NIELIT 2017 DEC Scientist B - Section B: 27

Question

If any string of a language $L$ can be effectively enumerated by an enumerator in a lexicographic order then language $L$ is _______.

• A. Regular
• B. Context free but not necessarily regular
• C. Recursive but not necessarily context free
• D. Recursively enumerable but not necessarily recursive

Comments

The language is decidable and hence RE

---

ashwin it is REC but not CFl ryt? since find most appropriate answer.

If any string of a language L can be effectively enumerated by an enumerator  then language L = RE

If any string of a language L can be effectively enumerated by an enumerator in a lexicographic order then language L  = REC

---

Ohh yes @Anu we can reject the strings which are not that order Hence Recursive.

Hence answer will be option C)

Is it previous gate Question? I think I saw this question somewhere earlier.

---

@Ashwin Kulkarni Languages enumerated in LEXICOGRAPHIC order are decidable, and hence, are Recursive, not Recursively Enumerable.

Answer 1

option c

https://gateoverflow.in/120/gate2003-15

Answer 2

if the string of a language L is enumerated then definitely it is countable, so there exists a turning machine which accepts it and halts.so it is Recursive but it cannot be Recursively enumerable because for this language the turning machine doesn't get halt.

Answer:opt c