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LuaInstance class

The wrapper consists primarily of a class known as LuaInstance, that contains an instance of the Lua interpreter and can be used to execute Lua code. Each instance is independent of every other instance, and has its own global environment. This class is made available by including the LuaInstance.hpp file, but the class methods are defined in LuaInstance.cpp.

Lua type classes

Another header file is also included called LuaTypeClasses.hpp. This defines a few simple classes that represent Lua data types that lack a simple counterpart in C++. These are lua_Table, lua_Function and lua_Userdata.

lua_Value typedef

This type represents a Lua value of an unspecified type, and is defined as the following: std::variant<nullptr_t, bool, void*, lua_Integer, lua_Number, std::string, std::shared_ptr<lua_Table>, lua_CFunction, lua_Function, lua_Userdata>. A table of what types in Lua correspond to what types in C++ is below:

Lua	C++
nil	nullptr_t
boolean	bool
light userdata	void*
(integer) number	lua_Integer
(non-integer) number	lua_Number
string	std::string
table	std::shared_ptr<lua_Table>
(C) function	lua_CFunction
(Lua) function	lua_Function
(full) userdata	lua_Userdata
thread	Not Supported

Other typedefs

lua_Integer, lua_Number and lua_CFunction are all typedefs supplied by the Lua Library. lua_Integer and lua_Number are by default long long int and double respectively, but are intended to be customisable from within luainclude/luaconf.h. Exactly why they are this way is unclear, but it is presumably to allow avoiding more expensive 64-bit math on 32-bit systems.

Lua_CFunction is the type of function pointers to C functions that can be called from Lua. It is defined as int(*)(lua_State*).