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NAME

Tie::Array - base class for tied arrays


SYNOPSIS

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

    package 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 the perltie manpage for a list of the functions required in order to tie an array to a package. The basic Tie::Array package provides stub DELETE and EXTEND methods, 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 overloading of methods.

For developers wishing to write their own tied arrays, the required methods are briefly defined below. See the the perltie manpage 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 the AnyDBM_File manpage 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 assoicated 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 assoicated with object this.

FETCHSIZE this

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

STORESIZE this, count

Sets the total number of items in the tied array assoicated 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.

CLEAR this

Clear (remove, delete, ...) all values from the tied array assoicated 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 begining 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>


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