Create a Hash

Create a Hash
You are encouraged to solve this task according to the task description, using any language you may know.

Create a Hash object that links keys to values and returns a pre-specified element when a key is unknown.

C++

Compiler: g++ 4.0.2

#include <map>

int
main( int argc, char* argv[] )
{
 std::map< std::string, std::string > hash ;
 
 hash[ "key-1" ] = "val1" ;
}

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);

Python

Hashes are a built-in type called dictionaries (or mappings) in Python.

 hash = dict()  # 'dict' is the dictionary type.
 hash = dict(red="FF0000", green="00FF00", blue="0000FF")
 hash = { 'key1':1, 'key2':2, }
 value = hash[key]

Numerous methods exist for the mapping type http://docs.python.org/lib/typesmapping.html

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'

C#

Defining a Hash

 System.Collections.HashTable h = new System.Collections.HashTable();

Adding values

 h.add( "key1" , "foo" );
 h.add( "key2" , "bar" );

or

 h["key1"] = "foo";
 h["key2"] = "bar";

---

Hash in .NET 2.0

 Dictionary<string, string> hash = new Dictionary<string,string>();
 hash.Add( "key1", "foo" );

or

 Dictionary<string, string> hash = new Dictionary<string,string>();
 hash[ "key1" ] = "foo";

Smalltalk

 states := Dictionary new.
 states at: 'MI' put: 'Michigan'.
 states at: 'MN' put: 'Minnesota'.