struct NumArray{    size_t size;    double values[1];};static int newarray(lua_State*L){    int n = luaL_checkint(L,1);    size_t nbytes = sizeof(NumArray) + (n-1)*sizeof(double);    NumArray*a = (NumArray*)lua_newuserdata(L,nbytes);    a->size = n;    return 1;}static int setarray(lua_State *L){    NumArray*a = (NumArray*)lua_touserdata(L,1);    int index = luaL_checkint(L,2);    double value = luaL_checknumber(L,3);    luaL_argcheck(L,a!= NULL,1,"array expected");    luaL_argcheck(L,1<= index && index <= a->size ,2,"index out of range");    a->values[index - 1] = value;    return 0;}static int getarray (lua_State *L){    NumArray *a = (NumArray *)lua_touserdata(L, 1);    int index = luaL_checkint(L, 2);    luaL_argcheck(L, a != NULL, 1, "'array' expected");    luaL_argcheck(L, 1 <= index && index <= a->size, 2,                  "index out of range");    lua_pushnumber(L, a->values[index-1]);    return 1;}static int getsize (lua_State *L){    NumArray *a = (NumArray *)lua_touserdata(L, 1);    luaL_argcheck(L, a != NULL, 1, "`array' expected");    lua_pushnumber(L, a->size);    return 1;}static const struct luaL_Reg arraylib [] = {    {"new", newarray},    {"set", setarray},    {"get", getarray},    {"size", getsize},    {NULL, NULL}};int luaopen_array (lua_State *L) {    luaL_newlib(L,arraylib);    lua_setglobal(L,"array");    return 1;}

a = array.new(1000)print(a)                 --> userdata: 0x8064d48print(array.size(a))     --> 1000for i=1,1000 do    array.set(a, i, 1/i)endprint(array.get(a, 10))  --> 0.1