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  • in Rails, with check_box_tag, how do I keep the checkboxes checked after submitting query?

    - by Sebastien Paquet
    Ok, I know this is for the Saas course and people have been asking questions related to that as well but i've spent a lot of time trying and reading and I'm stuck. First of all, When you have a model called Movie, is it better to use Ratings as a model and associate them or just keep Ratings in an array floating in space(!). Second, here's what I have now in my controller: def index @movies = Movie.where(params[:ratings].present? ? {:rating => (params[:ratings].keys)} : {}).order(params[:sort]) @sort = params[:sort] @ratings = Ratings.all end Now, I decided to create a Ratings model since I thought It would be better. Here's my view: = form_tag movies_path, :method => :get do Include: - @ratings.each do |rating| = rating.rating = check_box_tag "ratings[#{rating.rating}]" = submit_tag "Refresh" I tried everything that is related to using a conditional ternary inside the checkbox tag ending with " .include?(rating) ? true : "" I tried everything that's supposed to work but it doesn't. I don't want the exact answer, I just need guidance.Thanks in advance!

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  • PHP OOP: Avoid Singleton/Static Methods in Domain Model Pattern

    - by sunwukung
    I understand the importance of Dependency Injection and its role in Unit testing, which is why the following issue is giving me pause: One area where I struggle not to use the Singleton is the Identity Map/Unit of Work pattern (Which keeps tabs on Domain Object state). //Not actual code, but it should demonstrate the point class Monitor{//singleton construction omitted for brevity static $members = array();//keeps record of all objects static $dirty = array();//keeps record of all modified objects static $clean = array();//keeps record of all clean objects } class Mapper{//queries database, maps values to object fields public function find($id){ if(isset(Monitor::members[$id]){ return Monitor::members[$id]; } $values = $this->selectStmt($id); //field mapping process omitted for brevity $Object = new Object($values); Monitor::new[$id]=$Object return $Object; } $User = $UserMapper->find(1);//domain object is registered in Id Map $User->changePropertyX();//object is marked "dirty" in UoW // at this point, I can save by passing the Domain Object back to the Mapper $UserMapper->save($User);//object is marked clean in UoW //but a nicer API would be something like this $User->save(); //but if I want to do this - it has to make a call to the mapper/db somehow $User->getBlogPosts(); //or else have to generate specific collection/object graphing methods in the mapper $UserPosts = $UserMapper->getBlogPosts(); $User->setPosts($UserPosts); Any advice on how you might handle this situation? I would be loathe to pass/generate instances of the mapper/database access into the Domain Object itself to satisfy DI - At the same time, avoiding that results in lots of calls within the Domain Object to external static methods. Although I guess if I want "save" to be part of its behaviour then a facility to do so is required in its construction. Perhaps it's a problem with responsibility, the Domain Object shouldn't be burdened with saving. It's just quite a neat feature from the Active Record pattern - it would be nice to implement it in some way.

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  • how do I get a new line, after using float:left?

    - by codeman73
    What I am trying to do is have rows of images, 6 images in each row. Some of these images need to have another image floating on top of them (flush with the lower-right corner). I was able to get that to work from this thread: http://stackoverflow.com/questions/48474/how-do-i-position-one-image-on-top-of-another-in-html However, now I'm unable to get the new row after the 6th image. Neither <BR> or <P> create a new line. They simply push the next image down several pixels, but the image is still in the same line. It seems like the float style is interfering with the <BR> and/or <P>. I tried using different styles for the image that starts a new row, like float:none and display:block, but neither worked. The odd thing is that the new line starts after the 7th image. Here's what I'm using so far: <style type="text/css"> .containerdiv { float: left; position: relative; } .containerdivNewLine { float: none; display: block; position: relative; } .cornerimage { position: absolute; bottom: 0; right: 0; } </style> <div class="containerdiv"> <img border="0" height="188" src="myImg" width="133" /> <img class="cornerimage" height="140" src="imageOnTop" width="105" /> </div> For the 7th image, when I'm trying to start a new row, I'm simply replacing the 'containerdiv' class with 'containerdivNewLine'.

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  • Are there any downsides in using C++ for network daemons?

