CMSC 330, Spring 2009, Midterm 2 Practice Problems
1. Programming languages
a. Describe the difference between OCaml modules and Java classes.
b. Describe the difference between strong and weak typing.
c. Explain how call-by-name simplifies implementing lazy evaluation.
d. Describe the difference between an L-value and an R-value.
e. What is an activation record, and why is it usually allocated on a stack?
f. Describe short circuiting.
2. Function arguments
For each code, explain whether g is an upward or downward funarg.
a. let f x = let g y = x + y in let app a b = a b in app g 1 ;;
b. let f x = let g y = x + y in g ;;
3. Static vs. Dynamic Scoping
Consider the following OCaml code.
let a = 1 ;;
let f = fun ( ) -> a ;;
let a = 2 ;;
f ( );;
a. What value is returned by the invocation of f( ) with static scoping? Explain.
b. What value is returned by the invocation of f( ) with dynamic scoping? Explain.
Consider the following OCaml code.
let app f w = let x = 1 in f w ;;
let add x y = let incr z = z+x in app incr y;;
(add 2 3) ;;
c. What is the order of invocation for the functions app, add, and incr when
evaluating the expression (add 2 3)?
d. What value is returned by (add 2 3) with static scoping? Explain.
e. What value is returned by by (add 2 3) with dynamic scoping? Explain.
