Both compilers have support for hash arrays. They are similar to normal arrays but also allow to use non integer values as indexes like string, date, non integer number or pointer (in Harbour) items.
They can be created using => for list of keys and values enclosed
inside {}, f.e.:
hVal := { "ABC" => 123.45, ;
100.1 => date(), ;
100.2 => 10, ;
100 => 5, ;
date()-1 => .t. }
and then items can be accessed using [] operator, f.e.:
? hVal[ "ABC" ] // 123.45
? hVal[ 100 ] // 5
? hVal[ date()-1 ] // .t.
? hVal[ 100.2 ] // 10
? hVal[ 100.1 ] // date()
By default hash items in both compiler support automatic adding new elements
on assign operation. It can be disabled using one of hash item functions.
Harbour has additional extension which allows to enable autoadd with default
values also for access operation and reference operator. It also supports
well passing hash array items by reference and has some other minor
extensions.
xHarbour does not support autoadd on access or reference operations and
passing hash array items by reference does not work (see passing array and
hash item by reference).
Both compilers have set of functions to make different operations on hash
arrays which give similar functionality. In Harbour they use HB_H prefix
(f.e. HB_HSCAN()) in xHarbour H prefix (f.e. HSCAN())
xHarbour has additional functionality which can be enabled for each hash
array using HSetAACompatibility() function. It's an index where is stored
information about the order in which items were added to hash array and
set of functions with HAA prefix to operate on hash array items using this
index instead of real position in hash array, i.e. HAAGETVALUEAT() which
works like HGETVALUEAT().
In Harbour such functionality also exists and it's enabled by HB_HKEEPORDER() function but the internal implementation is completely different. Harbour does not emulate associative arrays by special index which keeps assign order but it uses real natural order in hash array. It means that associative array indexes are equal to regular hash indexes so it does not need any translation between them and Harbour users can use regular hash array functions for associative array indexes. So separated functions for accessing by other index are not necessary. The Harbour implementation is also more efficient because it does not introduce linear index updated each time new key is added to hash array.
Harbour emulates HAA*() xHarbour functions in XHB library but only for
compatibility with existing xHarbour code.
since 3 June 1996.