I have a question involving the Pumping Lemma for Regular Languages and Pumping Lemma for Context-free Languages: Is it possible that there's a language which doesn't meet the criteria for the pumping-lemma for context-free languages but does meet the criteria for the pumping-lemma for regular languges?
Or is there a hierachy similar to the Chomsky-Hierachy?
I'm just trying to understand that and pumping lemma in general
Let's consider the classic a^nb^n language. aabb is in it, while abb is not.
We know it is a CFL. (S -> aSb | epsilon)
We can proof that is is not a regular language using the PL for CFL (cf. https://stackoverflow.com/a/2309755)
The PL for CFL is used to proof that a language is NOT CF. But the language IS CF (see above!).
Thus we can never use the PL for CFL for the language to proof that is it not CF.
Yes, any RL is also a CFL (and also a CSL and also a REL). You are wrong in your conclusion though.
The PL is used to proof that a given language is NOT in the class. So we use the PL for RL to show that a language is not a RL, so "at most" CF. And we use the PL for CFL to show that a language is not even a CFL, so "at most" context sensitive.
Well if you can proof a language is not context free, it can also not be regular, as RL is a subset of CFL.