isNumeric()

For some reason many C++ programmers believe there is an isNumeric() function available as part of the language. In fact I was searching for the header file to include to get a piece of code to work.

Its not difficult to create a function that will be able to check if the string is numeric or not. Here is the code.

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
#include <iostream>
#include <string>
#include <sstream>

using namespace std;
 
bool isNumeric1(string stringToCheck)
{
  bool numeric = false;
 
  if(stringToCheck.find_first_not_of("0123456789.") == string::npos)
    numeric = true;
 
  return numeric;
}
 
bool isNumeric2(string stringToCheck)
{
  bool numeric = true;
  unsigned i = 0;
 
  while(numeric && i < stringToCheck.length())
  {
    switch (stringToCheck[i])
    {
    case '0': case '1': case '2': case '3': case '4': case '5': 
    case '6': case '7': case '8': case '9': case '.':
      //do nothing
      break;
    default:
      numeric = false;
    }
    i++;
  }
 
  return numeric;
}
 
bool isNumeric3(string stringToCheck)
{
  stringstream streamVal(stringToCheck);
  double tempVal;
 
  streamVal >> tempVal; //If numeric then everything transferred to tempVal

  if(streamVal.get() != EOF)
    return false;
  else
    return true;
}
 
int main()
{
  string str1("123"), str2("134.567"), str3("12AB");
  cout << "Approach 1" << endl;
  cout << str1 << (isNumeric1(str1) ? " is Numeric" : " is Not Numeric") << endl;
  cout << str2 << (isNumeric1(str2) ? " is Numeric" : " is Not Numeric") << endl;
  cout << str3 << (isNumeric1(str3) ? " is Numeric" : " is Not Numeric") << endl;
 
  cout << "\nApproach 2" << endl;
  cout << str1 << (isNumeric2(str1) ? " is Numeric" : " is Not Numeric") << endl;
  cout << str2 << (isNumeric2(str2) ? " is Numeric" : " is Not Numeric") << endl;
  cout << str3 << (isNumeric2(str3) ? " is Numeric" : " is Not Numeric") << endl;
 
  cout << "\nApproach 3" << endl;
  cout << str1 << (isNumeric3(str1) ? " is Numeric" : " is Not Numeric") << endl;
  cout << str2 << (isNumeric3(str2) ? " is Numeric" : " is Not Numeric") << endl;
  cout << str3 << (isNumeric3(str3) ? " is Numeric" : " is Not Numeric") << endl;
 
  return 0;
}
 

Output is as follows:

There are few problems in the program above:

1. It does not cater for negative numbers

2. It will return wrong result when you have incorrect string like 12.34.56.78

I have intentionally left it as an exercise.

Other approaches are possible as well. Why not try and think of an approach yourself.

string::find_next()

I met this new starter who has come from Java background. He was upset because he couldn't find string::find_next() as C++ function. He said Java is much more flexible this way. In reality, its not that bad if you look at the definition of find carefully.

size_t find ( const string& str, size_t pos = 0 ) const;

size_t find ( const char* s, size_t pos, size_t n ) const;

size_t find ( const char* s, size_t pos = 0 ) const;

size_t find ( char c, size_t pos = 0 ) const;

The first one works as find_next as I show in the example below:

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy

#include <iostream>
#include <string>

using namespace std;
 
int main()
{
  string someString("Tom is not in. Infact Tom is not going to be in Tomorrow or day after Tomorrow");
  string findTheString("Tom");
 
  unsigned position = 0;
 
  position = someString.find(findTheString);
  cout<<"First position of " << findTheString << " is " << position << endl;
 
  //We want to find all the next positions which is after position + findTheString.length()
  while(position != string::npos)
  {
    position = someString.find(findTheString, (position + findTheString.length()));
    cout<<"Next position of " << findTheString << " is " << position << endl;
  }
 
  return 0;
}

The output is as follows:

Exercise for new programmers:

1. The last two Tom's are part of 'Tomorrow', how can you make sure they are not printed
2. The last Tom which is 4294... is equal to -1 or string::npos. How can you stop that being printed without making another check for string::npos

Please dont post answers as they should be trivial exercise and you should be able to figure out without much problems.

