Here are some arithmetic expressions for you to use to test your
Prolog project, due Oct 16th. Remember that you need to input them to 
our provided tokenizer as Prolog strings (i.e., sequences of characters 
surrounded by double quotes). 

1 + 2

5 - 3 - 2

5 ^ 3 ^ 2

abs(1 - 5 * 3)

(1 + 2) * 3

2 + (( 4 - 1) * 3) / 3

1 + ( 2 - ( 3 + 5 ))