pow function - float and int

pow returns double. So if you try to store its return value in int , you may get some problem.
 eg. consider the following
int a,b,c;
float d;

now if you try :
a = pow(10,2);
then a = 99
but if you try
d= pow (10,2); or try out cout<<pow(10,2)
you will get 100.

Blogged with the Flock Browser

String Class in cpp(Standard cpp strings)

Here is how to test the string class already present in cpp.
To use simple strings u have to include <iostream>. For example consider the program,
#include <iostream>
#include <conio.h>
using namespace std;

int main()
{
    string word="hello";
    cout<<word;
    getch();
   
}

There are various functions and operators in this string class. These operators are present in string -
=        assignment
+ , +=  concatenation etc
 == , != . < , <= , >= , >   equality etc.
[]       subscription
<<     output
>>     input

Following are the functions which are present in the string class

Consider the program:
#include <iostream>
#include <conio.h>
using namespace std;
int main( )
{
    string s1 ( "kicit" ) ;
    string s2 ( "Nagpur" ) ;

    cout << endl ;
    cout << "String s1: " ;
    cout<<s1;
    cout << "\nLength of string s1: " << s1.length( ) << endl ;

    cout << "\nString s2: " ;
    cout<<s2;

    string s3 = s1;// copy
    cout<<"\ns3="<<s3;

    s3=s3+s1;
    cout << "\nString s3 after concatenation: " ;
    cout<<s3;

    if ( s1.compare(s2)== 0 )
        cout << "\nThe strings s1 and s2 are similar" << endl ;
    else
        cout << "\nThe strings s1 and s2 are not similar" << endl ;
        getch();
}



Some more cases of string:
string s1;                                    //s1 contains 0 character
string s2 =  "New York";             //s1 contains 8 character
string s3(60,'*');                          //s1 contains 60 asterisk
string s4=s3;                             //s1 contains 60 asterisk
string s5(s2, 4,2);                      //s1 contains 2 characters , i.e. "Yo"
Some more:
string s= "ABCDEFG";
getline(s,cin);           // reads the entire string with spaces into s
char c = s[2];           // c = C;
s[4]='*';                   //s= "ABCD*FG";

const char * cs = s.c_str();   // CONVERT s TO C STRING

Using find, substr(), erase() and replace
s6=s+"HIJK";
s4= s6.substr();
s6.erase(4, 2);
s6.replace(5,2,  "xyz")
s6 = "Missisippi River";

hello i am not hter

constructors 1.

#include 
#include 
using namespace std;

int main () 
{
    char *line = "short line for testing";
    
    // with no arguments
    string s1;
    s1 = "Anatoliy";
    cout << "s1  is: " << s1 << endl;

    // copy constructor
    string s2 (s1);
    cout << "s2  is: " << s2 << endl;

    // one argumen
    string s3 (line);
    cout << "s3  is: " << s3 << endl;

    // first argumen C string
    // second number of characters
    string s4 (line,10);
    cout << "s4  is: " << s4 << endl;

    // 1 - C++ string
    // 2 - start position
    // 3 - number of characters
    string s5 (s3,6,4); // copy word 'line' from s3
    cout << "s5  is: " << s5 << endl;

    // 1 - number characters
    // 2 - character itself
    string s6 (15,'*');
    cout << "s6  is: " << s6 << endl;

    // 1 - start iterator
    // 2 - end iterator
    string s7 (s3.begin(),s3.end()-5);
    cout << "s7  is: " << s7 << endl;

    // you can instantiate string with assignment
    string s8 = "Anatoliy";
    cout << "s8  is: " << s8 << endl;

    return 0;
}
OUTPUT:
// s1  is: Anatoliy
// s2  is: Anatoliy
// s3  is: short line for testing
// s4  is: short line
// s5  is: line
// s6  is: ***************
// s7  is: short line for te
// s8  is: Anatoliy


getline 1.


/* 1  getline ( intut_stream, str, delim );
  Extracts characters from intut_stream and stores them
  in str until s.max_size() characters have been extracted,
  the end of file occurs, or delim is encountered, in which
  case delim is extracted from istr but is not stored in s
  2 getline( Iter, str )
  Inputs a string value for str as in the preceding func�
  tion with delim =
*/
#include 
#include 
#include 
#include 
using namespace std;

int main () 
{
    string str;
    cout << "Enter string (EOL = $) : ";
    getline (cin, str, '$');
    cout << "Str is : " << str << endl;

    ifstream In("data.dat");
    vector v;

    cout << endl << "Read data from file" << endl;
    while ( ! In.eof() )
    {
     getline (In, str);
     v.push_back(str);
    }

    copy (v.begin(),v.end(),
      ostream_iterator(cout,"\n"));
    cout << endl;
     

    return 0;
}
OUTPUT:
// Enter string (EOL = $) : Str is : first line
// second line$
// 
// Read data from file
// file: "data.dat"
// second line
// last line


 << >> operators 1.

#include 
#include 
using namespace std;

int main () 
{
    string str;

    cout << "Enter string for testing : ";
    cin  >> str;
    cout << "\nString is : " << str << endl;

    cout << "Enter string for testing "
      << "(d to quit) : ";
    while ( cin >> str )
    {
     cout << endl;
     cout << "String is : " << str << endl;
     cout << "Enter string for testing "
             << "(d to quit) : ";
    }

    return 0;
}
OUTPUT:
// Enter string for testing : first
// String is : first
// Enter string for testing (d to quit) : second
// String is : second
// Enter string for testing (d to quit) : third
// String is : third
// Enter string for testing (d to quit) : 


 + += = operators 1.

#include 
#include 
using namespace std;

int main () 
{
    string str = "Hello";
    cout << "str is : " << str << endl;
    str += ",";
    str += ' ';
    cout << "str is : " << str << endl;

    string s;
    s = str + "World";
    cout << "s is : " << s << endl;

    char ch = '!';
    s += ch;
    cout << "s is : " << s << endl;

    return 0;
}
OUTPUT:
// str is : Hello
// str is : Hello, 
// s is : Hello, World
// s is : Hello, World!


append 1.

