CharRepresentationWords( rep , elts )
given a list rep of matrices corresponding to generators and a list elts of words in the generators it returns the list of traces of the corresponding representation on the elements in elts.
gap> H := Hecke(CoxeterGroup( "F", 4 ));; gap> r := ChevieClassInfo( Group( H ) ).classtext;; gap> t := HeckeReflectionRepresentation( H );; gap> CharRepresentationWords( t, r ); [ 4, -4, 0, 1, -1, 0, 1, -1, -2, 2, 0, 2, -2, -1, 1, 0, 2, -2, -1, 1, 0, 0, 2, -2, 0 ]
GAP 3.4.4