The form of the context-free grammar can be important. Tools are often
sensitive to the particular you write the grammar and while there are many ways to
write a grammar for the same language, only some of them may be accepted by the
tools. And as we'll see there are cases where it's necessary to modify the grammar
in order to get the tools to accept it. This happens actually sometimes as well
with regular expressions but it's much less common. So normally for most regular
expressions you would want to write the tools would be able to digest them. That's
fine. That's not also true. That's not true of an arbitrary context-free grammar.
xxleyi
commented
3 years ago 
