Tie::Array(3pm) 					 Perl Programmers Reference Guide					   Tie::Array(3pm)

NAME

       Tie::Array - base class for tied arrays

SYNOPSIS

	   package Tie::NewArray;
	   use Tie::Array;
	   @ISA = ('Tie::Array');

	   # mandatory methods
	   sub TIEARRAY { ... }
	   sub FETCH { ... }
	   sub FETCHSIZE { ... }

	   sub STORE { ... }	    # mandatory if elements writeable
	   sub STORESIZE { ... }    # mandatory if elements can be added/deleted
	   sub EXISTS { ... }	    # mandatory if exists() expected to work
	   sub DELETE { ... }	    # mandatory if delete() expected to work

	   # optional methods - for efficiency
	   sub CLEAR { ... }
	   sub PUSH { ... }
	   sub POP { ... }
	   sub SHIFT { ... }
	   sub UNSHIFT { ... }
	   sub SPLICE { ... }
	   sub EXTEND { ... }
	   sub DESTROY { ... }

	   package Tie::NewStdArray;
	   use Tie::Array;

	   @ISA = ('Tie::StdArray');

	   # all methods provided by default

	   package main;

	   $object = tie @somearray,Tie::NewArray;
	   $object = tie @somearray,Tie::StdArray;
	   $object = tie @somearray,Tie::NewStdArray;

DESCRIPTION

       This module provides methods for array-tying classes. See perltie for a list of the functions required in order to tie an array to a pack-
       age. The basic Tie::Array package provides stub "DESTROY", and "EXTEND" methods that do nothing, stub "DELETE" and "EXISTS" methods that
       croak() if the delete() or exists() builtins are ever called on the tied array, and implementations of "PUSH", "POP", "SHIFT", "UNSHIFT",
       "SPLICE" and "CLEAR" in terms of basic "FETCH", "STORE", "FETCHSIZE", "STORESIZE".

       The Tie::StdArray package provides efficient methods required for tied arrays which are implemented as blessed references to an "inner"
       perl array.  It inherits from Tie::Array, and should cause tied arrays to behave exactly like standard arrays, allowing for selective over-
       loading of methods.

       For developers wishing to write their own tied arrays, the required methods are briefly defined below. See the perltie section for more
       detailed descriptive, as well as example code:

       TIEARRAY classname, LIST
	   The class method is invoked by the command "tie @array, classname". Associates an array instance with the specified class. "LIST" would
	   represent additional arguments (along the lines of AnyDBM_File and compatriots) needed to complete the association. The method should
	   return an object of a class which provides the methods below.

       STORE this, index, value
	   Store datum value into index for the tied array associated with object this. If this makes the array larger then class's mapping of
	   "undef" should be returned for new positions.

       FETCH this, index
	   Retrieve the datum in index for the tied array associated with object this.

       FETCHSIZE this
	   Returns the total number of items in the tied array associated with object this. (Equivalent to "scalar(@array)").

       STORESIZE this, count
	   Sets the total number of items in the tied array associated with object this to be count. If this makes the array larger then class's
	   mapping of "undef" should be returned for new positions.  If the array becomes smaller then entries beyond count should be deleted.

       EXTEND this, count
	   Informative call that array is likely to grow to have count entries.  Can be used to optimize allocation. This method need do nothing.

       EXISTS this, key
	   Verify that the element at index key exists in the tied array this.

	   The Tie::Array implementation is a stub that simply croaks.

       DELETE this, key
	   Delete the element at index key from the tied array this.

	   The Tie::Array implementation is a stub that simply croaks.

       CLEAR this
	   Clear (remove, delete, ...) all values from the tied array associated with object this.

       DESTROY this
	   Normal object destructor method.

       PUSH this, LIST
	   Append elements of LIST to the array.

       POP this
	   Remove last element of the array and return it.

       SHIFT this
	   Remove the first element of the array (shifting other elements down) and return it.

       UNSHIFT this, LIST
	   Insert LIST elements at the beginning of the array, moving existing elements up to make room.

       SPLICE this, offset, length, LIST
	   Perform the equivalent of "splice" on the array.

	   offset is optional and defaults to zero, negative values count back from the end of the array.

	   length is optional and defaults to rest of the array.

	   LIST may be empty.

	   Returns a list of the original length elements at offset.

CAVEATS

       There is no support at present for tied @ISA. There is a potential conflict between magic entries needed to notice setting of @ISA, and
       those needed to implement 'tie'.

       Very little consideration has been given to the behaviour of tied arrays when $[ is not default value of zero.

AUTHOR

       Nick Ing-Simmons <nik@tiuk.ti.com>

perl v5.8.0							    2002-06-01							   Tie::Array(3pm)