Chapter 7

Question 1

What are expressions?

Answer 1

Fundamental means of specifying computations in a programming language

Question 2

What is needed to understand expression evaluation?

Answer 2

The orders of operator and operand evaluation

Question 3

What do arithmetic expressions consist of?

Answer 3

Operators
Operands
Parentheses
Function calls

Question 4

What are some design issues with Arithmetic expressions?

Answer 4

Operator precedence rules
Operator associativity rules
Order of operand evaluation
Are operand evaluation side effects restricted
Is user-defined operator overloading allowed?
What type mixing is allowed

Question 5

How many operators does a Unary/Binary/Ternary operand have?

Answer 5

Unary = 1
Binary = 2
Ternary = 3

Question 6

Typical precedence levels of a language

Answer 6

Parentheses. Unary operators. ** or ^. * and /. + and -

Question 7

Operator associativity rules

Answer 7

Define order in which adjacent operators with the same precedence level are evaluated

Question 8

Typical associativity rules

Answer 8

Left to right (** = right to left)

Question 9

How are operators implemented in Ruby?

Answer 9

As methods
(Arith, relational, assignment)

Question 10

Can you overwrite operators in Ruby?

Answer 10

Yes because they are methods

Question 11

Scheme and Common LISP arithmetic and logic operations are implemented as?

Answer 11

Explicitly called subprograms

Question 12

Operand Evaluation Order

Answer 12

Variables, Constants, Parenthesized expressions

Question 13

Problematic operator overloading

Answer 13

& in C and C++. Loss of readability and loss of compiler error detection

Question 14

Can user-defined overloaded operators increase readability?

Answer 14

Yes but only when sensibly used (+)

Question 15

What is narrowing conversions in Type Conversions

Answer 15

Converts an object to a type that cannot include all of the values of the origin type (float to int)

Question 16

What is widening conversion in Type Conversions

Answer 16

Converts an object to a type including at least approximations of all the original type’s values. May lose accuracy (int to float)

Question 17

What is Mixed-mode expression?

Answer 17

Expression that has operands of different types. ( a is int, b is float. a + b = mixed mode)

Question 18

What is Coercion in Type Conversions?

Answer 18

The auto type conversion of operands. Decreases compiler’s type error detection ability.

Question 19

What is explicit type conversion?

Answer 19

Programmer-specified type conversions. Can be either narrowing or widening? Compiler may give warnings. ( (int) in C languages)

Question 20

What causes errors in expressions with type conversions?

Answer 20

Type checking and coercion.
Limitations of arithmetic, Inherent and computer.
Run time errors can be ignored but may require exception handling mechanisms

Question 21

What do relational expressions evaluate to?

Answer 21

Booleans

Question 22

What does short circuit evaluation do?

Answer 22

Doesnt evaluate all operands and operators (13a)(b) if a = 0 b isnt evaluated

Question 23

When can short circuit evaluation be a problem?

Answer 23

When there are side effects in expressions.

Question 24

What is the problem with = overloading

Answer 24

There is ambiguity between assignment and equality

Question 25

What are conditional targets?

Answer 25

Similar to conditional expressions ($flag ? $total : $subtotal

Question 26

How does a compound assignment operator look like?

Answer 26

A += B

Question 27

Can assignments also be mixed-mode?

Answer 27

Yes