Function Basics

# Function Basics - CHAPTER 3 FUNCTION BASICS In this chapter...

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CHAPTER 3 FUNCTION BASICS

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In this chapter, you will: Learn about standard (predefined) functions Learn about user-defined functions Construct value-returning functions, including actual and formal parameters
Functions are like building blocks . They allow complicated programs to be divided into manageable pieces. They are often referred to as modules. They are like miniature programs. They can be put together to form a larger program.

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Advantages of functions: Its lets you focus on a part of the program and thereby you can construct it, debug it, and perfect it independently. Different people can work on different functions simultaneously. If a function is needed in more than one place in a program, or in different programs, you can write it once and use it many times.
Pre-defined Functions Some of the pre-defined mathematical functions are abs(x) , sqrt(x) , and pow(x,y) . The power function, pow(x,y) , calculates x y ; that is, the value of pow(x,y) = x y . pow(2,3) = 8.0 and pow(2.5,3) = 15.625 . The function pow is of the type double or that the function pow returns a value of the type double . x and y are called the parameters (or arguments) of the function pow .

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The s quare root function, sqrt(x) , calculates the non- negative square root of x for x >= 0.0 . sqrt(2.25) is 1.5 . The function sqrt is of the type double and has only one parameter. I/O functions are contained in the header file iostream . Math functions are contained in the header file cmath .

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Example: // How to use predefined functions. #include <iostream> #include <cmath> #include <cctype> #include <cstdlib> using namespace std; int main() { int x; double u,v; cout<<"Line 1: Uppercase a is " << static_cast < char >(toupper('a')) <<endl; //Line 1 u = 4.2; //Line 2 v = 3.0; //Line 3 cout<<"Line 4: "<<u<<" to the power of " <<v<<" = "<<pow(u,v)<<endl; //Line 4 cout<<"Line 5: 5 to the power of 4 = " <<pow(5,4)<<endl; //Line 5
u = u + pow(3,3); //Line 6 cout<<"Line 7: u = "<<u<<endl; //Line 7 x = -15; //Line 8 cout<<"Line 9: Absolute value of "<<x <<" = "<<abs(x)<<endl; //Line 9 return 0; } Output: Line 1: Uppercase a is A Line 4: 4.2 to the power of 3 = 74.088 Line 5: 5 to the power of 4 = 625 Line 7: u = 31.2 Line 9: Absolute value of -15 = 15

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USER-DEFINED FUNCTIONS User-defined functions in C++ Value-returning functions - functions that have a data type. Void functions - functions that do not have a data type.
VALUE-RETURNING FUNCTIONS Some predefined C++ functions are: pow , islower, toupper . To use these functions in our programs we must know: • Name of the header file containing this function. • The name of the function

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## This note was uploaded on 04/14/2008 for the course CS 115 taught by Professor Ryon during the Fall '06 term at NJIT.

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Function Basics - CHAPTER 3 FUNCTION BASICS In this chapter...

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