[GAP Forum] IsomorphismTypeFiniteSimpleGroup results in an error.

[Alexander Konovalov]

Hello,

The correct name of this function is IsomorphismTypeInfoFiniteSimpleGroup. Using the input from the question, it produces the expected result:

gap> IsomorphismTypeInfoFiniteSimpleGroup( f );
rec( name := "A(1,7) = L(2,7) ~ B(1,7) = O(3,7) ~ C(1,7) = S(2,7) ~ 2A(1,7) = U(2,7) ~ A(2,2) = L(3,2)", parameter := [ 2, 7 ], series := "L" )
gap> 

I don't know for sure if this is a typo or the function was renamed in GAP, but it could be the former - I can see IsomorphismTypeInfoFiniteSimpleGroup mentions dated back to 2003. It seems that the document you mention is dated 2002 and refers to GAP 4.2, so it is plausible that some examples are not reproducible and should be adapted to GAP 4.7. Most of such cases are covered in the Chapter "Replaced and Removed Command Names" of the GAP Reference manual (http://www.gap-system.org/Manuals/doc/ref/chap77.html), and in doubt please just ask.

Best wishes
Alexander

P.S. It should be possible to produce GAP teaching materials in various languages using GAPDoc package, and run automated tests of their examples to check that they all still work with new versions of GAP. This will simplify their maintenance and their upgrading after major GAP releases.


On 15 Sep 2014, at 05:06, buynnnmmm1 at yahoo.co.jp wrote:

> 
> 
> Hello.
> It is an error to try to do in the Gap4.7.5 IsomorphismTypeFiniteSimpleGroup of P.27 of http://sci.kj.yamagata-u.ac.jp/~waki/jpn/gap_docs/take_gap.pdf. 
> 
> gap> s8:=Group((1,2),(1,2,3,4,5,6,7,8));
> Group([ (1,2), (1,2,3,4,5,6,7,8) ])
> gap> a8:=CommutatorSubgroup(s8,s8);
> Group([ (1,3,2), (2,4,3), (2,3)(4,5), (2,4,6,5,3), (2,5,3)(4,7,6), (2,3)(5,6,8,7) ])
> gap> elab:= Group( (1,2)(3,4)(5,6)(7,8), (1,3)(2,4)(5,7)(6,8),  (1,5)(2,6)(3,7)(4,8));
> Group([ (1,2)(3,4)(5,6)(7,8), (1,3)(2,4)(5,7)(6,8), (1,5)(2,6)(3,7)(4,8) ])
> gap> norm:= Normalizer( a8, elab );;
> gap> hom:=NaturalHomomorphismByNormalSubgroup( norm , elab );
> <action epimorphism>
> gap> f := Image( hom );
> Group([ (), (), (), (4,5)(6,7), (4,6)(5,7), (2,3)(6,7), (2,4)(3,5), (1,2)(5,6) ])
> gap> IsomorphismTypeFiniteSimpleGroup( f );
> Error, Variable: 'IsomorphismTypeFiniteSimpleGroup' must have a value
> not in any function at line 16 of *stdin*
> 
> 
> However, I should be able to get the following output: In P.27 of this PDF file.
> 
> gap> IsomorphismTypeFiniteSimpleGroup( f );
> rec( series := "L", parameter := [ 2, 7 ],
> name := "A(1,7) = L(2,7) ~ B(1,7) = O(3,7) ~ C(1,7) = S(2,7) ~
> 2A(1,7) = U(2\
> ,7) ~ A(2,2) = L(3,2)" )
> 
> 
> Could you tell me how to solve this problem? 
> How to use or probably been changed in accordance with the version up? 
> Or bug or probably are mixedin Gap version up?
> 
> 
>                                   buynnnmmm1
> 
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