Chapter 11

Answers to Exam Preparation Exercises

2. Valid and invalid set expressions:

(a) 'A' IN Digits Valid

(b) ['X','Y','Z'] >= ['N'..'Y'] Valid

(c) Digits / ['1'] Invalid; / is illegal

(d) Digits * ['1'] Valid; * means intersection

(e) ['1'] + ['2'] + ['3'] = ['1'..'3'] Valid

(f) ['1'..'9'] >= ['0'..'9'] - ['3'..'7'] Valid

(g) 4 IN Digits Invalid; 4 is an integer

4. Definitions:

record: a nonhomogeneous unstructured data type in which the components are accessed by field name

field identifier: the name of a component in a record

field selector: the expression used to access a field of a record variable; made up of the name of the record variable and the field identifier, separated by a period

hierarchical record: a record that contains another record as a component

5. False

6. Identify an appropriate data structure:

(a) hierarchical record containing strings (b) record containing strings (c) record (d) enumerated type or strings

7. Values in records.

Today.Month = 1

Today.Day = 1

Today.Year = 1995

A_Name = ' '

Friend.First_Name = ' '

Friend.Last_Name = ' '

Friend.Birth_Date.Month = 1

Friend.Birth_Date.Day = 1

Friend.Birth_Date.Year = 1995

Self.First_Name = ' '

Self.Last_Name = ' '

Self.Birth_Date.Month = 1

Self.Birth_Date.Day = 1

Self.Birth_Date.Year = 1995

8. Friend and Self are both of type Person. Because Self is the inner scope, the fields of Friend can never be accessed.

Answers to Programming Warm-Up Exercises

2. Set operations:

(a)

TYPE

UP_Letters_Type = SET OF 'A'..'Z';

VAR

Set_A, Set_B, Set_C: UP_Letters_Type;

(b) Set_A := ['A'..'N'];

(c) Set_B := ['K'..'Z'];

(d) Show contents of Set_C:

Set_A + Set_B: ['A'..'Z']

Set_A - Set_B: ['A'..'J']

Set_A * Set_B: ['K'..'N']

Set_B - Set_A: ['O'..'Z']

(e) Evaluate expressions:

Set_A <> Set_B True; expression is ['A'..'Z'] <> ['K'..'Z']

Set_A <= Set_B False; expression is ['A'..'Z'] <= ['K'..'Z']

Set_A * Set_B >= Set_A False; expression is ['K'..'N'] <= ['A'..'N']

Set_A + Set_B >= Set_A True; expression is ['A'..'Z'] >= ['A'..'N']

5. Hierarchical record definition

CONST

Name_Length = 20;

Max_Courses = 50;

TYPE

Course_Index = 1..Max_Courses;

Name_String = String[Name_Length];

Date_Type = RECORD

Month : 1..12;

Year : 1950..2020

END; (* Record *)

Class_Type = (Freshman, Sophomore, Junior, Senior);

Grade_Type = (A, B, C, D, F, Q):

Student_Type = RECORD

Name : Name_String;

Student_ID : Integer;

Hours_To_Date : Integer;

Courses_To_Date : 0..Max_Courses;

First_Enrolled : Date_Type;

Class : Class_Type;

GPA : Real

END; ( Record )

6. Record type for an apartment locator service:

(a)

CONST

Max_String = 20;

TYPE

A_String = String[Max_String];

Apt = RECORD

Landlord,

Address : A_String;

Bedrooms : Integer;

Price : Real

END; (* Record *)

(b)

VAR

An_Apt : Apt;

(c)

PROCEDURE Read_Record (VAR For_Lease: Apt);

BEGIN (* Read_Record *)

WITH For_Lease DO

BEGIN

Readln(Landlord);

Readln(Address);

Readln(Bedrooms);

Readln(Price)

END

END; (* Read_Record *)