ArrayMap and ArrayList

Rationale

Lists and maps need to be distinguishable. PHP arrays are one or the other, or even both. For a more detailled explanation, see the blog entry http://news.xp-framework.net/article/293/2009/04/05/.

Usage examples

The array operations are overloaded to give this class the typical "array" usability:

  $m= new ArrayMap(array('one' => 1, 'two' => 2));
  
  // Size
  $s= $m->size;       // := 2
  
  // Reading
  $n= $m['one'];      // := 1
  $four= $m['four']); // *** lang.IndexOutOfBoundsException
  
  // Writing
  $m['one']= 10;      // Overwrites existing value
  $m['three']= 3;     // Adds new mapping
  $m[]= 7;            // *** lang.IllegalArgumentException
  
  // Removing
  unset($m['one']);   // Map now: { "two" => 2 }
  unset($m['four']);  // *** lang.IndexOutOfBoundsException
  
  // Testing
  isset($m['one']);   // := true
  isset($m['zero']);  // := false
  
  // Iteration
  foreach ($m as $key => $value) {
    Console::writeLine($key, ' => ', $value);
  }

Refactoring

Although this class behaves like a typical PHP array, it isn't one. Keep this in mind when code uses sizeof or any of the array functions such as array_keys, asort or array_map. The places where a real array is required need to be passed the ArrayMap's array member.

Example:

  // Old code
  $a= array('name' => 'Timm', 'id' => 1549);
  ksort($a);
  
  // New code
  $a= new ArrayMap(array('name' => 'Timm', 'id' => 1549));
  ksort($a->array);

Code that uses foreach() or array access syntax as shown above does not need to be changed.

StringOf

The xp::stringOf() function will be extended to produce the following output:

  xp::stringOf(new ArrayList(1, 2, 3));
  // [1, 2, 3];
  
  xp::stringOf(new ArrayMap(array('key' => 'value', 'color' => 'green')));
  // [
  //   "key" : "value"
  //   "color" : "green"
  // ]

XP language integration

The XP language will use these two types as backing for the array and map literals.

  // Equivalent of: $a= new ArrayList(1, 2, 3);
  $a= [1, 2, 3];
  
  // Equivalent of: $m= new ArrayMap(array('one' => 1, 'two' => 2));
  $m= [ 'one' : 1, 'two' : 2 ];

Consistency

The ArrayList class will be changed to adapt the array member (instead of values). Also, to follow the general strategy of replacing native arrays by the wrapper types provided in the XP framework, the restriction of not being able to add elements to an ArrayList will be removed:

  $a= new ArrayList(1, 2, 3);
  $a[]= 4;

This used to throw an IllegalArgumentException and will now be allowed, resulting in a list with four elements.

None.

Slower than native array implementation.

BC break for public member "value" in ArrayList class, renamed to "array".

• http://de3.php.net/types.array - Arrays
• http://docs.xp-framework.net/xml/api/package?util.collections - XP Collections
• http://msdn.microsoft.com/en-us/library/system.collections.ienumerable.aspx - IEnumerable
• RFC #0168: Integrate lang.types
• http://xp-framework.net/rfc/contrib/rfc0184.diff - Implementing patch

friebe, Mon Apr 6 08:19:04 2009

What additional methods should this class provide? What comes to my mind would be keys() and values() methods returning ArrayLists. I don't think this class should be a full-featured "swiss-army knife"-style hashtable implementation, there's util.collections.HashTable for this and we could also think about extension methods.

friebe, Mon Apr 6 08:23:16 2009

In the same course I think the util.Hashmap class could be deprecated.

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