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• MATLAB: What is an appropriate Data Structure for a Matrix with Random Variable Entries?

  - by user568249

  I'm currently working in an area that is related to simulation and trying to design a data structure that can include random variables within matrices. To motivate this let me say I have the following matrix: [a b; c d] I want to find a data structure that will allow for a, b, c, d to either be real numbers or random variables. As an example, let's say that a = 1, b = -1, c = 2 but let d be a normally distributed random variable with mean 0 and SD 1. The data structure that I have in mind will give no value to d. However, I also want to be able to design a function that can take in the structure, simulate an uniform(0,1), obtain a value for d using an inverse CDF and then spit out an actual matrix. I have several ideas to do this (all related to the MATLAB icdf function) but would like to know how more experienced programmers would do this. In this application, it's important that the structure is as "lean" as possible since I will be working with very very large matrices and memory will be an issue.

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• How do I choose what and when to cache data with ob_start rather than query the database?

  - by Tim Santeford

  I have a home page that has several independent dynamic parts. The parts consist of a list of recent news from the company, a site statistics panel, and the online status of certain employees. The recent news changes monthly, site statistics change daily, and online statuses change on a per minute bases. I would like to cache these panels so that the db is not hit on every page load. Is using ob_start() then ob_get_contents() to cache these parts to a file the correct way to do this or is there a better method in PHP5 for doing this? In asking this question I'm trying to answer these additional questions: How can I determine the correct approach for caching this data without doing extensive benchmarking? Does it make sense to cache these parts in different files and then join them together per requests or should I re-query the data and cache once per minute? I'm looking for a rule of thumb for planning pages and for situations where doing testing is not cost effective (The client is not paying enough for it I mean). Thanks!

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• Loading more than 10 images on iPhone??

  - by SeniorLee

  I'm trying to add more than 10 pictures on ScrollView. NSUInteger i; for (i = 1; i <= numberOfImage; i++) { NSString *imageName = [NSString stringWithFormat:@"d%dimage%d.png", imageSection, i]; UIImage *image = [UIImage imageNamed:imageName]; UIImageView *imageView = [[UIImageView alloc] initWithImage:image]; // setup each frame to a default height and width, it will be properly placed when we call "updateScrollList" CGRect rect = imageView.frame; rect.size.height = kScrollObjHeight; rect.size.width = kScrollObjWidth; imageView.frame = rect; imageView.tag = i; // tag our images for later use when we place them in serial fashion [scrollView addSubview:imageView]; [imageView release]; } This code is from Apple example and it works fine. But if the variable 'i' is bigger than 10, 'UIImage *image' is empty. The imageName seems to correct. But I don't know why it does not load image. Does anybody sees the problem?? And one more thing. If I do like that, does iOS controls memory automatically? I mean it's kind of wasting memory if all (more than 10) images are loaded on memory even they are not displayed. I've heard that iOS loads images only displayed on screen and free images those are not displayed. Is that right? Thanks for reading.

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• Grouping by date, with 0 when count() yields no lines

  - by SCO

  I'm using Postgresql 9 and I'm fighting with counting and grouping when no lines are counted. Let's assume the following schema : create table views { date_event timestamp with time zone ; event_id integer; } Let's imagine the following content : 2012-01-01 00:00:05 2 2012-01-01 01:00:05 5 2012-01-01 03:00:05 8 2012-01-01 03:00:15 20 I want to group by hour, and count the number of lines. I wish I could retrieve the following : 2012-01-01 00:00:00 1 2012-01-01 01:00:00 1 2012-01-01 02:00:00 0 2012-01-01 03:00:00 2 2012-01-01 04:00:00 0 2012-01-01 05:00:00 0 . . 2012-01-07 23:00:00 0 I mean that for each time range slot, I count the number of lines in my table whose date correspond, otherwise, I return a line with a count at zero. The following will definitely not work (will yeld only lines with counted lines 0). SELECT extract ( hour from date_event ),count(*) FROM views where date_event > '2012-01-01' and date_event <'2012-01-07' GROUP BY extract ( hour from date_event ); Please note I might also need to group by minute, or by hour, or by day, or by month, or by year (multiple queries is possible of course). I can only use plain old sql, and since my views table can be very big (100M records), I try to keep performance in mind. How can this be achieved ? Thank you !

