Talk:Closed-form expression

message: The current lede says a closed form expression may contain a bounded number of operations. To me that is not clear, and I think it should be "finite" instead. Obviously infinite summations are not closed forms. But a summation whose number of terms varies with the argument of the expression would be bounded (for each argument), but not involve a finite number of operations because there is no bound in the expression itself. For instance I would not consider the definition \textstyle\sum_{i=1}^ni of a triangular number to be a closed-form expression for it, while \textstyle\frac{n^2+n}2 does give a closed-form expression. By the same token there would be no closed-form expression for factorials at all, unless we explicitly place them in our repertoire of "well-known"" functions. If my interpretation is agreed upon, I think "finite" would be the correct term to use. Marc van Leeuwen (talk) 10:33, 9 March 2010 (UTC)
thread_title:  Bounded or finite? 

message: I propose that the Analytical expression article be merged into this one. The reason is that it is a very short article, a stub really though not marked as such, on basically the same or a very closely related topic, and that if there is any distinction this could be treated more clearly in a single article. I am personally neutral to the question whether the name Analytical expression or Closed-form expression should be preferred, but given the relative sizes, a merger of this article into the other seems less natural. Marc van Leeuwen (talk) 07:14, 6 May 2011 (UTC)
thread_title:  Proposed merger from Analytical expression 

message: The first paragraph has the following:
" Unlike the broader analytic expressions, the closed-form expressions do not include infinite series or continued fractions; neither includes integrals or limits."
"Neither" refers to infinite series and continued fractions, because 'neither' means something along the lines of "not the one nor the other of two people or things". But I am guessing here that the sentence was meant to say that closed-form expressions do also not include integrals or limits? (I don't know, I'm not a mathematician). If, OTOH, it is meant to say that neither infinite series or continued fractions include integrals or limits, then I wonder why this information is given, as it feels unrelated to the definition of closed-form expressions? maye (talk) 16:49, 26 September 2013 (UTC)
thread_title: Unclear sentence

message: Is this grammar of the Wikipedia article correct? "to numbers defined in explicitly or implicitly in terms of algebraic operations"— Preceding unsigned comment added by Wilkibur (talk • contribs) 18:35, 28 March 2015 (UTC)
thread_title:  Is this grammar of the Wikipedia article correct? 

message: The phrase "analytic function" is a technical term with a precise meaning.  The term "analytic" is defined twice in this article; one definition is possibly consistent with that meaning, but the other is not.  It is tempting to assume that an analytic expression is the value of an analytic function.  The article should mention that there are such things as analytic functions, and how they relate to the expressions.
2001:388:6080:109:D578:2477:98CA:8194 (talk) 04:34, 20 March 2017 (UTC)
thread_title:  This should at least mention analytic functions 

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thread_title:  External links modified 

message: Hi. Why did you write in a comment that sin(x)+sin(y) is not an analytic expression?
Maybe the sentence should say, "Closed-form expressions are an important sub-class of analytic expressions, which contain a finite or infinite number of applications of well-known functions".
Please ping me when you answer. Eric Kvaalen (talk) 16:51, 21 February 2021 (UTC)
replies: text: Both formulations are nonsensical as none of the involved terms are clearly defined. In particular, the difference between an analytic expression of a function and an analytic function is never defined. Difficult to clarify sech a mess. D.Lazard (talk) 21:34, 21 February 2021 (UTC)
thread_title: Number of applications of well-known functions

message: The article mentions that differentiation usually isn't allowed to take place in closed-form expressions. However, isn't it always possible to expressed the derivative of a closed-form expression as another close-form expression? If so, should perhaps differentiation be allowed in closed-form expressions? Or maybe it doesn't matter whether an expression is equivalent or not to another expression that is on a closed form? —Kri (talk) 15:43, 16 March 2023 (UTC)
replies: text: Good catch. I have edited the article for fixing it. Feel free to improve my wording if needed. D.Lazard (talk) 17:32, 16 March 2023 (UTC)
thread_title:  Differentiation 

message: Two editors are trying to re-introduce in the article talking about "size" of an expression. One of them linking to a Quora post, that they themselves wrote, that doesn't even support the use of that terminology. The other, based on nothing.
Size, is not a meaningful measure of anything. It could mean anything, from number of operations, operands, font, number of lines, etc. The article should instead mention at least one actual concrete reason that makes the expressions in radicals for quartics, cubic (and sometimes even quadratics) less useful as the degree increases. An ambiguous notion of size is irrelevant to usefulness. It is not uncommon to have expressions, procedures, algorithms, that are more sizable than others, longer to write, but are more useful for performing better than others that are less sizable, simpler to describe. The article should mention objective notions that make the expressions less useful: Number or operations, numerical instability, complexity of the symmetries (Galois group), complexity when testing the identity problem, complexity of rationalization of radicals, any, some, or all, but not a bogus reference to "size", which does not imply any lack of usefulness. Thatwhichislearnt (talk) 11:23, 27 March 2024 (UTC)
replies: text: Mathematics does not exclude common sense; here, "size" has its common meaning. It suffices to look at the solution of a general quartic equation to understand that it is too large to be used, and even to be read by humans. If you want for such a huge formula, ask your preferred computer algebra system. If you would try to verify the solution by putting it in the equation, I guess that you would never succeed to simplify the result to zero. D.Lazard (talk) 12:08, 27 March 2024 (UTC)
replies: text: Utter nonsense, and you know it. Size and usefulness are unrelated. Also, using intuition as a way of judging usefulness is also nonsense. Multiple examples, including your favorite Sturm vs Vincent's theorem, show how the size of a description is unrelated to usefulness. There are concrete mathematical reasons that make these formulas less useful as the degree increases. Those should be given as reasons, not size. Thatwhichislearnt (talk) 12:17, 27 March 2024 (UTC)

text: It is impressive how you are always behind efforts to make Mathematical articles worse, less precise, less mathematical. What's up with that? Is it a quest of yours? 12:19, 27 March 2024 (UTC)
replies: text: Be careful not to make personal attacks against other editors like D.Lazard. If you disagree with what an editor claims, then attack the claim or the material—not the editor. If you continue, you may be blocked. And do not edit war. Instead, continue discussing the issue here on the talk page until consensus is reached.—Anita5192 (talk) 13:31, 27 March 2024 (UTC)
thread_title:  Size of an expression is not a mathematical notion