Re: Lua C API can't be used from other languages without C wrappers

[Andrew Gierth <andrew@...>]

>>>>> "albertmcchan" == albertmcchan  <albertmcchan@yahoo.com> writes:

 albertmcchan> Thanks Andrew,
 albertmcchan> Can I assume call B with argument "foo!", "whatever" like
 albertmcchan> this ?

Of course you can, but you had a -1 there where you probably meant -2:

    lua_pushcfunction(L, B);          // stack = foo! B
                                      // -1 here is B as a function
                                      // value, -2 is "foo!"
    lua_pushvalue(L, -2);             // stack = foo! B foo!
    lua_pushstring(L, "whatever");
    lua_call(L, 2, 1);                // == lua call B("foo!", "whatever")
    return 2;                         // stack = foo! foo!, thus return everything

I sometimes find it more convenient to do this:

    /* set up the arguments to B: */
    lua_pushvalue(L, -1);
    lua_pushstring(L, "whatever");
    /* insert B below its arguments on stack: */
    lua_pushcfunction(L, B);
    lua_insert(L, -3);  /* -(nargs+1) */
    lua_call(L, 2, 1);

This is especially handy if you have the args on stack already and don't
need them afterwards. You can also wrap the pushcfunction/insert/call in
your own convenience function too.

-- 
Andrew.