/* presentation on standard generators for HS.2 */ PresentationHSAutm := function (G : UserGenerators := [], Projective := false) Fct := Projective select ProjectiveOrder else Order; if #UserGenerators eq 0 then UserGenerators := [G.i : i in [1..Ngens (G)]]; end if; if #UserGenerators ne 2 then "Require 2 user generators"; return false; end if; c := UserGenerators[1]; d := UserGenerators[2]; return Fct (c) eq 2 and Fct (d) eq 5 and Fct ((c,d)) eq 3 and Fct ((c,d^2)) eq 4 and Fct((c*d)^4*c*d^-2*c*d^-1*c*d^-1*c*d^-2) eq 2 and Fct((c,d*c*d*c*d^2*c*d^-2*(c*d^2)^2*c*d^-1)) eq 1 and Fct ((c,d*c*d*c*d^-2*c*d^-1*(c*d^-2)^3)) eq 1 and Fct ((c,d^-1*c*d^-1*c*d^2*c*d*(c*d^2)^3)) eq 1; end function;