Associative array/Creation

Associative array/Creation
You are encouraged to solve this task according to the task description, using any language you may know.

In this task, the goal is to create an associative array.

Perl

Interpeter: Perl

Defining a Hash

# using => key does not need to be quoted unless it contains special chars
my %hash = (
  key1 => 'val1',
  'key-2' => 2,
  three => -238.83,
  4 => 'val3',
);

# using , both key and value need to be quoted if containing something non-numeric in nature
my %hash = (
  'key1', 'val1',
  'key-2', 2,
  'three', -238.83,
  4, 'val3',
);

Defining a HashRef

my $hashref = {
  key1 => 'val1',
  'key-2' => 2,
  three => -238.83,
  4 => 'val3',
}

Using a Hash

print $hash{'key1'};

$hash{'key1'} = 'val1';

@hash{'key1', 'three'} = ('val1', -238.83);

Using a HashRef

print $hash->{'key1'};

$hash->{'key1'} = 'val1';

@hash->{'key1', 'three'} = ('val1', -238.83);

Ruby

 #a hash object that returns nil for unknown keys
 hash={}
 hash[666]='devil'
 hash[777]  # => nil
 hash[666]  # => 'devil'

 #a hash object that returns 'unknown key' for unknown keys
 hash=Hash.new('unknown key')
 hash[666]='devil'
 hash[777]  # => 'unknown key'
 hash[666]  # => 'devil'

 #a hash object that returns "unknown key #{key}" for unknown keys
 hash=Hash.new{|h,k|h[k]="unknown key #{k}"}
 hash[666]='devil'
 hash[777]  # => 'unknown key 777'
 hash[666]  # => 'devil'

Python

In Python, hashes are called dictionaries.

 # empty dictionary
 d = {}
 d['spam'] = 1
 d['eggs'] = 2  

 # dictionaries with two keys
 d1 = {'spam': 1, 'eggs': 2}
 d2 = dict(spam=1, eggs=2)

 # dictionaries from tuple list
 d1 = dict([('spam', 1), ('eggs', 2)])
 d2 = dict(zip(['spam', 'eggs'], [1, 2]))

 # iterating over keys
 for key in d:
   print key, d[key]

 # iterating over (key, value) pairs
 for key, value in d.iteritems():
   print key, value

Create a generic mapping function that applys a callback to elements in a list: