30 Input/output library [input.output]

As in the case of the inserters, these extractors depend on the locale's num_­get<> object to perform parsing the input stream data. These extractors behave as formatted input functions (as described in [istream.formatted.reqmts]). After a sentry object is constructed, the conversion occurs as if performed by the following code fragment:

using numget = num_get<charT, istreambuf_iterator<charT, traits>>;
iostate err = iostate::goodbit;
use_facet<numget>(loc).get(*this, 0, *this, err, val);
setstate(err);

In the above fragment, loc stands for the private member of the basic_­ios class. [ Note: The first argument provides an object of the istreambuf_­iterator class which is an iterator pointed to an input stream. It bypasses istreams and uses streambufs directly.  — end note ] Class locale relies on this type as its interface to istream, so that it does not need to depend directly on istream.

The conversion occurs as if performed by the following code fragment (using the same notation as for the preceding code fragment):

using numget = num_get<charT, istreambuf_iterator<charT, traits>>;
iostate err = ios_base::goodbit;
long lval;
use_facet<numget>(loc).get(*this, 0, *this, err, lval);
if (lval < numeric_limits<short>::min()) {
  err |= ios_base::failbit;
  val = numeric_limits<short>::min();
} else if (numeric_limits<short>::max() < lval) {
  err |= ios_base::failbit;
  val = numeric_limits<short>::max();
}  else
  val = static_cast<short>(lval);
setstate(err);

The conversion occurs as if performed by the following code fragment (using the same notation as for the preceding code fragment):

using numget = num_get<charT, istreambuf_iterator<charT, traits>>;
iostate err = ios_base::goodbit;
long lval;
use_facet<numget>(loc).get(*this, 0, *this, err, lval);
if (lval < numeric_limits<int>::min()) {
  err |= ios_base::failbit;
  val = numeric_limits<int>::min();
} else if (numeric_limits<int>::max() < lval) {
  err |= ios_base::failbit;
  val = numeric_limits<int>::max();
}  else
  val = static_cast<int>(lval);
setstate(err);

Effects: None. This extractor does not behave as a formatted input function (as described in [istream.formatted.reqmts]).

Returns: pf(*this).308

Effects: Calls pf(*this). This extractor does not behave as a formatted input function (as described in [istream.formatted.reqmts]).

Returns: *this.

Effects: Calls pf(*this).309 This extractor does not behave as a formatted input function (as described in [istream.formatted.reqmts]).

Returns: *this.

Effects: Behaves like a formatted input member (as described in [istream.formatted.reqmts]) of in. After a sentry object is constructed, operator>> extracts characters and stores them into successive locations of an array whose first element is designated by s. If width() is greater than zero, n is width(). Otherwise n is the number of elements of the largest array of char_­type that can store a terminating charT(). n is the maximum number of characters stored.

Characters are extracted and stored until any of the following occurs:

• (8.1)

  n-1 characters are stored;

• (8.2)

  end of file occurs on the input sequence;

• (8.3)

  letting ct be use_­facet<ctype<charT>>(in.getloc()), ct.is(ct.space, c) is true.

operator>> then stores a null byte (charT()) in the next position, which may be the first position if no characters were extracted. operator>> then calls width(0).

If the function extracted no characters, it calls setstate(failbit), which may throw ios_­base​::​​failure ([iostate.flags]).

Returns: in.

Effects: Behaves like a formatted input member (as described in [istream.formatted.reqmts]) of in. After a sentry object is constructed a character is extracted from in, if one is available, and stored in c. Otherwise, the function calls in.setstate(failbit).

Returns: in.

Effects: Behaves as an unformatted input function. If sb is null, calls setstate(failbit), which may throw ios_­base​::​failure ([iostate.flags]). After a sentry object is constructed, extracts characters from *this and inserts them in the output sequence controlled by sb. Characters are extracted and inserted until any of the following occurs:

• (14.1)

  end-of-file occurs on the input sequence;

• (14.2)

  inserting in the output sequence fails (in which case the character to be inserted is not extracted);

• (14.3)

  an exception occurs (in which case the exception is caught).

If the function inserts no characters, it calls setstate(failbit), which may throw ios_­base​::​​failure ([iostate.flags]). If it inserted no characters because it caught an exception thrown while extracting characters from *this and failbit is on in exceptions() ([iostate.flags]), then the caught exception is rethrown.

Returns: *this.