#include 
#include 
using namespace std;

int main () 
{
    string str = "Nobody is perfect";
    string s   = ""; // empty string
    char *ch   = "abcdef";

    // append string str at the end of s; 
    // return s
    
    // appends at the end of s a copy of the n characters
    // in str, starting at position pos; if n is too
    // large, characters are copied only until the end  
    // of str is reached;
    // returns s
    s.append(str,0,6);
    cout << "s is : " << s << endl;

    // appends copies of the characters in the range [inpIt1,
    // inpIt2] to s; returns s
    string::iterator inpIt1 = str.begin()+6;
                    //start from ' is'
    string::iterator inpIt2 = str.end();

    s.append(inpIt1,inpIt2);
    cout << "s is : " << s << endl;

    // appends three !
    s.append(3,'!');
    cout << "s is : " << s << endl;
    
    // appends the first n characters in ch at the end
    // of s; returns s
    s.append(ch,3);
    cout << "s is : " << s << endl;
    
    // appends charArray at the end of s; returns s
    s.append(ch,3);
    cout << "s is : " << s << endl;

    return 0;
}
OUTPUT:
// s is : Nobody
// s is : Nobody is perfect
// s is : Nobody is perfect!!!
// s is : Nobody is perfect!!!abc
// s is : Nobody is perfect!!!abcabc


assign 1.

#include 
#include 
using namespace std;

int main () 
{
    string str = "Nobody is perfect";
    string s   = "";
    char *ch   = "Robert Frost";

    // assigns a copy of str to s; returns s
    s.assign(str);
    cout << "s is : " << s << endl;

    
    // assigns to s a copy of the n characters in str, start�
    // ing at position 10: if n is too large, characters are
    // copied only until the end of str is reached: returns s
    s.assign(str,10,7); // perfect
    cout << "s is : " << s << endl;

    // assigns to s a string consisting of the first n charac�
    // ters in ch: returns s
    s.assign(ch,6);
    cout << "s is : " << s << endl;

    // assigns to s a copy of ch: returns s
    s.assign(ch);
    cout << "s is : " << s << endl;

    // assigns  to s a string consisting of the characters in
    // the range str.begin(), str.end(); returns s
    s.assign(str.begin(),str.end());
    cout << "s is : " << s << endl;

    // assigns to s a string consisting of n copies of ch;
    // returns s
    s.assign(17,'*');
    cout << "s is : " << s << endl;

    return 0;
}
OUTPUT:
// s is : Nobody is perfect
// s is : perfect
// s is : Robert
// s is : Robert Frost
// s is : Nobody is perfect
// s is : *****************


at 1.

// returns s[pos]
#include 
#include 
using namespace std;

int main () 
{
    string s = "Nobody is perfect";

    // Returns s[pos]
    for ( int pos = 0; pos < s.length(); ++pos )
     cout << s.at(pos) << " ";
    cout << endl;

    return 0;
}
OUTPUT:
// N o b o d y   i s   p e r f e c t 


begin 1.

// Returns an iterator positioned at the
// first character in a string
#include 
#include 
using namespace std;

int main () 
{
    string str = "C++ is best computer language";

    string::iterator It = str.begin();

    while ( It != str.end() )
    {
     if ( *It == ' ' )
      *It = '\n';
     cout << *It++;
    }
    cout << endl;
    
    return 0;
}
OUTPUT:
// C++
// is
// best
// computer
// language


c_str 1.

// returns (the base address of) a char 
// array containing the characters stored in s, 
// terminated by a null character.
#include 
#include 
using namespace std;

int main () 
{
    string str = "Anatoliy";
    char *ary = new char[str.length()+1];

    // strcpy ( ary, str ); that is wrong way
    strcpy ( ary, str.c_str() ); // that is correct

    cout << ary << endl;
    
    return 0;
}
OUTPUT:
// Anatoliy


capacity 1.

// returns the size (of type size_type)
// of the storage allocated in string
#include 
#include 
using namespace std;

int main () 
{
    string str = "C++ is best computer language";

    string::size_type cap;
    cap = str.capacity();

    cout << "Capacity of str is: " << cap << endl;
    cout << "Size of str is    : " << str.size() 
         << endl;
    cout << "Length of str is  : " << str.length() 
         << endl;

    cout << "Resize the str for 50 character" << endl;
    str.resize(50);
    cap = str.capacity();
    
    cout << "Capacity of str is: " << cap << endl;
    cout << "Size of str is    : " << str.size() 
         << endl;
    cout << "Length of str is  : " << str.length() 
         << endl;

    return 0;
}
OUTPUT:
// Capacity of str is: 32
// Size of str is    : 29
// Length of str is  : 29
// Resize the str for 50 character
// Capacity of str is: 64
// Size of str is    : 50
// Length of str is  : 50


compare 1.

#include 
#include 
using namespace std;

int main () 
{
    string str1 = "string";
    string str2 = "String";
    string str3 = "second string";
    char ch[]   = "first string";

    cout << "string str1 is : " << str1 << endl;
    cout << "string str2 is : " << str2 << endl;
    cout << "char ary ch is : " << ch   << endl;
    cout << "string str3 is : " << str3 << endl;
    cout << endl;

    // compare str1 and str2
    cout << "1." << endl;
    size_t comp = str1.compare(str2);
    cout << "String str1 is ";
    ( comp == 0 ) ? cout << "equal" : cout 
         << "not equal";
    cout << " to string str2" << endl;

    // compare str1 and literal string "string"
    cout << "2." << endl;
    comp = str1.compare("string");
    cout << "String str1 is ";
    ( comp == 0 ) ? cout << "equal" : cout 
        << "not equal";
    cout << " to array of char \"string\"" << endl;

    // 3. and 4. doesn't work with Microsoft 
    // Visual Studio compiler
 
    // compare str3 start from pos 7 to 5
    // with str1
    cout << "3." << endl;
    comp = str3.compare(str1,7,5);
    cout << "Part of string str3 is ";
    ( comp == 0 ) ? cout << "equal" : cout 
        << "not equal";
    cout << " to str1" << endl;

