I read this link  But this answer doesn't look enough to me.  Can I have more explanations about uses of unions. I don't want any memory related examples like, this will take max 4 bytes (float occupy 4 bytes ).  union un{     char ch;     int iNum;     float fNum; };   So my question is,  what exactly the use of union?   why we need this?  Please help me, its confusing me. Thanks.
When should unions be used? Why do we need them?
Merge flash site into one executable Polynomial degree 3 Equation Why might one also use a blank constructor? I was reading some Java recently and came across something (an idiom?) new to me: in the program, classes with multiple constructors would also always include a blank constructor. For example:   public class Genotype {   private boolean bits[];   private int rating;   private int length;   private Random random;    public Genotype() {              //  &lt;= THIS is the bandit, this one right here     random = new Random();   }    /* creates a Random genetoype */   public Genotype(int length, Random r) {     random = r;     this.length = length;     bits = new boolean[length];      for(int i=0;i&lt;length;i++) {         bits[i] =random.nextBoolean();     }   }    /* copy constructor */   public Genotype(Genotype g,Random r) {     random = r;     bits = new boolean[g.length];     rating = g.rating;     length = g.length;      for(int i=0;i&lt;length;i++) {         bits[i] = g.bits[i];     }    } }   The first constructor doesn't seem to be a "real" constructor, it seems as though in every case one of the other constructors will be used. So why is that constructor defined at all? How to configure Micromax 352g USB Modem? I want the driver software for my Micromax 352g USB modem for Ubuntu 12.04 LTS. On Ubuntu 10.04 sakis3g was working well, but it is not working on Ubuntu 12.04 LTS. Inverse images of images, images of inverse images of a set of vectors What can be said about$\ f^{-1}(f(S))$ and$\ S$, where$\ f(S):=\{f(x):x \in S\}$?   I feel as if$\ f^{-1}(f(S))$ will be smaller than or equal in size (number of elements) to$\ S$.  For example, if$\ f(x)=x$, then$\ f(\{-1, 0, 1, 2\})=\{-1, 0, 1, 2\}$and$\ f^{-1}(f\{-1, 0, 1, 2\})=\{-1, 0, 1, 2\}$ (same size).  But if$\ f(x)=x^2$, then$\ f(\{-1, 0, 1, 2\})=\{0, 1, 4\}$ and$\ f^{-1}(f\{0, 1, 4\})=\{0, 1, 2\}$, which is a little bit smaller than$\ S$.   What can be said about$\ f(f^{-1}(U))$ and$\ U$, where$\ f^{-1}(U):=\{x \in X:f(x) \in U\}$?   The same size as each other? Always?? What is the difference between fixed effect, random effect and mixed effect models? In simple terms, how would you explain (perhaps with simple examples) the difference between fixed effect, random effect and mixed effect models? Acces VBA code combination not working, issue with exit sub? I'm very new at VBA and I can't seem to solve this problem. It seems like it should be an easy problem to fix, I just don't know how.   So what the code does: In the main form is a record. This record will be copied to another table bij pressing a button on the form. Before the copying begins, the code checks first if the 'OMnummer' has been filled in in the subform.  If not, a message box appears saying that the user should fill in the subform and the code stops running.   Secondly the code checks if the record is allready present in the other table. If so, a messagebox appears and the record will not be copied. If not, the record will be copied to the other table.   Both pieces of code work ok seperately. However, when I try to include both pieces in the same private sub, only the first one works. It may be something with the 'Exit Sub' code or I am not using the If - Then right.   Hope you can help me!  Monika   Private Sub KnopProjectVersturen_Click() On Error GoTo ErrProc  If IsNull(Me!Subform_OMnummers.Form!Omnr) Then  If MsgBox("Vul het OMnummer in. Je kan het project niet exporteren zonder OMnummer.")     Then       Exit Sub      DoCmd.OpenQuery "Qry_Depo_ControleAanwezig"  If DCount("Deponering.projectnummer", "Qry_Depo_ControleAanwezig") = 0 Then         DoCmd.SetWarnings False         DoCmd.OpenQuery "Qry_projectnaarDepot"          DoCmd.OpenQuery "Qry_ToevoegProjectDepot"         DoCmd.OpenForm "Depot_uitvoer", , , "[Projectnummer] = '" &amp; Me![Projectnummer] &amp; "' And [subID]=[subID]"     Me.Status = 8     DoCmd.Close acQuery, ("Qry_Depo_ControleAanwezig")     DoCmd.SetWarnings True  Else         MsgBox "Dit project bestaat al in de Depot_Uitvoer, verander de status in het projectformulier", vbInformation, "Example"         DoCmd.Close acQuery, ("Qry_Depo_ControleAanwezig")     End If  End If  End If    'Als er fouten zijn laat deze code een messagebox zien met het nummer en de melding.  