std::basic_ios<CharT,Traits>::clear - cppreference.com (original) (raw)

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 | std::ios_base::badbit is assigned.

[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 #include 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] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.