    - by badcat
    Hey guys! I've been writing a number of network daemons in different languages over the past years, and now I'm about to start a new project which requires a new custom implementation of a properitary network protocol. The said protocol is pretty simple - some basic JSON formatted messages which are transmitted in some basic frame wrapping to have clients know that a message arrived completely and is ready to be parsed. The daemon will need to handle a number of connections (about 200 at the same time) and do some management of them and pass messages along, like in a chat room. In the past I've been using mostly C++ to write my daemons. Often with the Qt4 framework (the network parts, not the GUI parts!), because that's what I also used for the rest of the projects and it was simple to do and very portable. This usually worked just fine, and I didn't have much trouble. Being a Linux administrator for a good while now, I noticed that most of the network daemons in the wild are written in plain C (of course some are written in other languages, too, but I get the feeling that 80% of the daemons are written in plain C). Now I wonder why that is. Is this due to a pure historic UNIX background (like KISS) or for plain portability or reduction of bloat? What are the reasons to not use C++ or any "higher level" languages for things like daemons? Thanks in advance! Update 1: For me using C++ usually is more convenient because of the fact that I have objects which have getter and setter methods and such. Plain C's "context" objects can be a real pain at some point - especially when you are used to object oriented programming. Yes, I'm aware that C++ is a superset of C, and that C code is basically C++. But that's not the point. ;)

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  • Working with QWords

    - by Glenn1234
    I'm learning and in the course of that working on an assembler conversion which uses QWORDs a lot (x86-32bit). Now my reference material doesn't have anything on working with such values beyond the obvious of splitting them up into the 32-bit registers. I guess they're on the old side. The newer processors have mmx and sse instructions and the like. Would I be served well to look into those instructions for solving this? What is the best way to handle doing work on QWORD values?

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  • C++'s char * by swig got problem in Python 3.0

    - by gpliu3
    Our C++ lib works fine with Python2.4 using Swig, returning a C++ char* back to a python str. But this solution hit problem in Python3.0, error is: Exception=(, UnicodeDecodeError('utf8', b"\xb6\x9d\xa.....",0, 1, 'unexpected code byte') Our definition is like(working fine in Python 2.4): void cGetPubModulus( void* pSslRsa, char* cMod, int* nLen ); %include "cstring.i" %cstring_output_withsize( char* cMod, int* nLen ); Suspect swig is doing a Bytes-Str conversion automatically. In python2.4 it can be implicit but in Python3.0 it's no long allowed.. Anyone got a good idea? thanks

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  • Tagging in Subversion - how do I make the decision about continuing to work on my trunk vs. the new

    - by Howiecamp
    I'm running Tortoise SVN to manage a project. Obviously the principles around tagging apply to any implementation of SVN but in this question I'll be referring to some TortoiseSVN-specific dialog boxes and messages. My working directory and the subversion repository structure both have a Source root directory and the Trunk, Tags and Branches directories underneath. (I couldn't figure out how to do a multilevel indented hierarchy in markdown without using bullets, so if someone could edit and fix this I'd appreciate it.) I'm working out of the Trunk directory in my working copy and it's pointing at the Trunk directory in the repo. I want to apply a Tag "Release1" so I click the "Branch/tag..." menu option and set the repo path as my [repo_path/bla/Source/Tags/Release1" tag. This dialog box gives me the option to "Switch my working copy to new branch/tag". I understand that if this option is left unchecked, the new "Release1" branch under /Tags" will be created but my working copy will remain on the previous "Trunk" path. If I do check this option (or use the Switch command) I understand that my working copy will switch to the new "Release1" branch under "/Tags". Where I'm missing a concept is how to make this decision. It doesn't seem like I want to switch my working directory to the recently created tag since by definition (?) I want that tag to be a snapshot of my code as of a point in time. If I don't switch the working directory, I'll continue working off Trunk and when I'm ready to take another snapshot I'll make another tag. And so on... Am I understanding this right or am I stating something incorrectly in the previous paragraph (e.g. the statement about not wanting to switch to the tag since the tag should represent a point in time snapshot) or otherwise missing something regarding how to make this decision?

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  • What algorithm can I use to determine points within a semi-circle?

    - by khayman218
    I have a list of two-dimensional points and I want to obtain which of them fall within a semi-circle. Originally, the target shape was a rectangle aligned with the x and y axis. So the current algorithm sorts the pairs by their X coord and binary searches to the first one that could fall within the rectangle. Then it iterates over each point sequentially. It stops when it hits one that is beyond both the X and Y upper-bound of the target rectangle. This does not work for a semi-circle as you cannot determine an effective upper/lower x and y bounds for it. The semi-circle can have any orientation. Worst case, I will find the least value of a dimension (say x) in the semi-circle, binary search to the first point which is beyond it and then sequentially test the points until I get beyond the upper bound of that dimension. Basically testing an entire band's worth of points on the grid. The problem being this will end up checking many points which are not within the bounds.

