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] ExceptionsIf the new error state includes a bit that is also included in the exceptions() mask, throws an exception of type failure.
[edit] Exampleclear() 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] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior LWG 412 C++98 an excption would be thrown if the current error stateRetroSearch is an open source project built by @garambo | Open a GitHub Issue
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