lua_isfunction   6268 host/minilua.c if(lua_isfunction(L,1))lua_pushvalue(L,1);
lua_isfunction    294 lib_debug.c      if (lua_isfunction(L, -1)) {
lua_isfunction    427 lib_package.c      if (lua_isfunction(L, -1))  /* did it find module? */
lua_isfunction    353 luajit.c         if (!lua_isfunction(L, -1)) {