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• Limiting Row Selection in JTable

  - by Pat

  Is there an easy way to limit the total selection of rows in a JTable? I mean I'd like to allow the user to use shift and ctrl to select a maximum of X rows. If he clicks again on a row it would cancel out all the selections. Sort of how it currently behaves, but while limiting the total amount of selected rows. Here's my current implementation, I'm kind of clueless on how to limit the selection graphically. public class RoomsListView extends AbstractViewPanel { public RoomsListView(DefaultController controller) { this.controller = controller; initUI(); } private void initUI() { tableT = new JTable(RoomsModel.getInstance()); sorter = new TableRowSorter<RoomsModel>(RoomsModel.getInstance()); tableT.setRowSorter(sorter); tableT.setPreferredScrollableViewportSize(new Dimension(CUSTOM_TABLE_WIDTH, CUSTOM_TABLE_HEIGHT)); tableT.addMouseListener(new MouseAdapter() { public void mouseClicked(MouseEvent e) { rowClickedPerformed(e); } }); } private void rowClickedPerformed(MouseEvent e) { } public void modelPropertyChange(PropertyChangeEvent evt) { } public JTable getTable() { return tableT; } private final int CUSTOM_TABLE_WIDTH = -1; private final int CUSTOM_TABLE_HEIGHT = 150; private JTable tableT; private DefaultController controller; private TableRowSorter<RoomsModel> sorter; }

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• rendering a TextView in a Bitmap for an android widget

  - by foke

  I'm building a widget which displays some text. By widget I mean the kind which lies on the desktop. The problem is that I want to change text's font at runtime. There is several textview I would like, at runtime, to set the first as bold, the second blue and italic for example, etc. I came up with this : TextView tv = new TextView(context); tv.setText(stringToDisplay); tv.setTextColor(0xa00050ff); // example tv.setTextSize(30); // example Bitmap b = loadBitmapFromView(tv); updateViews.setImageViewBitmap(R.id.id_of_the_imageview, b); with private static Bitmap loadBitmapFromView(View v) { Bitmap b = Bitmap.createBitmap(v.getLayoutParams().width, v.getLayoutParams().height, Bitmap.Config.ARGB_8888); Canvas c = new Canvas(b); v.layout(0, 0, v.getLayoutParams().width, v.getLayoutParams().height); v.draw(c); return b; } but it wont work (NullPointerException on first line of loadBitmap), until I replace v.getLayoutParams().width, v.getLayoutParams().height by fixed sizes like 250, 50 Bitmap b = Bitmap.createBitmap(250, 50, Bitmap.Config.ARGB_8888); // ... v.layout(0, 0, 250, 50); But that's not a good solution ... so I tried this : LayoutInflater li = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); View row = li.inflate(R.layout.widget_text, null); TextView tv = (TextView) row.findViewById(R.id.id_of_the_textview); widget_text being a layout similar to the displayed one but with TextViews instead of ImageViews, in the hope to get some size information out of it .. but it's not working and I get this exception : 01-02 17:35:06.001: ERROR/AndroidRuntime(11025): Caused by: java.lang.IllegalArgumentException: width and height must be > 0 on the call to Bitmap.createBitmap() so, someone could point me in the right direction?

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• How to have variables with dynamic data types in Java?

  - by Nazgulled

  Hi, I need to have a UserProfile class that it's just that, a user profile. This user profile has some vital user data of course, but it also needs to have lists of messages sent from the user friends. I need to save these messages in LinkedList, ArrayList, HashMap and TreeMap. But only one at a time and not duplicate the message for each data structure. Basically, something like a dynamic variable type where I could pick the data type for the messages. Is this, somehow, possible in Java? Or my best approach is something like this? I mean, have 2 different classes (for the user profile), one where I host the messages as Map<K,V> (and then I use HashMap and TreeMap where appropriately) and another class where I host them as List<E> (and then I use LinkedList and ArrayList where appropriately). And probably use a super class for the UserProfile so I don't have to duplicate variables and methods for fields like data, age, address, etc... Any thoughts?

