Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2019/ii/paper-3/12h/e/solution

No. The property
is an index set: it depends only on the domain of the partial function computed, not on the syntax of its program. It is nontrivial. For example, an index whose domain is a singleton belongs to , whereas an index whose domain has two elements does not. The Rice theorem therefore shows that is not a computable set, so no algorithm can decide the requested property for arbitrary .
Invoking the Church–Turing thesis, this also rules out any effective procedure in the informal sense, because such a procedure would be represented by a computable function.

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