Why Does the Pumping Lemma Require |xy| ≤ p?

  • Context: Graduate 
  • Thread starter Thread starter colt
  • Start date Start date
  • Tags Tags
    Condition
Click For Summary

Discussion Overview

The discussion centers around the Pumping Lemma in formal language theory, specifically addressing the condition |xy| ≤ p and its implications for finite automata. Participants are exploring the reasoning behind this condition and its significance in the context of proofs related to regular languages.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant questions the interpretation of the condition |xy| < p, suggesting that in a scenario with a four-state DFA, |x| could equal p, leading to a contradiction with |y| > 0.
  • Another participant seeks clarification on the specific version of the Pumping Lemma being referenced, indicating that there may be multiple formulations of the lemma.
  • A request is made for the proof of the Pumping Lemma to facilitate understanding of the discussion.
  • A participant acknowledges confusion regarding the existence of multiple pumping lemmas and mentions an attempt to provide a proof but ultimately decides against it.

Areas of Agreement / Disagreement

Participants express differing interpretations of the Pumping Lemma and its conditions, indicating that there is no consensus on the reasoning behind |xy| ≤ p.

Contextual Notes

There is a lack of clarity regarding which specific version of the Pumping Lemma is being discussed, and the implications of the proof are not fully resolved. The discussion reflects uncertainty about the conditions and their applications.

Who May Find This Useful

Individuals studying formal languages, automata theory, or related topics in computer science may find this discussion relevant.

colt
Messages
20
Reaction score
0
It says that |xy| < p. But I don't understand why even after reading the proof. If I have a four state DFA, whose last state is the one that is going to repeat for a given input string of length p, |x| is already going to be four, since it represents the states necessary to reach the repetition state. So in this worst case scenery, |x| is already equal to p, so with |y|>0 we already have |xy|>p. SO what's wrong with my line of thought
 
Physics news on Phys.org
If I understand correctly, the pumping lemma gives you a number, p, such that a bunch of stuff happens. Can you reference the exact pumping lemma you are talking about?
 
And show us the proof so we can understand.
 
I am sorry, I forgot that there is more than one pumping lemma so I aborted the copy that I was doing. Very clever from my part. Anyway I attached a screenshot of the proof:
 

Attachments

  • Screenshot.png
    Screenshot.png
    49.4 KB · Views: 481

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 12 ·
Replies
12
Views
5K
  • · Replies 16 ·
Replies
16
Views
3K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 5 ·
Replies
5
Views
1K
  • · Replies 0 ·
Replies
0
Views
4K
  • · Replies 3 ·
Replies
3
Views
5K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 5 ·
Replies
5
Views
5K
  • · Replies 3 ·
Replies
3
Views
2K