How do i get from 2 character words to 4 character words or 5 character words??
can anyone show me how to do that plz...


Q) Consider a language of words, where each word is a string of dots and dashes. The following grammar describes this language:

<word> ::= <dot> | <dash><word> | <word> <dot>
<dot> ::= .
<dash> ::= -

The meta-symbols of BNF are:

::= meaning “is defined as�
| meaning is “or�
<> angle brackets are used to surround category names


Question: List all strings with exactly three characters that are in this language?
Is the string ...---(three dots followed by three dashes) in this language?



Let's start listing the possible words. The only word consisting of one character is a single dot. By applying the second production rule, you can add a dash in front of the word, which gives you <dash> <dot>. If you apply the third rule instead, you add a dot after the first dot, resulting in <dot> <dot>.

So now I have two valid words consisting of two characters each:

-.
..

Now I can go on and apply the two production rules again to these two words, resulting in four three-character words. Of course, in the same way, you get 8 four-character words, 16 five-character words and so on.

How do I apply the production rule to get to the four 3 character word??