Re: Check for ipairs() compat mode

[tobias@...]

Quoting Dirk Laurie <dirk.laurie@gmail.com>:

> 2018-07-19 1:52 GMT+02:00  <tobias@justdreams.de>:
>
>
> > I guess I can shorten it to the minimum but it's still clumsy:
> >
> > local t = setmetatable( {},{__ipairs=function(tbl) return function() return
> > nil,nil,true end,tbl,0 end})
> >
> > local a,b,c = ipairs(t)
> > local _,_,_isCompat = a(b,c)
>
> I replied to the first post before reading this one. Here you do have an
> example. This example runs perfectly for me in both Lua 5.3 and 5.4.
>
> But maybe it is a simpler case than the one on which you observed
> the offending behaviour.

When running that code in 5.4, _isCompat==true for you? For me it's only in
5.3.

the implementation in lua-5.4:
static int luaB_ipairs (lua_State *L) {
  luaL_checkany(L, 1);
  lua_pushcfunction(L, ipairsaux);  /* iteration function */
  lua_pushvalue(L, 1);  /* state */
  lua_pushinteger(L, 0);  /* initial value */
  return 3;
}

in Lua-5.3:
static int luaB_ipairs (lua_State *L) {
#if defined(LUA_COMPAT_IPAIRS)
  return pairsmeta(L, "__ipairs", 1, ipairsaux);
#else
  luaL_checkany(L, 1);
  lua_pushcfunction(L, ipairsaux);  /* iteration function */
  lua_pushvalue(L, 1);  /* state */
  lua_pushinteger(L, 0);  /* initial value */
  return 3;
#endif
}

This is by design. It's not an error. In 5.3, LUA_COMPAT_IPAIRS is default.
I'm just trying to detect the new behavior.