# convert to y(n,t), derivative holder;


toyt(a_=b_):=toy(a)=toy(b);
toyt(ds(y,x_,n_)) := y(n,x);
toyt(ds(y)):=y(1,t);
toyt(d(y(x_),x_)):=y(1,x);
toyt(d(y(x_),x_,p_)):=y(p,x);
toyt(y(n_,x)):=y(n,t);