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  • How do I Convert ARGB value from string to color?

    - by James
    I am trying to use the MakeColor method in the GDIAPI unit but the conversion from int to byte is not returning me the correct value. Example var argbStr: string; A, R, G, B: Byte; begin argbStr := 'ffffcc88'; A := StrToInt('$' + Copy(AValue, 0, 2)); R := StrToInt('$' + Copy(AValue, 3, 2)); G := StrToInt('$' + Copy(AValue, 5, 2)); B := StrToInt('$' + Copy(AValue, 7, 2)); Result := MakeColor(A, R, G, B); end; What am I doing wrong?

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  • Is there a table of OpenGL extensions, versions, and hardware support somewhere?

    - by Thomas
    I'm looking for some resource that can help me decide what OpenGL version my game needs at minimum, and what features to support through extensions. Ideally, a table of the following format: 1.0 1.1 1.2 1.2.1 1.3 ... multitexture - ARB ARB core core texture_float - EXT EXT ARB ARB ... (Not sure about the values I put in, but you get the idea.) The extension specs themselves, at opengl.org, list the minimum OpenGL version they need, so that part is easy. However, many extensions have been accepted and became core standard in subsequent OpenGL versions, but it is very hard to find when that happened. The only way I could find is to compare the full OpenGL standards document for each version. On a related note, I would also very much like to know which extensions/features are supported by which hardware, to help me decide what features I can safely use in my game, and which ones I need to make optional. For example, a big honkin' table like this: MAX_TEXTURE_IMAGE_UNITS MAX_VERTEX_TEXTURE_IMAGE_UNITS ... GeForce 6xxx 8 4 GeForce 7xxx 16 8 ATi x300 8 4 ... (Again, I'm making the values up.) The table could list hardware limitations from glGet but also support for particular extensions, and limitations of such extension support (e.g. what floating-point texture formats are supported in hardware). Any pointers to these or similar resources would be hugely appreciated!

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  • C# Image.Clone to byte[] causes EDIT.COM to open on Windows XP

    - by JayDial
    It appears that cloning a Image and converting it to a byte array is causing EDIT.COM to open up on Windows XP machines. This does not happen on a Windows 7 machine. The application is a C# .NET 2.0 application. Does anyone have any idea why this may be happening? Here is my Image conversion code: public static byte[] CovertImageToByteArray(Image imageToConvert) { imageToConvert.Clone() as Image; if(clone == null) return null; imageToConvert.Dispose(); byte[] imageByteArray; using (MemoryStream ms = new MemoryStream()) { clone.Save(ms, clone.RawFormat); imageByteArray = ms.ToArray(); } return imageByteArray; } public static Image ConvertByteArrayToImage(byte[] imageByteArray, ImageFormat formatOfImage) { Image image; using ( MemoryStream ms = new MemoryStream(imageByteArray, 0, imageByteArray.Length)) { ms.Write(imageByteArray, 0, imageByteArray.Length); image = Image.FromStream(ms, true); } return image; } Thanks Justin

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  • Approaches for animating a C# property over time?

    - by Mario Fritsch
    I'm currently trying to animate a bunch of public properties on certain objects. Usually they are of type float or vectors of floats (the type is known at compile-time). I want to be able to: assign a static value to them (MyObject.Duration = 10f;) or assign a random value to them by specifying a minimum and maximum value and optionally also a weight (MyObject.Duration = new RandomFloat(5f, 20f, 2f);) or "bind" this property to the property of another object (think of a child object binding some of its properties to its parent object, like its color or size or sth.) or assign sort of a keyframe animation to them, specifying a variable number of keyframes with timecode and the property's value at that specific point in time as well as information about how to interpolate between these frames The keyframes should be able to accept random values for each frame, both for the time and the property's value. What would be a practical approach for this kind of system? Currently I'm thinking about polymorphism: implement a base class or interface with a public Value-property and/or GetValue(float time)-method and then creating different sub classes like StaticValue, RandomValue, BindingValue and AnimatedValue implementing this base class or interface. Doesn't seem very elegant, though, and the initialization of even simple objects becomes a bit tedious. Another idea would be to implement these properties just as regular floats or vectors and create special "Modifier"-types binding to these properties. To retrieve the "real" value of the property, I'd first call any Modifier bound to the property, which would in turn update the actual object's property for me to retrieve later on. That would most likely mean using reflection at some point, which could be quite bad for performance as I'll probably have thousands of properties to update dozens of times per second. Any suggestions on this? Being a novice I'm (hopefully) missing some far more elegant and/or practical solution than I'm already playing around with :( Edit: Probably should have mentioned this earlier, but WPF isn't an option - it's not available on all targetted platforms, so I can't rely on it. I'm aware of its powerful databinding and animation capabilities, but I need to roll my own (or find some other lightweight alternative meeting my needs).

