Talk:Free variables and bound variables

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The transition from the list of examples to the proposed precise definition, which I suspect may be too narrow, is abrupt. The article needs polishing, by someone familiar with logic and with the lambda calculus. Michael Hardy 22:51 Feb 23, 2003 (UTC)

The see also link for Closure appears to be the wrong kind of closure. It should probably be Closure (computer science). Glenn Willen (Talk) [[]] 16:18, 2 Sep 2004 (UTC)

I wonder if the explanation free to be varied as was recently inserted in the article is not misleading. My guess is that the etimologically bound variable precedes free variable. CSTAR 05:47, 13 Dec 2004 (UTC)

OK, I'm thinking about your first point. As to your second point, the words free and bound in common language go together so intimately that it's difficult to imagine one of the two having been introduced earlier than the other. Michael Hardy 23:47, 13 Dec 2004 (UTC)

What I had in mind was the following. (As I know you know) bound is used in a related sense: A variable binding is similar to an assignment (in both mathematical languages and in programming languages). Alternatively, we can say a variable is bound to a value. This sense of bound is certainly different than being within the scope of a binder although I am not exactly sure how to express the difference. CSTAR 00:19, 14 Dec 2004 (UTC)

PIVOT variable = BOUND variable DUMMY variable is (special case of) bound variable that can have only values 0 or 1.

The above is utter nonsense and is already covered in the article. Statisticians use the term "dummy variable" to mean something that can only be either 0 or 1. That is a completely different concept from that of dummy variable discussed in this article. And the article already says that. The "dummy variables" used by statisticians that only take the values 0 or 1 are NOT bound variables at all. Michael Hardy 22:31, 29 Apr 2005 (UTC)

I searched for "dummy variable" hopeing to get to the "indicator variable" page. There is a fundamental difference between the mathematical dummy variable and statistical dummy variable. Nevertheless, I think those who are searching for the statistical version (as I was) may be confused by what they read here. Unless they read through the article, they will not see the link to "indicator variable". In my opinion, rather than having a single line buried in the text stating that "unfortunately the term dummy variable is used by many statisticians to mean an indicator variable or some variant thereof", I have added a "for the statisitcal dummy variable..." link at the top. I think this should remove much of the confusion (at least the initial confusion I had). Mustard 20:41, 20 January 2006 (UTC)[reply]

We need to get rid of the redirect and have a proper article on statistical dummy variables. The link to indicator variables only makes things worse JQ 23:36, 23 April 2006 (UTC)[reply]

Fixed. David-Sarah Hopwood (talk) 14:20, 27 July 2008 (UTC)[reply]

Recursive function link

Michael Hardy reverted the link I edited this morning. There are several places you could link the words recursive function to:

I'm not planning to edit the page again; decide for yourself which of the above links is the meaning you want. Note that recursive function is a disambiguation page, so you shouldn't link there.CMummert 02:13, 17 July 2006 (UTC)[reply]

Within this general area of mathematics, it usually means a computable function. Michael Hardy 17:53, 17 July 2006 (UTC)[reply]

That usage doesn't make sense in the sentence

Similarly, an identifier bound to a recursive function is also technically a free variable within its own body but is treated specially.

CMummert 17:55, 17 July 2006 (UTC)[reply]

I'm not going to vouch for all changes made throughout WP by CMummert from computable to recursive (since I haven't looked at them all) but I think in the instance being discussed here, his change is correct. Recursion in this instance means (a least) fixed point of some ~~equation~~ function. --CSTAR 19:04, 17 July 2006 (UTC)[reply]

There is no explaination of what a bound variable is in software development.

