Each formatted output function begins execution by constructing an object of class
sentry.If this object returns
true
when converted to a value of type
bool,
the function endeavors
to generate the requested output
.If the generation fails, then the formatted output function does
setstate(ios_base::failbit),
which might throw an exception
.If an exception is thrown during output, then
ios::badbit
is turned on
in
*this's
error state
.If
(exceptions()&badbit) != 0
then the exception is rethrown
.Whether or not an exception is thrown, the
sentry
object is destroyed before leaving the formatted output function
.If no exception is thrown, the result of the formatted output function
is
*this.If a formatted output function of a stream
os determines
padding, it does so as
follows
.Given a
charT character sequence
seq where
charT is the character type of the stream, if
the length of
seq is less than
os.width(), then enough copies of
os.fill() are added to this sequence as necessary to pad to a
width of
os.width() characters
.If
(os.flags() & ios_base::adjustfield) == ios_base::left is
true, the fill characters are placed
after the character sequence; otherwise, they are placed before the
character sequence
.