Chapter 7

Question 1

___ are the fundamental means of specifying computations in a programming language.

Answer 1

Expressions

Question 2

It is crucial for a programmer to understand both the ___ and ___ of expressions of the used language.

Answer 2

syntax and semantics

Question 3

To understand expression evaluation, it is necessary to be familiar with the ___ of ___ and ___ evaluation.

Answer 3

order, operator, operand

Question 4

Although the value of an expression sometimes depends on it, the order of operand evaluation in expressions is often ___ by language designers.

Answer 4

unstated

Question 5

Implementors being allowed to choose order of operand evaluations in expressions can lead to the possibility of programs producing ___ results in different implementations.

Answer 5

different

Question 6

Other issues in expression semantics are ___ ___, ___, and ___-___ evaluation.

Answer 6

type mismatches, coercions, short-circuit

Question 7

The essence of imperative programming languages is the ___ role of assignment statements.

Answer 7

dominant

Question 8

The purpose of assignment statements in imperative languages is to cause the ___ ___ of changing the values of variables, or the state, of the program.

Answer 8

side effect

Question 9

An integral part of all imperative languages is the concept of variables whose values change during program ___.

Answer 9

execution.

Question 10

Functional languages use variables of a different sort, such as the parameters of ___.

Answer 10

functions

Question 11

Functional languages, like imperative languages, also have declaration statements that bind values to ___.

Answer 11

names

Question 12

Declarations of functional languages are similar to assignment statements, but do not have ___ ___

Answer 12

side effects

Question 13

Automatic evaluation of arithmetic expressions similar to those found in mathematics, science, and engineering was one of the ___ of the first ___-___ programming languages.

Answer 13

goals, high-level

Question 14

Most of the characteristics of arithmetic expressions in programming languages were inherited from convention that had evolved in ___.

Answer 14

mathematics.

Question 15

In programming languages, arithmetic expressions consist of ___, ___, ___, and ___ ___.

Answer 15

operators, operands, parentheses, and function calls.

Question 16

An operator can be ___, meaning it has a single operand, ___, meaning it has two operands, or ___, meaning it has three operands.

Answer 16

unary, binary, ternary

Question 17

In most programming languages, binary operators are ___, which means they appear between their operands.

Answer 17

infix

Question 18

Some languages, such as Perl, has some operators that are ___, which means they precede their operands.

Answer 18

prefix

Question 19

Some languages have operators that are ___, which means they come after their operands.

Answer 19

postfix

Question 20

The ___ precedence and ___ rules of a language dictate the order of evaluation of its operators.

Answer 20

operator, associativity

Question 21

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

Answer 21

operator precedence rules

Question 22

The operator precedence rules for expressions are based on the ___ of operator priorities, as seen by the language designer.

Answer 22

hierarchy

Question 23

The operator precedence rules of the common imperative languages are nearly all the same, because they are based on those of ____.

Answer 23

mathematics

Question 24

Unary addition is called the ___ operator because it usually has no associated operation and thus has no effect on its operand.

Answer 24

identity

Question 25

Associatiativity in common languages is __ to __; however, there are exceptions in, such as in exponentiation in Fortran & Ruby which is ___ to __.

Answer 25

left to right; right to left

Question 26

An ___ exception can cause addition/subtraction not to be associative.

Answer 26

overflow

Question 27

All arithmetic and logic operations in Lisp are performed by ___.

Answer 27

subprograms

Question 28

If neither of the operands of and operator has ___ ___, then operand evaluation order is irrelevant.

Answer 28

side effects

Question 29

Operand evaluation order becomes relevant when there are ___ ___.

Answer 29

side effects

Question 30

A ___ ____ of a function, occurs when the function changes either one of its parameters or a global variable.

Answer 30

side effect

Question 31

Two possible solutions to the problem of operand evaluation order and side effects are:

Answer 31

1) Language designer could disallow functional side effects | 2) The language definition could state that operands in expressions are to be evaluated in a particular order

Question 32

The problem with disallowing function side effects in the imperative languages is difficult and it eliminates some ___ for the programmer.

