Exception handling

hi guys,
i declare a variable as int and if i get d input from user and and if user gives float value r character instead of int program shows undesired output and it goes on executin.. cannot stop d program...... i want to write exception handling for dis.... how can i write??pls help me.....

 

With numbers, you could try something like

Code:

int x;
do {
   // prompt for and store input
   if(std::cin.fail()) {
      std::cin.clear();
      while(std::cin.get() != '\n'){}
      std::cout << "that wasn't a number\n";
   }
} while(....);

That *should* help with bad input from chars or punct. A floating point would probably survive but be truncated to its integer part.

If you needed something more, you could probably use the stringstream class along with a string to read in the data. From there, parse the string to make sure it's an integer - if it is, use istringstream member to store into your int variable.

 

hey thank u very much for replyin... but i cant understand d code... could u explain me pls....

 

The do-while loop sits and waits for a test condition to be true (or false depending on what you're wanting to do). For example, say you want a user to enter an integer that is between 1 and 50.

Code:

int num = 0; // initialize to 0; should cin fail on bad input,
                 // it will have a good value for the test condition

do {
   std::cout << "Enter an integer (1-50): ";
   std::cin >> num;

   if(std::cin.fail()) { 

      // if a user enters bad data, cin will be in a fail state
      // to restore it, clear the eof and fail bits using clear()

      std::cin.clear();

      // because the stream failed, there is probably unwanted
      // data in the keyboard buffer.  To "clean" it out, loop
      // through using cin.get until a newline char is encountered.  

     while(std::cin.get() != '\n'){}  

      // if all went okay, the input stream (cin) should be
      // restored, so let the user know the input was bad

      std::cout << "invalid input\n";
    }
} while(num < 1 || num > 50); // only want range of 1-50

With cpp, I usually don't include the std namespace. If you add using namespace std; to your source, then you wouldn't use std::cin, std::cout, etc. You'd only need cin, cout, etc.

Hope that helps.

 

ya thanx a lot i understood the program. if u giv an character value cin.fail() become true but if u enter any integer followed by character it cin.fail() doesnt become true.. for example if u giv (7e)as input to num, cin.fail() doesnt become true and in num the value is stored as (7) .and in keyboard buffer the value (e) is stored... i dont want my program to do lik dis... my program shuld say error for dis type of value also...wat can i do for dis??thanks for ur immense help



p.s:my english is very bad....if u cant understand clearly sorry pa....