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• In Ruby or Python can the very idea of Class be rewritten?

  - by John Berryman

  Howdy All... first time at stack overflow. I'm looking into using some of the metaprogramming features provided by Ruby or Python, but first I need to know the extent to which they will allow me to extend the language. The main thing I need to be able to do is to rewrite the concept of Class. This doesn't mean that I want to rewrite a specific class during run time, but rather I want to make my own conceptualization of what a Class is. To be a smidge more specific here, I want to make something that is like what people normally call a Class, but I want to follow an "open world" assumption. In the "closed world" of normal Classes, if I declare Poodle to be a subclass of Dog to be a subclass of Animal, then I know that Poodle is not going to also be a type of FurCoat. However, in an open world Class, then the Poodle object I've defined may or may not be and object of type FurCoat and we won't know for sure until I explain that I can wear the poodle. (Poor poodle.) This all has to do with a study I'm doing concerning OWL ontologies. Just so you know, I've tried to find information online, but due to the overloading of terms here I haven't found anything helpful. Super thanks, John

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• Rails 4 testing bug?

  - by Jamato

  Situation: if we add two identic line items into a cart, we update line item quantity instead of adding a duplicate.In browser everything works fine but in unit testing section something fails because of an empty cycle in code. Which I wanted to use to update all prices. Why? Is that a unit test engine bug? LineItem.all and cart.line_items in process of testing produce two DIFFERENT structures. #<LineItem id: 980190964, product_id: 1, cart_id: 999, created_at: "2014-06-01 00:21:28", updated_at: "2014-06-01 00:21:28", quantity: 2, price: #<BigDecimal:ba0fb544,'0.4E1',9(27)>> #<LineItem id: 980190964, product_id: 1, cart_id: 999, created_at: "2014-06-01 00:21:28", updated_at: "2014-06-01 00:21:28", quantity: 1, price: #<BigDecimal:ba0d1b04,'0.4E1',9(27)>> cart.line_items guy did not update quantity Code itself (produces LineItem which is then saved in line_item_controller which calls this method) class Cart < ActiveRecord::Base has_many :line_items, dependent: :destroy def add_product(product_id) # LOOK THIS CYCLE BREAKS UNIT TEST, SRSLY, I MEAN IT line_items.each do |item| end current_item = line_items.find_by(product_id: product_id) fresh_price = Product.find_by(id: product_id).price if current_item current_item.quantity += 1 else current_item = line_items.build(product_id: product_id, price: fresh_price) end return current_item end ... Unit test code test "non-unique item added" do cart = Cart.new(:id => 999) line_item0 = cart.add_product(2) line_item0.save line_item1 = cart.add_product(1) line_item1.save assert_equal 2, cart.line_items.size #success line_item2 = cart.add_product(1) line_item2.save assert_equal 2, cart.line_items.size, "what?" assert cart.total_price > 15 #fail, prices are not enough, quantity of product1 = 1 #we get total price from quantity, it's a simple method in model end And once again: IT DOES WORK in browser as it should. Even with cycle. I feel so dumb right now...

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• C++ private inheritance and static members/types

  - by WearyMonkey

  I am trying to stop a class from being able to convert its 'this' pointer into a pointer of one of its interfaces. I do this by using private inheritance via a middle proxy class. The problem is that I find private inheritance makes all public static members and types of the base class inaccessible to all classes under the inheriting class in the hierarchy. class Base { public: enum Enum { value }; }; class Middle : private Base { }; class Child : public Middle { public: void Method() { Base::Enum e = Base::value; // doesn't compile BAD! Base* base = this; // doesn't compile GOOD! } }; I've tried this in both VS2008 (the required version) and VS2010, neither work. Can anyone think of a workaround? Or a different approach to stopping the conversion? Also I am curios of the behavior, is it just a side effect of the compiler implementation, or is it by design? If by design, then why? I always thought of private inheritance to mean that nobody knows Middle inherits from Base. However, the exhibited behavior implies private inheritance means a lot more than that, in-fact Child has less access to Base than any namespace not in the class hierarchy!

