From: Neal Becker 10 January 2008 12:16 To: boost@lists.boost.org Subject: Re: [boost] bounded_iterator
Sounds interesting.
What is the point of unspecified_bool_helper?
It's generally agreed that unspecified_bool_type should be a pointer-to-member of some class. unspecified_bool_helper is that class. If you use bounded_iterator as the class, then you have to consider what the "true" value is going to be. You either have to point at a member which you have introduced for the purpuse (which adds space overhead), or you have to point at an existing member - but once you have pointed at an existing member, then people can return access that member via the pointer. So if unspecified_bool_helper was declared as: typedef base_iterator bounded_iterator::*unspecified_bool_type; (which avoids the extra helper class), then Machiavelli could write: bounded_iterator::*base_iterator pm = it; it.*pm = new_end; I can't immediately see how Murphy could come to grief, but given his ingenuity, there may be a way. Using unspecified_bool_helper, there cannot be a problem. -- Martin Bonner Senior Software Engineer/Team Leader PI SHURLOK LTD Telephone: +44 1223 441434 / 203894 (direct) Fax: +44 1223 203999 Email: martin.bonner@pi-shurlok.com www.pi-shurlok.com disclaimer