The [a, b .. c] in GAP means { a, b, 2b-a, ..., a+i(b-a), ..., c } in
mathematics.GAP is not exactly a programming language; there are *objects* and their *representations*, and GAP is allowed to change a representation to another one in case it's provably more efficient (i.e. there are more or faster algorithms for it). Hope this helps, Laurent On Sun, Feb 10, 2013 at 5:58 AM, Dmitrii (Dima) Pasechnik <d...@ntu.edu.sg>wrote: > On 10 February 2013 10:52, Gordon Royle <gordon.ro...@uwa.edu.au> wrote: > > Well, thanks for the feedback, but I remain somewhat confused… > > I think this is definitely a bug, and must be fixed ASAP... > > Best, > Dima > > > > > Firstly, why does GAP unilaterally choose to change the format .. .the > program is simply a recursive program with a single Print statement, and > yet the output changes format , and then changes back again, without me > asking it to... > > > > [ 1, 5, 51 ] > > [ 1, 6 .. 11 ] > > [ 1, 6, 12 ] > > > > > > > > > > Secondly, why is > > > > 6 .. 11 > > > > the "range representation" for > > > > 6, 11 > > > > In most languages that support it, the ".." means "everything from the > first to the last (or perhaps the first to the last-minus-one)" > > > > > > Actually, it means the same in GAP too: > > > > gap> for x in [6 .. 11] do > >> Print(x," "); > >> od; > > 6 7 8 9 10 11 > > > > So, naively I would expect > > > > [1, 6 .. 11] > > > > to be a fancy way of saying > > > > [1, 6, 7, 8, 9, 10, 11] > > > > > > But it's not: > > > > gap> for x in [1, 6 .. 11] do > >> Print(x," "); > >> od; > > 1 6 11 > > > > > > It seems dangerous to me to have the expression a .. b mean something > different to (a) other uses in the same language, (b) mathematical usage > and (c ) other programming languages. > > > > > > Thirdly, why has this happened RIGHT NOW, when I've been using this > program for years without ever seeing anything like this before… > > > > > > Thanks again > > > > Gordon > > > > > > > > Professor Gordon Royle > > School of Mathematics and Statistics > > University of Western Australia > > gordon.ro...@uwa.edu.au<mailto:gordon.ro...@uwa.edu.au> > > > > > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > Forum mailing list > > Forum@mail.gap-system.org > > http://mail.gap-system.org/mailman/listinfo/forum > > CONFIDENTIALITY:This email is intended solely for the person(s) named and > may be confidential and/or privileged.If you are not the intended > recipient,please delete it,notify us and do not copy,use,or disclose its > content. > > Towards A Sustainable Earth:Print Only When Necessary.Thank you. > > _______________________________________________ > Devel mailing list > de...@gap-system.org > http://mail.gap-system.org/mailman/listinfo/devel > -- Prof. Dr. Laurent Bartholdi \ laurent.bartholdi<at>gmail<dot>com G.-A. Universität zu Göttingen \ Phone: +49 551 39 7826 Bunsenstraße 3-5 \ Secr: +49 551 39 7752 D-37073 Göttingen, Germany \ Fax: +49 551 39 22674 _______________________________________________ Forum mailing list Forum@mail.gap-system.org http://mail.gap-system.org/mailman/listinfo/forum