    // compare str3 start from pos 7
    // with literal string "string"
    cout << "4." << endl;
    comp = str3.compare("string",7);
    cout << "Part of string str3 is ";
    ( comp == 0 ) ? cout << "equal" : cout 
        << "not equal";
    cout << " to C string \"string\"" << endl;

    // next 4 'compare' functions
    // doesn't work with GNU compiler
 
    cout << "5." << endl;
    comp = str1.compare(6,10,ch);
    cout << "String str1 is ";
    ( comp == 0 ) ? cout << "equal" : cout 
    << "not equal";
    cout << " to part of char ary \"first string\"" 
    << endl;

    cout << "6." << endl;
    comp = str1.compare(0,3,str3);
    cout << "Part of str1 is ";
    ( comp == 0 ) ? cout << "equal" : cout 
    << "not equal";
    cout << " to string \"second string\"" 
    << endl;

    cout << "7." << endl;
    comp = str1.compare(1,3,str2,1,3);
    cout << "String str1 is ";
    ( comp == 0 ) ? cout << "equal" : cout 
    << "not equal";
    cout << " to part of string \"second string\"" 
    << endl;

    cout << "8." << endl;
    comp = str1.compare(1,3,str2,1,3);
    cout << "String str1 is ";
    ( comp == 0 ) ? cout << "equal" : cout 
    << "not equal";
    cout << " to part of string \"second string\"" 
    << endl;

    return 0;
}
OUTPUT: GNU compiler
// string str1 is : string
// string str2 is : String
// char ary ch is : first string
// string str3 is : second string
// 
// 1.
// String str1 is not equal to string str2
// 2.
// String str1 is equal to array of char "string"
// 3.
// Part of string str3 is equal to str1
// 4.
// Part of string str3 is equal to C string "string"
// 5.
// 6.
// 7.
// 8.

OUTPUT: Microsoft Visual Studio compiler
// string str1 is : string
// string str2 is : String
// char ary ch is : first string
// string str3 is : second string
//
// 1.
// String str1 is not equal to string str2
// 2.
// String str1 is equal to array of char "string"
// 3.
// 4.
// 5.
// String str1 is not equal to part of char ary "first
// string"
// 6.
// Part of str1 is not equal to string "second string"
// 7.
// String str1 is equal to part of string "second string"
// 8.
// String str1 is equal to part of string "second string"
// Press any key to continue


copy 1.

#include 
#include 
using namespace std;

int main () 
{
    string str = "First Name: Robert";
    char fname[255];
    cout << "str is: " << str << endl;

    int n = str.find(':');

    str.copy(fname, // copy to array
            n+1,    // how many char
            0);     // start position from str
    
    // must terminate fname with '\0';
    fname[n+1] = 0;
    
    cout << "fname is: " << fname << endl;

    return 0;
}
OUTPUT:
// str is: First Name: Robert
// fname is: First Name:


empty 1.

#include 
#include 
using namespace std;

int main () 
{
    string str = "*******";

    while ( ! str.empty() )
    {
     cout << str << endl;
     str.erase(str.end()-1);
    }
    cout << endl;

    return 0;
}
OUTPUT:
// *******
// ******
// *****
// ****
// ***
// **
// *


end 1.

// returns an iterator porsitioned immediately
// after the last character in string
#include 
#include 
using namespace std;

int main () 
{
    string s;
    string str = "*************************";
    size_t pos = str.length();

    while ( pos )
    {
     s.assign ( str.begin(),str.end() - pos+1);
     cout << s << endl;
     pos -= 5;
    }

    return 0;
}
OUTPUT:
// *
// ******
// ***********
// ****************
// *********************


erase 1.

#include 
#include 
#include 
using namespace std;

int main () 
{
    string str, s;

    for ( char ch = 'a'; ch <= 'z'; ch++ )
        str.append(1,ch);
    s = str;
    cout << "str is: " << str << endl;
    cout << "s   is: " << str << endl;
    
    // removes 13 characters from the beginning
    str.erase(0,13);
    cout << "Erased range fron str : " << str << endl; 
    // removes 13 characters starts from 14
    str = s.erase(13,13);
    cout << "Erased range from s   : " << str << endl;

    // removes one character pointed by s.begin()
    cout << endl << "Erase one, second character from s"
         << endl;
    s.erase(s.begin()+1);
    cout << "s     is: " << s << endl;
    
    // removes range of characters
    s.erase(s.begin(),s.begin()+4);
    cout << "s     is: " << s << endl;

    return 0;
}
OUTPUT:
// str is: abcdefghijklmnopqrstuvwxyz
// s   is: abcdefghijklmnopqrstuvwxyz
// Erased range fron str : nopqrstuvwxyz
// Erased range from s   : abcdefghijklm
// 
// Erase one, second character from s
// s     is: acdefghijklm
// s     is: fghijklm


find 1.

#include 
#include 
#include 
using namespace std;

int main () 
{
    string  str("C++ is best language");
    int pos1, pos2; // size_t or size_type 
                    // work not correct
    // search for first string "best" inside of str
    // default position is 0
    pos1 = str.find ("best");
    cout << "Word best is found on position " << pos1+1 
         << endl;
    
    // if pattern is not found - return -1
    pos2 = str.find ("best",pos1+1);
    cout << "Word best is found on position " << pos2+1 
         << endl;

    // search for first occurrence of character
    pos1 = str.find('g');
    cout << "First character 'g' found on position " 
         << pos1
      << endl;

    // search for first occurrence of string
    string s = "is";
    pos1 = str.find (s);
    cout << "Word 'is' is found on position " << pos1+1 
         << endl;
    
    return 0;
}
OUTPUT:
// Word best is found on position 8
// Word best is found on position 0
// First character 'g' found on position 15
// Word 'is' is found on position 5


find_first_not_of 1.

#include 
#include 
using namespace std;

int main () 
{
    string  str("C++ is best language");
    cout << "str is: " << str << endl;

    int n = str.find_first_not_of("aeiouAEIOU");

    cout << "First consonant found at " << n+1
      << " position" << endl;
    
    return 0;
}
OUTPUT:
// str is: C++ is best language
// First consonant found at 1 position


find_first_not_of 2.

