Consider the following expression BNF:

::=* |/|

:==+ | - |

::={}|

::=0|1|2|3|4|5|6|7|8|9

Using recursive descent, andonly recursive descent, scan expressions that adhere to this BNF to build their expression tree; write an integer valued function that scans the tree to evaluate the expression represented by the tree.

Input:

A numeric expression adhering to this BNF.

Output:

Some representation of the expression tree.

The result of evaluating the expression