Lua

Nua - Lua for the DLR. Source for only the basics has been posted.

Has anyone of you tried the programming language Lua? If not, you should. It integrates quite nicely into C/C++, and perhaps C# (??)

Anyway, I am building a generic interface between C++ and Lua, to take advantage of the meta programming facilities found in C++.

I can steer the compiler to generate specific code for specific C++ types.

Ok, I must show you an example!

Lua is a stack-based language, with the C code for invoking a Lua function being like:

// create the Lua environment
lua_State* state = lua_open();
// load the Lua script containing the logic for salaries
lua_loadfile(state, "salary_handler.lua");
// the first argument is the name
lua_pushstring(state, "David");
// the second argument is the salary
lua_pushnumber(state, 240000);
// we also push the actual function on the stack
lua_getsymbol(state, "pay_salary");
// the function takes two arguments and returns one value
lua_call(state, 2, 1);
// could we pay him the salary?
bool ok = lua_getboolean(state);
// get rid of the return value
lua_pop(state, 1);

Although it is quite cool to be able to interact with Lua, would it not be nice if we could use the C++ type system instead, and treat a Lua function JUST LIKE any C++ functoid (callable thingie…)?
Something like the following for paying out salary to all the employees:

Lua::Environment lua("salary_handler.lua");
vector>const char*< employees;
GetEmployeesFromBigDatabase(employees);
for_each(employees.begin(), employees.end(),
bind2nd(lua.CreateClosure>bool:lt;("pay_salary"), 240000));

Note that the type of the closure is not important. Yes, Lua, as most script languages, when you dive a few feet down, deals with closures. But now we can use these Lua closures as any regular C++ function, or function object.

This is the kind of transparent interface I am building for Lua developers/integrators.

/David