#include 
#include 
using namespace std;

int main () 
{
    string  str("C++ is best language");
    cout << "str is: " << str << endl;

    // search first not ' ',
    // start from position 7
    int n = str.find_first_not_of(' ',7);
    cout << "first not of space character "
      << "found at position " << n+1 << endl;
    
    return 0;
}
OUTPUT:
// str is: C++ is best language
// first not of space character found at position 8


find_first_not_of 3.

#include 
#include 
using namespace std;

int main () 
{
    string  str("C++ is best language");
    string  s = "C++";
    
    cout << "str is: " << str << endl;
    
    // search character from pattern 
    // using the first x ch�racters in pattern.
    // the value position must be given
    int n = str.find_first_not_of("CBCD",0,3);
    cout << "first not 'C' is found at position "
      << n+1 << endl;
    
    // search first not of 
    // pattern is string
    n = str.find_first_not_of(s);
    cout << "first not of C++ is found "
      << "at position " << n+1 << endl;
    
    return 0;
}
OUTPUT:
// str is: C++ is best language
// first not 'C' is found at position 2
// first not of C++ is found at position 4


find_first_of 1.

#include 
#include 
using namespace std;

int main () 
{
    string  str("C++ is best language");
    string  s = "be";
    
    cout << "str is: " << str << endl;

    // search be start from position 2
    // if position is ommited - default is 0
    int n = str.find_first_of(s,2);
    cout << "first 'be' found at position "
      << n+1 << endl;

    // same as above but search for character
    n = str.find_first_of('l');
    cout << "first character 'l' found at "
      << "position " << n+1 << endl;

    // search 'first of' for the characters in
    // charary
    char charary[] = " bea";
    cout << "charary[] = \" bea\"" << endl;
    n = str.find_first_of(charary,0);
    cout << "first character from charary "
      << "found at position " << n+1 << endl;
    cout << "Note: position 4 is space" << endl;

    // same as above but third argumen is
    // number of character from which searching
    // starts
    // this variant of find_first_of dosn't
    // work properly with GNU compiler
    n = str.find_first_of(" bae",0,3);
    cout << "first character from charary "
      << "found at position " << n+1 << endl;

    return 0;
}
OUTPUT:
// str is: C++ is best language
// first 'be' found at position 8
// first character 'l' found at position 13
// charary[] = " bea"
// first character from charary found at position 4
// Note: position 4 is space
// first character from charary found at position 4


find_last_not_of 1.

#include 
#include 
using namespace std;

int main () 
{
    string  str("C++ is best language");
    string  s  = "langue";
    int pos = str.length()-1;
    cout << "str is: " << str << endl;
    
    // returns the highest position <= pos of a character
    // in str that does not match any charcter in s; 
    // returns nopos if there  is  no such position:
    // npos is the default value for pos
    int n =  str.find_last_not_of(s, pos);
    cout << "last_not_of 'langue' found at position "
      << n+1 << endl;

    // same as above but search for single character
    n = str.find_last_not_of('e');
    cout << "last_not_of 'e' found at position "
      << n+1 << endl;

    char ary[] = "be";
    // seawrch for occurence last_not_of
    // from pattern ary in str
    n = str.find_last_not_of(ary);
    cout << "last_not_of 'be' found at position "
      << n+1 << endl;
    
    return 0;
}
OUTPUT:
// str is: C++ is best language
// last_not_of 'langue' found at position 12
// last_not_of 'e' found at position 19
// last_not_of 'be' found at position 19


find_last_of 1.

#include 
#include 
using namespace std;

int main () 
{
    string  str("C++ is best language");
    string  s  = "g";
    cout << "str is: " << str << endl;
    cout << "s   is: " << s   << endl;

  int n = str.find_last_of(s);
  cout << "last_of '" << s << "' faund"
    << " at position " << n+1 << endl;

    n = str.find_last_of(' ');
    cout << "last_of ' ' faund"
      << " at position " << n+1 << endl;

    n = str.find_last_of(" la");
    cout << "last_of \" la\" faund"
      << " at position " << n+1 << endl;
    
    return 0;
}
OUTPUT:
// str is: C++ is best language
// s   is: g
// last_of 'g' faund at position 19
// last_of ' ' faund at position 12
// last_of " la" faund at position 18


insert 1.

#include 
#include 
using namespace std;

int main () 
{
    string str = "C++ language";
    string s   = "is best";
    char ch[]  = "C++ language";
    
    cout << "str is: " << str << endl;
    cout << "s   is: " << s   << endl;
    cout << "ch  is: " << s   << endl;
    
    // insert a copy of s into str
    // at position pos;
    string::size_type pos = 4;
    str.insert(pos,s);
    cout << "str is: " << str << endl;
    
    // insert a copy of ch into str at
    // the position specified by iterator
    // return an iterator positioned at
    // this copy
    int n = str.find('l');
    str.insert(str.begin() + n,' ');
    cout << "str is: " << str << endl;
    
    // like above but n x copies of char
    str.insert(str.end(),3,'!');
    cout << "str is: " << str << endl;
    
    // insert 4 char from ch into s
    // at the position 0
    s.insert(0,ch,4);
    cout << "s   is: " << s   << endl;
    
    // insert 8 characters from str
    // start from position n ('langu...')
    // into s at position x (end string)
    n = str.find('l');
    int x = s.length();
    s.insert(x,str,n,8);
    cout << "s   is: " << s   << endl;
    
    n = s.find('l');
    s.insert(s.begin()+n,' ');
    cout << "s   is: " << s   << endl;
    
    // insert range (begin - begin+7) of str 
    // into s at position begin+4
    s.insert(s.begin()+4,str.begin(),str.begin()+7);
    cout << "s   is: " << s   << endl;
    return 0;
}
OUTPUT:
// str is: C++ language
// s   is: is best
// ch  is: is best
// str is: C++ is bestlanguage
// str is: C++ is best language
// str is: C++ is best language!!!
// s   is: C++ is best
// s   is: C++ is bestlanguage
// s   is: C++ is best language
// s   is: C++ C++ is is best language


length 1.

