We consider termination of the LCTRS with only rule scheme Calc: Signature: cond :: Bool -> Int -> Int -> Int minus :: Int -> Int -> Int Rules: minus(x, y) -> cond(x > y, x, y) | x = x /\ y = y cond(false, x, y) -> 0 | x = x /\ y = y cond(true, x, y) -> 1 + minus(x, y + 1) | x = x /\ y = y The system is accessible function passing by a sort ordering that equates all sorts. We start by computing the initial DP problem D1 = (P1, R, i, c), where: P1. (1) minus#(x, y) => cond#(x > y, x, y) | x = x /\ y = y (2) cond#(true, x, y) => minus#(x, y + 1) | x = x /\ y = y ***** We apply the Usable Rules Processor on D1 = (P1, R, i, c). We obtain 0 usable rules (out of 3 rules in the input problem). Processor output: { D2 = (P1, {}, i, c) }. ***** No progress could be made on DP problem D2 = (P1, {}, i, c).