Can someone please define what a bound variable is in computer programming. —Preceding unsigned comment added by 71.237.89.49 (talk) 21:47, 2 March 2008 (UTC)[reply]

I would like to point out more importantly that there is no explanation of what a bound variable is ANYWHERE. There is only an explanation of what it is not. In the first section a free variable is clearly defined, but then it jumps directly to an example of a bound variable, but not a definition. Emry (talk) 07:27, 9 October 2008 (UTC)[reply]

Whether a variable is bound or not depends always on the context. --77.1.51.135 (talk) 11:24, 7 February 2011 (UTC)[reply]

Free variables in programming

Free variables only apply to lexical scoping, there's no distinction between bound and and free variables in dynamic scope. 85.221.147.47 (talk) 12:01, 10 August 2009 (UTC)[reply]

That's what the article claims, and it also states that this is the reason why closures only exist in lexical scoping, but PHP 5.3 is getting closures and supposedly PHP isn't lexically scoped. So how does that work?--Subversive Sound (talk) 01:14, 13 March 2010 (UTC)[reply]

Contradiction

" *Ashleyi met heri. (interpretation #1: her = Ashley)

   Ashleyi met herj. (interpretation #2: her = a female that is not Ashley)

The first interpretation is impossible, but the second interpretation is grammatical (and in this case, is the only interpretation)."

I think that the author might mean this would seem to be a contradiction in objective ordinary experience, not a grammatical error as the context of the article suggests. "Ashley met her(self)" is a valid statement that may be written for a number of reasons, probably to highlight a contradiction, discontinuity, unusual condition or perception. It might be said in realty, as the effective summary of a situation, from a certain point of view, without it being a grammatical error. For instance, Ashley may have never seen herself in a mirror, or met her twin who was previously unknown for the first time. If one fails to perceive an extensive mirror as part of a wall, and sees it as a passage way, one might meet oneself. Various medical or mental or memory conditions might lead to a case where one effectively "meets" oneself. It may be used in rhetoric. It may be used in pure fiction for dramatic effect, i.e. in romatic fiction to bring about an emotional response or as part of speculative fiction to bring a contradictory set of conditions to a focus. Since the article seems to be making a grammatical argument and uses the words "impossible" and "only interpretation", it would seem to have overreached. This point may seem picky, but, a collection of such logical overreaches and similar rigidity erects barriers to automated natural language interpretation, interpreting perception, or interpreting fiction. — Preceding unsigned comment added by 209.151.137.168 (talk) 15:35, 21 August 2013 (UTC)[reply]

No, you have misunderstood. The point has nothing to do with ‘objective ordinary experience’. The point is about grammar.

Basically, if you are reporting the event that Ashley has met herself, then you can only say Ashley met herself. You can't say Ashley met her to report that event. I think that you recognize this because you added (self) to the sentence. And, if you are reporting the event that Ashley has met another female that is Ashley, then you can only say Ashley met her. You can't say Ashley met herself. So, the point was that herself (a reflexive) is always a bound variable while her can be either a free variable or an obligatorily unbound variable depending on where the variable occurs within the syntax of a sentence.

Now whether or not people can meet themselves via a mirror or psychosis or whatever is a completely different issue. Maybe we can change the verb met to hit since it's obvious that people can hit themselves as well as other people. Therefore, we make it clear that we are really talking about grammar and variable assignment in natural language. – ishwar (speak) 02:21, 8 September 2013 (UTC)[reply]

alpha conversion

A brief description of alpha conversion would be nice. Currently, a google of alpha conversion points one to either the haskell wiki, or to the Lambda calculus article, here. But of course, alpha conversion is a far more general concept than that, and its awkward to tell my readers that they have to first grok lambda calculus before they can understand this more basic concept. 67.198.37.16 (talk) 23:15, 20 July 2017 (UTC)[reply]

Topic suggestion: Trivial cases

It would be nice if there was a simple explanation for cases where the domain of a variable has only 1 or 0 elements.

For instance, would a variable x in the integers modulo 1 be free or bound? (the only element it can denote it 0)

Or what about indeterminates which are variables with an empty domain? Why?

I feel like these cases deserve at least a mention somewhere in the article. Farkle Griffen (talk) 17:39, 22 August 2024 (UTC)[reply]