MirOS Manual: Tie::Array(3p)


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".

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     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 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 speci-
         fied 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 associ-
         ated 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 associ-
         ated 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

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         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, mov-
         ing 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.

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AUTHOR

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

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