Switch Case using string

When I started thinking of this example, I also faced some of the other problems that I have encountered in my initial days of C++. One of these problems was how to convert String to multiple Ints and how to split strings easily, etc. Hopefully you will find the example useful.

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
#include<iostream>
#include<string>
#include<sstream>
#include<map>

using namespace std;

void split(const string& input, int& num1, int& num2, string& operation);
int calculate(int num1, int num2, string operation);

int main()
{
 string s[5] = {"2 + 2", "4 - 1", "4 * 6", "18 / 3", "12 ^ 2"};

 for(int i = 0; i < 5 ; i++)
 {
   int num1=0, num2=0;
   string op;
   split(s[i], num1, num2, op);
   int retVal = calculate(num1, num2, op);
   cout<<s[i]<<" = "<<retVal<<endl;
 }

 return 0;
}

void split(const string& input, int& num1, int& num2, string& operation)
{
 istringstream iss(input);
 iss >> num1;
 iss >> operation;
 iss >> num2;
}

int calculate(int num1, int num2, string operation)
{
 enum Operators {unknown, add, sub, mul, div};
 map<string, Operators> mapOfOperators;
 mapOfOperators["+"] = add;
 mapOfOperators["-"] = sub;
 mapOfOperators["*"] = mul;
 mapOfOperators["/"] = div;

 switch(mapOfOperators[operation])
 {
 case add:
   return num1 + num2;
 case sub:
   return num1 - num2;
 case mul:
   return num1 * num2;
 case div:
   return num1 / num2;
 default:
   cout<<"Unrecognised Operator "<<operation<<endl;
 }
 return 0;
}

The output is as follows:

See Also: Codeguru article on 'Switch on Strings in C++'.

Removing all white-spaces from a string

Continuing on the same theme as the last post. What if all the spaces need to be stripped out from the input string:

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
#include<iostream>
#include<string>

using namespace std;

string removeAllSpaces(const string& s)
{
 string newStr(s);
 bool spacesLeft = true;

 while(spacesLeft)
 {
   int pos = newStr.find(" ");
   if(pos != string::npos)
   {
     newStr.erase(pos, 1);
   }
   else
     spacesLeft = false;
 }

 return newStr;
}

int main()
{
 string aString("This  string   has        multiple spaces     problem!");

 cout<<"Original : "<<aString<<endl;
 cout<<"Modified : "<<removeAllSpaces(aString)<<endl;

 return 0;
}

The output is as follows:

Removing Multiple White-spaces from a string

A simple program to remove an arbitrary number of white spaces in between words. Program as follows:

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
#include<iostream>
#include<string>

using namespace std;
 
bool removeDoubleSpaces(string& s)
{
  bool found = true;
 
  int i = s.find("  "); //Search for 2 spaces
  if(i != string::npos)
  {
    s.replace(i, 2, " ");
  }
  else
    found = false;
 
  return found;
}
 
string removeMultipleSpaces(const string& s)
{
  string newStr(s);
  bool found = true;
 
  while(found)
  {
    found = removeDoubleSpaces(newStr);
  }
 
  return newStr;
}
 
int main()
{
  string aString("This  string   has        multiple spaces     problem!");
 
  cout<<"Original : "<<aString<<endl;
  cout<<"Modified : "<<removeMultipleSpaces(aString)<<endl;
 
  return 0;
}
 

The output is as follows:

An example of replacing part of strings

Taking a bit of break from the Design Patterns this week. We look at a simple example of replacing part of the strings. For example you may have a program which prints out some customised letter. You may want to replace the default name with the name of a person that can be input on command line.



