const value_type &a, const value_type &b, const value_type &c, const value_type &d,
const time_type &r=0.0, const time_type &s=1.0):
a(a),b(b),c(c),d(d) { set_rs(r,s); sync(); }
const value_type &a, const value_type &b, const value_type &c, const value_type &d,
const time_type &r=0.0, const time_type &s=1.0):
a(a),b(b),c(c),d(d) { set_rs(r,s); sync(); }