Array +keys

diff -r 89d6a7a84779 -r 25a17d01db0c Symbian3/PDK/Source/GUID-9309D482-8931-58FC-9B34-D0E5E942E404.dita --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Symbian3/PDK/Source/GUID-9309D482-8931-58FC-9B34-D0E5E942E404.dita Fri Jan 22 18:26:19 2010 +0000 @@ -0,0 +1,72 @@ + + + + + +Array +keysThis document provides an introduction to array keys. +

A key is used by an array for sorting and finding elements and can also +be used to locate the insertion position for new elements.

The characteristics of a key are defined by a key object, constructed from +one of the three concrete classes: TKeyArrayFix, TKeyArrayVar and TKeyArrayPak. +In general, the choice of key class depends on the type of array being used +and the specific member function of that array.

TKeyArrayFix is used by the following functions accessible +through the CArrayFixFlat and CArrayFixSeg classes:

Sort()
InsertIsqL()
Find()
FindIsq()

TKeyArrayVar is used by the following functions accessible +through the CArrayVarFlat and CArrayVarSeg classes:

Sort()
InsertIsqL()
Find()
FindIsq()

TKeyArrayVar is also used by CArrayPakFlat::SortL().

TKeyArrayPak is used by the following functions accessible +through the CArrayPakFlat class:

InsertIsqL()
Find()
FindIsq()

The concrete classes are all derived from the abstract base class TKey that +encapsulates the characteristics of a key and defines the basic behaviour +of keys. A class such as TKeyArrayFix provides an implementation +for specific arrays or types of array.

A key object is not a component of an array class but is constructed separately +and passed, as an argument, to the appropriate array class member function. +A key definition is not an integral part of an array, but is used by +an array.

A TKey derived object is also passed as an argument to +the User::BinarySearch() and User::QuickSort() functions.

An array can use various different key definitions during its life.

The characteristics of a key as defined by the base TKey class +are:

The type of data forming +the key.
The type of comparison +to be made between two keys.
The length of the key +within an array element.
The location of the +key within an array element.