H G Rice 1953: every nontrivial semantic property of partial computable functions is undecidable; index-set {e : phi_e in P} not recursive when P is nontrivial; corollary of recursion theorem.
H G Rice 1953: every nontrivial semantic property of partial computable functions is undecidable; index-set {e : phi_e in P} not recursive when P is nontrivial; corollary of recursion theorem.