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  • Help! Getting an error copying the data from one column to the same column in a similar recordset..

    - by Mike D
    I have a routine which reads one recordset, and adds/updates rows in a similar recordset. The routine starts off by copying the columns to a new recordset: Here's the code for creating the new recordset.. For X = 1 To aRS.Fields.Count mRS.Fields.Append aRS.Fields(X - 1).Name, aRS.Fields(X - 1).Type, aRS.Fields(X - _ 1).DefinedSize, aRS.Fields(X - 1).Attributes Next X Pretty straight forward. Notice the copying of the name, Type, DefinedSize & Attributes... Further down in the code, (and there's nothing that modifies any of the columns between.. ) I'm copying the values of a row to a row in the new recordset as such: For C = 1 To aRS.Fields.Count mRS.Fields(C - 1) = aRS.Fields(C - 1) Next C When it gets to the last column which is a numeric, it craps with the "Mutliple-Step Operation Generated an error" message. I know that MS says this is an error generated by the provider, which in this case is ADO 2.8. There is no open connect to the DB at this point in time either. I'm pulling what little hair I have left over this one... (and I don't really care at this point that the column index is 'X' in one loop & 'C' in the other... I'll change it later when I get the real problem fixed...)

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  • Sizing issues while adding a .Net UserControl to a TabPage

    - by TJ_Fischer
    I have a complex Windows Forms GUI program that has a lot of automated control generation and manipulation. One thing that I need to be able to do is add a custom UserControl to a newly instatiated TabPage. However, when my code does this I get automatic resizing events that cause the formatting to get ugly. Without detailing all of the different Containers that could possibly be involved, the basic issue is this: At a certain point in the code I create a new tab page: TabPage tempTabPage = new TabPage("A New Tab Page"); Then I set it to a certain size that I want it to maintain: tempTabPage.Width = 1008; tempTabPage.Height = 621; Then I add it to a TabControl: tabControl.TabPages.Add(tempTabPage); Then I create a user control that I want to appear in the newly added TabPage: CustomView customView = new CustomView("A new custom control"); Here is where the problem comes in. At this point both the tempTabPage and the customView are the same size with no padding or margin and they are the size I want them to be. I now try to add this new custom UserControl to the tab page like this: tempTabPage.Controls.Add(customView); When making this call the customView and it's children controls get resized to be larger and so parts of the customView are hidden. Can anyone give me any direction on what to look for or what could be causing this kind of issue? Thanks ahead of time.

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  • read angles in radian and convert them in degrees/minutes/seconds

    - by Amadou
    n=0; disp('This program performs an angle conversion'); disp('input data set to a straight line. Enter the name'); disp('of the file containing the input Lambda in radian: '); filename = input(' ','s'); [fid,msg] = fopen(filename,'rt'); if fid < 0 disp(msg); else A=textscan(fid, '%g',1); while ~feof(fid) Lambda = A(1); n = n + 1; A = textscan(fid, '%f',1); end fclose(fid); end Alpha=Lambda*180/pi; fprintf('Angle converted from radian to degree/minutes/seconds:\n'); fprintf('Alpha =%12d\n',Alpha); fprintf('No of angles =%12d\n',n);

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  • How do I handle editing of custom types in a C# datagridview?

    - by Ian Hopkinson
    I have a datagridview in which one column contains a custom class, which I have set using: dgvPeriods.Columns[1].ValueType = typeof(ExDateTime); It is rigged up to display correctly by handling the CellFormatting event, but I'm unsure what event to handle for cell editing. In the absence of doing anything I get a FormatException as the datagridview tries to convert String to ExDateTime as I try to move focus out of the edited cell. I tried adding type conversion to my ExDateTime custom class: public static implicit operator ExDateTime(string b) { return new ExDateTime(b); } But this this didn't work. I also tried handling the DataError event, but this seems to fire too late. The datagridview is not databound.

