lua-users home
lua-l archive

[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index] [Thread Index]

Am 07.10.2015 um 02:29 schröbte Soni L.:

On 06/10/15 09:26 PM, Claire Lewis wrote:
How does order factor in, if the code refers to them by name? I think
I'm overlooking something.

In Rio Lua, the order is as they appear. So if a global access
appears before any other upvalue access on a function, _ENV is the
first upvalue.

local u2, u3, u4, u5
   print(u2, u3, u4, u5) -- _ENV is the first upvalue, because
"print" is actually "_ENV.print" (or "_ENV['print']")

Unless I'm missing something, I don't think this is reliable, that's
an implementation detail, and could change any future version, even a
patch release of 5.3.

The Lua 5.3 manual states: "Upvalues have no particular order, as they
are active through the whole function. They are numbered in an
arbitrary order."

I'd probably recommend finding a different way to achieve this for a
public module.

- Claire

But it's resonable to assume they're consistent between dump and reload.

That's not the issue. The problem is between dump/load on one side and the party who supplies the extra upvalues for load on the other side. Using a table for named upvalues is only an option if debug info is available in the bytecode, so IMHO there is no easy solution to this.