classes and concat operator

[Paul Matthews <paulmatthews@...>]

The following class overrides the concat operator,
however using it, as one can use a string, produces 
`=' expected near `..'

How to achive this?

Note I don't need the result of the concat, as
eventually, the side effect of "chaining" will 
produce the results required.


-- Chain Class

function Chain_concat( a, b )
  a:link(b);  
  return b;
end;

Chain      = {};
Chain_Meta = {
  __index  = Chain;
  __concat = Chain_concat;
};

function Chain:new()
  local chain  = {};
  chain.ichain = nil;
  setmetatable( chain, Chain_Meta );
  return chain;
end;

function Chain:link( a, b )
  if ( nil ~= b.ichain ) then
    error( "chain already linked" );
  end
  b.ichain = a;
end;


-- use chain

do
  achain = Chain:new();
  bchain = Chain:new();
  achain .. bchain;
end;


=====
-- Paul Matthews
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