ex3.txt

a. 2+3

      expr
  /    |    \
 term  +   expr
  |         |
factor     term
  |         |
 nat      factor
  |         |
  2        nat
            |
            3

b. 2*3*4

          expr
           |
          term
  /        |        \
factor     *       term
  |            /    |    \
 nat         factor *   term
  |            |         |
  2           nat      factor
               |         |
               3        nat 
                         |
                         4

c. (2+3)+4

                expr
       /         |       \
      term       +      expr
       |                 |
     factor             term
  /    |     \           |
  (   expr   )         factor
  /    |     \           |
 term  +   expr         nat
  |         |            |
factor     term          4
  |         |
 nat      factor
  |         |
  2        nat
            |
            3