ExitProc:  Exit Sub  ErrProc:     Select Case Err.Number     Case Else         MsgBox Err.Number &amp; "--" &amp; Err.Description         Resume ExitProc         End Select End Sub Getting the location from an IP address I want to retrieve information like the city, state, and country of a visitor from their IP address, so that I can customize my web page according to their location. Is there a good and reliable way to do this in PHP? I am using JavaScript for client-side scripting, PHP for server-side scripting, and MySQL for the database. Why is Linux's filesystem designed as a single directory tree? Limit of function of hyperbolic How can I - without using derivatives - find the limit of the function  $f(x)=\frac{1}{\cosh(x)}+\log \left(\frac{\cosh(x)}{1+\cosh(x)} \right)$  as $x \to \infty$ and as $x \to -\infty$?  We know that $\cosh(x) \to \infty$ as $x \to \pm \infty$ thus $\frac{1}{\cosh(x)} \to 0$ as $x \to \pm \infty$.  And I imagine that $\frac{\cosh(x)}{1+\cosh(x)} \to 1$ as $x \to \pm \infty$ thus $\log\left(\frac{\cosh(x)}{1+\cosh(x)}\right) \to 0$ as $x \to \pm \infty$.  Is this approach sufficiently formal?  Any help is appreciated. Add a transparent image on top of a material Understanding QGIS buffer tool units I  have had no luck getting the buffer tool to accept anything but degrees as units of measure.  I have found lots of stuff saying the layer needs to be reprojected and saved but it hasn't worked at all for me.   Is there a way I could create a buffer without using ftools or at least force the units to meters somehow?  As a workaround I converted meters to degrees (lat) and used that but the final product needs to be as close to reality as possible.  Things I've tried:   setting every unit option I could find to meters (where possible). setting everything to NAD83/Maryland (data is for Washington, DC) and saving it as such (as layers in ESRI shape files). reimporting the reprojected layers setting relevant layers to Google Mercator   The was tried followed by creating a buffer. Many were tried in combination. QGIS 1.7.3 Slackware64 current (qgis from SBo-13.37 repo, tried on multilib and plain 64it with same results) What does Geordi see on the holodeck? We've seen how he interprets people and things with his VISOR, but if the holodeck is all force-fields and holographic imaging, how does he interact in a similar way to other members?   What does the holodeck look like to Geordi LaForge using his VISOR? How can I get CSS comments with jQuery? I am wondering how I can read CSS comments out of a linked stylesheet.  I have this sample CSS loaded via:  &lt;link rel="stylesheet" type="text/css" media="all" href="test.css" /&gt;   &nbsp;  #test1{ border:1px solid #000; } #test2{ border:1px solid #000; } #test3{/* sample comment text I'm trying to read */}   I'm testing this in FF3. The following javascript reads the rules but doesn't read the comments in#test3.  window.onload = function(){     s=document.styleSheets;     for(i=0;i &lt; s[0].cssRules.length;i++){         alert(s[0].cssRules[i].cssText);     } } "In and of itself" is a phrase I find myself using all the time. But in and of itself, the phrase "in and of itself" has no meaning. That is, the individual words don't seem to contribute to the whole meaning of the phrase. How to set spawnpoint? Does DTIME(O(n)) = REGULAR? Is imperative Quicksort in situ (in-place) or not? Do I have to buy or need a 3D-enabled phone to use Google Cardboard? Google cardboard comes with 3D glasses. Does that mean that we will be able to watch 3D videos using a smartphone like the Moto-G (1st edition) which is not 3D enabled? Why are trivial edits discouraged? Looking at  privilege, I find this to be a surprising requirement:  Try to make the post substantively better when you edit, not just change a single character. Tiny, trivial edits are discouraged.  What motivated this, or rather, what does this mean exactly? Does that, for example, include removing stuff like &quot;Hi, all&quot;, and &quot;thanks in advance&quot;? [update] I was led to a  talking about this topic, but it has a million Comments, and doesn't really justify the rule (unless it's hidden in those million Comments). However, looking at Jeff's Comments gives me an idea that this was meant as a general guideline, instead of a hard-and-fast rule: If you edit a post, check elsewhere on that post if there are other improvements that can be made.