Note: This paper was adopted into draft C++14 on Saturday at the Bristol UK ISO C++ meeting.

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Document number: N3672

Date: 2013-04-19

A proposal to add a utility class to represent optional objects (Revision 4)

by Fernando Cacciola and Andrzej Krzemieński

Excerpt:

The basic usage of optional<T> can be illustrated with the following example.

optional<int> str2int(string);    // converts int to string if possible

int get_int_form_user()
{
  string s;

  for (;;) {
    cin >> s;
    optional<int> o = str2int(s); // 'o' may or may not contain an int
    if (o) {                      // does optional contain a value?
      return *o;                  // use the value
    }
  }
}