C++ Tutorial/Data Types/Your string

convert between ordinary strings and class String

<source lang="cpp">#include <iostream>

 using namespace std;  
 #include <string.h>             
 
 class String                    
   {  
    private:  
       enum { SZ = 80 };         
       char str[SZ];             
    public:  
       String() { str[0] = "\0"; }  
       String( char s[] ) { strcpy(str, s); }    
       void display() const { cout << str; }  
       operator char*() { return str; }        
   };  
 int main()  
   {  
    String s1;                   
                                 
    char xstr[] = "this is a test";  
   
    s1 = xstr;                   
                                   
    s1.display();                
   
    String s2 = "this is another test";  
                                 
    cout << static_cast<char*>(s2);
     cout << endl;                   
     return 0;                     
   }</source>

Define and use a string class

<source lang="cpp">/* The following code example is taken from the book

* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/

1. include <string>
2. include <iostream>
3. include <cctype>

/* replace functions of the standard char_traits<char>

* so that strings behave in a case-insensitive way
*/

struct ignorecase_traits : public std::char_traits<char> {

   // return whether c1 and c2 are equal
   static bool eq(const char& c1, const char& c2) {
       return std::toupper(c1)==std::toupper(c2);
   }
   // return whether c1 is less than c2
   static bool lt(const char& c1, const char& c2) {
       return std::toupper(c1)<std::toupper(c2);
   }
   // compare up to n characters of s1 and s2
   static int compare(const char* s1, const char* s2,
                      std::size_t n) {
       for (std::size_t i=0; i<n; ++i) {
           if (!eq(s1[i],s2[i])) {
               return lt(s1[i],s2[i])?-1:1;
           }
       }
       return 0;
   }
   // search c in s
   static const char* find(const char* s, std::size_t n,
                           const char& c) {
       for (std::size_t i=0; i<n; ++i) {
           if (eq(s[i],c)) {
               return &(s[i]);
           }
       }
       return 0;
   }

}; // define a special type for such strings typedef std::basic_string<char,ignorecase_traits> icstring; /* define an output operator

* because the traits type is different than that for std::ostream
*/

inline std::ostream& operator << (std::ostream& strm, const icstring& s) {

   // simply convert the icstring into a normal string
   return strm << std::string(s.data(),s.length());

} int main() {

   using std::cout;
   using std::endl;
   icstring s1("hallo");
   icstring s2("otto");
   icstring s3("hALLo");
   cout << std::boolalpha;
   cout << s1 << " == " << s2 << " : " << (s1==s2) << endl;
   cout << s1 << " == " << s3 << " : " << (s1==s3) << endl;
   icstring::size_type idx = s1.find("All");
   if (idx != icstring::npos) {
       cout << "index of \"All\" in \"" << s1 << "\": "
            << idx << endl;
   }
   else {
       cout << "\"All\" not found in \"" << s1 << endl;
   }

}</source>

hallo == otto : false
hallo == hALLo : true
index of "All" in "hallo": 1

strings defined using array and pointer notation

<source lang="cpp">#include <iostream>

 using namespace std;  
   
 int main(){  
    char str1[] = "Defined as an array";  
    char* str2 = "Defined as a pointer";  
   
    cout << str1 << endl; 
    cout << str2 << endl;  
   
    str2++;   
   
    cout << str2 << endl; 
    return 0;  
 }</source>

Your own string class

<source lang="cpp">#include<iostream.h>

1. include<string.h>
2. include<stdlib.h>

class String {

 char *p;
 int length;

public:

 String();
 String(char *str,int len);
 char *getstring(){return p;}
 int getlength(){return length;}

}; String::String() {

 p=new char[255];
 if(!p)
 {
   cout<<"Allocation erroe\n";
      exit(1);
 }
 *p="\0";
 length=255;

} String::String(char * str,int len) {

 if(strlen(str)>=len)
 {
   cout<<"Allcation too little memory! \n";
      exit(1);
 }
 p=new char[len];
 if(!p)
 {
   cout<<"Allocation error\n";
      exit(1);
 }
 strcpy(p,str);
 length=len;

} main() {

 String ob1;
 String ob2("This is a string.",100);
 cout<<"ob1:"<<ob1.getstring()<<"-Allocation length:";
 cout<<ob1.getlength()<<"\n";
 cout<<"ob2:"<<ob2.getstring()<<"-Allocation length:";
 cout<<ob2.getlength()<<"\n";
 return 0;

}</source>

ob1:-Allocation length:255
ob2:This is a string.-Allocation length:100