#include 
#include 
using namespace std;

int main () 
{
    string str = "C++ is best computer language";
    cout << "str is: " << str << endl;
    
    cout << "Length of str is : "
         << str.length() << endl;
    
    return 0;
}
OUTPUT:
// str is: C++ is best computer language
// Length of str is : 29


max_size 1.

// returns a reverse iterator positioned
// at the last character in string
#include 
#include 
using namespace std;

int main () 
{
    string str = "C++ is best computer language";
    cout << "str is: " << str << endl;

    cout << "max_size of str is: "
         << str.max_size() << endl;

    return 0;
}
OUTPUT:
// str is: C++ is best computer language
// max_size of str is: 4294967294


rbegin 1.

#include 
#include 
using namespace std;

int main () 
{
    string str = "C++ is best computer language";
    cout << "str is: " << str << endl;

    // usual iterator doesn't work
    string::reverse_iterator It = str.rbegin();
    while ( It != str.rend() )
        cout << *It++;
    cout << endl;

    return 0;
}
OUTPUT:
// str is: C++ is best computer language
// egaugnal retupmoc tseb si ++C


replace 1.

#include 
#include 
using namespace std;

int main () 
{
    string str = "STL is created from Dennis Ritchie";
    string s1  = "was";
    string s2  = "developed";
    string s3  = "Stepanov alexander";
    cout << "str is: " << str << endl;

    cout << "replace 'is' for 'was'" << endl;
    str.replace(4, // start position in str
            2,     // how many characters
            s1);   // source for replasment
    
    cout << "str is: " << str << endl;
    
    cout <<"replace 'created' for 'developed'" << endl;
    int n = str.find('c'); // pos of 'created'
    int x = str.find("from") -1;

    str.replace(str.begin()+n,// start pointer
            str.begin()+x,    // end pointer
            s2);              // source
    
    cout << "str is: " << str << endl;

    cout << "replace 'Dennis' for 'alexander'" << endl;
    int x1 = str.find('D'); // search Dennis
    int x2 = str.find(' ',x1+1); // space after
    int y1 = s3.find("alex"); // search 'alex'
    int y2 = strlen("alexander");

    str.replace(x1, // start position in str
            x2-x1,  // how characters to replace
            s3,     // source for replacement
            y1,     // start positio from source
            y2);    // how chracter start from y1
    
    cout << "str is: " << str << endl;

    cout << "replace 'from' for 'by'" << endl;
    char ary[] = "bytes";
    n = str.find("from");

    // same variant possible with iterators
    // instead of number of position
    str.replace(n, // start position in str
            4,     // how many characters
            ary,   // source
            2);    // first 2 characters from source
    
    cout << "str is: " << str << endl;

    cout << "replace 'a' for 'A' (alexander)" << endl;
    n = str.find("alexander");

    str.replace(n,  // start position in str
            1,      // how character(s)
            1,      // how many copies of character
            'A');   // character for replasment
    cout << "str is: " << str << endl;

    cout << "replace 'Ritchie' for 'Stepanov'" << endl;
    x1 = str.find('R');
    y1 = s3.find(' ');

    str.replace(str.begin()+x1, // start pointer
            str.end(), // to the end of str
            s3.begin(), // start pointer from source
            s3.begin()+y1 // end pointer from
            );              // source
    cout << "str is: " << str << endl;

    return 0;
}
OUTPUT:
// str is: STL is created from Dennis Ritchie
// replace 'is' for 'was'
// str is: STL was created from Dennis Ritchie
// replace 'created' for 'developed'
// str is: STL was developed from Dennis Ritchie
// replace 'Dennis' for 'alexander'
// str is: STL was developed from alexander Ritchie
// replace 'from' for 'by'
// str is: STL was developed by alexander Ritchie
// replace 'a' for 'A' (alexander)
// str is: STL was developed by Alexander Ritchie
// replace 'Ritchie' for 'Stepanov'
// str is: STL was developed by Alexander Stepanov


reverse 1.

#include 
#include 
using namespace std;

int main () 
{
    string str = "Anatoliy Urbanskiy";
    cout << str.reverse() << endl;

    return 0;
}
OUTPUT:


resize 1.

// if  <=s.size(),  truncates rightmost 
// character in s to make it of size n; otherwise, adds
// copies of character ch to end of s to increase it size
// to n, or adds a default character value (usually a
// blank) if ch is omitted; return type is void
#include 
#include 
using namespace std;

int main () 
{
    string str = "Alexander Stepanov";
    cout << "str is: " << str << endl;
    cout << "size of str is: "
         << str.size() << endl;

    str.resize(11);

    cout << "after str.resize(11)" << endl;
    cout << "str is: " << str << endl;
    cout << "size of str is: "
         << str.size() << endl;

    str.resize(20,'.');

    cout << "after str.resize(20,'.')" << endl;
    cout << "str is: " << str << endl;
    cout << "size of str is: "
         << str.size() << endl;

    return 0;
}
OUTPUT:
// str is: Alexander Stepanov
// size of str is: 18
// after str.resize(11)
// str is: Alexander S
// size of str is: 11
// after str.resize(9,'.')
// str is: Alexander S.........
// size of str is: 20


rfind 1.

#include 
#include 
using namespace std;

int main () 
{
    string str = "We go step by step to the target";
    string s1  = "step";
    cout << "str is: " << str << endl;
    cout << "s1  is: " << s1  << endl;

    cout << "int n1 = str.find(s1)" << endl;
    int n1 = str.find(s1);
    cout << "n1 = " << n1+1 << endl;
    
    cout << "int n2 = str.rfind(s1)" << endl;
    int n2 = str.rfind(s1);
    cout << "n2 = " << n2+1 << endl;
    
    cout << "n3 = str.rfind(s1,n2-1)" << endl;
    int n3 = str.rfind(s1,n2-1);
    cout << "n3 = " << n3+1 << endl;

    cout << "n1 = str.rfind('t')" << endl;
    n1 = str.rfind('t');
    cout << "n1 = " << n1+1 << endl;
    
    cout << "n2 = str.rfind('t',n1-1)" << endl;
    n2 = str.rfind('t',n1-1);
    cout << "n2 = " << n2+1 << endl;
    
