#!/usr/bin/perl

# This script reads in a file with two columns
# of numbers.  The first number is a bond length, and
# the second is an error.  It finds the min and max
# errors (within the user-specified interval) and
# computes their difference (the "nonparallelity error")
#
# Arteum Bochevarov, 2006

print "Enter the start of the interval: \n";
chomp($start=<STDIN>);
print "Enter the end of the interval: \n";
chomp($end=<STDIN>);

if($ARGV[0]=~/--/){
  $arg=1;
}
else {
  $arg=0;
}

open(IN,$ARGV[$arg]);
@input=<IN>;
close(IN);
  
$c1=0;
foreach $line (@input) {
  chomp $line;
  @tmp=split / +/, $line;
  $bg[$c1]=$tmp[0];
  $en[$c1]=$tmp[1]; 
  $c1++;
}

# We determine the first element we're going to start with
# in order to assign $minel and $maxel to this first element
for($i=0;$i<@bg;$i++){ 
    if($bg[$i]<$start){
	next;
    }
    $firstelt=$i;
    last;
}

$minel=$en[$firstelt];
$maxel=$en[$firstelt];
for($i=0;$i<@bg;$i++){ 
    if($bg[$i]<$start || $bg[$i]>$end){
	next;
    }
    if($en[$i]<=$minel){
	$minel=$en[$i];
    }
    if($en[$i]>=$maxel){
	$maxel=$en[$i];
    }   
}

print "minel = ",$minel,"\n";
print "maxel = ",$maxel,"\n";
print "Diff = ",$maxel-$minel,"\n";