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Dear Mrs. and Mr. Forum,

Kay Magaard writes

Using the 3.1 version of GAP I noticed the following:

On the one hand I get:

gap> A:=CharTable("Symmetric",6);;

gap> PermChars(A,6);

[ ]

gap> PermChars(A);

Error, Variable: 'mino' must have a value at

for <var> in [ maxu .. mino ] ... in

suche( 2 ) called from

Permut( tbl, arec ) called from

PermChars( A ) called from

main loop

brk> quit;On the other hand I get:

gap> A:=CharTable("S6");; gap> PermChars(A,6); [ [ 6, 2, 0, 3, 0, 1, 0, 4, 2, 0, 1 ], [ 6, 2, 3, 0, 0, 1, 4, 0, 2, 1, 0 ] ] gap>Does a generic character table need to be reordered before

asking for permutaion characters?

If so how?

As Kay suspected and Goetz Pfeiffer told in his message to the forum,

the reason for the error message and the incorrect answer in the case

of the generic table is that the trivial character is not the first

one in the list of irreducibles. Of course this is a bug (in fact there

are two bugs, since 'PermChars' calls different algorithms for the

calculation of all permutation character candidates or of all of a

prescribed degree), since according to the manual (section 'Conventions'),

no program shall expect the trivial character to be the first one.

These bugs will be fixed in the next upgrade. In the current version of

GAP, the user should move the trivial character to the first position when

using 'PermChars', as proposed by Goetz.

Kind regards

Thomas Breuer

(sam@ernie.math.rwth-aachen.de)

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