No-method-found in WedderburnDecomposition

Reported by Andreas Bächle and communicated to me by @angeldelriomateos:

The problem is with the function WedderburnDecomposition. If you want to apply this function to a group algebra A over an ANF field which has been defined before launching wedderga then an error message occurs. However if you call the wedderga function IsSemisimpleANFGroupAlgebra with A as argument then WedderburnDecomposition(A) works.

However if you define the group algebra A after launching wedderga then there is no problem.

The strange thing is that the same problem does not happen with the function WedderburnDecompositionInfo which basically does the same as WedderburnDecomposition but show different information or with the function WeddDecomp which is the function call by both of them (namely both WedderburnDecomposition and WedderburnDecompositionInfo are dully functions calling to WeddDecomp).

 ┌───────┐   GAP 4.8.10, 15-Jan-2018, build of 2018-04-26 09:19:25 (CEST)
 │  GAP  │   https://www.gap-system.org
 └───────┘   Architecture: x86_64-apple-darwin17.5.0-gcc-default64
 Libs used:  gmp
 Loading the library and packages ...
 Components: trans 1.0, prim 2.1, small* 1.0, id* 1.0
 Packages:   AClib 1.2, Alnuth 3.1.0, AtlasRep 1.5.1, AutPGrp 1.8, 
             Browse 1.8.7, CRISP 1.4.4, Cryst 4.1.13, CrystCat 1.1.6, 
             CTblLib 1.2.2, FactInt 1.6.0, FGA 1.3.1, GAPDoc 1.6.1, IO 4.5.1, 
             IRREDSOL 1.4, LAGUNA 3.8.0, Polenta 1.3.8, Polycyclic 2.11, 
             RadiRoot 2.7, ResClasses 4.7.1, Sophus 1.23, SpinSym 1.5, 
             TomLib 1.2.6, utils 0.49
 Try '??help' for help. See also '?copyright', '?cite' and '?authors'
gap> QG := GroupRing(Rationals,SymmetricGroup(3));
<algebra-with-one over Rationals, with 2 generators>
gap> LoadPackage("wedderga");
#I  You may wish to install the xgap package
#I  and enjoy the graphic capabilities of SONATA.

  ___________________________________________________________________________
 /        ___
||       /   \                 /\    Version2.8
||      ||   ||  |\    |      /  \               /\       Erhard Aichinger
 \___   ||   ||  |\\   |     /____\_____________/__\      Franz Binder
     \  ||   ||  | \\  |    /      \     ||    /    \     Juergen Ecker
     ||  \___/   |  \\ |   /        \    ||   /      \    Peter Mayr
     ||          |   \\|  /          \   ||               Christof Noebauer
 \___/           |    \|                 ||

 System    Of   Nearrings     And      Their Applications
 Info: http://www.algebra.uni-linz.ac.at/Sonata/

   ____                          |
  /            \           /   --+--  Version 3.13
 /      |    | |\\        //|    |
|    _  |    | | \\      // |     GUAVA Group
|     \ |    | |--\\    //--|     
 \     ||    | |   \\  //   |     
  \___/  \___/ |    \\//    |      

─────────────────────────────────────────────────────────────────────────────
Loading  Wedderga 4.9.1 (Wedderga)
by Gurmeet Kaur Bakshi (gkbakshi@pu.ac.in),
   Osnel Broche Cristo (osnel@ufla.br),
   Allen Herman (aherman@math.uregina.ca),
   Alexander Konovalov (https://alexk.host.cs.st-andrews.ac.uk),
   Sugandha Maheshwary (sugandha@iisermohali.ac.in),
   Gabriela Olteanu (http://math.ubbcluj.ro/~olteanu),
   Aurora Olivieri (olivieri@usb.ve),
   Angel del Rio (http://www.um.es/adelrio), and
   Inneke Van Gelder (http://homepages.vub.ac.be/~ivgelder).
Homepage: https://gap-packages.github.io/wedderga
─────────────────────────────────────────────────────────────────────────────
true
gap> WedderburnDecomposition(QG);
Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 1st choice method found for `WedderburnDecomposition' on 1 arguments called from
<function "HANDLE_METHOD_NOT_FOUND">( <arguments> )
 called from read-eval loop at line 3 of *stdin*
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue
brk> IsSemisimpleANFGroupAlgebra(QG);
true
brk> quit;
gap> WedderburnDecomposition(QG);
[ Rationals, Rationals, <crossed product with center Rationals over CF(
    3) of a group of size 2> ]

