Perl II Problem Set:
 
1. Create a script ("add.pl") that takes two numbers from the command line and adds them.
   % add.pl 2 3
 
   5


#!/usr/bin/perl
use strict;
use warnings;

my $x = shift;
my $y = shift;

print $x + $y, "\n";


 
2. Modify the "add.pl" script from the previous problem set so that it checks that both arguments are defined (hint, use function defined.)
 
   % add.pl 2 3
 
   5
 
   % add.pl 2
 
   Please provide two numbers.    



#!/usr/bin/perl
#File: add.pl                                                                                                                                                                                                
#Author: Jessen Bredeson


use strict;
use warnings;

my $x = shift;
my $y = shift;

if (! defined($x) or ! defined($y)) {
    print "Please provide two positive numbers.\n";
} else {
    print $x + $y, "\n";
}



 
3. Modify the script again so that it checks that both arguments are positive numbers. Zero is allowed, but -1 is not:
 
  % add.pl 2 -3
 
  Please provide two positive numbers.    
 


use strict;
use warnings;

my $x = shift;
my $y = shift;

if (! defined($x) or ! defined($y)) {
    print "Please provide two positive numbers.\n";
} elsif ($x < 0 or $y < 0) {
    print "Please provide two positive numbers.\n";
} else {
    print $x + $y, "\n";
}



4.   Write a script ("order.pl") to compare two strings given on the command line arguments and print "right order" if they are in alphabetic order, and "wrong order" if they are not:
 
 % order.pl Fred Lucy
 
 right order
 
 % order.pl Lucy Fred
 
wrong order

 
#!/usr/bin/perl
#File: reorder.pl
#Author: Jessen Bredeson

use strict;
use warnings;

my $name1 = shift;
my $name2 = shift;

if (! defined($name1) or ! defined($name2)) {
    print "Please provide two names.\n";
} else {
    # we want to use the cmp operator, which will return -1 if the left value sorts higher 
    # (ascending), return 1 if the right value sorts higher, and 0 if they are equal.
    if (($name1 cmp $name2) > 0) {
    print "$name2 $name1\n"
    } else {
    print "$name1 $name2\n";
    }
}





5.  Write a script ("reorder.pl") to compare two strings given on the command line and print them out in correct alphabetic order:
 
 % reorder.pl Fred Lucy
 
 Fred Lucy
 
 % reorder.pl Lucy Fred
 
  Fred Lucy
 

#!/usr/bin/perl
#File: reorder.pl
#Author: Jessen Bredeson

use strict;
use warnings;

my $name1 = shift;
my $name2 = shift;

if (! defined($name1) or ! defined($name2)) {
    print "Please provide two names.\n";
} else {
    # we want to use the cmp operator, which will return -1 if the left value sorts higher 
    # (ascending), return 1 if the right value sorts higher, and 0 if they are equal.
    if (($name1 cmp $name2) > 0) {
    print "$name2 $name1\n"
    } else {
    print "$name1 $name2\n";
    }
}




6. Write a script named "same.pl" to read two strings from the terminal. Compare them in a case-sensitive manner and print "same" if they are the same, "different" if they are different:
 
 % same.pl
 
 Enter string 1: lucy
 
 Enter string 2: Lucy
 
 different
 

#!/usr/bin/perl
#File: same.pl
#Author: Jessen Bredeson

use strict;
use warnings;

my $string1 = shift;
my $string2 = shift;

if (! defined($string1) or ! defined($string2)) {
   print "Please provide two strings to compare.\n";
} elsif ($string1 eq $string2) {
   print "same\n";
} else {
   print "different\n";
}




7. Modify this script to compare the strings in a case-INsensitive manner (hint, use the "lc" or "uc" functions to change string to upper or lowercase.


#!/usr/bin/perl
#File: same.pl
#Author: Jessen Bredeson

use strict;
use warnings;

my $string1 = shift;
my $string2 = shift;

if (! defined($string1) or ! defined($string2)) {
   print "Please provide two strings to compare.\n";
} elsif (uc($string1) eq uc($string2)) {
   print "same\n";
} else {
   print "different\n";
} 



8.  Write a script named "percent.pl" to calculate percentages, where the percentage is $i/($i+$j) * 100. Make sure that the script does not crash when given two numbers that add up to zero:
 
% percent.pl 50 150
 
25%
 
% percent.pl 50 -50
 
You are trying to trick me! at line 4.
 

#!/usr/bin/perl
#File: percent.pl
#Author: Jessen Bredeson

use strict;
use warnings;

# we cannot use $a and $b here, as they are reserved global variables
my $x = shift;
my $y = shift;

if (! defined($x) or ! defined($y)) {
    print "Please provide two numbers.\n";
} elsif (($x + $y) == 0) {
    print "You are trying to trick me!\n";
} else {
    print 100 * ($x / ($x + $y)),"%\n";
}




9. Modify this script to use the printf() function to produce nicely formatted floating point numbers (hint:  try "man sprintf" and "man printf" or look it up online to learn about this wonderful function).
 
% percent.pl 50 150
 
25.00 %
 
 
#!/usr/bin/perl
#File: percent.pl
#Author: Jessen Bredeson

use strict;
use warnings;

# we cannot use $a and $b here, as they are reserved global variables
my $x = shift;
my $y = shift;

if (! defined($x) or ! defined($y)) {
    print "Please provide two numbers.\n";
} elsif (($x + $y) == 0) {
    print "You are trying to trick me!\n";
} else {
    printf "%0.2f%%\n", 100 * ($x / ($x + $y)),"%\n";
}