#!/usr/local/bin/perl
#This is a perl script for Simpson's (paraboloid) approximation.
#Unless you konw something about perl script, you will need some help.
#To run this program, save it as trapiz.pl (or as any dot-pl file).
#You will change the function in ourFunction sub-program.
# a is lower limit, b is upper limit and n is the number of subinterval.

$a = 0;
$b= 1;
$n=100;
$delX = ($b - $a)/$n; 
$z=$a;
$y= ourFunction($z);
$sum =$y; 

for($i=0; $i<$n-1; $i++) {

$z= $z+$delX;
$y= ourFunction($z);
$j=$i+1;
$odd=$j % 2;
if ($odd == 1) 
   {$mult = 4;}
else 
   {$mult = 2;} 

$sum=$sum+$mult*$y; 

} 


$z= $z+$delX;
$y= ourFunction($z);
$sum=$sum+$y;

$int= $delX*$sum/3; 


print " \n int =  $int \n "; 

sub ourFunction {
local ($x); 
$x = @_[0];
#$f= sqrt(1+$x*$x); 
$f=10 * $x*$x * exp (-$x); 
print " x=$x  and f= $f \n "; 

return $f;
}