April 7, 2013

KBP chapter 7


Review Questions

Rickvian Aldi / 02PCT / 1601253441
Assignment By Mr. Tri Djoko Wahjono


1. Define operator precedence and operator associativity.

-The operator precedence rules for expression evaluation partially define
the order in which the operators of different precedence levels are evaluated.

-An operator can have either left or right associativity, meaning that when
there are two adjacent operators with the same precedence, the left operator is
evaluated first or the nright operator is evaluated first, respectively.

2. What is a ternary operator?

-ternary, meaning it has three operands.


3. What is a prefix operator?

-means they precede their operands.


8. Define functional side effect.

-A side effect of a function, naturally called a functional side effect, occurs
when the function changes either one of its parameters or a global variable. (A
global variable is declared outside the function but is accessible in the
function.)


10. What is a conditional expression?

-is a if-then-else that has more convinient form :

expression_1 ? expression_2 : expression_3
where expression_1 is interpreted as a Boolean expression.

If expression_1 evaluates to true, the value of the whole expression is the
value of expression_2;
otherwise, it is the value of expression_3.


13. In JavaScript, what is the difference between == and ===?

== is equality relational operator
=== is similiar to == but prevent their operands from being coerced.


14. What is a mixed-mode expression?

-language that allow expressions is whether an operator can have operands of
different types.

15. What is referential transparency?

-A program has the property of referential transparency if any two
expressions in the program that have the same value can be substituted for one
another anywhere in the program, without affecting the action of the program.

20. How does C support relational and Boolean expressions?
relational :
-for example, inequality, the C-based languages use !=

boolean :
-Highest postfix ++, --
unary +, -, prefix ++, --, !
*, /, %
binary +, -
<, >, <=, >=
=, !=
&&
Lowest ||

21. What is the purpose of a compound assignment operator?

-A compound assignment operator is a shorthand method of specifying a
commonly needed form of assignment. The form of assignment that can be
abbreviated with this technique has the destination variable also appearing as
the first operand in the expression on the right side.

28. What is a cast?

-In the C-based languages, explicit type conversions are called casts.



Problem Set

1. When might you want the compiler to ignore type differences in an
expression?

ANSWER :
-When it's overflow or underflow.


3. Do you think the elimination of overloaded operators in your favorite
language would be beneficial? Why or why not?

ANSWER:

-no.
overloaded operators can give more advantages, if it's eliminated, it will only
have one function.
the benefit in the following will be no more exist, which harden the coding
process.

For example, if + and * are overloaded for a matrix abstract data type and A,
B,
C, and D are variables of that type, then

A * B + C * D

can be used instead of

MatrixAdd(MatrixMult(A, B), MatrixMult(C, D))



9. Assume the following rules of associativity and precedence for
expressions:

Precedence Highest *, /, not
+, –, &, mod
– (unary)
=, /=, < , <=, >=, >
and
Lowest or, xor
Associativity Left to right

Show the order of evaluation of the following expressions by parenthesizing
all subexpressions and placing a superscript on the right parenthesis
to indicate order. For example, for the expression

a + b * c + d

the order of evaluation would be represented as

((a + (b * c)1)2 + d)3

a. a * b - 1 + c
b. a * (b - 1) / c mod d
c. (a - b) / c & (d * e / a - 3)
d. -a or c = d and e
e. a > b xor c or d <= 17
f. -a + b

ANSWER :

a. (((a * b)1 - 1)2 + c)3
b. ( (a * (b - 1)1)3 / (c mod d)2 )4
c. ( ((a - b)1 / c)2 & ((d * e)3 / (a – 3)4)5 )6
d. ((-a)1 or ((c = d)2 and e)3 )4
e. ((a > b)1 xor (c or (d <= 17)2)3)4
f. ((-a)1 + b)2


21. Why does Java specify that operands in expressions are all evaluated in
left-to-right order?

ANSWER: 
-because left-to-right order is a common used.

22. Explain how the coercion rules of a language affect its error detection
ANSWER:

-As a simple illustration of the problem, consider the following Java code:

int a;
float b, c, d;
. . .
d = b * a;

Assume that the second operand of the multiplication operator was supposed
to be c, but because of a keying error it was typed as a. Because mixed-mode
expressions are legal in Java, the compiler would not detect this as an error.
It would simply insert code to coerce the value of the int operand, a, to
float. If mixed-mode expressions were not legal in Java, this keying error
would have been detected by the compiler as a type error.