    char ch[] = "step";
    cout << "char ch[] = \"step\"" << endl;
    cout << "n1 = str.rfind(ch)" << endl;
    n1 = str.rfind(ch);
    cout << "n1 = " << n1+1 << endl;
    
    cout << "n2 = str.rfind(\"stabc\",10,2)" << endl;
    n2 = str.rfind("stabc", // pattern
            10,             // start position
            2);             // for first 2 char
                            // in pattern
    cout << "n2 = " << n2+1 << endl;
    
    return 0;
}
OUTPUT:
// str is: We go step by step to the target
// s1  is: step
// int n1 = str.find(s1)
// n1 = 7
// int n2 = str.rfind(s1)
// n2 = 15
// n3 = str.rfind(s1,n2-1)
// n3 = 7
// n1 = str.rfind('t')
// n1 = 32
// n2 = str.rfind('t',n1-1)
// n2 = 27
// char ch[] = "step"
// n1 = str.rfind(ch)
// n1 = 15
// n2 = str.rfind("stabc",10,2)
// n2 = 7


size 1.

#include 
#include 
using namespace std;

int main () 
{
    string str = "We go step by step to the target";
    string::size_type size = str.size();

    cout << "str is: " << str << endl;
    cout << "size of str = " << size << endl;
    
    return 0;
}
OUTPUT:
// str is: We go step by step to the target
// size of str = 32


substr 1.

// str.subsr(pos,n);
// returns a copy of the substring consisting
// of n characters from str, beginning at position pos
// (default value 0); if n is too large or is omitted,
// characters are copied only until the end of s is
// reached
#include 
#include 
using namespace std;

int main () 
{
    string str = "We go step by step to the target";
    cout << "str is: " << str << endl;

    int n = str.find("step");
    
    string s = str.substr(n);
    cout << "s   is: " << s << endl;

    s = str.substr(n,12);
    cout << "s   is: " << s << endl;
    
    return 0;
}
OUTPUT:
// str is: We go step by step to the target
// s   is: step by step to the target
// s   is: step by step


swap 1.

#include 
#include 
using namespace std;

int main () 
{
    string str1 = "Robert";
    string str2 = "Forest";
    cout << "str1 is: " << str1 << endl;
    cout << "str2 is: " << str2 << endl;
    cout << endl;

    cout << "str1.swap(str2)" << endl;
    cout << endl;

    str1.swap(str2);
    cout << "str1 is: " << str1 << endl;
    cout << "str2 is: " << str2 << endl;
    
    return 0;
}
OUTPUT:
// str1 is: Robert
// str2 is: Forest
// 
// str1.swap(str2)
// 
// str1 is: Forest
// str2 is: Robert

Stack

template <class T>
class stack
{
    private :

        T arr[MAX] ;
        int top ;

    public :
       
        stack( ) ;
        int empty();
       
        void push ( T item ) ;
        T pop(void ) ;
        void print(void);
        void clear();


        ~stack();

} ;
 
I have implemented this in sat1.h.
This is the class of stack , I wrote. T is the type like int , etc. This can be tested as:
#include <iostream>
#include<conio.h>
#include <sat1.h>
using namespace std;

int main( )
{
    stack<int>  s ;
   
    int i=0; /*it is very imprttant to initialise the i value otherwise u will get the error that "prgm is insantiated "at the
                  line i=s.pop();*/
    s.push ( 11 ) ;
    s.push ( 23 ) ;
    s.push ( -8 ) ;
    s.push ( 16 ) ;
    s.push ( 27 ) ;
    s.push ( 14 ) ;
    s.push ( 20 ) ;
    s.push ( 39 ) ;
    s.push ( 2 ) ;
    s.push ( 15 ) ;
    s.push ( 7 ) ;
    s.print();
    i=s.pop();
    cout << "\n\nItem popped: " << i ;

    i = s.pop( ) ;
    cout << "\nItem popped: " << i ;

    i = s.pop( ) ;
    cout << "\nItem popped: " << i ;

    i = s.pop( ) ;
    cout << "\nItem popped: " << i ;

    i = s.pop( ) ;
    cout << "\nItem popped: " << i ;
    s.print();
    getch();
    return 0;
}

Blogged with the Flock Browser

Miscellaneous cases with printf

Strings

1. printf(5+Fascimile);
O
mile
2. printf(5+"Good Morning");
O
Morning
3. printf("%c", abcdefg[4]);
O.
e

Strings

static char s[]= "Oinks Grunts and Guffaws";

Now we see some results on this string:
1. *(&s[2])=s[2]=*(s+2)=*(2+s ) = n
2. strlen(s) = length of the string
so strlen(s)+s= last character of the string = \0 , whose ascii value is 0.
So when %c is used , \0 is printed and when %d is used 0 is printed.
3. when is printed with %d we get the base address of the string.
4. s+5 with %s prints ^Grunts and Guffaws, that is base address + 5 and rest of the string.

Now let i=0;
ch = s[++i]; // ch = s[1] i.e. i
ch=s[i++];  // ch=s[1] but i=2
ch =i++[s]  // ch = 2[s] = s[2 ] but i = 3.
ch = ++i[s]; // ++3[s] = ++s[3] = k+1 = l(ell)

Method Overriding

Suppose bc and dc have same functions:
In case of java for eg.
Method overriding occurs only when the names and the type signatures of the two
methods are identical. If they are not, then the two methods are simply overloaded. For
example, consider this modified version of the preceding example:
// Methods with differing type signatures are overloaded – not overridden.
class A {
int i, j;
A(int a, int b) {
i = a;
j = b;
}
// display i and j
void show() {
System.out.println("i and j: " + i + " " + j);
}
}
// Create a subclass by extending class A.
class B extends A {
int k;
B(int a, int b, int c) {
super(a, b);
k = c;
}
// overload show()
void show(String msg) {
System.out.println(msg + k);
}
}
class Override {
public static void main(String args[]) {
B subOb = new B(1, 2, 3);
subOb.show("This is k: "); // this calls show() in B
subOb.show(); // this calls show() in A
}
}
The output produced by this program is shown here:
This is k: 3
i and j: 1 2
The version of show( ) in B takes a string parameter. This makes its type signature
different from the one in A, which takes no parameters. Therefore, no overriding (or
name hiding) takes place.

