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std::basic_ios<CharT,Traits>::clear

From cppreference.com
< cpp‎ | io‎ | basic ios
 
 
 
 

Sets the stream error state flags by assigning them the value of state. By default, assigns std::ios_base::goodbit which has the effect of clearing all error state flags.

If rdbuf() is a null pointer (i.e. there is no associated stream buffer), then state | badbit is assigned.

Contents

[edit] Parameters

state - new error state flags setting. It can be a combination of the following constants:
Constant Explanation
goodbit no error
badbit irrecoverable stream error
failbit input/output operation failed (formatting or extraction error)
eofbit associated input sequence has reached end-of-file


[edit] Return value

(none)

[edit] Exceptions

If the new error state includes a bit that is also included in the exceptions() mask, throws an exception of type failure.

[edit] Example

clear() without arguments can be used to unset the failbit after unexpected input; for std::cin.putback(c) see ungetc.

#include <iostream>
#include <string>
 
int main()
{
    for (char c : {'\n', '4', '1', '.', '3', '\n', 'Z', 'Y', 'X'})
        std::cin.putback(c); // emulate user's input (not portable: see ungetc Notes)
 
    double n;
    while( std::cout << "Please, enter a number: " && ! (std::cin >> n) )
    {
        std::cin.clear();
        std::string line;
        std::getline(std::cin, line);
        std::cout << line << "\nI am sorry, but '" << line << "' is not a number\n";
    }
    std::cout << n << "\nThank you for entering the number " << n << '\n';
}

Output:

Please, enter a number: XYZ
I am sorry, but 'XYZ' is not a number
Please, enter a number: 3.14
Thank you for entering the number 3.14

[edit] See also

sets state flags
(public member function) [edit]
returns state flags
(public member function) [edit]