CODEWITHSUNDEEP
c++
CRT_flow
CRT_flow

Reputation: 117

How to end a whole program

I have a pretty simple C++ console program. It's working fine, but I have some issues. I have 2 functions. First function called "input" asks from user to input numbers from 6 to 10. In that function I declared:

if ((a[i][j] < 6) || (a[i][j] > 10))
{
    cout<<"Invalid input!";
    return 0; 
}

Second function called "output", prints out those numbers from first function.

In the main it is like:

int main ()
{
    ...
    input (matrix, number);
    output (matrix, nubmer);
}

My question is this. When I input number that isn't 6-10, my program still do "output" function, so it prints some random numbers. How can I break whole program in exact time when input rules are broken? Without any random output and stuff, just to print "Invalid output", then to start program from the start?

Upvotes: 1

Views: 471

Answers (6)

Sarfaraz Nawaz
Sarfaraz Nawaz

Reputation: 361732

An idiomatic code would be this:

while(input (matrix, number)) //idiomatic loop
{
    output (matrix, nubmer);
}

The input() function should return false or 0 when the input is invalid, and true or non-zero, when the input is valid.

The loop above has the same form as we write std::istream idioms:

 std::string word;
 while( std::cin >> word ) 
 {
     //..
 }

 //Or

 ifstream file;
 //...
 while( file >> word ) 
 {
     //..
 }

 //Or
 while( std::getline(file, word)) 
 {
     //..
 }

I just explained this idiom here, as to how it works:

Upvotes: 2

Chris
Chris

Reputation: 2896

There are plenty of solutions. One is to declare the input function to return an integer. On success input can return 0. On failure (the input is outside the range 6-10) input returns a negative number (-1 for simplicity). Inside your main function, use a while loop to continue calling input until it returns 0 for success. Each time input fails you can print a message telling the client to enter try again. If you want to exit immediately after the first input failure, you can call exit(1) inside your main.

Upvotes: 1

Fox32
Fox32

Reputation: 13570

If your input function return 0 on invalid input and another value on success you can run a loop until your input is valid

...

while(input(matrix,number) == 0);

...

Upvotes: 2

Puppy
Puppy

Reputation: 147028

The usual way to indicate errors is to throw an exception.

int main() {
    ...
    try {
        input(matrix, number);
        output(matrix, number);
    } catch(std::exception& e) {
        std::cout << "Error: " << e.what();
    }
}

In input:

if ((a[i][j] < 6) || (a[i][j] > 10))
{
    throw std::runtime_error("Invalid input!");
}

Upvotes: 2

Maxim Krizhanovsky
Maxim Krizhanovsky

Reputation: 26739

You may check the return value of input() before calling output(). You can use the exit() function to terminate the program

Upvotes: 7

user744186
user744186

Reputation: 

 if(input(matrix,number) != 0) output(matrix,number); 
 // You don't {} for a single instruction

This should fix your problem.

Upvotes: 3

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