Hi, we don't understand the exact definition of a symetric gremmer.

Is the following gremmer also symetric?

s- > A | B

A-> 111

B-> 22 | A

if this is symetric gremmer, the lanugange it creates is not symetric so answer A (which is marked as the correct one) is disproved.

What are we missing in the definition?

Thank you.

But it is a symmetric grammar, and it's language is: L={111,22}, which is symmetric according to the definition.

What about

S => BB

B => b | A

A => a | Aa

?

It is not in CNF though, but it doesn't say you have to use CNF in the question, and this grammar generates the word baaaaaaaaaaa (Which is not symmetric, but it does express my current feelings).

I think that the question was not well put. When written "A->w" with a capital 'A' and a regular 'w' it implies by convention that 'w' means a terminal and not a variable. In which case the rule mentioned does not apply for rules of the form A->AB where 'A' and 'B' are variables.

למה תשובה ב אינה נכונה?

כלומר למה לא לכל שפה סימטרית קיים דקדוק חסר הקשר סמטרי שמייצר אותה?

לא הצלחתי למצוא דוגמה נגדית.

למישהו יש רעיון?