infix custom operator HACK! - Printable Version

Code:
-- Custom operator to evaluate (class)

local CustomOp = {}

function CustomOp:__div(b) -- eval full operation.

  return getmetatable(self.a)['__' .. self.op](self.a, b)

end

setmetatable(CustomOp, {__call =

  function(class, a, op) -- construct left-half of operation.

    return setmetatable({a = a, op = op}, CustomOp)

  end

})

function enable_custom_ops(mt) -- enable custom ops on metatable.

  function mt:__div(op)

    return CustomOp(self, op)

  end

  return mt

end



-- Output stream (class)

ostream  = {}

ostream.__index = ostream

enable_custom_ops(ostream)

function ostream:write(s)

  io.write(s)

end

ostream['__<<'] = function(self, s)  -- '<<' operator

  self:write(s)

  return self

end

setmetatable(ostream, {__call =

  function(class, file) -- construct output stream

    file = file or io.output()

    return setmetatable({file = file}, ostream)

  end

})

cout = ostream()

endl = "\n"  -- end of line



-- example usage



local _ = cout /'<<'/ "hello" /'<<'/ endl