1. EECS 111 Review 11/13/2016

2. Imperative Programming
Prior to learning imperative programming, all expressions had some “value”
Constants have their own value (i.e. 5 is 5)
Variables have whatever value they were assigned
Some special forms exist (define, local, lambda, if)
If it’s none of the above, it’s a procedure call

3. That’s Nice and All… But imperatives are different
For example, set! is a void function
Ex:
(define x 5)
(set! x 10)
> x 10

4. Define vs. Set!
Set! changes an existing variable’s value while the program is executing
Define makes new variables

5. Functional vs Imperative
The only effect of a functional program is its return value
Result does not depend on order
Value determined entirely by inputs
Imperative programs on the other hand…
Many different effects
Return value, variable changes, delete files, etc.
Can influence other functions as well

6. Imperative Advantages
Usually more efficient
(less steps to machine code) = faster code
Can be simpler
Simulations (these are basically just a bunch of changes, so it makes sense)
More natural

7. Composing Imperatives
Sequencing
Begin
Conditionals
If, when, unless, cond
Repetition
for-each
recursion

8. begin
Executes a bunch of expressions in order, and then returns the value of the last thing executed
(begin (set! balance (+ balance amount)) balance)
Would return balance after setting the balance to balance + amount

9. Imperative Special Forms
Set!
Begin
When/unless
cond

10. Debugging!
I’d look at Ian’s slides on this, but let’s walk through an example!

11. Exercise 6 Any other questions?
Any questions about the homework so far?