theoretical computer science

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hie
Question from the textbook by Daniel Cohen
problem 4
Consider the language S* = {a , ab , ba}.
i) Is the string (abbba) a word in the language?
ii) Write out all the words in this language with six or fewer letters.
iii) What is another way in which to describe the words in the language ?Be
careful this is not simple the language of all words without bbb.

My suggestion
i) the string abbba is not a word in the languge but i do not know the explanation.
ii) { null string , a, ab , ba , aab , aba , aaab , aaba , abba , aabba , baaab}
iii) A word with at least one a's and which contains even number of b's.

Can anyone of you guys give other words in the language with proper explanations because i do not understand this topic.

[nanosani]

i) Is the string (abbba) a word in the language?
ii) Write out all the words in this language with six or fewer letters.
iii) What is another way in which to describe the words in the language ?Be
careful this is not simple the language of all words without bbb.

My suggestion
i) the string abbba is not a word in the languge but i do not know the explanation.
ii) { null string , a, ab , ba , aab , aba , aaab , aaba , abba , aabba , baaab}
iii) A word with at least one a's and which contains even number of b's.

i) construct the word from the language ... ab is a word ... next ... b or bb is not a word from the language ... so the whole word abbba is not a word in the language.

ii){a , ab , ba}.
{null, a,ab,ba,aab,aba,aba,abba,abab,baa,baab,baba,aabba,abaab,ababa,abbaa,baaab,baaba}
these are less than 6 letter words ...

iii) ... you're right.

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hie
thank you very much nanosani
later