Example as follows:

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
#include<iostream>
#include<string>

using namespace std;

int main()
{
  string s1 = "Hello is that Tom? Are you ok Tom? Take Care tom!";
  string s2 = "Tom";
  string s3 = "William";

  cout << "s1 = " << s1 << endl;

  //Find s2 and replace by s3
  bool flag = true;
  while(flag)
  {
    size_t found = s1.find(s2);
    if(found != string::npos)
    {
      s1.replace(found, s2.length(), s3);
    }
    else
    {
      flag = false;
    }
  }

  cout << "s1 = " << s1 << endl;

  return 0;
}

The output is as follows:

Client/Server communication via sockets

The following is a simple Client Server example that actually covers quite a few different topics. The code is modified from the MadWizard.org Winsock Tutorial. It may be a good idea to go through the StringStreams example here and C/C++ String differences example here.

Please note that the code below is not the best example of coding practice.

Server code:

//Original Client-Server code from www.MadWizard.org
//Part of the Winsock networking tutorial by Thomas Bleeker
//Modified and tested on Microsoft Visual Studio 2008 - Zahid Ghadialy

#include <iostream>
#include <string>
#include <sstream>

#define WIN32_MEAN_AND_LEAN
#include <winsock2.h>
#include <windows.h>

//Add ws2_32.lib in Properties->Linker->Input->Additional Dependencies

using namespace std;

const int  REQ_WINSOCK_VER   = 2; // Minimum winsock version required
const int  DEFAULT_PORT      = 4444; 
const int  TEMP_BUFFER_SIZE  = 128;

//Forward Declarations
bool RunServer(int portNumber);

//MAIN
int main()
{ 
 int iRet = 1;
 WSADATA wsaData;

  cout << "SERVER STARTED" << endl;
 cout << "Initializing winsock... ";

 if (WSAStartup(MAKEWORD(REQ_WINSOCK_VER,0), &wsaData)==0)
 {
  // Check if major version is at least REQ_WINSOCK_VER
  if (LOBYTE(wsaData.wVersion) >= REQ_WINSOCK_VER)
  {
   cout << "initialized.\n";
   
   int port = DEFAULT_PORT;
   iRet = !RunServer(port);
  }
  else
  {
   cerr << "required version not supported!";
  }

  cout << "Cleaning up winsock... ";

  // Cleanup winsock
  if (WSACleanup()!=0)
  {
   cerr << "cleanup failed!\n";
   iRet = 1;
  }   
  cout << "done.\n";
 }
 else
 {
  cerr << "startup failed!\n";
 }
 return iRet;
}


string GetHostDescription(const sockaddr_in &sockAddr)
{
 ostringstream stream;
 stream << inet_ntoa(sockAddr.sin_addr) << ":" << ntohs(sockAddr.sin_port);
 return stream.str();
}

void SetServerSockAddr(sockaddr_in *pSockAddr, int portNumber)
{
 // Set family, port and find IP
 pSockAddr->sin_family = AF_INET;
 pSockAddr->sin_port = htons(portNumber);
 pSockAddr->sin_addr.S_un.S_addr = INADDR_ANY;
}

void HandleConnection(SOCKET hClientSocket, const sockaddr_in &sockAddr)
{
 // Print description (IP:port) of connected client
 cout << "Connected with " << GetHostDescription(sockAddr) << ".\n";
  exception e;

 char tempBuffer[TEMP_BUFFER_SIZE];

 // Read data
 while(true)
 {
  int retval;
  retval = recv(hClientSocket, tempBuffer, sizeof(tempBuffer), 0);
  if (retval==0)
  { 
   break; // Connection has been closed
  }
  else if (retval==SOCKET_ERROR)
  {
   exception e("socket error while receiving.");
      throw e;
  }
  else
  {
      string tempBufferString(tempBuffer);
      cout<<"Received over the socket :"<<tempBufferString<<endl;
      string tempString = "Loopbacked: " + tempBufferString + '\0';
      strcpy_s(tempBuffer, tempString.length() + 1, tempString.c_str());
   if (send(hClientSocket, tempBuffer, strlen(tempBuffer)+1, 0)==SOCKET_ERROR)
    {
     exception e("socket error while sending.");
        throw e;
    }
  }
 }
 cout << "Connection closed.\n";
}

bool RunServer(int portNumber)
{
 SOCKET hSocket = INVALID_SOCKET, hClientSocket = INVALID_SOCKET;
 bool bSuccess = true;
 sockaddr_in sockAddr = {0};
 
 try
 {
  // Create socket
  cout << "Creating socket... ";
  if ((hSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == INVALID_SOCKET)
    {
      cout << "failed Creating socket... \n";
      return false;
    }
  cout << "created.\n";
  
