A very simple program about "cin", What's the matt

[Yile]

Code: Select all

#include <iostream.h>
void main(){
  int a;
  while(true){
    cin>>a;
    if(cin.fail()){
      cout<<"error"<<endl;
      cin.clear();
    }
    else{
      break;
    }
  }
}

When the input is

Code: Select all

a

Why the output is

Code: Select all

error
error
error
error
error
error
error
error
error
error
error
...

I do use the cin.clear()! But why still the cin doesn't work.
Why?????

[sahand]

Use this:

Code: Select all

#include <iostream.h>
void main(){
  int a;
  while(true){
    cin>>a;
    if(cin.fail()){
      cout<<"error"<<endl;
      cin.clear();
      break;
    }
    else{
      break;
    }
  }
}

cin.clear() does not do what you think it does. read the documentations.

[CDiMa]

I do use the cin.clear()! But why still the cin doesn't work.
Why?????

Clearing cin simply resets the error flag but doesn't remove the offending char from the input stream. You have to cin.ignore(...) to go past it and resume reading...

Ciao!!!

[Yile]

Thank you very much!