Functions & Strings

CIS 23008-Feb-06

Quiz1. Write a function Prototype for the function

findSmallest that takes three integers and returns an integer.

2. Write a function call for findSmallest storing the value in a variable named smallest. Use the values num1, num2, and num3 as arguments.

3. Write a function header for the function findSmallest that takes three integers, x, y, and z, and returns an integer.

Function: Return Type• Data type hierarchy:• long double• double• float• unsigned long int• long int• unsigned int• int• unsigned short int• short int• unsigned char• short• char

Promotion occurs in this direction

Recursion

• Recursion is the ability of a function to call itself. • Consider the mathematical function n! (factorial)

– n! = n * (n-1) … * 2 * 1– Not mathematically precise because we use an

ellipsis (…). • Consider the following formal definition

– n! = 1, if n = 0– n! = n * (n-1)!, if n > 0

• The factorial function is defined in terms of itself

Recursion

• C++ function mirrors the mathematical factorial definition

– If the value of n is 0, the value 1 is returned.– Otherwise, the product of n and Factorial(n-1)

is returned.

Recursion

Recursionint Factorial(int n) {

if (n == 0) {

return (1);}else {

return (n * Factorial(n-1));}

}

Recursion#include <iostream>using namespace std;int Factorial(int); int main() {

cout << "Enter a positive integer: ";int n;cin >> n;cout << n << "! = " << Factorial(n) << endl;return 0;

}

Recursion vs. Iteration

• Write a factorial function using iteration:int factorial (int n){ int result = 1; for (int i = n; i >= 1; i--) result *= i; result = result * I; return result;}

Parameters by Reference

• When you want more than one item to change.

• Changes (uses) the original variables• No need to return• Use & before the parameter variable

declaration

Parameters by Reference• Switch two values:void swap (float &first, float &second){ float temp; temp = first; first = second; second = temp;}

• In main:if ( a > b ) swap (a, b);

Parameters by Reference• & (Reference character) must go in the prototype and

the definition.void getData(int, int &);

void getData(int a, int & b){

int one, two;a = a + 1;b = 2;cout << "Enter two integers: ";cin >> one >> two;

}

Reference Practice

• Write a function header for a function named time that has an integer parameter named seconds and three integer reference parameters named hours, min, and sec.

Strings

• #include <string>• Character sequence enclosed in double

quotes

Declaring & Initializing Strings• string objectName = value;

– string str1 = “Good Morning”;– string str2 = str1;– string str3 = str1 + str2;

• string objectName(stringValue);– string str4(“Hot”);– string str5(str4 + “ Dog”);

• string objectName(str, n);– string str6(“Good Morning”);– string str7(str6, 5); //str7 = “Morning”;

Declaring & Initializing Strings

• string objectName(str, n, p);– string str8(“Good Morning”);– string str9(str8, 5, 2); //str9 = “Mo”;

• string objectName(n, char);– string str10(5, ‘*’); //str10 = “*****”;

• string objectName;– string message; //message = “”;

String Input

string message;cin >> message;cout << message;

This may have problems….

Extraction Operator >>

• >> skips any leading whitespace characters

• >> stops at (before) the first trailing whitespace character

• trailing whitespace character is left in stream, and will become “next” leading whitespace character.

String Input Using >>

string firstName;string lastName;cin >> firstName >>

lastName;

• Input stream:Joe Hernandez 23

Results:“Joe” “Hernandez”firstName lastName

getline() Function

• >> cannot be used to input a string with blanks in it.

• Use getline(inFileStream, str) • First argument is an input stream variable

(cin), second is the string variable.

string message;getline(cin, message);

getline(inFileStream, str)

• getline does not skip leading whitespace characters

• getline reads all characters (including blanks) into the string.

• getline stops when it reaches ‘\n’• ‘\n’ is not stored in the string variable

String Input: getline

string firstName;string lastName;getline (cin, firstName);getline (cin, lastName);

• Input stream:Joe Hernandez 23

Results:“Joe Hernandez 23” ?firstName lastName

String Operations

Character Manipulation

• #include <cctype>• tolower(value)• toupper(value)• isalpha(value)• isdigit(value)

• String -> Integer:– atoi(string.c_str());

• String -> Float:– atof(string.c_str());

Example code:

Located in:/class-files/samples/

strings/stringpractice.cppstringinput.cppstringoperations.cpp

Located in:/class-files/samples/filesask.cppinfile.cppmixed.cppint.datparts.dat