  // Bind socket
  cout << "Binding socket... ";
  SetServerSockAddr(&sockAddr, portNumber);
  if (bind(hSocket, reinterpret_cast<sockaddr*>(&sockAddr), sizeof(sockAddr))!=0)
    {
      cout << "failed Binding socket... \n";
      return false;
    }
  cout << "bound.\n";

  // Put socket in listening mode
  cout << "Putting socket in listening mode... ";
  if (listen(hSocket, SOMAXCONN)!=0)
    {
      cout << "failed Putting socket in listening mode... \n";
      return false;
    }
  cout << "done.\n";

  // Wait for connection
  cout << "Waiting for incoming connection... ";
  
  sockaddr_in clientSockAddr;
  int clientSockSize = sizeof(clientSockAddr);
  
  // Accept connection:
  hClientSocket = accept(hSocket,
       reinterpret_cast<sockaddr*>(&clientSockAddr),
       &clientSockSize);
 
  // Check if accept succeeded
  if (hClientSocket==INVALID_SOCKET)
    {
      cout << "accept function failed... \n";
      return false;
    }
  cout << "accepted.\n";
 
  // Wait for and accept a connection:
  HandleConnection(hClientSocket, clientSockAddr);

 }
 catch(exception& e)
 {
  cerr << "\nError: " << e.what() << endl;
  bSuccess = false; 
 }

 if (hSocket!=INVALID_SOCKET)
  closesocket(hSocket);
 
 if (hClientSocket!=INVALID_SOCKET)
  closesocket(hClientSocket);
  
 return bSuccess;
} 

Client code:

//Original Client-Server code from www.MadWizard.org
//Part of the Winsock networking tutorial by Thomas Bleeker
//Modified and tested on Microsoft Visual Studio 2008 - Zahid Ghadialy

#include <iostream>
#include <sstream>

#define WIN32_MEAN_AND_LEAN
#include <winsock2.h>
#include <windows.h>

using namespace std;

//Add ws2_32.lib in Properties->Linker->Input->Additional Dependencies

using namespace std;

const int  REQ_WINSOCK_VER   = 2; // Minimum winsock version required
const char DEF_SERVER_NAME[] = "127.0.0.1"; //localhost - can be your server name like "www.google.com"
const int  SERVER_PORT       = 4444; 
const int  TEMP_BUFFER_SIZE  = 128;

// IP number typedef for IPv4
typedef unsigned long IPNumber;

//Forward Declarations
bool RunClient(const char *pServername);

//MAIN
int main(int argc, char* argv[])
{
 int iRet = 1;
 WSADATA wsaData;

  cout << "CLIENT STARTED" << endl;
 cout << "Initializing winsock... ";

 if (WSAStartup(MAKEWORD(REQ_WINSOCK_VER,0), &wsaData)==0)
 {
  // Check if major version is at least REQ_WINSOCK_VER
  if (LOBYTE(wsaData.wVersion) >= REQ_WINSOCK_VER)
  {
   cout << "initialized.\n";
   
   // Set default hostname:
   const char *pHostname = DEF_SERVER_NAME;
   iRet = !RunClient(pHostname);
  }
  else
  {
   cerr << "required version not supported!";
  }

  cout << "Cleaning up winsock... ";

  // Cleanup winsock
  if (WSACleanup()!=0)
  {
   cerr << "cleanup failed!\n";
   iRet = 1;
  }   
  cout << "done.\n";
 }
 else
 {
  cerr << "startup failed!\n";
 }
 return iRet;
}


