clear the input buffer

in c i would

while(c == getchar()) != '\n');

but how do i do this in c++?

cin.clear();

cin.clear() just clears the errorbit evaluated by cin.good() and cin.fail(). It doesn't clear the input buffer. In short there is no great way to clear the input buffer that I know of. Some people usie cin.ignore() with large ints. Some people use a loop reading all data in buffer to dummy variable and ignore it (they address the buffer directly with something like rdbuf()).

you were close....
this is one way....

while(getchar() != '\n'); // notice semi colon

Code:

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while (cin.rdbuf()->in_avail() > 0) cin.get();

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Hammer, that code doesn't work in CodeWarrior C++.

Works fine in MSVC++, though.

Quote:

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Originally posted by elad
In short there is no great way to clear the input buffer that I know of.

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That's the only bad thing about C++, IMO.

Quote:

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Originally posted by Sang-drax
Hammer, that code doesn't work in CodeWarrior C++.

Works fine in MSVC++, though.

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... and there was me trusting one of your previous posts ;) (yes, I cut paste that line from here)

Heh, at that time I thought my method was good.

I discovered the CodeWarrior problem when I tried it yesterday.

I don't know what the standard has to say about in_avail(), but in CW it always seems to return 0.

But there must be some way to clear the buffer!

Well, you can always stick with cin.ingore

>cin.ignore(INT_MAX, '\n')

I think one of the problems is different i/o operations rely on the state being in a certain condition (such as whether a '\n' is already present in the buffer or not). But isn't

while ((c = cin.get())!='\n');

the equivilent of

while((c = getchar()) != '\n');

Quote:

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Originally posted by Hammer
Well, you can always stick with cin.ingore

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How to implement func() so that cin ALWAYS is empty before reading in var2?

Code:

---

void func();

int main()
{

  if (randomcondition)
  {
    int var;
    cout << "var:";
    cin >> var;
  }

  func();

  int var2
  cout << "var2";
  cin >> var2;
}

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Assuming the in_avail() method is not standard, here's an imperfect version:

Code:

---

void func()
{
    if (cin.eof())
        cin.clear();
    else if (cin.fail())
    {
        cin.clear();
        cin.ignore(10000,'\n');   
    }
    else if (cin.bad())
        cin.clear();
}

---

It won't work if the user enters "123 456" in the first cin>>

Quote:

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Originally posted by JoeSixpack
But isn't

while ((c = cin.get())!='\n');

the equivilent of

while((c = getchar()) != '\n');

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are they equivilent?