dict{lc $word}++;
    #print "$word\n";
  }
}

sub find_missing{
  our %dict;
  my $line = shift;
  my @words = split $line;
  foreach my $word (@words){
    print "$word\n";
    my $word = lc shift;
    print "* $word\n" if !defined $dict{$word};
  }
}
  
sub read_file{
  my $file=shift;
  my $subref = shift || \&read_line;

  open (FILE, $file) || die "couldn't open $file $!";
  while (my $line = <FILE>) {
    $subref->($line);
  }
}

read_file $wordfile, \&dict_line;
read_file $otherfile, \&find_missing;
[download]

The $line variable that is being split prints fine
just before the call to split.

Comment on uninitialized value in split Download Code

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Re: uninitialized value in split by dragonchild (Archbishop) on May 17, 2005 at 02:57 UTC
What are you splitting $line on? The first argument to split is the delimiter to split on. The second argument is the scalar to split up. If it's unspecified, it defaults to $_, which is undefined in your examples. You probably want `my @words = split ' ', $line;` - try that out and see if it helps. I want to commend you on using strict and warnings. Excellently done! In general, if you think something isn't in Perl, try it out, because it usually is. :-) "What is the sound of Perl? Is it not the sound of a wall that people have stopped banging their heads against?"	[reply] [d/l]
Re^2: uninitialized value in split by jjohhn (Scribe) on May 17, 2005 at 03:07 UTC
I thought that after a shift in a subroutine, $_ contains the value of the shift. But I did what you said, and now have a different problem which I will look at for awhile.	[reply]
Re^3: uninitialized value in split by TheStudent (Scribe) on May 17, 2005 at 03:15 UTC
According to perldoc -f shift shift ARRAY shift Shifts the first value of the array off and returns it, shortening the array by 1 and moving everything down. If t +here are no elements in the array, returns the undefined value. + If ARRAY is omitted, shifts the @_ array within the lexical s +cope of subroutines and formats, and the @ARGV array at file sc +opes or within the lexical scopes established by the "eval ''", "BEGIN {}", "INIT {}", "CHECK {}", and "END {}" constructs +. See also "unshift", "push", and "pop". "shift" and "unshif +t" do the same thing to the left end of an array that "pop" and +"push" do to the right end. [download] No mention of setting $_ TheStudent	[reply] [d/l]
Re^4: uninitialized value in split by jjohhn (Scribe) on May 17, 2005 at 03:22 UTC
Re: uninitialized value in split by Skeeve (Parson) on May 17, 2005 at 10:14 UTC
Just a note about how I do the check which words are not defined. If Ihave both files properly splitted and word-counted in %dict and %file I usually do it like this: `delete @file{keys %dict};` [download] what remains in %file are the words not found in %dict. `$\=~s;s.;q^\|D9JYJ^^qq^\//\\\///^;ex;print`	[reply] [d/l] [select]