''a'' ''b'' ''a'' turing reducible ''b'' many one reducible ''b'' shown every computably enumerable set many one reducible halting problem thus halting problem complicated computably enumerable set respect many one reducibility respect turing reducibility post asked whether ''every'' computably enumerable set either computable turing equivalent halting problem whether computably enumerable set turing degree intermediate two intermediate results post defined natural types computably
Formal science Computer science Theory of computation Computability theory