Perl Exercise 1

Assignment

Write a Perl subroutine named unique that will accept a list as an argument, and return a list of all the unique items in the original list.

#!/usr/bin/perl

my @list = (2, 1, 1, 1, 2, 2, 3, 4, 5, 6, 6);

my @unique_items = &unique(@list);

$,=', ';

print @unique_items,"\n";

sub unique{
### YOUR CODE HERE #####
### YOUR CODE HERE #####
### YOUR CODE HERE #####
### YOUR CODE HERE #####
### YOUR CODE HERE #####
}

Output of your program:
1, 2, 3, 4, 5, 6 (any order of numbers is fine)

Details

The special variable $, is the default record seperator. This is a set of characters (or none at all) that seperate multiple items written at the same time. In this case we set it to ', '
In a subroutine, the value(s) returned is/are the last values processed or those explicitly returned with the command return.
When a list is passed to a subroutine, the list passed is called @_ inside the subroutine.

Tips

Be creative

Many possible solutions

sub unique{
  $max_el=@_-1;
  my @u_list;
  $u_list[0]=$_[0];
  for $i (1 .. $max_el){
    $original=1;
    foreach $item (@u_list){
      if ($item == $_[$i]){
        $original=0;
      }
    }
    if ($original){
      push (@u_list, $_[$i]);
    }
  }
  return @u_list;
}

sub unique{
  my @u_list= keys %{{ map {$_ => 1} @_ }};
  return @u_list;
}

sub unique{
  return keys %{{ map {$_ => 1} @_ }};
}

sub unique{
  keys %{{ map {$_ => 1} @_ }}
}

sub unique{
  grep{!$l{$_}++}@_
}