27 Input/output library [input.output]

27.7 Formatting and manipulators [iostream.format]

27.7.2 Input streams [input.streams]

27.7.2.2 Formatted input functions [istream.formatted]

27.7.2.2.2 Arithmetic extractors [istream.formatted.arithmetic]

operator>>(unsigned short& val); operator>>(unsigned int& val); operator>>(long& val); operator>>(unsigned long& val); operator>>(long long& val); operator>>(unsigned long long& val); operator>>(float& val); operator>>(double& val); operator>>(long double& val); operator>>(bool& val); operator>>(void*& val);

1

As in the case of the inserters, these extractors depend on the locale's num_get<> ([locale.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:

typedef num_get< charT,istreambuf_iterator<charT,traits> > numget;
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.

operator>>(short& val);

2

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

typedef num_get<charT,istreambuf_iterator<charT,traits> > numget;
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);

operator>>(int& val);

3

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

typedef num_get<charT,istreambuf_iterator<charT,traits> > numget;
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);