stdcinclear

stdcinclear is a colloquial term used in C++ programming to refer to the common technique of resetting the standard input stream (std::cin) after an input error and discarding the remainder of the current line. It is not a function provided by the C++ standard library; rather, it describes a pair of operations that are often used together to recover from invalid user input.

The typical sequence involves two steps. First, std::cin.clear() is called to reset the stream's error flags (such as failbit or badbit) so that subsequent input operations can proceed. Second, the remaining characters on the current line are discarded, usually with std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'). This requires including the header <limits> and ensures that any stray input does not affect the next read operation.

This technique is commonly employed after input extraction fails, for example when a user enters non-numeric data where a number is expected. It helps bring the program back to a known good state so that further prompts can be processed cleanly. It is important to note that stdcinclear specifically applies to std::cin; if other input streams are used, similar steps may be necessary for those streams as well.

Alternatives and complements include repeatedly prompting for input within a loop and validating the input before accepting it, or using input handling utilities that encapsulate the clearing and discarding logic. See also: std::cin, std::ignore, std::limits, and iostream.

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