Talk:Subsequence

This is not right. A subsequence is a subsequence of something (of another sequence). At the moment it is an oxymoron - it says that it doesn't contain some of its own elements. --Zero 22:46, 31 Mar 2004 (UTC)

Example
Could you fix the example there? The intro says that you're not supposed to change the order of elements but the example does that!

Edit: There does not seem to be any example doing that, at least not anymore.

I tried fixing that but it gave me an error after I saved. —Preceding unsigned comment added by 65.93.127.142 (talk) 14:27, 27 January 2010 (UTC)

Subsequence vs. subset
Aren't they very similar? We should point that out to avoid confusion.

My take is that a set is not the same as a sequence (set = don't care about order and no repeat, sequence = care about order and repeats OK). But basically a subset of a subsequence is also a subsequence (if consider every element of the sequence by their index to avoid deleting duplicates).

You can't claim that they are the same, but since set/subset are so fundamental to mathematics, I would point out the similarities. — Preceding unsigned comment added by Nothing1212 (talk • contribs) 23:38, 18 January 2016 (UTC)

A list of all possible distinct subsets for "apple" would be 	"a,p,l,e,ap,ap,al,ae,pp,pl,pe,pl,pe,le,app,apl,ape,apl,ape,ale,ppl,ppe,ple,ple,appl,appe,aple,aple,pple,apple". While, the list of all distinct subsequences for the word "apple" would be "apple,appl,appe,aple,pple,app,apl,ape,ale,ppl,ppe,ple,ap,al,ae,pp,pl,pe,le,a,p,l,e".

Safe to say a complete collection of subsequences may be a subsequence of a complete collection of subsets if order for generating subset is defined. >Antonio "Atoi" V. de Jesus III — Preceding unsigned comment added by Antonio "Atoi" V. de Jesus III (talk • contribs) 01:00, 18 August 2017 (UTC)

Sequence vs string
An edit 2006 19:22:35 stating A subsequence is a more general term than a substring, which is a consecutive part of the original string. was reverted with the reason ''revert, a string and a sequence is not the same thing as far as I know. I never heard of a subsequence of consecutive terms to be called a substring. References?''

Both the terms string (computer science) and sequence are used for a list of objects, where the order of the objects matter, and an object may occur multiple times. I guess the difference in usage between the words is that the term string is usually not used when the objects are not symbols. The term string is also often used to denote the more spesific meaning a sequence of ASCII characters in a computer program.

From Gusfield, Algorithms on strings trees and sequences, 1st edition, page 4: ''..., the words "string" and "sequence" are often used synomymously, particularly in the biological literature. This can be the source of much confusion because "substrings" and "subsequences" are very different objects... and The characters in a substring of $$S$$ must occur contiguously in $$S$$, whereas characters in a subsequence might be intersped with characters not in the subsequence.'' See also longest common subsequence problem and longest common substring problem.

Nils Grimsmo 06:52, 30 March 2006 (UTC)


 * Right, so the words string and substring are usually used in computer science and related, but not in other areas, like mathematics. As such, that usage is much more particular than the usage of sequence, which is why mentioning substrings here would not be as appropriate I think.


 * In short, talking about a subsequence of a string is I think fine at all times, talking about the substring of a sequence is not accepted terminology except in computer science. Oleg Alexandrov (talk) 15:54, 30 March 2006 (UTC)


 * But people confusing the terms subsequence and substring is a problem in computer science. So maybe it is appropriate to state something like ''In computer science, the term string is often used as a synonym for a sequence, but it is important to note that substring and subsequence are not synonyms. Substrings are consecutive parts of a string, while subsequences need not be. This means that a substring of a string is always a subsequence of the string, but the opposite is not true. -- Nils Grimsmo 17:04, 30 March 2006 (UTC)


 * Yes, writing a text like that, starting with "in computer science" makes sense to me. Probably not in the very first introductory paragraph, but somewhere in the text where you find appropriate. Oleg Alexandrov (talk) 00:19, 31 March 2006 (UTC)


 * Done. Nils Grimsmo 07:29, 31 March 2006 (UTC)


 * Thanks, your addition is very well-written. Oleg Alexandrov (talk) 16:51, 31 March 2006 (UTC)

Mathematical proofs
In the article, longest common subsequence, two "properties" of subsequences are presented. It would be nice to have formal proofs in this article of those two properties, especially the second one, which isn't at all obvious.--Christopher King (talk) 19:26, 17 January 2009 (UTC)

Infinite sequences
Several articles link here when discussing sub-sequences of infinite sequences. This article makes no mention of these. Generally it is assumed that a sub-sequence of an infinite sequence should also be infinite. — Preceding unsigned comment added by 217.84.28.96 (talk) 16:22, 25 September 2012 (UTC)

"Subsequently" listed at Redirects for discussion
An editor has identified a potential problem with the redirect Subsequently and has thus listed it for discussion. This discussion will occur at until a consensus is reached, and readers of this page are welcome to contribute to the discussion.  J947  † edits 10:28, 8 January 2023 (UTC)