Access specification

This topic tells when is contructor called and when not

1.formation of object(lolz)

2.passing objects to the function
class X
{
    int i;
public:
    X(int b)    {            cout<<"love";         i=b;     }
    void  set_i(int b){s=b;}
    put_i()     {         cout<<"i="<<     }
    X()//destructor     {         cout<<"hate"    }
}; // class over

void f(X ob)
{
    ob.set_i(2);//i is now 2
    ob.put_i();
}

int main()
{
    X o(1);//i is 1
    o.put_i();
    f(o);//i is now 2
    o.put_i();
    return 0;
}

This program produces this output
love
i=1
i=2
hate
i=1
hate
Notice that two calls to the destructor function are executed, but only one call is
made to the constructor function. 
As the output illustrates, the constructor function
is not called when the copy of o (in main() ) is passed to ob (within f() ). The reason
that the constructor function is not called when the copy of the object is made is easy to
understand. When you pass an object to a function, you want the current state of that
object. If the constructor is called when the copy is created, initialization will occur,
possibly changing the object. Thus, the constructor function cannot be executed when
the copy of an object is generated in a function call.
Although the constructor function is not called when an object is passed to a
function, it is necessary to call the destructor when the copy is destroyed. (The copy
is destroyed like any other local variable, when the function terminates.) Remember,
a new copy of the object has been created when the copy is made. This means that
the copy could be performing operations that will require a destructor function to
be called when the copy is destroyed. For example, it is perfectly valid for the copy to
allocate memory that must be freed when it is destroyed. For this reason, the destructor
function must be executed when the copy is destroyed.
To summarize: When a copy of an object is generated because it is passed to a
function, the object's constructor function is not called. However, when the copy of the
object inside the function is destroyed, its destructor function is called.
By default, when a copy of an object is made, a bitwise copy occurs. This means
that the new object is an exact duplicate of the original. The fact that an exact copy is
made can, at times, be a source of trouble. Even though objects are passed to functions
by means of the normal call-by-value parameter passing mechanism, which, in theory,
protects and insulates the calling argument, it is still possible for a side effect to occur
that may affect, or even damage, the object used as an argument. For example, if an
object used as an argument allocates memory and frees that memory when it is
destroyed, then its local copy inside the function will free the same memory when its
destructor is called. This will leave the original object damaged and effectively useless.
It is possible to prevent this type of problem by defining
the copy operation relative to your own classes by creating a special type of constructor
called a copy constructor.

3.When the objects are returned by the function

A function may return an object to the caller. For example, this is a valid C++ program:
// Returning objects from a function.
#include
using namespace std;
class myclass {
int i;
public:
void set_i(int n) { i=n; }
int get_i() { return i; }
};// end class
myclass f(); // return object of type myclass
int main()
{
myclass o;
o = f();
cout << o.get_i() << "\n";
return 0;
}
myclass f()
{
myclass x;
x.set_i(1);
return x;
}
When an object is returned by a function, a temporary object is automatically
created that holds the return value. It is this object that is actually returned by the
function. After the value has been returned, this object is destroyed. The destruction of
this temporary object may cause unexpected side effects in some situations. For
example, if the object returned by the function has a destructor that frees dynamically
allocated memory, that memory will be freed even though the object that is receiving
the return value is still using it. There are ways to overcome this problem that involve
overloading the assignment operator and defining a copy constructor. 

 4.Initialised vs non initialised constructor

class X
{
    int a;
    public;
        X(){a=0;}
        X(int b){b=a;}
};

int main()
{
    X x;//con1
    X x(4);//con2
}

5.Copy constructor
It is important to understand that C++ defines two distinct types of situations in
which the value of one object is given to another. The first is assignment. The second is
initialization, which can occur any of three ways:

•  When one object explicitly initializes another, such as in a declaration
•  When a copy of an object is made to be passed to a function
•  When a temporary object is generated (most commonly, as a return value)

The copy constructor applies only to initializations. For example, assuming a class
called myclass, and that y is an object of type myclass, each of the following statements
involves initialization.
myclass x = y; // y explicitly initializing x
func(y); // y passed as a parameter
y = func(); // y receiving a temporary, return object
Following is an example where an explicit copy constructor function is needed.
This program creates a very limited "safe" integer array type that prevents array
boundaries from being overrun. Storage for each array is allocated by the use of new,
and a pointer to the memory is maintained within each array object.
/* This program creates a "safe" array class. Since space for the array is allocated using new, a copy constructor is provided to allocate memory when one array object is used to initialize another.
*/
#include
#include
#include
using namespace std;
class array {
int *p;
int size;
public:
array(int sz) {
try {
p = new int[sz];
} catch (bad_alloc xa) {
cout << "Allocation Failure\n";
exit(EXIT_FAILURE);
}
size = sz;
}
~array() { delete [] p; }
// copy constructor
array(const array &a);
void put(int i, int j) {
if(i>=0 && i
}
int get(int i) {
return p[i];
}
};
// Copy Constructor
array::array(const array &a) {
int i;
try {
p = new int[a.size];
} catch (bad_alloc xa) {
cout << "Allocation Failure\n";
exit(EXIT_FAILURE);
}
for(i=0; i
}
int main()
{
array num(10);
int i;
for(i=0; i<10; i++) num.put(i, i);
for(i=9; i>=0; i--) cout << num.get(i);
cout << "\n";
// create another array and initialize with num
array x(num); // invokes copy constructor
for(i=0; i<10; i++) cout << x.get(i);
return 0;
}
Let's look closely at what happen s when num is used to initialize x in the statement
array x(num); // invokes copy constructor
The copy constructor is called, memory for the new array is allocated and stored in x.p,
and the contents of num are copied to x's array. In this way, x and num have arrays
that contain the same values, but each array is separate and distinct. (That is, num.p
and x.p do not point to the same piece of memory.) If the copy constructor had not
been created, the default bitwise initialization would have resulted in x and num
sharing the same memory for their arrays. (That is, num.p and x.p would have indeed
pointed to the same location.)
Remember that the copy constructor is called only for initializations. For example,
this sequence does not call the copy constructor defined in the preceding program:
array a(10);
// ...
array b(10);
b = a; // does not call copy constructor

Access in cpp classes

When a base class is inherited as private, all public and protected members of that class
become private members of the derived class. However, in certain circumstances, you
may want to restore one or more inherited members to their original access
specification. For example, you might want to grant certain public members of the base
class public status in the derived class even though the base class is inherited as private. 

