This parser estimates "costs" for assigmnents with arithmetic operations. 
The costs could be the number of cycles required for an operation, the
energy consumption, etc. The numbers given here are, of course, just
random examples.

Example:

$ echo "x=(y-3)*x+7*(z-q)" | ./costparser 
Cost: 47

The hash table has not been implemented and is left as an exercise to the reader :-).

