#20107: Add optional gap3_jm package
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       Reporter:  stumpc5            |        Owner:
           Type:  enhancement        |       Status:  needs_work
       Priority:  major              |    Milestone:  sage-7.1
      Component:  packages:          |   Resolution:
  experimental                       |    Merged in:
       Keywords:  gap3, optional     |    Reviewers:
  package                            |  Work issues:
        Authors:  Christian Stump    |       Commit:
Report Upstream:  N/A                |  ec01e305ae9dd29b90234183ad7b309172646ea6
         Branch:  u/stumpc5/20107    |     Stopgaps:
   Dependencies:                     |
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Comment (by jmichel):

 Replying to [comment:113 dimpase]:
 > Replying to [comment:112 jmichel]:
 > > Replying to [comment:107 stumpc5]:
 > > > Replying to [comment:104 dimpase]:
 > > > > IMvHO it is better to invest time into porting chevie to GAP4 than
 into this...
 > > >
 > > > Jean Michel clearly has a meaning about that, after not doing it in
 20 years...
 > >
 > > I asked for a new password, so I can reply myself.
 > > I examined several times over the past 15 years a possible port of
 Chevie to GAP4.
 > > My conclusions:
 > > -it would be as much work as rewriting everything completely,
 >
 > Really? What are the crucial features you miss in GAP4 that are used in
 Chevie?
 >
 > I use GAP (and hack a bit on it, too) for some 23 years, and I saw
 transitions of packages like GRAPE from GAP3 to GAP4 without too much
 pain. You don't need to make use of new GAP4 features, good old records
 are still there.

 First, I should tell you that I looked at the problem of porting chevie
 with Frank Luebeck, and he agrees with my conclusions. This is not the
 place/time to give a detailed answer, but roughly:
 chevie contains about a hundred different types of mathematical objects,
 which in gap3 are just records with a certain .operations fields, and
 methods are just functions which dispatch based
 on various features, and then call the appropriate component field of the
 .operations record. The way a new type of objects or a method is
 constructed in GAP4 is completely different. The worst of it is that any
 effort (which has been done by various people) to port any substantial
 part of chevie (a few hundred lines) to gap4 almost always produce longer
 and uglier code.

 > I (half)ported ve and anusq to GAP4, it was certainly not very trivial,
 but quite doable and quick.

 I wanted to thank you for your modifications to the makefile in ve (It
 seems you did not change anything else?). It also seems that you changed a
 few lines in one gap function in anusq to translate it to gap4. I am sorry
 to say that this is completely trivial compared to rewriting the several
 hundred thousand lines of chevie.

--
Ticket URL: <http://trac.sagemath.org/ticket/20107#comment:114>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
and MATLAB

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