Re: [boost] dynamic_bitset request

From: Victor A. Wagner, Jr. (vawjr_at_[hidden])
Date: 2002-07-30 22:23:35

Ok... my schedule precludes this from happening before the weekend unless 
some unusual things happen at my client's.
I'll see where I can get by then.
At Monday 2002/07/29 11:11, you wrote:

>That's a good start. Why don't you finish fleshing this out in C++.
>
>BTW, it would be nice if I could implement this "set" interface for
>dynamic_bitset without conflicting with current operations. For example,
>operator<= is already taken to mean lexicographically less or equal.
>However, if that leads to too much ugliness, we can always go the adaptor
>route.
>
>Also, we'd probably want the combination assignment operators, such as |=
>and &= that are already in std::bitset and dynamic_bitset.
>
>Cheers,
>Jeremy
>
>
>On Mon, 29 Jul 2002, Victor A. Wagner, Jr. wrote:
>vawjr> It seems to me that if we're seriously going to consider adding "set
>vawjr> semantics" to some set (pun intended) of classes; we could do a lot 
>worse
>vawjr> than look at a language that actually had set as part of its 
>fundamental
>vawjr> design (Pascal).
>vawjr>
>vawjr> IIRC Pascal (and I belive, Modula) sets supported the following 
>operators
>vawjr> -(unary) not (flip all truth elements in the set)
>vawjr> +       union (C++ would probably use |)
>vawjr> *       intersection (C++ would probably use &)
>vawjr> -       difference .... a - b is equivalent to   a * (-b)
>vawjr> xor(^)  bit for bit ^
>vawjr> in      set membership (usage:  if y in myset then.....)
>vawjr> <=      proper subset
>vawjr>  >=      proper superset
>vawjr> =       equality (in C++ we use ==)
>vawjr> <>      inequality (in C++ we use !=)
>vawjr>
>vawjr> all sets were "bounded" i.e. had a defined lower and upper bound of
>vawjr> possible members.
>vawjr>
>vawjr> IMO, there are good reasons to provide operators instead of just 
>standard
>vawjr> functions  especially if an algebraic notation already exists for the
>vawjr> concept.  for example, it's a _lot_ easier to write
>vawjr>
>vawjr> a = b ^ c;
>vawjr>
>vawjr> than
>vawjr>
>vawjr> a.clear();
>vawjr> set_symmetric_difference(b.begin(), b.end(), c.begin(), c.end(),
>vawjr> back_inserter(a));
>vawjr> //or whatever one would have to write to get the equivalent of
>vawjr> back_inserter() for a set.
>vawjr>
>vawjr>
>vawjr> At Monday 2002/07/29 08:37, you wrote:
>vawjr> >Hi Dave,
>vawjr> >
>vawjr> >On Sat, 27 Jul 2002, David Abrahams wrote:
>vawjr> >dave> How about operator-() for set difference? That seems like an 
>obvious
>vawjr> >dave> need...
>vawjr> >
>vawjr> >One small problem with this is that one metaphor for dynamic_bitset is
>vawjr> >that of a big integer. All the current operators are borrowed from the
>vawjr> >builtin operators on an unsigned int. The problem is that operator-
>vawjr> >doesn't mean set difference for unsigned int, but subtraction.
>vawjr> >
>vawjr> >One idea I've had in the past is to create a "Set"  concept, which 
>would
>vawjr> >include things like union, difference, intersection, etc.  For the 
>general
>vawjr> >idea of what the interface would look like, see:
>vawjr> >
>vawjr> >boost/graph/detail/set_adaptor.hpp
>vawjr> >
>vawjr> >Under this framework, it would make sense to implement this "Set"
>vawjr> >interface for dynamic_bitset, in addition to other classes that can be
>vawjr> >thought of as implementing sets, such as std::set.
>vawjr> >
>vawjr> >Cheers,
>vawjr> >Jeremy
>vawjr> >
>vawjr> >
>vawjr> >----------------------------------------------------------------------
>vawjr> >  Jeremy Siek                          http://php.indiana.edu/~jsiek/
>vawjr> >  Ph.D. Student, Indiana Univ. B'ton   email: jsiek_at_[hidden]
>vawjr> >  C++ Booster (http://www.boost.org)   office phone: [phone]
>vawjr> >----------------------------------------------------------------------
>vawjr> >
>vawjr> >
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>vawjr> Victor A. Wagner Jr.      http://rudbek.com
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>----------------------------------------------------------------------
>  Jeremy Siek                          http://php.indiana.edu/~jsiek/
>  Ph.D. Student, Indiana Univ. B'ton   email: jsiek_at_[hidden]
>  C++ Booster (http://www.boost.org)   office phone: [phone]
>----------------------------------------------------------------------
>
>
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Victor A. Wagner Jr.      http://rudbek.com
PGP RSA fingerprint = 4D20 EBF6 0101 B069 3817 8DBF C846 E47A
PGP D-H fingerprint = 98BC 65E3 1A19 43EC 3908 65B9 F755 E6F4 63BB 9D93
The five most dangerous words in the English language:
               "There oughta be a law"