and

 ┌───────┐   GAP 4.8.10, 15-Jan-2018, build of 2018-04-26 09:19:25 (CEST)
 │  GAP  │   https://www.gap-system.org
 └───────┘   Architecture: x86_64-apple-darwin17.5.0-gcc-default64
 Libs used:  gmp
 Loading the library and packages ...
Lo Components: trans 1.0, prim 2.1, small* 1.0, id* 1.0
 Packages:   AClib 1.2, Alnuth 3.1.0, AtlasRep 1.5.1, AutPGrp 1.8, 
             Browse 1.8.7, CRISP 1.4.4, Cryst 4.1.13, CrystCat 1.1.6, 
             CTblLib 1.2.2, FactInt 1.6.0, FGA 1.3.1, GAPDoc 1.6.1, IO 4.5.1, 
             IRREDSOL 1.4, LAGUNA 3.8.0, Polenta 1.3.8, Polycyclic 2.11, 
             RadiRoot 2.7, ResClasses 4.7.1, Sophus 1.23, SpinSym 1.5, 
             TomLib 1.2.6, utils 0.49
 Try '??help' for help. See also '?copyright', '?cite' and '?authors'
gap> LoadPackage("wedderga");
#I  You may wish to install the xgap package
#I  and enjoy the graphic capabilities of SONATA.

  ___________________________________________________________________________
 /        ___
||       /   \                 /\    Version2.8
||      ||   ||  |\    |      /  \               /\       Erhard Aichinger
 \___   ||   ||  |\\   |     /____\_____________/__\      Franz Binder
     \  ||   ||  | \\  |    /      \     ||    /    \     Juergen Ecker
     ||  \___/   |  \\ |   /        \    ||   /      \    Peter Mayr
     ||          |   \\|  /          \   ||               Christof Noebauer
 \___/           |    \|                 ||

 System    Of   Nearrings     And      Their Applications
 Info: http://www.algebra.uni-linz.ac.at/Sonata/

   ____                          |
  /            \           /   --+--  Version 3.13
 /      |    | |\\        //|    |
|    _  |    | | \\      // |     GUAVA Group
|     \ |    | |--\\    //--|     
 \     ||    | |   \\  //   |     
  \___/  \___/ |    \\//    |      

─────────────────────────────────────────────────────────────────────────────
Loading  Wedderga 4.9.1 (Wedderga)
by Gurmeet Kaur Bakshi (gkbakshi@pu.ac.in),
   Osnel Broche Cristo (osnel@ufla.br),
   Allen Herman (aherman@math.uregina.ca),
   Alexander Konovalov (https://alexk.host.cs.st-andrews.ac.uk),
   Sugandha Maheshwary (sugandha@iisermohali.ac.in),
   Gabriela Olteanu (http://math.ubbcluj.ro/~olteanu),
   Aurora Olivieri (olivieri@usb.ve),
   Angel del Rio (http://www.um.es/adelrio), and
   Inneke Van Gelder (http://homepages.vub.ac.be/~ivgelder).
Homepage: https://gap-packages.github.io/wedderga
─────────────────────────────────────────────────────────────────────────────
true
gap> QG:=GroupRing(Rationals,SymmetricGroup(3));      
<algebra-with-one over Rationals, with 2 generators>
gap> WedderburnDecomposition(QG);
[ Rationals, Rationals, <crossed product with center Rationals over CF(
    3) of a group of size 2> ]

gap-packages / wedderga

No-method-found in WedderburnDecomposition #49