EECS 12 Summer Session 1 Midterm

General Instructions

• You have until 11:50AM to complete this midterm.
• You may not have anything open except IDLE, this page, and the slides from class. If you have notes that you would like to have open, please get approval from the professor.
• Do not speak to the other students.
• Any violation of these rules will result in automatic failure of the midterm. If you have any questions, raise your hand.
• Turn in to dropbox when you have completed it.

Problem

• Create a calculator program that supports the following operations:
  • +
  • -
  • *
  • /
  • pow
  • store
  • clear
  • showall
  • exit
• The calculator should take input in prefix form (example below) and continue to take input until the user types exit.
• The following functions should work as expected: +, -, *, /, pow (pow can be found in the math module)
• The store command stores the last calculated value as a variable.
• The clear command clears all stored variables
• The showall command shows all variables
• The exit command quits the calculator

NOTE: This program has two types of variables. Normal variables are the ones that you are used to using. User variables are variables defined by the user with the store command. The term variable is used in both cases, so it is usually up to you to not get confused which one is intended in each context.

Requirements

• All numbers should be float
• User variables will be stored in a dictionary
• You must write a function resolve(argument) with the following properties:
  • argument is assumed to be a string
  • If argument starts with a letter, then it is assumed to be the name of a variable. Otherwise, it is assumed to be a number.
  • If argument is a variable that cannot be found in the dictionary of variables, then resolve returns 0.0
  • If argument is a variable that can be found in the dictionary of variables, then resolve returns the value of the variable
  • Otherwise, resolve returns the argument converted into floating point format.
• The messages printed out by the program should match the messages in the example below

Hints

• You will need the string and math modules.
• string.letters is a string that contains all of the characters that are considered letters
• Things that you initialize before the loop should be:
  • variables: a dictionary for keeping track of user variables
  • doLoop: a boolean varible set to True for the while loop
  • last: the result of the previous operation. Initialize it to zero.
• Use split to immediately split the raw_input into a list for easier processing
• You can clear a dictionary variable by assigning it to the empty dictionary
• Most importantly, do not try to cut and paste your homeworks to solve this problem. It is a special mixture designed to see how well you understand the individual concepts.

Example Session

Here is an example session, with user input in red.

? + 1 2
3.0
? store a
a = 3.0
? + a 5
8.0
? + a a
6.0
? * a a
9.0
? pow a 2
9.0
? store b
b = 9.0
? / b a
3.0
? - b a
6.0
? showall
a = 3.0
b = 9.0
? clear
Variables cleared.
? showall
? + a b
Unknown variable: a
Unknown variable: b
0.0
? + a 1
Unknown variable: a
1.0
? dance
Unknown operation.
? exit