4 Procedural Abstraction and Functions That Return a Value

1. 4.1 Top-Down Design 182

2. 4.2 Predefined Functions 183

   1. Using Predefined Functions 183

   2. Random Number Generation 188

   3. Type Casting 190

   4. Older Form of Type Casting 192

   5. Pitfall: Integer Division Drops the Fractional Part 192

3. 4.3 Programmer-Defined Functions 193

   1. Function Definitions 193

   2. Functions That Return a Boolean Value 199

   3. Alternate Form for Function Declarations 199

   4. Pitfall: Arguments in the Wrong Order 200

   5. Function Definition–Syntax Summary 201

   6. More About Placement of Function Definitions 202

   7. Programming Tip: Use Function Calls in Branching Statements 203

4. 4.4 Procedural Abstraction 204

   1. The Black-Box Analogy 204

   2. Programming Tip: Choosing Formal Parameter Names 207

   3. Programming Tip: Nested Loops 208

   4. Case Study: Buying Pizza 211

   5. Programming Tip: Use Pseudocode 217

5. 4.5 Scope and Local Variables 218

   1. The Small Program Analogy 218

   2. Programming Example: Experimental Pea Patch 221

   3. Global Constants and Global Variables 221

   4. Call-by-Value Formal Parameters Are Local Variables 224

   5. Block Scope 226

   6. Namespaces Revisited 227

   7. Programming Example: The Factorial Function 230

6. 4.6 Overloading Function Names 232

   1. Introduction to Overloading 232

   2. Programming Example: Revised Pizza-Buying Program 235

   3. Automatic Type Conversion 238

1. Chapter Summary 240

2. Answers to Self-Test Exercises 240

3. Practice Programs 245

4. Programming Projects 247

There was a most ingenious architect who had contrived a new method for building houses, by beginning at the roof, and working downward to the foundation.

JONATHAN SWIFT, Gulliver’s Travels

Introduction

A program can be thought of as consisting of subparts, such as obtaining the input data, calculating the output data, and displaying the output data. C++, like most programming languages, has facilities to name and code each of these subparts separately. In C++ these subparts are called functions. In this chapter we present the basic syntax for one of the two main kinds of C++ functions—namely those designed to compute a single value. We also discuss how these functions can aid in program design. We begin with a discussion of a fundamental design principle.

Prerequisites

You should read Chapter 2 and at least look through Chapter 1 before reading this chapter.