Re: [Lua5.2] __len meta-method has two operand?

[Roberto Ierusalimschy <roberto@...>]

> I have modified my code to support this undocumented 'feature'.

It is not undocumented (although it is not listed in the incompatibility
section):

  http://www.lua.org/work/doc/manual.html#2.4

  For the unary - and # operators, the metamethod is called with a
  dummy second argument. This extra argument is only to simplify Lua's
  internals; it may be removed in future versions and therefore it is
  not present in the following code. (For most uses this extra argument
  is irrelevant.)

-- Roberto