cpp/string/basic string/operator ltltgtgt

@1@ Behaves as a. After constructing and checking the sentry object, determines the output format padding.

Then inserts each character from the resulting sequence (the contents of  plus padding) to the output stream  as if by calling, where  is

Finally, calls to cancel the effects of std, if any.

@2@ Behaves as a. After constructing and checking the sentry object, which may skip leading whitespace, first clears with, then reads characters from  and appends them to  as if by , until one of the following conditions becomes true:
 * characters are read, where is  if, otherwise  is ,
 * the end-of-file condition occurs in the stream, or
 * is for the next character  in  (this whitespace character remains in the input stream).

If no characters are extracted then std is set on, which may throw std.

Finally, calls to cancel the effects of std, if any.

Exceptions
@1@ May throw std if an exception is thrown during output.

@2@ May throw std if no characters are extracted from (e.g. the stream is at end of file, or consists of whitespace only), or if an exception is thrown during input.

Return value
@1@ @2@