III. return the bill to Congress for clarification on some point within the bill IV. allow the Congress to pocket veto the bill, thereby allowing the bill to become law without his signature a.
Decidability. Definition: A language is called decidable if there exists a method-any method at all-to determine whether a given word belongs to that language or not. Working hypothesis I: Decidability is well defined above.roof: Surely, a decidable language is recognizable. Moreover, if a language is decidable, then so is its complement, and hence that complement is recognizable. Now suppose a language L and its complement are recognizable. Let A be a recognizer for L, and B for its complement.
Definition: A language is called semi-decidable (or recognizable) if there exists an algorithm that accepts a given string if and only if the string belongs to that language. In case the string does not belong to the language, the algorithm either rejects it or runs forever.roof: Surely, a decidable language is recognizable. Moreover, if a language is decidable, then so is its complement, and hence that complement is recognizable. Now suppose a language L and its complement are recognizable. Let A be a recognizer for L, and B for its complement.