Comments on: looking for a sign
http://ask.metafilter.com/71600/looking-for-a-sign/
Comments on Ask MetaFilter post looking for a signSat, 15 Sep 2007 01:03:41 -0800Sat, 15 Sep 2007 01:03:41 -0800en-ushttp://blogs.law.harvard.edu/tech/rss60Question: looking for a sign
http://ask.metafilter.com/71600/looking-for-a-sign
Is there a symbol for the phrase "and/or"? <br /><br /> LIke a logical symbol or any other commonly accepted symbol. For example, "or" is often represented by "/", and "and" by "+". Is there a single symbol for "and/or"? (I dont want to just say "/+", i'm looking for a single symbol even if its an obscure one requiring a character code).<br>
Example of and/or: As in, "You can use the this hammer and/or that hammer".post:ask.metafilter.com,2007:site.71600Sat, 15 Sep 2007 00:48:16 -0800jak68mathsymbolslogicBy: Loser
http://ask.metafilter.com/71600/looking-for-a-sign#1066591
Are you talking about <a href="http://en.wikipedia.org/wiki/XOR">XOR</a>?comment:ask.metafilter.com,2007:site.71600-1066591Sat, 15 Sep 2007 01:03:41 -0800LoserBy: jak68
http://ask.metafilter.com/71600/looking-for-a-sign#1066592
Well, XOR is "exclusive OR", right? If so, I think that just means "a OR b but NOT both". So I dont think that works.comment:ask.metafilter.com,2007:site.71600-1066592Sat, 15 Sep 2007 01:10:37 -0800jak68By: IvyMike
http://ask.metafilter.com/71600/looking-for-a-sign#1066595
Technically, the symbol for <a href="http://en.wikipedia.org/wiki/Logical_disjunction">logical or</a> is the thing you're looking for. You'll just have to go convince everybody to stop saying "or" when they really mean "xor".comment:ask.metafilter.com,2007:site.71600-1066595Sat, 15 Sep 2007 01:20:03 -0800IvyMikeBy: blacklite
http://ask.metafilter.com/71600/looking-for-a-sign#1066596
Technically, in logic, the concept "or" means the same thing that we colloquially use "and/or" for.<br>
<br>
If you have two propositions <i>p</i> and <i>q</i>, and you would like a statement to be true if either of them are true, then you write:<br>
<i>p</i>∨<i>q</i><br>
... which you would read "p or q".<br>
<br>
In normal English, when you say "p and/or q", you mean that any of the following may be true: <br>
- p and not q<br>
- q and not p<br>
- p and q both.<br>
<br>
The logic statement "<i>p</i>∨<i>q</i>" is true in the same situations, i.e., its trueness requires only that one of the two propositions be true, not both.<br>
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In computer programming languages, instead of ∨, they use | or ||, depending on the specific language or context.comment:ask.metafilter.com,2007:site.71600-1066596Sat, 15 Sep 2007 01:20:26 -0800blackliteBy: tickingclock
http://ask.metafilter.com/71600/looking-for-a-sign#1066597
I don't think that the XOR is the correct answer. The XOR (exclusive OR) is like the "or" that we normally use in English. <br>
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e.g., "Use the hammer or the screwdriver."<br>
This sentence implies that you will use either the hammer or the screwdriver, but not both.<br>
<br>
I think that jak68 is asking for the <i>inclusive</i> OR, which allows the possibility of using both the hammer -and- the screwdriver, as well as simply choosing one or the other. In logic, this inclusive OR is simply referred to as OR, and it is the XOR that is marked differently.<br>
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Depending on what you want, you can use different symbols to represent then inclusive OR. Here are some examples off the top of my head:<br>
<br>
* V (e.g., p V q)<br>
* || (e.g., p || q; some programming languages use this)<br>
* U (e.g., p U q; only used in <a href="http://whatis.techtarget.com/definition/0,,sid9_gci838378,00.html">set theory</a>, and possibly inappropriate for applying to single items)<br>
<br>
If you wanted to be really wacky, you could try using the <a href="http://en.wikipedia.org/wiki/Image:OR_ANSI.svg">OR gate</a> symbol. I don't know where you would find the character for that, though. <br>
<br>
Hope this helps!comment:ask.metafilter.com,2007:site.71600-1066597Sat, 15 Sep 2007 01:29:56 -0800tickingclockBy: Steven C. Den Beste
http://ask.metafilter.com/71600/looking-for-a-sign#1066598
The usual unambiguous term is "inclusive OR" (as distinct from "exclusive OR"). In boolean algebra IOR is represented as a plus sign, and I think I've seen a symbol that looks like a plus sign with a circle around it used to represent XOR.<br>
<br>
As regards to programming languages, at least <a href="http://tigcc.ticalc.org/doc/opers.html">in C</a> the symbol "|" means "bitwise inclusive OR" and "||" means "logical inclusive OR". "^" is "bitwise exclusive OR". (Exponentiation is handled with a named function.)<br>
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And it turns out that the logical exclusive OR is "!=" so there isn't any special symbol for that one.comment:ask.metafilter.com,2007:site.71600-1066598Sat, 15 Sep 2007 01:30:29 -0800Steven C. Den BesteBy: Steven C. Den Beste
http://ask.metafilter.com/71600/looking-for-a-sign#1066599
