Chapter 5

Posted by : Unknown Minggu, 02 November 2014

Name : Romy Hermawan

NIM : 1801378902

Class : LD001

Lecturer: Ir. Tri Djoko Wahjono,M.Sc

REVIEW QUESTION

6. What is the l-values of a variables? What is the r-values?
Answer:

The l-values of a variable is its address while he r-values of a variable is its value.

7. Define binding and binding time.

Answer:
Binding is an association between an attribute and an entity, such as between a variable and its type/ value, or between an operation and a symbol. Binding time is the time at which a binding takes place.

8. After language design and implementation [what are the four times bindings can take place in a program?]

Answer:
compile time: a variable in java bound to a particular data type
load time: a variable bound to a storage cell when a program is loaded into memory
link time: a call to a library subprogram is bound to the subprogram code
run time: certain variables declared in pascal and in c++ functions

9. Define static binding and dynamic binding.

Answer:
A static binding is if it first occurs before run time and remains unchanged throughout program execution. A dynamic binding is if it first occurs during execution or can change during execution of the program.

10. What are the advantages and disadvantages of implicit declarations?

Answer:
The advantage is write ability.

PROBLEM SET

6. Consider the following JavaScript skeletal program:

// The main program

var x;

function sub1() {

var x;

function sub2() {

. . .

}

function sub3() {

. . .

}

Assume that the execution of this program is in the following unit order:

main calls sub1

sub1 calls sub2

sub2 calls sub3

a. Assuming static coping, in the following, which declaration of x is the correct one for a reference to x?
i. Sub1
ii. Sub2
iii. Sub3
b. Repeat part , but assume dynamic scoping.

Answer:

a. Static :

    1. Sub1 : sub1
    2. Sub2 : sub1
    3. Sub3: main

b. Dynamic :

    1. Sub1 : sub1
    2. Sub2 : sub1
    3. Sub3: sub1

7. Assume the following JavaScript program was interpreted using

static-scoping rules. What value of x is displayed in function sub1?

Under dynamic-scoping rules, what value of x is displayed in function

sub1?

var x;

function sub1() {

document.write("x = " + x + "<br />");

}

function sub2() {

var x;

x = 10;

sub1();

}

x = 5;

sub2();

Answer:

Static scope: x=5, Dynamic scoping: x=10.

8. Consider the following JavaScript:

         var x, y, z;
    function sub1() {
       var a, y, z;
       function sub2() {
         var a, b, z;
          ...
       }
       ...
    }
    function sub3() {
       var a, x, w;
       ...
    }

List all the variables, along with the program units where they are declared, that are visible in the bodies of sub1, sub2 and sub3, assuming static scoping is used.

Answer:

Sub1: a(sub1), y(sub1), z(sub1), x(main).

Sub2: a(sub2), b(sub2), z(sub2), y(sub1), x(main)

Sub3: a(sub3), x(sub3), w(sub3), y(main), z(main)

9. Consider the following Python program:
x = 1;
y = 3;
z = 5;
def sub1():
a = 7;
y = 9;
z = 11;
. . .
def sub2():
global x;
a = 13;
x = 15;
w = 17;
. . .
def sub3():
nonlocal a;
a = 19;
b = 21;
z = 23;
. . .
. . .
List all the variables, along with the program units where they are
declared, that are visible in the bodies of sub1, sub2, and sub3, assumingstatic scoping is used.

Answer:

point 1 : x = 1(main), y = 9 (sub1), z = 11(sub1) ,a = 7(sub1);
point 2 : x =15(sub2), w = 17(sub2), a = 13(sub2), y = 9(sub1);
point 3 : x = 15(sub2), b = 21(sub3), a = 19(sub1), z = 23(sub3), w = 17(sub 2);
point 4 : x = 15(sub2), b = 21(sub3), a = 19(sub1), z = 23(sub3), w = 17(sub 2);

10. Consider the following C program:

void fun(void) {
int a, b, c; /* definition 1 */
. . .
while (. . .) {
int b, c, d; /*definition 2 */
. . . 1
while (. . .) {
int c, d, e; /* definition 3 */
. . . 2
}
. . . 3
}
. . . 4
}
For each of the four marked points in this function, list each visible variable,
along with the number of the definition statement that defines it.