big job, starting with little script

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

Greetings, oh wise ones. I need to create a hash to process several million records (am building competitor to Google (yes, I am a dreamer)). I need to process something like this: file FOO contains single-field records of fruits and vegetables, and file BAR contains the arrays.

$cat foo
apple
apple
pear
pear
zucchini
zucchini
eggplant
eggplant
potato
potato

$cat bar
#!/usr/bin/perl
$map{'apple'} = 'fruit';
$map{'pear'} = 'fruit';
$map{'zucchini'} = 'vegetable';
$map{'eggplant'} = 'vegetable';
$map{'potato'} = 'vegetable';

open FILE, "foo" or die$!;
my @lines = <FILE>;

while (my $line = <FILE>)
{
chomp;
print "$map($_)\n";
[download]

Why does this give me nothing? I want to see this:

apple fruit
apple fruit
pear fruit
pear fruit
zucchini vegetable
zucchini vegetable
zucchini vegetable
eggplant vegetable
eggplant vegetable
eggplant vegetable
potato vegetable
potato vegetable
[download]

Thank you so much. Your humble servant, RickyD

Comment on big job, starting with little script Select or Download Code

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Re: big job, starting with little script by zek152 (Pilgrim) on Jul 14, 2010 at 17:43 UTC
Your problem is that you slurp in the file with "`my @lines = <FILE>;`" This means that it will never enter the while loop (<FILE> will return undef). Simply take that line out. Also chomp works on $_ but you have $line = <FILE>. The following should work: `while (<FILE>) { chomp; print "$_ $map{$_}\n"; }` [download] It looks like you have a missing "}" to close the while loop. Also you should close your FILE filehandle at the end of the program. Its a good habit. Hope that helps.	[reply] [d/l] [select]
Re: big job, starting with little script by Roy Johnson (Monsignor) on Jul 14, 2010 at 17:43 UTC
You're [also] looking up $_, but reading into $line. Try `while(<FILE>)` [download] instead. Caution: Contents may have been coded under pressure.	[reply] [d/l]
Re: big job, starting with little script by muba (Priest) on Jul 15, 2010 at 08:02 UTC
Try to find out where you put the line after reading from the file. Is it in `$line` (as `$line = <FILE>`) would suggest? Or is it in `$_`, where you seem to think it is, judging by your use of `chomp` with no further arguments and thusly implying `chomp $_`. And even more explicitely in the part where you try to `print "$map($_)";` That print statement brings us to another point - you're using parens here, not accolades, or curly braces. Keep an eye out for that kind of typo :) The interesting thing is that neither answer is true, as has been pointed out above me, due to you slurping in the entire file before the `while` loop. But I'd like to point out something else as well. I don't mean to discourage you but I think your approach deserves some further thought. Tomato: fruit or veggie?	[reply] [d/l] [select]
Re^2: big job, starting with little script by fullermd (Vicar) on Jul 15, 2010 at 16:43 UTC
But I'd like to point out something else as well. I don't mean to discourage you but I think your approach deserves some further thought. Tomato: fruit or veggie? Well, fruit, obviously. To a biologist, anyway. But then, so are zucchini and eggplant, right?	[reply]
Re: big job, starting with little script by Generoso (Prior) on Jul 15, 2010 at 23:00 UTC
You may what to take a look at this. #!/usr/bin/perl use strict; use warnings; #open FILE, "foo" or die$!; #my @lines = <FILE>; my %map=(); my $datapos = tell DATA; foreach (grep(/,/, <DATA>)) { chomp; my ($p1,$p2) = split /,/,$_; $map{$p1} = $p2; print '$map{',$p1,'} = \'',$map{$p1},"';\n"; } seek DATA, $datapos, 0; foreach (grep(!/,/, <DATA>)) { chomp; print "$_ $map{$_}\n"; } __DATA__ apple,fruit pear,fruit zucchini,vegetable eggplant,vegetable potato,vegetable apple apple pear pear zucchini zucchini eggplant eggplant potato potato [download]	[reply] [d/l]