The system is accessible function passing by a sort ordering that equates all sorts.

We start by computing the following initial DP problem:

  P1. (1) fapp#(lam(X), Y) => subst#(X, Y)
      (2) subst#(fapp(X, Z), Y) => subst#(X, Y)
      (3) subst#(fapp(X, Z), Y) => subst#(Z, Y)
      (4) subst#(fapp(X, Z), Y) => fapp#(subst(X, Y), subst(Z, Y))

***** No progress could be made on DP problem P1.