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  • How do you use stl's functions like for_each?

    - by thomas-gies
    I started using stl containers because they came in very handy when I needed functionality of a list, set and map and had nothing else available in my programming environment. I did not care much about the ideas behind it. STL documentations were only interesting up to the point where it came to functions, etc. Then I skipped reading and just used the containers. But yesterday, still being relaxed from my holidays, I just gave it a try and wanted to go a bit more the stl way. So I used the transform function (can I have a little bit of applause for me, thank you). From an academic point of view it really looked interesting and it worked. But the thing that boroughs me is that if you intensify the use of those functions, you need 10ks of helper classes for mostly everything you want to do in your code. The hole logic of the program is sliced in tiny pieces. This slicing is not the result of god coding habits. It's just a technical need. Something, that makes my life probably harder not easier. And I learned the hard way, that you should always choose the simplest approach that solves the problem at hand. And I can't see what, for example, the for_each function is doing for me that justifies the use of a helper class over several simple lines of code that sit inside a normal loop so that everybody can see what is going on. I would like to know, what you are thinking about my concerns? Did you see it like I do when you started working this way and have changed your mind when you got used to it? Are there benefits that I overlooked? Or do you just ignore this stuff as I did (and will go an doing it, probably). Thanks. PS: I know that there is a real for_each loop in boost. But I ignore it here since it is just a convenient way for my usual loops with iterators I guess.

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  • How to store and compare time-zone sensitive times

    - by Chad Moran
    I have a data structure where an entity has times stored as an int (minutes into the day) for fast comparison. The entity also has a Foreign Key reference back to a TimeZone table which contains the .NET CLR ID Name and it's Standard Time/Daylight Time acronyms. Since this information is stored as time-zone insensitive - I was wondering how in LINQ to SQL I could convert this into a UTC DateTime for comparison against other times that will be in UTC. Just to be clear this conversion has to be done server-side so that I can execute filtering on the SQL Server and not the client. I am using .NET 3.5 SP1 and SQL Server 2008.

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  • Why do R objects not print in a function or a "for" loop?

    - by Sal Leggio
    I have an R matrix named ddd. When I enter this, everything works fine: i <- 1 shapiro.test(ddd[,y]) ad.test(ddd[,y]) stem(ddd[,y]) print(y) The calls to Shapiro Wilk, Anderson Darling, and stem all work, and extract the same column. If I put this code in a "for" loop, the calls to Shapiro Wilk, and Anderson Darling stop working, while the the stem & leaf call and the print call continue to work. for (y in 7:10) { shapiro.test(ddd[,y]) ad.test(ddd[,y]) stem(ddd[,y]) print(y) } The decimal point is 1 digit(s) to the right of the | 0 | 0 0 | 899999 1 | 0 [1] 7 The same thing happens if I try and write a function. SW & AD do not work. The other calls do. > D <- function (y) { + shapiro.test(ddd[,y]) + ad.test(ddd[,y]) + stem(ddd[,y]) + print(y) } > D(9) The decimal point is at the | 9 | 000 9 | 10 | 00000 [1] 9 Why don't all the calls behave the same way?

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  • Service for converting SWFs with ActionScript to Video (MPEG, AVI, or MOV)

    - by pcooley
    The SWF files generated by our application are a basic template that reference external resources (images, and textual data) that actionscript uses to fuel the display. Thus the SWF is responsible for the creative layout of the screen the flash player. It is the results of this actions script, images, and textual data that need to be converted to a video format. Is anyone familiar with an online service that would be able to convert such .swf files that our site generates to a video format (say .avi, .mpeg, .mov). Or an application? Note: A more common case might be the conversion of an embedded FLV to a video, but this is not our need

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  • Resource placement (optimal strategy)

    - by blackened
    I know that this is not exactly the right place to ask this question, but maybe a wise guy comes across and has the solution. I'm trying to write a computer game and I need an algorithm to solve this question: The game is played between 2 players. Each side has 1.000 dollars. There are three "boxes" and each player writes down the amount of money he is going to place into those boxes. Then these amounts are compared. Whoever placed more money in a box scores 1 point (if draw half point each). Whoever scores more points wins his opponents 1.000 dollars. Example game: Player A: [500, 500, 0] Player B: [333, 333, 334] Player A wins because he won Box A and Box B (but lost Box C). Question: What is the optimal strategy to place the money? I have more questions to ask (algorithm related, not math related) but I need to know the answer to this one first. Update (1): After some more research I've learned that these type of problems/games are called Colonel Blotto Games. I did my best and found few (highly technical) documents on the subject. Cutting it short, the problem I have (as described above) is called simple Blotto Game (only three battlefields with symmetric resources). The difficult ones are the ones with, say, 10+ battle fields with non-symmetric resources. All the documents I've read say that the simple Blotto game is easy to solve. The thing is, none of them actually say what that "easy" solution is.

