C++ concepts: UnformattedInputFunction
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                    [edit] Requirements
An UnformattedInputFunction is a stream input function that performs the following:
-  Constructs an object of type basic_istream::sentry with automatic storage duration and with the noskipwsargument set to true, which performs the following
-  if eofbit or badbit are set on the input stream, sets the failbitas well, and if exceptions on failbit are enabled in this input stream's exception mask, throws ios_base::failure.
- flushes the tie()'d output stream, if applicable
 
-  if eofbit or badbit are set on the input stream, sets the 
-  Checks the status of the sentry by calling sentry::operator bool(), which is equivalent to basic_ios::good.
- If the sentry returned false or sentry's constructor threw an exception:
- sets the number of extracted characters (gcount) in the input stream to zero
-  if the function was called to write to an array of CharT, writesCharT()(the null character) to the first location of the array
 
- If the sentry returned true, performs the input as if by calling rdbuf()->sbumpc() or rdbuf()->sgetc().
-  if the end of the stream is reached (the call to rdbuf()->sbumpc() or rdbuf()->sgetc() returns Traits::eof(), sets eofbit. If exceptions on eofbit are enabled in this stream's exception mask, throws ios_base::failure.
-  if an exception is thrown during input, sets badbitin the input stream. If exceptions on badbit are enabled in this stream's exception mask, the exception is also rethrown.
- If no exception was thrown during input, sets the number of extracted characters (gcount) in the input stream.
 
-  if the end of the stream is reached (the call to rdbuf()->sbumpc() or rdbuf()->sgetc() returns Traits::eof(), sets 
- In any event, whether terminating by exception or returning, the sentry's destructor is called before leaving this function.
[edit] Standard library
The following standard library functions are UnformattedInputFunctions.
- std::getline, except that it does not modify gcount.
- basic_istream::operator>>(basic_streambuf*)
- basic_istream::get
- basic_istream::getline
- basic_istream::ignore
- basic_istream::peek
- basic_istream::read
- basic_istream::readsome
-  basic_istream::putback, except that it first clears eofbit
-  basic_istream::unget, except that it first clears eofbit
- basic_istream::sync, except that it does not modify gcount
- basic_istream::tellg, except that it does not modify gcount
-  basic_istream::seekg, except that it first clears eofbitand does not modify gcount
- std::ws, except that it does not modify gcount


