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


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 package. 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



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


       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 overloading
       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 compa-
           triots) 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 asso-
           ciated 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 associ-
           ated 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 asso-
           ciated 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.





perl v5.8.5                 2002-11-06                          2





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


       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 val-
           ues 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 off-
           set.

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 <nikATtiuk.com>






perl v5.8.5                 2002-11-06                          3