A congruence theorem for structured operational semantics with predicates and negative premises. Nordic Journal of Computing 2 (2), 274–302. A. Proof of Theorem 9 We show that the problem of deciding whether a universal two-counter machine diverges on inp (1995)

by C Verhoef
Venue:z s.x s → x . If the ith instruction is the increment of a counter, say inc I, then ℓi has rule ℓi(x, y) a → ℓi+1(s.x, y) . If the ith instruction is the decrement of a counter, say dec I, then ℓi has rules x z → x ′ ℓi(x, y) a → ℓi+1(x ′ , y) x s → x ′ ℓ