CFG_set S ::= "" | aSbS | bSaS ; CFG_tree

baabba

Example Context-Free Grammar Problems

The syntax has been changed. The empty string is no longer $ but "".

Throughout these problems, the alphabet is {a, b}. Consider the language of the strings that contain the same number of a's as b's. The empty string is denoted with "".

Write a string of length 4 that is in the language. CFG_set S ::= "" | aSbS | bSaS ; CFG_short 4 CFG_long 4 ok_text First correct! CFG_in
Write a string of length 4 that is not in the language. end_of_answer ok_text Second correct! CFG_not_in
or

Write a grammar for the language.
ok_text Your grammar is very good! CFG_set S ::= "" | aSbS | bSaS ; CFG_set2 S ::= ; CFG_compare
or

Suggestion: S ::= aSb | bSa | SS | ""

---