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Indicating Precedence

• If we use the parse tree to indicate precedence levels of the operators, we cannot have ambiguity:

      <expr> -> <expr> - <term>  |  <term>
      <term> -> <term> / const   |  cons
  

<expr> => <expr> - <term>

=> <term> - <term>

=> const - <term>

=> const - <term> / const

=> const - const / const