6.01SC Introduction to EECS I, Quiz 3 Solutions

Problem Wk.3.2: Nano Quiz This problem has been submitted previously; no changes will be saved. Due date: 2/17, 9:50am Do all parts of this problem and then click Submit. There is only one Submit button, you should only do that when you are finished with all the parts of the problem. Do not try to start another log in, you will lose what you typed. There is a limited checking budget (20 checks) on this quiz. You have 15 minutes. You must click submit before: 2/17, 9:50am Part 1: Constructing a State Machine Define a state machine for a vending machine. The vending machine has an unlimited number of sodas that it sells for 75 cents apiece. The user can deposit quarters in the machine. If the user presses the cancel button, all the coins she's put in so far are returned. If the user presses the dispense button, If she had not deposited at least 75 cents, she gets no soda and no change. If she had deposited 75 cents or more, she gets a soda and any amount over 75 cents that she has deposited. More concretely, The input for the machine is one of: 'quarter' (25 cents) indicates that a coin has been deposited 'cancel' indicates that the user wants her money back 'dispense' indicates that the user wants a soda The output of the machine is: (change, soda) where change is an integer that indicates (in cents) the amount of change (possibly 0) that is returned soda is a boolean that indicates whether or not the machine will dispense a soda For example: Vending().transduce(['dispense', 'quarter', 'quarter', 'quarter', 'quarter', 'dispense', 'quarter', 'cancel', 'dispense']) would return: [(0, False), (0, False), (0, False), (0, False), (0, False), (25, True), (0, False), (25, False), (0, False)] class Vending(sm.SM): startState = 0 def getNextValues(self, state, inp): if inp=='quarter': return (state+1, (0, False)) if inp=='cancel': return (0, (25*state, False)) if inp=='dispense': if state<3: return (state, (0, False)) return (0, (25*(state-3), True)) This is the answer we wrote: class Vending(sm.SM): startState = 0 def getNextValues(self, state, inp): if inp == 'cancel': return (0, (state, False)) elif inp == 'dispense': if state >= 75: return (0, (state - 75, True)) else: return (state, (0, False)) else: # 'quarter' return (state + 25, (0, False)) 19 checks left Check Part 2: Enable Submit Current time is: 3/1/2011, 9:10pm Click Submit before: 2/17, 9:50am The Check button will update the current time. Enter Done below [] and click Submit. If this problem is submitted past the due time, this subproblem will be marked incorrect. 19 checks left Check This is a multi-part problem, each part has its own Save and Check buttons but there is ONLY ONE Submit button for the WHOLE problem. Finish working on all the parts before you click on Submit. Get Answers