> < ^ Date: Tue, 20 Jan 1998 12:30:03 +0000 (GMT)
> < ^ From: Alexander Hulpke <hulpke@math.colostate.edu >
< ^ Subject: Re: Move List

Dear GAP-Forum,

What is the GAP3.4.4 function that returns a list of the points moved by a
permutation?

J"urgen Ecker pointed out already that there is no such function in GAP344.
In GAP4 there is a function which does essentially this and I append
the (slightly modified for GAP3) code for it. It takes a list of
permutations and determines all points moved by its elements.

Best regards,

Alexander Hulpke

```#############################################################################
##
#F  MovedPointsPerms( <gens> )  . . . . . . . .  moved points of permutations
##
MovedPointsPerms := function( gens )
local   mov,  gen,  pnt;

mov := [  ];
for gen  in gens  do
if gen <> ()  then
for pnt  in [ SmallestMovedPointPerm( gen ) ..
LargestMovedPointPerm( gen ) ]  do
if pnt ^ gen <> pnt  then
mov[ pnt ] := pnt;
fi;
od;
fi;
od;
return Set( mov );
end;
```

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