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  • Move camera to fit 3D scene

    - by Burre
    Hi there. I'm looking for an algorithm to fit a bounding box inside a viewport (in my case a DirectX scene). I know about algorithms for centering a bounding sphere in a orthographic camera but would need the same for a bounding box and a perspective camera. I have most of the data: I have the up-vector for the camera I have the center point of the bounding box I have the look-at vector (direction and distance) from the camera point to the box center I have projected the points on a plane perpendicular to the camera and retrieved the coefficients describing how much the max/min X and Y coords are within or outside the viewing plane. Problems I have: Center of the bounding box isn't necessarily in the center of the viewport (that is, it's bounding rectangle after projection). Since the field of view "skew" the projection (see http://en.wikipedia.org/wiki/File:Perspective-foreshortening.svg) I cannot simply use the coefficients as a scale factor to move the camera because it will overshoot/undershoot the desired camera position How do I find the camera position so that it fills the viewport as pixel perfect as possible (exception being if the aspect ratio is far from 1.0, it only needs to fill one of the screen axis)? I've tried some other things: Using a bounding sphere and Tangent to find a scale factor to move the camera. This doesn't work well, because, it doesn't take into account the perspective projection, and secondly spheres are bad bounding volumes for my use because I have a lot of flat and long geometries. Iterating calls to the function to get a smaller and smaller error in the camera position. This has worked somewhat, but I can sometimes run into weird edge cases where the camera position overshoots too much and the error factor increases. Also, when doing this I didn't recenter the model based on the position of the bounding rectangle. I couldn't find a solid, robust way to do that reliably. Help please!

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  • Why is forwarding variadic parameters invalid?

    - by awesomeyi
    Consider the variadic function parameter: func foo(bar:Int...) -> () { } Here foo can accept multiple arguments, eg foo(5,4). I am curious about the type of Int... and its supported operations. For example, why is this invalid? func foo2(bar2:Int...) -> () { foo(bar2); } Gives a error: Could not find an overload for '_conversion' that accepts the supplied arguments Why is forwarding variadic parameters invalid? What is the "conversion" the compiler is complaining about?

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  • How to get this to compile?

    - by ShaChris23
    I have this code which compiles and works as expected: class Right {}; class Left { public: Left& operator = (Right const&) { //... Do something ... return *this; } }; int main() { Right right; Left left; // Assign individual object -- this works left = right; } But now, this one surprises me, I thought the template would work itself out since I already provided the = operator() to the Left class. int main() { ... std::list<Right> rightLst; std::list<Left> leftLst; // Assign a list of objects -- this doesn't compile leftLst = rightLst; } What can I do so that I could convert the rightLst to leftLst conversion in a single line?

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  • How to deal with a Java serialized object whose package changed?

    - by Alex
    I have a Java class that is stored in an HttpSession object that's serialized and transfered between servers in a cluster environment. For the purpose of this explanation, lets call this class "Person". While in the process of improving the code, this class was moved from "com.acme.Person" to "com.acme.entity.Person". Internally, the class remains exactly the same (same fields, same methods, same everything). The problem is that we have two sets of servers running the old code and the new code at the same time. The servers with the old code have serialized HttpSession object and when the new code unserializes it, it throws a ClassNotFoundException because it can't find the old reference to com.acme.Person. At this point, it's easy to deal with this because we can just recreate the object using the new package. The problem then becomes that the HttpSession in the new servers, will serialize the object with the new reference to com.acme.entity.Person, and when this is unserialized in the servers running the old code, another exception will be thrown. At this point, we can't deal with this exception anymore. What's the best strategy to follow for this kind of cases? Is there a way to tell the new servers to serialize the object with the reference to the old package and unserialize references to the old package to the new one? How would we transition to using the new package and forgetting about the old one once all servers run the new code?

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