Homework 3 Solution

Description

1. (28 pts) Using the C++ programming language, indicate the binding time (language design, language implementation, compilation, link, run, etc.) for each of the following attributes. Justify your answer.

1. 1. The variable declaration that corresponds to a certain variable reference (use)

   2. The range of possible values for integer numbers

   3. The meaning of char

1. 4. The address of a local variable

   5. The address of a library function

   6. The referencing environment of a function passed as a parameter

   7. The total amount of memory needed by the data in a program

2. (24 pts) Can a language that uses dynamic scoping do type checking at compile time? Why? Can a language that uses static scoping do type checking at run time? Why?

3. (24 pts) Does Scheme use static or dynamic scoping? Write a short Scheme program that proves your answer.

4. (24 pts) Consider the following pseudo-code:

x : integer; — global

procedure set_x (n : integer)

x := n;

procedure print_x

write_integer (x);

procedure foo (S, P : procedure; n : integer)

x : integer;

if n in {1,3}

set_x(n);

else

S(n);

if n in {1,2}

print_x;

else

P;

— main program

set_x(0); foo (set_x, print_x, 1); print_x; set_x(0); foo (set_x, print_x, 2); print_x; set_x(0); foo (set_x, print_x, 3); print_x; set_x(0); foo (set_x, print_x, 4); print_x;

Assume that the language uses dynamic scoping. What does this program print if the language uses shallow binding? Why? What does it print with deep binding? Why?

Note: At exactly one point during execution in the deep binding case, the program will attempt to print an uninitialized variable. Simply write a “?” for the value printed at that point.