private static ImmutableList<double> AddModMasses(IList<double> modMasses1, IList<double> modMasses2) { double[] masses = modMasses1.ToArrayStd(); for (int i = 0, count = Math.Min(masses.Length, modMasses2.Count); i < count; i++) masses[i] += modMasses2[i]; return MakeReadOnly(masses); }