HeckeCharValues( T [,irreds])
T is  an element of an  Iwahori-Hecke algebra  (expressed in any basis)
and irreds is a set of irreducible characters of  the algebra (given as
vectors).  HeckeCharValues   returns the  values  of  irreds   on the
element T (the method used is to convert to the T basis, and then use
HeckeClassPolynomials).  If irreds is not given, all character values
are returned.
    gap> q := X( Rationals );; q.name := "q";;
    gap> H := Hecke( CoxeterGroup( "B", 2 ), q ^ 2, q );;
    gap> HeckeCharValues( Basis( H, "C'" )( 1, 2, 1 ) );
    [ 0*q^0, q + q^(-1), 0*q^0, q^3 + 2*q + 2*q^(-1) + q^(-3), 
      -q - q^(-1) ] 
See also HeckeClassPolynomials.
This function requires the package "chevie" (see RequirePackage).
GAP 3.4.4