Associative array/Creation

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: