Strings

1. Strings Sujana Jyothi C++ Workshop Day 4

2. A String also called character string is a sequence of contiguous characters in memory terminated by the NUL character ‘\0’. The C++ header file <string> is included to deal with string manipulations Initialisation: char Exforsys[30]= {‘T’,’r’,’a’,’i’,’n’,’i’,’n’,’g’,’\0’}; char Exforsys[30]= “Training”; char Exforsys[ ]=”Company”; Example: #include <iostream>#include <string>void main( ){char examp1[] = “Exforsys”;char examp2[80];for(int i=0; i<strlen(exampl1);i++)examp2[i]=examp1[i];examp2[i]=’\0’;cout<< “The copied string is: “<< examp2;}

3. Dynamic Array of Characters Example: #include <iostream> using namespace std; int main() { char *Country = new char[20]; Country = "Equatorial Guinea"; cout << "Country Name: " << Country; cout << "\n\n"; return 0; } Passing an array of characters #include <iostream> using namespace std; void ShowCountry(const char S[]) { cout << "Country Name: " << S <<"\n\n"; } int main() { char Country[] = “Republic of Ireland"; ShowCountry(Country); return 0; }

4. Two- dimensional arrays #include <iostream> using namespace std; void ShowCountries(char S[][15]) { cout << "Countries Names"; for(int i = 0; i < 3; ++i) cout << "\nCountry " << i + 1 << ": " << S[i]; } int main() { char Country[][15] = { "Afrique du Sud", "Australia", "Zimbabwe", "Sri Lanka", "Yemen", "El Salvador" }; ShowCountries(Country); cout << "\n\n"; return 0; } String manipulations Strlen(), Strcat(), Strcpy(), Strcmp() Try out programs involving these string manipulation functions

5. cin Member Functions Read input character-by-character Char ch; ch=cin.get(); Char ch; cin.get(ch); Char name[40]; Cin.get(name,40); Cin.getline(Arrayname, Dimension, Delimiter): #include <iostream> using namespace std; int main () { char name[256], title[256]; cout << "Enter your name: "; cin.getline (name,256); cout << "Enter your favourite movie: "; cin.getline (title,256); cout << name << "'s favourite movie is " << title; return 0; }

6. String class #include <iostream> #include <string> using namespace std; main() { string str1, str2; const char *s2; char *s3; str1 = "Hello World"; cout << str1.length() << " " << str1 << "\n"; str2 = str1; cout << str2 << "\n"; str1[0] = 'J'; cout << str1 << "\n" << str2 << "\n"; s3 = "Daffy Duck"; str2 = s3; str2[0] = 'T'; cout << s3 << " " << str2 << "\n"; str2 += " "; str2 += str1; cout << str2 << "\n"; } Declaring a string: using namespace std; string my_string; Specifying an initial value for the string in a constructor: using namespace std; string my_string("starting value");

7. Structures Sujana Jyothi C++ workshop Day 4

8. From Structures to Objects • Classes in C++ are a natural evolution of the C notion of struct • A typical structure example: • struct Time { • int hour; // 0-23 • int minute; // 0-59 • int second; // 0-59 • }; • By exposing weaknesses of this struct example (which are typical of all structures) we will motivate the evolution towards classes

9. Using Structures … a word of warning The arrow operator requires some care: timePtr->hour is equivalent to (*timePtr).hour Parentheses are needed because the dot operator (.) has a higher precedence than the pointer dereferencing operator (*) Writing *timePtr.hour is a syntax error because the precedence rules define it as *(timePtr.hour) … since with a pointer you must use the arrow operator to refer to a member! NOTE: pointers are difficult for beginners and experts! (esp. C++) NOTE: (the concept of) pointers (is)are fundamental to (most) programming

10. Declaring structure variables Structure_name Structure_variable Eg: Customer cust1; Example: #include <iostream>using namespace std;struct MyStructure{int n;float f;float f2;};int main(){  MyStructure myMyStructure; MyStructure *ptrMyStructure; //set the f of the structure myMyStructure.f = 1000; //intialize the pointer ptrMyStructure = &myMyStructure; //change the pointers f ptrMyStructure->f = 2000; //print out the structures f cout << myMyStructure.f << endl;return 0;} Use -> for structure pointer #include <iostream>using namespace std;struct account{int accountnum;float balance;float interestrate;};int main(){  account myaccount; account *ptraccount; ptraccount->balance = 1000;return 0;} Pointer to a structure

11. Using Structures … with a function • With the Time structure a typical function would be to print out the time on the screen: • void print (Time t) \\ Just hours and minutes • { cout << (t.hour < 10 ? “0”: “”) << t.hour <<“:” • << t.minute <10 ? “0”: “”) << t.minute; • } • Notes: • structures are normally call-by-value • could pass a constant reference (or pointer) • the test? True-do-this: False-do-this construct

12. Recursion // Recursion - factorial & fibonacci #include<iostream> int factorial (int x){ if (x<1) return 1; else return x*(factorial (x-1));} int fibonacci (int x){ if (x==1) return 1; if (x==2) return 1; else return (fibonacci(x-2) + fibonacci(x-1));} int main() { cout << "factorial 5 =" <<factorial(5)<<endl; cout << "fibonacci 5 =" <<fibonacci(5); }