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Got it working now.  (see - no smiley.. :!)

Diff for Lua 5.1.1 (some 650 lines if it was cleansed):
svn cat svn:// patch.diff

The Whole Lot (try "make test"):
  svn co svn://

The approach this patch takes -- and I'm only testing the approaches -- is to be all Lua-internal, except for "" that is offered for Lua script side creation of these 'enum's.

Enum's are basically unsigned 32-bit values, with family info. You cannot do operations between them and numbers (numbers are _not_ bitfields), and you cannot do inter-family operations either. This protects one from using the wrong kind of 0x10 in an API call. Should be a good thing.


The patch works, but...

mutability of enums (val[9]=1) needs to be turned off. And if it is, the same can be
achieved with a dynamically loaded module, as well.

The question becomes (performance issues aside) whether having a standard 'built-in' solution for enum/bitfield handling within Lua itself is so preferable that it's worth
the added 700+ lines (including comments) that are required. Maybe not.

On the other hand, enums do need both Lua/C API and Lua side support (= C modules should be able to bind bitfield types and values effortlessly, and in a standard way). For this reason, a certain Lua C API add-on will anyways be needed, and if such an add-on is not delivered with Lua, chances are there will be incompatible approaches even in the future.

Survey's done, prototype's working, the rest is ... politics.

- Asko Kauppi

I'll also place an entry to the Wiki PowerPatches page, just in case.

-asko kirjoitti 28.9.2006 kello 9.11:

I've been developing a suggestion to the enum/bitwise operations issue, discussed extensively on the List lately. Seems like the best way to cut that thread?

Now, I'm in a dead end position with 2 places in the code causing headaches. Would like to pleed for help, anyone with under the hood Lua core understanding, would you please do the rest? :)


  svn co svn://
  cd bitwise
  make test

Mod top level Makefile if you're not running OS X (one liner).

What the patch does:

- value_int [,family_str] ) provides a means for Lua code to create 'enums', which belong to a family. If you leave the family part out, they are "anonymous" (which in a way is just a family itself, too)

- existing operators offer bitwise manipulation to the enums, _within_ their family. See test.lua for samples. New operators can also be used, but I don't personally see that vital.

- inter-family operations are not allowed (that's the whole purpose!)

- C API has means to generate enums from C modules

typedef struct _lua_enum_tag *lua_EnumTag;
LUA_API lua_EnumTag lua_newenumtag (lua_State *L, const char *family);
LUA_API lua_EnumTag lua_enumtag (lua_State *L, int idx);
LUA_API lua_Enum lua_toenum (lua_State *L, int idx, lua_EnumTag tag);
LUA_API void lua_pushenum (lua_State *L, lua_Enum v, lua_EnumTag tag);
LUA_API const char *lua_enumtagname (lua_State *L, lua_EnumTag tag);

Warning: I may be moving the folder to another URL soon, since it's not a 'rock' after all. bitwise.[lua|c] files are not needed; they're leftovers of when I thought this could be done as a pure module. There's limitations, if it's done that way.


ps. thanks to the recent 4x listing in top-smileys, I'm currently cutting my emotions back heavily. I am... ;)