/* black box recognition procedure for M23 */ StandardGeneratorsM23 := function (G : Projective := false, Limit := 450) Fct := Projective select ProjectiveOrder else Order; P := RandomProcessWithWords (G); x, xw := ElementOfOrder (P, 2, Limit: Fct := Fct); if Type (x) eq BoolElt then return false, _; end if; b, bw := ElementOfOrder (P, 4, Limit: Fct := Fct); if Type (b) eq BoolElt then return false, _; end if; nmr := Limit; repeat nmr -:= 1; c, cw := Random (P); a := x^c; until (Fct (a * b) eq 23 and (Fct ((a * b)^2 * (a * b * a * b^2)^2 * a * b^2) eq 8 or Fct ((a * b)^2 * (a * b * a * b^2)^2 * a * b^2) eq 11)) or nmr eq 0; if nmr eq 0 then return false, _; end if; aw := xw^cw; if Fct ((a * b)^2 * (a * b * a * b^2)^2 * a * b^2) eq 11 then b := b^-1; bw := bw^-1; end if; if not PresentationM23 (G: UserGenerators := [a, b], Projective := Projective) then return false, _; end if; return [a, b], [aw, bw]; end function;