IPNumber FindHostIP(const char *pServerName)
{
 HOSTENT *pHostent;

 // Get hostent structure for hostname:
 if (!(pHostent = gethostbyname(pServerName)))
  {
    exception e("could not resolve hostname.");
    throw e;
  }
 
 // Extract primary IP address from hostent structure:
 if (pHostent->h_addr_list && pHostent->h_addr_list[0])
  return *reinterpret_cast<IPNumber*>(pHostent->h_addr_list[0]);
 
 return 0;
}

void FillSockAddr(sockaddr_in *pSockAddr, const char *pServerName, int portNumber)
{
 // Set family, port and find IP
 pSockAddr->sin_family = AF_INET;
 pSockAddr->sin_port = htons(portNumber);
 pSockAddr->sin_addr.S_un.S_addr = FindHostIP(pServerName);
}

bool RunClient(const char *pServername)
{
 SOCKET     hSocket = INVALID_SOCKET;
 char      tempBuffer[TEMP_BUFFER_SIZE];
 sockaddr_in sockAddr = {0};
 bool      bSuccess = true;
 
 try
 {
  // Lookup hostname and fill sockaddr_in structure:
  cout << "Looking up hostname " << pServername << "... ";
  FillSockAddr(&sockAddr, pServername, SERVER_PORT);
  cout << "found.\n";
 
  // Create socket
  cout << "Creating socket... ";
  if ((hSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == INVALID_SOCKET)
    {
      cout<<"could not create socket. "<<endl;
      return false;
    }
  cout << "created.\n";
  
  // Connect to server
  cout << "Attempting to connect to " << inet_ntoa(sockAddr.sin_addr)
       << ":" << SERVER_PORT <<  "... ";
  if (connect(hSocket, reinterpret_cast<sockaddr*>(&sockAddr), sizeof(sockAddr))!=0)
    {
      cout<<"could not connect. "<<endl;
      return false;
    }
  cout << "connected.\n";
  
  cout << "Sending requests and checking for loopbacks... "<<endl;

    //Lets sent 100 packets and get it looped back from Server
    for(int i = 0; i < 10; i++)
    {
      int retval = 0;
      stringstream ss (stringstream::in | stringstream::out);
      ss << "Message " << i <<"\n";

      std::string s = ss.str() + '\0'; //Adding the null charachter
      if (send(hSocket, s.c_str(), s.size() + 1, 0)==SOCKET_ERROR)
      {
        cout<<"failed to send data. "<<endl;
        return false;
      }

      retval = recv(hSocket, tempBuffer, sizeof(tempBuffer), 0);
      if (retval==0)
      {
        cout<<"Connection closed"<<endl;
        break;
      }
      else if (retval==SOCKET_ERROR)
      {
        exception e("socket error while receiving.");
        throw e;
      }
      else
      {
    // retval is number of bytes read
    // Terminate buffer with zero and print as string
    tempBuffer[retval] = 0;
        cout << "Received " << retval << " bytes. Received : " <<tempBuffer;
      }
    }  
 }
 catch(exception& e)
 {
  cerr << "\nError: " << e.what() << endl;
  bSuccess = false; 
 }

 if (hSocket!=INVALID_SOCKET)
 {
  closesocket(hSocket);
 }
 return bSuccess;
} 

The Server Output is as follows:

The Client output is as follows:

Example of Permutations in C++

Example of how you can let the Algorithm class generate permutations of String

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
#include<iostream>
#include<algorithm>
#include<string>
#include<vector>

using namespace std;

int main()
{
  string someString="ABC";
  vector<string> someVector;

  someVector.push_back(someString);

  string::iterator itBegin = someString.begin();
  string::iterator itEnd = someString.end();

  while(next_permutation(itBegin, itEnd)) //std::next_permutation defined in algorithm
  {
    someVector.push_back(string(itBegin, itEnd));
  }
  copy(someVector.begin(), someVector.end(), ostream_iterator<string>(cout, "\n"));

  return 0;
}

The output is as follows:

Via: Learning C++: Permutations in C++

std::search example on vector and string

Continuing from last weeks theme, here is a simple example of std::search.

