How do I stop cin from crashing my prog

say i have:

int x;
cin>>x;

and i enter a char, the program crashes
or if i enter 9999999999, it also crashes
how do i stop that from happening?

also, i want the data to be input without pressing enter
i.e. for single digit input, i want to input the data as the key is pressed

e.g. "Press any key to continue" *presses d*

How do i achieve that?
thanks

Heres a hint: when you have:

Code:

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int x;
cin>>x;

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and you input a character cin gets set to a failed state. You can test for this state by calling the fail() member function. If its true its in a failed state. You can then clear() cin and remove the offending character and try the input again.

ok thanks
where do i get a list of cin's member functions?

http://www.cplusplus.com/ref/iostream/istream/

thanks man
ur da bomb

The downside of using the stream states analysis route is that when user inputs 1o1 instead of 101 the fail bit will not be set. Instead the value of 1 will be assigned to the variable. This has two potential problems. First, the user won't know that 1 was assigned to the variable instead of 101 (until some time later, maybe), and second, I believe the o1 will remain in the input buffer to potentially screw up your next input sequence.

An alternative is to only accept input only as a string and parse the string for appropriateness. True, this isn't foolproof either. It also requires a little more coding on your part, particularly if you want to screen for float/doubles instead of just ints.

another way to go at it is to use getch() and parse it as it comes in. again, this is going to mean more coding for you.

usually I just take in a string, and if it fails simple validation, throw an exception, flush the string, and make the user input it again...

and in reference to the topic of this thead:

Quote:

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How do I stop cin from crashing my prog

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should be

Quote:

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How do I stop dumb users from crashing my prog

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Except that getch() isn't standard ;)

User input validation can become a major pain in the arse to code for and I really didn't want to scare away the OP, yet.

Quote:

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Originally Posted by Thantos

Except that getch() isn't standard ;)

User input validation can become a major pain in the arse to code for and I really didn't want to scare away the OP, yet.

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yeah, I kinda cringed when I hit submit (or one of it's variations)... but elad has a good point with the 1o1 post...

for example, say you have this:

Code:

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int x,y;
cin>>x>>y;

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but the input is:

Quote:

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1o1
552

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But what if you had this:

Code:

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char x;
int y, z;
cin>>y>>x>>z;

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Then an input of 1o1 would be just fine. Oh the funs of user validation :)

Quote:

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Originally Posted by Thantos

But what if you had this:

Code:

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char x;
int y, z;
cin>>y>>x>>z;

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Then an input of 1o1 would be just fine. Oh the funs of user validation :)

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then you could also always have this:

Code:

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int ix,iy;
float fx,fy;
char c;

cin>>ix>>c>>fx>>c>>iy;
cin.ignore(1);
cin>>fy;

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then an input of 1o1.5x3F3.1415 would be fine too...