Epsilon

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10 kinds of people in the world, those who understand binary and those who don't.

	274 reputation	bio	website		visits	member for	4 months
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Mar 18	comment	The following Post Correspondence Problem unsolvable? +1, Thanks for the reply. Can you please explain how you got this?
Mar 17	asked	The following Post Correspondence Problem unsolvable?
Mar 17	comment	Why is showing a language is Turing recognizable trickier than showing Turing decidable? I see what you mean by me not being to easily explain what it means proves that it is tricky...
Mar 17	accepted	Why is showing a language is Turing recognizable trickier than showing Turing decidable?
Mar 17	comment	Why is showing a language is Turing recognizable trickier than showing Turing decidable? If A runs forever, then it hasn't found the string it was looking for yet, but it still might, sometime in the future, right? <---- This thought is what is confusing me.
Mar 17	revised	Why is showing a language is Turing recognizable trickier than showing Turing decidable? added 17 characters in body
Mar 17	comment	Why is showing a language is Turing recognizable trickier than showing Turing decidable? Thanks for the reply. But Turing Decidable guarantees that it will eventually come to a halt, even if it runs for an extremely long time. With Turing Recognizable, if it checks if a string is in A and doesn't find it for 1000 years, it still may come up a second after it 'gives up' and goes to Turing Machine B, so its not really tricky, it is just doing what it is supposed to do, which is run for as long as it needs to. Its hard for me to explain what I mean, but I still don't get why proving a Recognizable language is closed under some operation is 'tricky' when compared to the contrary...
Mar 17	asked	Why is showing a language is Turing recognizable trickier than showing Turing decidable?
Mar 14	revised	Showing the following language is not contex free deleted 3 characters in body
Mar 14	asked	Showing the following language is not contex free
Mar 14	accepted	Sipser Pumping Lemma Clarification
Mar 14	accepted	Converting to regular expressions
Mar 13	asked	Pumping Lemma to show that a language is not Context Free
Mar 10	awarded	Critic
Mar 10	comment	Sipser Pumping Lemma Clarification Thanks for the reply. It is not clear to me why s=$0^p$$1^p$ means what you claim it means, in the first line of your explanation, I would appreciate any clarification.
Mar 10	comment	Sipser Pumping Lemma Clarification Thanks for pointing that out. See edited.
Mar 10	revised	Sipser Pumping Lemma Clarification added 9 characters in body
Mar 10	asked	Sipser Pumping Lemma Clarification
Mar 10	comment	Proving that a Turing Machine that only accepts even length strings is undecidable Not necessarily, just pointing out that infinitely long strings are allowed.
Mar 9	comment	Proving that a Turing Machine that only accepts even length strings is undecidable @Tony, your assumption is wrong. Infinitely long strings are most definitely allowed. Otherwise it wouldn't be much of a Turing Machine, would it? Infinitely long input strings is what separates 'decidability' from 'recognizably', or in other words, what make undecidable problems possible. Moreover, the article says that inputs can be natural numbers, it is not a requirement, and nowhere does it say infinitely long input strings are not allowed.