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
#include <iostream>
#include <vector>
#include <string>
#include <algorithm> //needed for std::search

using namespace std;

bool isOdd(int i) 
{
  return ((i%2)==1);
}

int main()
{
  vector<int> v1;
  v1.push_back(88);
  v1.push_back(99);
  v1.push_back(22);
  v1.push_back(33);
  v1.push_back(44);
  v1.push_back(55);
  v1.push_back(66);
  v1.push_back(77);

  //Demonstrating Search - Matching Case
  vector<int> v2;
  v2.push_back(22);
  v2.push_back(33);
  v2.push_back(44);

  vector<int>::const_iterator it = search(v1.begin(), v1.end(), v2.begin(), v2.end());
  if(it != v1.end())
  {
    cout<<"Found: "<<*it<<endl;
    cout<<"Position = "<<it - v1.begin() + 1<<endl;
  }
  else
  {
    cout<<"Not Found"<<endl;
    cout<<"Position = -1"<<endl;
  }

  //Demonstrating Search - Non-Matching Case
  vector<int> v3;
  v3.push_back(22);
  v3.push_back(33);
  v3.push_back(444); //non matching

  it = search(v1.begin(), v1.end(), v3.begin(), v3.end());
  if(it != v1.end())
  {
    cout<<"Found: "<<*it<<endl;
    cout<<"Position = "<<it - v1.begin() + 1<<endl;
  }
  else
  {
    cout<<"Not Found"<<endl;
    cout<<"Position = -1"<<endl;
  }

  //Use the search to find strings
  string s1="Hello, this is Zahid";

  //Matching case
  string s2="Zahid";

  string::const_iterator it2 = search(s1.begin(), s1.end(), s2.begin(), s2.end());
  if(it2 != s1.end())
  {
    cout<<"Found: "<<*it2<<endl;
    cout<<"Position = "<<it2 - s1.begin() + 1<<endl;
  }
  else
  {
    cout<<"Not Found"<<endl;
    cout<<"Position = -1"<<endl;
  }

  //Non-Matching case
  string s3="None";

  it2 = search(s1.begin(), s1.end(), s3.begin(), s3.end());
  if(it2 != s1.end())
  {
    cout<<"Found: "<<*it2<<endl;
    cout<<"Position = "<<it2 - s1.begin() + 1<<endl;
  }
  else
  {
    cout<<"Not Found"<<endl;
    cout<<"Position = -1"<<endl;
  }

  return 0;
}

The output is as follows:

Case-Insensitive String comparison

It is often a problem that we ask someone to input some string for comparison but they often put different case and the comparison fails. For example if we are expecting a string, say, 'true'. The user may input 'True' or 'TRUE'. A simple comparison will fail in this case.

The following is a simple program to convert the input string to lower case. What this would allow is to do a case-insensitive search.

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
#include<iostream>
#include<string>

using namespace std;

//First approach for converting into lower case
string toLowerString(string& input)
{
  int length = input.length();
  string output;
  for(int i = 0; i < length; i++)
  {
    output += tolower(input[i]);
  }
  return output;
}

//Second approach for converting into lower case
string toLowerString(string& input, bool approach2) //Overloaded method
{
  int length = input.length();
  string output;
  for(int i = 0; i < length; i++)
  {
    if(input[i] >= 0x41 && input[i] <= 0x5A) //Ascii for A-Z
      output += (input[i] + 0x20); //ascii for a-z
    else 
      output += input[i];
  }
  return output;
}

int main()
{
  string s1="true";
  string s2("TRUE");
  string s3;
  s3 = "True";

  //Check if s1 = s2
  if(s1 == s2)
    cout<<"s1 == s2"<<endl;
  else
    cout<<"s1 != s2"<<endl;

