Re: Lua hashes

[Mark Hamburg <mark@...>]

Your __index and __newindex functions can also store string to integer  
maps as upvalues and do the following:

	lua_pushvalue( L, 2 );	/* The key */
	lua_gettable( L, lua_upvalueindex( kKeyTableIndex ) );
	int keyIndex = lua_tointeger( L, -1 );

You could also use the environment index for the functions to do this.

Note that you don't want to have 0 be a valid result index (offset  
everything by 1 if need be) since undefined keys will come back as 1.

The actual lookup will probably be about as fast as your hash table so  
the overhead is in the other API calls.

You could become more clever for __index by having the translation  
table itself have an __index method that returns the key for any  
undefined items and you could then avoid the need to copy the key and  
instead could just translate it in place.

Mark