Tuesday 2/5 Week 4

Chapter 4

Student Notes

Objectives

Collect Project 2

Subtypes

Program development

Return last reading quizzes

1. Subtypes

· Subtypes allow us to define a

·

· Here are two we have seen all ready:

SUBTYPE Natural IS Integer RANGE 0..Integer’Last;

SUBTYPE Positive IS Integer Range 1..Integer’Last;

· Integer’Last is the largest integer value. More info on ‘Last in enumeration types

· The largest integer on our system is 2147483647 which is 2³⁶-1

· The smallest integer is -2147483648 which is -2³⁶

·

·

· SUBTYPE NonNegFloat IS Float RANGE 0..Float’Last;

2. Working with subtypes

SUBTYPE SmallInt IS Integer RANGE -50..50;

SUBTYPE CapitalLetter IS Character RANGE ‘A’..’Z’;

X, Y, Z : SmallInt;

NextChar : CapitalLetter;

Hours_Worked : NonNegFloat;

The following statements will raise a

at run time, but will compile correctly. Why?

X := 26;

Y := 25;

Z := X + Y;

NextChar : = ‘a’;

6. Compatibility between subtypes

· Types are considered compatible if

·

· (ex. Integer and SmallInt)

· or

· ( ex. Positive and SmallInt)

· X : Integer;

Y : SmallInt;

X := Y; <=

Y := X; <=

7. A Handy program development Technique

· (Program 4.1)

· Put your algorithm right into the code file as comments. This will help keep you on track as you code. It also largely completes any commenting necessary.

· Use the NULL; statement to make a valid program