MLIST Parameter Passing
MLISTs can be passed by reference to functions and procedures. This is similar to the way it works with Ordered Maps except that with MLISTs there is also a variation for passing sublists.
To pass a regular MLIST to a function or procedure, use the following syntax (nearly identical to that for ORDMAPs except for the "AS" clause):
call Proc( $m() ) ! passing the entire $m list by reference
Procedure Proc( $mloc() as MLIST(varstr) )
$mloc(.PUSHBACK) = "new element"
EndProcedure
The above example adds the element "new element" to the MLIST $m(). Note that the local list $mloc() is effectively just an alias for the $m() list. As with passing ORDMAP arrays and other DIMX arrays by reference, you have to initialize the array first in the calling routine.
The pre-initialization requirement does not apply to sublists though, which are automatically initalized when passing them to another routine:
call Proc( $m(.back).SUBLIST )
In the above example, the SUBLIST for the last element of the $m() list is passed to the Proc procedure (given in the previous example). Note that the procedure does not know, or care, that the caller passed a sublist rather than an MLIST base reference; they are indistinguishable from the perspective of the procedure. Also note that since the sublist gets auto-initialized if necessary, the same syntax works regardless of whether the sublist initially exists.
You can also pass a sublist of an iterator, e.g.
foreach $$i in $m()
if $$i = "something" then
call Proc($$i.sublist)
endif
next $$i
In the above example, for each element in the MLIST $m() whose value is "something", we pass the sublist to the Proc procedure, which adds a "new element" to the end of that sublist.