Answer 32

flexibility (i.e., disallowing access to global variables)

Question 33

The problem with having a strict evaluation order is that some code optimization techniques used by compilers involve ___ operand evaluations.

Answer 33

reordering

Question 34

A program has the property of ___ ___ 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.

Answer 34

referential transparency

Question 35

``` result1 = (fun(a) + b / (fun(a) - c); temp = fun(a) result2 = (temp = b)/ (temp - c) ``` The example code above has referential transparency if ___?

Answer 35

result 1 = result2

Question 36

The most important advantage of referentially transparent programs is that the ___ of such programs is much easier to understand than those that are not referentially transparent.

Answer 36

easier

Question 37

Being referentially transparent makes a function equivalent to a ___ function, in terms of ease of understanding.

Answer 37

mathematical

Question 38

Because they do not have variables, programs written in pure ___ languages are referentially transparent.

Answer 38

functional

Question 39

Functions in a pure functional languages cannot have ___, which would be stored in local variables.

Answer 39

state

Question 40

The multiple use of an operator is called ___ ___ and is generally thought to be acceptable, as long as neither readability nor reliability suffers.

Answer 40

operator overloading

Question 41

A ___ conversion converts a value to a type that cannot store even approximations of all of the values of the original type.

Answer 41

Narrowing Ex: converting a double to a float in Java is a narrowing conversion because the range of double is much larger than that of float.

Question 42

A ___ conversion converts a value to a type that can include at least all of the values of the original type.

Answer 42

Widening

Question 43

Between widening and narrowing conversions, ___ is nearly always safe, although they can result in ___ accuracy.

Answer 43

widening, reduced ex: integer to float can be a loss in precision because both are stored in 32 bits; float allows for 7 decimal places while integer allows for 9 (in many language implementations)

Question 44

Expressions that allow operands of different types are called ___-___ expressions.

Answer 44

mixed mode

Question 45

Languages that allow mixed-mode expressions must define ___ for implicit operand type conversions.

Answer 45

conventions

Question 46

Explicit type conversions are called ___.

Answer 46

casts

Question 47

The most common error occurs when the result of an operation cannot be represented in the memory cell where it must be stored; this is called ___ or ___ depending on whether the result was too large or too small.

Answer 47

overflow, underflow

Question 48

Floating-point overflow, underflow, and division by zero are examples of run-time errors, which are sometimes called ___.

Answer 48

exceptions

Question 49

A ___ operator is an operator that compares the values of its two operands.

Answer 49

relational

Question 50

Unless not available in the language, the value of a relational expression is ___.

Answer 50

Boolean

Question 51

Boolean expressions consist of Boolean ___, Boolean ___, ___ ___, and Boolean ___.

Answer 51

variables, constants, relational expressions, operators (ex: AND OR NOT XOR)

Question 52

A ___-___ evaluation of an expression is one in which the result is determined without evaluating all of the operands and/or operators.

Answer 52

short-circuit

Question 53

(13 * a) * (b / 13 - 1) can be short-circuited when a = ___

Answer 53

0 because anything multiplied by 0 is 0

Question 54

The Boolean expression | (A >= 0) && (b < 10) can be short-circuited when

Answer 54

A < 10 because && dictates both statements must be true, if the first is false, no need to continue

Question 55

Programming languages that use an ___ as an assignment operator must use something different for the equality relational operator to avoid confusion with their assignment operator.

Answer 55

=

Question 56

A ___ assignment operator is a shorthand method of specifying a commonly needed form of assignment.

Answer 56

compound ex: sum += value same as sum = sum + value

Question 57

What are the two special unary arithmetic operators and what do they do?

Answer 57

++ increment, -- decrements ex: sum = ++ count (The value of count is incremented by 1 and assigned to sum) sum = count ++ (The value of count is assigned to sum, then count is incremented