 

In Standard C++, you have two ways to accomplish this. First, you can use a
using statement, which is the preferred way. The second way to restore an inherited 

member's access specification is to employ an access declaration
within the derived class. Access declarations are currently supported by Standard C++,
but they are deprecated. This means that they should not be used for new code. Since
there are still many, many existing programs that use access declarations, they will be
examined here.
An access declaration takes this general form:
base-class::member;
The access declaration is put under the appropriate access heading in the derived class'
declaration. Notice that no type declaration is required (or, indeed, allowed) in an
access declaration.
To see how an access declaration works, let's begin with this short fragment:
class base {
public:
int j; // public in base
};
// Inherit base as private.
class derived: private base {
public:
// here is access declaration
base::j; // make j public again
.
.
.
};
Because base is inherited as private by derived, the public member j is made a private
member of derived. However, by including
base::j;
as the access declaration under derived's public heading, j is restored to its public status.
You can use an access declaration to restore the access rights of public and
protected members. However, you cannot use an access declaration to raise or lower a
member's access status. For example, a member declared as private in a base class
cannot be made public by a derived class. (If C++ allowed this to occur, it would
destroy its encapsulation mechanism!)
The following program illustrates the access declaration; notice how it uses access
declarations to restore j, seti(), and geti() to public status.
#include
using namespace std;
class base {
int i; // private to base
public:
int j, k;
void seti(int x) { i = x; }
int geti() { return i; }
};
// Inherit base as private.
class derived: private base {
public:
/* The next three statements override
base's inheritance as private and restore j,
seti(), and geti() to public access. */
base::j; // make j public again - but not k
base::seti; // make seti() public
base::geti; // make geti() public
// base::i; // illegal, you cannot elevate access
int a; // public
};
int main()
{
derived ob;
//ob.i = 10; // illegal because i is private in derived
ob.j = 20; // legal because j is made public in derived
//ob.k = 30; // illegal because k is private in derived
ob.a = 40; // legal because a is public in derived
ob.seti(10);
cout << ob.geti() << " " << ob.j << " " << ob.a;
return 0;
}
Access declarations are supported in C++ to accommodate those situations in
which most of an inherited class is intended to be made private, but a few members are
to retain their public or protected status.
While Standard C++ still supports access declarations, they are deprecated. This
means that they are allowed for now, but they might not be supported in the future.
Instead, the standard suggests achieving the same effect by applying the using
keyword.

User defined data types

C supports following
typedef
struct
enum

cpp adds following :
classes

typedef
C support the feature known as type definition that allows user to define an identifier that would represent an exiting data type. The user defined datatype isentifier can later be used to declare variables. It takes the general form.
typedef type identifier;
Where type refers to an existing data type may belong to any class of type , including the user defined ones. Remember that the new type is 'new' only in name , but not the data type. typedef can not create a new type. Some example of type definition are :
typedef int units;
typedef float marks; 
Here , unit symbolizes int and mark symbolizes folat. They can be later used to declare variables as follows.
units batch1, batch2;
 marks name1[50], name2[50];
Enum
Consider the following PPD = #define

#define APPLE 1 OR const int APPLE = 1;//in cpp
#define PEAR  2
#define PEACH 3
#define PLUM  4

The C preprocessor processes all C and C++ files before the compiler is called. The C preprocessor will fill in the defined value for every occurance of the define name. So where ever PEAR appears in the code, the C preprocessor will fill in 2.
While #define constants are better than just using unnamed numeric values, this is a crude way to define a set of values. Later versions of C added enumerations, which are also in C++. Here is the syntax:

enum { single, married, divorced, widower};

enum mar_status { single, married, divorced, widower};

Here single has value = 0 , rest increase by 1.
An example of a C++ enumeration, defining the same values is shown below:

typedef enum { APPLE = 1, PEAR, PEACH, PLUM } fruit;

In C++ enumerations also got a thin veneer of type safety. To convert an enumeration to an integer it was necessary to use a cast.

fruit basket = (fruit)42;

The range for enumeration values is not enforced in C++, so the statement above compiles without error, even though 42 is beyond the enumeration range. In C++ enumeration values can also be assigned to integers without a cast operation:

int y = PLUM;

Java does not provide an enumeration type, so it is tempting to use something like the C #define. For example:

class StateMachine
{
    public static final int WAIT    = 1;
    public static final int NICKLE  = 2;
    public static final int DIME    = 3;
    public static final int QUARTER = 4;
    ....
    private int currentState = WAIT;
}

Examples:
1. enum { v1 = -1, v2, v3=6, v4, v5, v6, v7} var;

printf("%d" , sizeof(var));

O
2(DOS)
4(VC++)
2. printf2(v1, v2, v3, v4, v5, v6, v7);
O
-1 0 6 7 8 9
3. Operators like ++ don't work, because enum are const int.

printf2(++v1);

O.
error

Unions
 A union is a variable which may hold (at different times) objects of different sizes and types. That is a union hold only one member at a time. C uses the union statement to create unions, for example.

union number     {      short shortnumber;      long longnumber;      double floatnumber;    } anumber

defines a union called number and an instance of it called a number. number is a union tag and acts in the same way as a tag for a Structure. All operation on union like that of Structure.

Difference between Structure and union is Structure allocate storage space for all the members where as union allow only one  member at a time. Application of union is when we need only one member of a Structure  for a particular application that time we can use union.

Escape characters and printf

Escape Sequence	Character represented
\n	newline
\t	tab
\\	backslash itself
\'	quote ``'''
\"	double quote ``"''

For example,

printf("\t\"My name is \'%s\'\"\n", "Jim");

Which prints

"My name is 'Jim'"