Hey Jim,
Makes perfect sense now. Thanks.
Just so I make sure I understand it correctly: So every time I use a while
(<FILEHANDLE>) loop each line of input from the file gets assigned to $_ in
each iteration of the loop?
Cheers,
Tiago
On Mon, Apr 9, 2012 at 1:00 PM, Jim Gibson <jimsgib...@gmail.com> wrote:
> At 10:21 AM -0230 4/9/12, Tiago Hori wrote:
>
>> Sorry guys,
>>
>> Another quick question:
>>
>> I got this from perlmonks:
>>
>> #!/usr/bin/perl -w use strict; my @desired_cols = qw(colname1 colname3);
>> #order matters here # reads first line to get actual column names my
>> $header_line = (<DATA>); my @actual_cols = split(/\s+/,$header_line); #
>> get
>> column number of the actual column names my $pos =0; my %col2_num = map
>> {$_
>> => $pos++}@actual_cols; # translate the desired col names into position
>> numbers my @slice = map{$col2_num{$_}}@desired_**cols; print
>> join("\t",@desired_cols),"\n"; #header line while (<DATA>) { my @row =
>> (split)[@slice]; print join("\t",@row),"\n"; #each data row }
>>
>>
>> It is working great fro me and I understand almost all of it. The only
>> thing I don't get is why you have to split the @slice array into the new
>> @row array inside the while loop instead of using the @slice array.
>> Doesn't
>> using split on a array creates a list, which is then assigned to an array
>> and in effect creates a copy of the original array?
>>
>
> The line
>
> my @row =(split)[@slice];
>
> does not split the @slice array because split is enclosed in parentheses.
> 'split' by itself with no arguments will split the $_ variable on
> whitespace. This results in a list, which is then indexed by @slice, an
> array of integers. That results in a slice of the list returned by split,
> consisting of the desired columns in the line, which are the stored in the
> @row array.
>
> .
>
>
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>
--
"Education is not to be used to promote obscurantism." - Theodonius
Dobzhansky.
"Gracias a la vida que me ha dado tanto
Me ha dado el sonido y el abecedario
Con él, las palabras que pienso y declaro
Madre, amigo, hermano
Y luz alumbrando la ruta del alma del que estoy amando
Gracias a la vida que me ha dado tanto
Me ha dado la marcha de mis pies cansados
Con ellos anduve ciudades y charcos
Playas y desiertos, montañas y llanos
Y la casa tuya, tu calle y tu patio"
Violeta Parra - Gracias a la Vida
Tiago S. F. Hori
PhD Candidate - Ocean Science Center-Memorial University of Newfoundland