  //Check if s1 = s2 with first approach
  if(s1 == toLowerString(s2))
    cout<<"s1 == Approach1::toLowerString(s2)"<<endl;
  else
    cout<<"s1 != Approach1::toLowerString(s2)"<<endl;

  //Check if s1 = s2 with second approach
  if(s1 == toLowerString(s2,true))
    cout<<"s1 == Approach2::toLowerString(s2)"<<endl;
  else
    cout<<"s1 != Approach2::toLowerString(s2)"<<endl;


  //Check if s1 = s3 with second approach
  if(s1 == s3)
    cout<<"s1 == s3"<<endl;
  else
    cout<<"s1 != s3"<<endl;

  if(s1 == toLowerString(s3,true))
    cout<<"s1 == Approach2::toLowerString(s3)"<<endl;
  else
    cout<<"s1 != Approach2::toLowerString(s3)"<<endl;

  //Check if s1 = s3 with second approach
  if(s1 == toLowerString(s3)) 
    cout<<"s1 == Approach1::toLowerString(s3)"<<endl;
  else
    cout<<"s1 != Approach1::toLowerString(s3)"<<endl;

  return 0;
}

The output is as follows:


I am aure much better approaches are possible. If you have a better example please share.

Example of Stringstreams

Here is an example of stringstream that I picked up from here and modified it slightly.

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
//Simple example of C++ stringstreams

#include<iostream>
#include<sstream>
#include<string>

using namespace std;

int main()
{
  string input;

  cout<< "Please enter some numbers speretaed by space and press enter once done: ";
  getline(cin, input);

  cout<< "input = " << input << endl;

  stringstream memString(input, ios_base::in); //stringstream( string s, openmode mode )

  cout<<"memString = " << memString << endl;
  cout<<"memString (contents) = " << memString.str() << endl;

  double summ = 0; 
  double temp;
  while (memString >> temp)
  { 
    summ+= temp;
  }

  cout<<"summ = " << summ << endl;

  return 0;
}

The output is as follows:


See Also:
C++ Reference on stringstreams
Using Stringstreams in C++
String Stream example
String Streams Constructors

C String and C++ Strings: Similarities and Differences

I came across this scenario recently when a C style string (as some people refer to char[] as) had to be compared to a C++ string and even though this is straightforward, i fell in the same trap as a lot of people about forgetting that there is a Nul charachter as the end of C style string. Anyway, here is an example to demonstrate both the strings.

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
//Program to demonstrate length and size of char* and string
//and to show similarity and difference between them
#include<iostream>

using namespace std;

int main()
{
  cout<<endl;
  char a[10]="Hello";
  cout<<"Size of a = "<<sizeof(a)<<endl;
  a[5]='\0'; //Terminating the C string in between with Nul character
  cout<<"Size of a = "<<sizeof(a)<<endl;

  cout<<endl;
  char b[]="Hello";
  cout<<"Size of b = "<<sizeof(b)<<endl; //Note the size
                                         //Automatic Nul charachter added

  cout<<endl;
  string c("Hello");
  cout<<"Size of c = "<<sizeof(c)<<endl;
  cout<<"Length of c = "<<c.length()<<endl;

  c += " Zahid";
  cout<<"Size of modified c = "<<sizeof(c)<<endl;
  cout<<"Length of modified c = "<<c.length()<<endl;

  //Add an extra NULL charachter
  cout<<endl;
  char d[]="Hello\0";
  cout<<"Size of d = "<<sizeof(d)<<endl;
  for(int i = 0; i < sizeof(d); i++)
  {
    cout<<"d["<<i<<"] = "<<d[i]<<endl;
  }

  //When is a char[] similar to string?
  cout<<endl;
  char e[]="Zahid";
  string f = "Zahid\0";
  const char* temp = f.c_str();
  if(strcmp(e , temp) == 0)
  {
    cout<<"e == f"<<endl;
  }
  else
  {
    cout<<"e != f"<<endl;
  }

  return 0;
}

The output is as follows: