RE: Forward Declaration

[virgil@... (Virgil Smith)]

Sigh, this answer has been given twice and is needlessly roundabout.
Forward referencing is a problem for systems that use strictly closed
declarations (not at all like Lua and tables).  You can add a table entry at
any time.

The direct answer has been given once, but I will repeat it with slightly
more explanation.
Here it is...
---------
SubMenu1 =
{
        ["New Campaign"] = ID_CAMPAIGN,
        ["New Random Map"] = ID_RANDOMMAP,
};

Menu =
{
        ["New"] = SubMenu1,
        ["Load Game"] = ID_LOADGAME,
        ["Exit"] = ID_EXIT
}

SubMenu1["Back"] = Menu
---------

Note that the first table construction/assignment statement creates a table
and assigns a reference to it into SubMenu1. The second assigns a reference
to the same table value that is referenced by SubMenu1 (inside a new table).
The last statement adds an entry to the table referenced by SubMenu1 (and
Menu.New).  This new entry happens to be a reference to the table referenced
by Menu.  This of course makes for a circular reference (Menu ==
Menu.New.Back), however, this is not necessarily a problem since Lua uses a
mark and sweep garbage collection system.  Of course if you are using
anything that "blindly" recurses tables (such as a naive lazy copy or
serializer mechanism) it will have a problem with this.

-----Original Message-----
From: lua-bounces@bazar2.conectiva.com.br
[mailto:lua-bounces@bazar2.conectiva.com.br]On Behalf Of Bilyk, Alex
Sent: Tuesday, October 14, 2003 11:04 AM
To: Lua list
Subject: RE: Forward Declaration


Use "Menu" instead of Menu. Then, at run time, you can resolve the name
"Menu" to the object under it.

        ["Back"] = "Menu"                      <-- No problem :)

-----Original Message-----
From: Speight.Marcus [mailto:marcus.speight@vivid-gaming.com]
Sent: Tuesday, October 14, 2003 3:51 AM
To: LUA (E-mail)
Subject: Forward Declaration

Hi,

I'm fairly new to LUA and hoped someone could answer a problem for me.

I have a menu system that loads an lua script. But I need a menu to back
reference.

e.g.

SubMenu1 =
{
        ["New Campaign"] = ID_CAMPAIGN,
        ["New Random Map"] = ID_RANDOMMAP,
        ["Back"] = Menu                      <-- Problem
};

Menu =
{
        ["New"] = SubMenu1,
        ["Load Game"] = ID_LOADGAME,
        ["Exit"] = ID_EXIT
};

I tried adding Menu = {}; at the beginning of the file but it did not help.
How to I do this?


Marcus Speight
Software Engineer
Vivid Gaming

The views expressed in this message are those of the sender and not
necessarily those of IGT - UK Limited and its associated companies.

<<attachment: winmail.dat>>