Jakob Kofoed wrote:
I have a file with some navigation (x and y's) and needed to fill in
point between exiting points.
My in put file:
600000 6174210
600017 6174213
600028 6174206
600035 6174216
600045 6174209
For calculation I need to use line 1 and 2 for calculating one point
and then line 2 and 3 and so on ...
I solved it by using Xaviers tip on Tie::File:
use Tie::File;
tie my @line, 'Tie::File', $ARGV[0] or die "could not open $ARGV[0]: $!";
my $cnt1 = 0;
my $cnt2 = 0;
while ( $cnt1 < $ARGV[1] ) {
$cnt2++;
#print " $cnt1 $cnt2\n";
my @rec1 = split(' ', $line[$cnt1]);
my @rec2 = split(' ', $line[$cnt2]);
my $newin = (($rec1[0] - $rec2[0]) / 2) + $rec2[0];
my $newxl = (($rec1[1] - $rec2[1]) / 2) + $rec2[1];
print "@rec1\n";
print "$newin $newxl\n";
$cnt1 = $cnt2;
}
This code will not print the very last line of the file. You need to add the
line (below) after you exit the while loop.
print "@rec2\n";
where $ARGV[1] is the number of lines in the file.
How do you know beforehand the number of lines in the file?
By the way, I think that the test in the while loop should be:
while ( $cnt1 < $ARGV[1] - 1 ) {
Could I have used an array as you mentioned in the bottom of your comment?
Yes, you could have (and not needed both: Tie::File and $ARGV[1]). The code
below
reads the file in $ARGV[0] into @line
my @line = <>;
while ($cnt1 < $#line) {
etc.
As a last note, I wouldn't have read the whole file into an array (which is
often called 'slurping' a file) and wouldn't have needed to keep the 2 count
variables. Instead, I used $first and $second to capture the needed lines.
This way, if you are dealing with a very large file, you only read 1 line at
a time into memory instead of 'slurping' the entire file into an array. But
the method you chose should work as well (if not a huge file). :-)
#!/usr/bin/perl
use strict;
use warnings;
my $first;
my $second;
while (<>) {
chomp;
$first = $_, next unless $first;
$second = $_;
my @rec1 = split ' ', $first;
my @rec2 = split ' ', $second;
my $newin = (($rec1[0] - $rec2[0]) / 2) + $rec2[0];
my $newxl = (($rec1[1] - $rec2[1]) / 2) + $rec2[1];
print "$first\n";
print "$newin $newxl\n";
$first = $second;
}
print "$second\n";
Chris
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