-- Objects amenable to basic arithmetic operation

deferred class interface NUMERIC
exported features
  infix "+" (other:NUMERIC):NUMERIC
      -- Sum of current object and 'other'
    deferred
  infix "-" (other:NUMERIC):NUMERIC
      -- Difference between current object and 'other'
    deferred
  infix "*" (other:NUMERIC):NUMERIC
      -- Product of current object by 'other'
    deferred
  prefix "+":NUMERIC
      -- Unary addition applied to current object
    deferred
  prefix "-":NUMERIC
      -- Unary substraction applied to current object
    deferred
end interface  -- class 'NUMERIC'