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Currently, I am not sure constant folding is worth the trouble. We had all kinds of problems with it: division and module by zero, NaN results, problems with exotic lua_Number types (which may need a state to create new values), etc. And it adds very little to the language: it is very easy for the programmer to define suitable local "constants" to avoid recomputing constant expressions, when needed.
Except for embedded systems where every constant with a name uses up valuable RAM :-) How much code is there related to constant folding? At some point in the development of the Gems related to this topic, it would be nice to get some ideas for building Lua for systems where constants can be stored in ROM and the tables that store them don't end up getting allocated in RAM when the library is opened. Sorry if the meaning is unclear, but I am playing with these ideas right now and have not fully understood the issues... Ralph