Recursion theoretic operators and morphisms on numbered sets
Henk P Barendregt, Giuseppe Longo · Fundamenta Mathematicae · 1983
An operator is a map ?: Pω->Pω. By embedding Pω in two natural ways into the λ-calculus model Pω^2 (and T^ω) the computable maps on this latter structure induce several classes of recursion theoretic operators.