Unfortunately, I don't think there's any symbol that means IOR which is in common use except for "and/or". All the other ways of representing it are used by specialists: mathematicians and programmers.comment:ask.metafilter.com,2007:site.71600-1066599Sat, 15 Sep 2007 01:32:08 -0800Steven C. Den BesteBy: jak68
http://ask.metafilter.com/71600/looking-for-a-sign#1066601
everyone, thanks. That makes sense. Ordinary "or" is already inclusive and so is already and/or; but in common practice we dont think of it that way. I'll use one of the symbols from <strong>tickingclock's </strong>post. I'll probably use || cuz its easiest to type.comment:ask.metafilter.com,2007:site.71600-1066601Sat, 15 Sep 2007 01:36:07 -0800jak68By: jak68
http://ask.metafilter.com/71600/looking-for-a-sign#1066605
This could wreak havoc at a restaurant: "This sandwich comes with soup OR fries OR mashed potatoes" -- isn't that an "inclusive or" by default? ;Dcomment:ask.metafilter.com,2007:site.71600-1066605Sat, 15 Sep 2007 02:24:31 -0800jak68By: TheOnlyCoolTim
http://ask.metafilter.com/71600/looking-for-a-sign#1066647
<em>* U (e.g., p U q; only used in set theory, and possibly inappropriate for applying to single items)</em><br>
<br>
I can use my years of education to conclusively state that you can use this for single items, as they are sets of one item, although pedantically you might be supposed to write it {p} U {q} or something.comment:ask.metafilter.com,2007:site.71600-1066647Sat, 15 Sep 2007 06:49:06 -0800TheOnlyCoolTimBy: monkeymadness
http://ask.metafilter.com/71600/looking-for-a-sign#1066651
Add '|' to tickingclock's reply. It's at least one way Google handles inclusive or.comment:ask.metafilter.com,2007:site.71600-1066651Sat, 15 Sep 2007 06:55:24 -0800monkeymadnessBy: abcde
http://ask.metafilter.com/71600/looking-for-a-sign#1066673
<b>SCDB</b>: Derailing, but C's != is only directly equivalent to XOR when you're working with strictly boolean values. Since everything but 0 is considered true, 1 != 5 is true, whereas a proper 1 XOR 5 would be false. However, !!a != !!b will convert all nonzero values to 1. The logical opposite, !a != !b, works too, but it's slightly less obvious what it's trying to achieve.comment:ask.metafilter.com,2007:site.71600-1066673Sat, 15 Sep 2007 07:48:13 -0800abcdeBy: LobsterMitten
http://ask.metafilter.com/71600/looking-for-a-sign#1066703
jak68, there's some debate among people who study this stuff over whether ordinary English "or" is usually inclusive or exclusive. My own feeling is that it's more frequently exclusive. <br>
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It's easy enough to get people to understand what you mean, though - eg and/or. either/or, or you can just emphasize the word "OR" (to indicate exclusivity), or you can add "or both" at the end (to indicate inclusivity).comment:ask.metafilter.com,2007:site.71600-1066703Sat, 15 Sep 2007 08:50:42 -0800LobsterMittenBy: lastyearsfad
http://ask.metafilter.com/71600/looking-for-a-sign#1066894
Yep, you want "U" or "V".<br>
<br>
As a follow up to tickingclock's excellent answer, in the contexts in which "U" comes up (set theory and probability theory in my world) it is a-okay to use it with single elements (or events.)comment:ask.metafilter.com,2007:site.71600-1066894Sat, 15 Sep 2007 13:50:24 -0800lastyearsfadBy: advil
http://ask.metafilter.com/71600/looking-for-a-sign#1066921
<i>you can use this for single items, as they are sets of one item</i><br>
<br>
A single item is _not_ a set containing one item: {a} != a.comment:ask.metafilter.com,2007:site.71600-1066921Sat, 15 Sep 2007 14:29:46 -0800advilBy: Zach!
http://ask.metafilter.com/71600/looking-for-a-sign#1066951
"U" is also sometimes used with predicates. The meaning is the set of models(or states in a transition system) that satisfy at least one of the predicates.comment:ask.metafilter.com,2007:site.71600-1066951Sat, 15 Sep 2007 15:14:51 -0800Zach!By: jak68
http://ask.metafilter.com/71600/looking-for-a-sign#1067213
well the problem with using U or V, I thought, is that they're alphabets and that might cause confusion in text or narrative. So I thought either | or || is sufficiently different looking. I thought I'd use | for inclusive or and || for exclusive or. <br>
I might just end up using +/ I suppose. || seems easiest to type. I suppose I like V as well. These are mostly to be used in my own personal notes so I'm not terribly worried about causing confusion; just have to decide on a system for myself. <br>
Thanks for all the info though.comment:ask.metafilter.com,2007:site.71600-1067213Sat, 15 Sep 2007 22:37:27 -0800jak68By: jak68
http://ask.metafilter.com/71600/looking-for-a-sign#1067216
(actually I meant that I'd use | for "EXCLUSIVE or" and || for "inclusive or").comment:ask.metafilter.com,2007:site.71600-1067216Sat, 15 Sep 2007 22:46:44 -0800jak68By: TheOnlyCoolTim
http://ask.metafilter.com/71600/looking-for-a-sign#1067326
<em>A single item is _not_ a set containing one item: {a} != a.</em><br>
<br>
Fucking pedant.comment:ask.metafilter.com,2007:site.71600-1067326Sun, 16 Sep 2007 06:09:38 -0800TheOnlyCoolTim