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• Can't referr to my get method

  - by chility

  I have this amazing and good looking class: public class SayingsHolder extends Application{ ArrayList<String> SayingsList = new ArrayList<String>(){{ SayingsList.add("1"); SayingsList.add("2"); }}; public ArrayList<String> getSayingsList() { return SayingsList; } } Now I'm trying to call the getSayingsList method inside of my activity's FragmentStatePagerAdapter by: private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter { final SayingsHolder holder = (SayingsHolder).getApplication(); } Everything fine for now, but when I make my code like this: private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter { final SayingsHolder holder = (SayingsHolder).getApplication(); holder.getSayingsList(); } it says: Syntax error on token "getSayingsList", Identifier expected after this token The problem is that holder is not functional at all. What I mean is that when i type the this holder. the getSayingsList is not showing at all. What am I missing here? I know that it is an extremely small issue, but it seems that I can't spot it. My activity extends FragmentActivity if it's important It seems that I'm missing something here. I can't call my method anywhere in my activity. I'm starting a bounty, because I need an example.

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• Php string handling triks

  - by Dam

  Hi my question Need to get the 10 word before and 10 words after for the given text . i mean need to start the 10 words before the keyword and end with 10 word after the key word. Given text : "Twenty-three" The main trick : content having some html tags etc .. tags need to keep that tag with this content only . need to display the words from 10before - 10after content is bellow : <div id="hpFeatureBoxInt"><h3><a href="/go/homepage/i/int/news/world/1/-/news/1/hi/world/europe/8592190.stm">Suicide bombings hit Moscow Metro</a></h3><p>Past suicide bombings in Moscow have been blamed on Islamist rebels At least 35 people have been killed after two female suicide bombers blew themselves up on Moscow Metro trains in the morning rush hour,<h2><span class="dy">Top News Story</span></h2> officials say.<img height="150" width="201" alt="Emergency services carry a body from a Metro station in Moscow (29 March 2010)" src="http://wwwimg.bbc.co.uk/feedengine/homepage/images/_47550689_moscowap203_201x150.jpg">Twenty-three died in the first blast at 0756 (0356 GMT) as a<a href="#"> train stood </a>at the central Lubyanka station, beneath the offices of the FSB intelligence agency.About 40 minutes later, a second explosion ripped through a train at Park Kultury, leaving another 12 dead.No-one has said they carried out the worst attack in the capital since 2004. </p><p id="fbilisten"><a href="/go/homepage/i/int/news/heading/-/news/">More from BBC News</a></p></div> Thank you

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• Android lifecycle: Fill in data in activity in onStart() or onResume()?

  - by pjv

  Should you get data via a cursor and fill in the data on the screen, such as setting the window title, in onStart() or onResume()? onStart() would seem the logical place because after onStart() the Activity can already be displayed, albeit in the background. Notably I was having a problem with a managed dialog that made me rethink this. If the user rotates the screen while the dialog is still open, onCreateDialog() and onPrepareDialog() are called between onStart() and onResume(). If the dialog needs to be based on the data you need to have the data before onResume(). If I'm correct about onStart() then why does the Notepad example give a bad example by doing it in onResume()? See http://developer.android.com/resources/samples/NotePad/src/com/example/android/notepad/NoteEditor.html NoteEditor.java line 176 (title = mCursor.getString...). Also, what if my Activity launches another Actvity/Dialog that changes the data my cursor is tracking. Even in the simplest case, does that mean that I have to manually update my previous screen (a listener for a dialog in the main activity), or alternatively that I have to register a ContentObserver, since I'm no longer updating the data in onResume() (though I could update it twice of course)? I know it's a basic question but the dialog only recently, to my surprise, made me realize this.

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• Opening up process and grabbing window title. Where did I go wrong?

  - by user1632018

  In my application I allow for the users to add a program from a open file dialog, and it then adds the item to a listview and saves the items location into the tag. So what I am trying to do is when the program in the listview is selected and the button is pressed, it starts a timer and this timer checks to see if the process is running, and if it isn't launches the process, and once the process is launched it gets the window title of the process and sends it to a textbox on another form. EDIT: The question is if anyone can see why it is not working, by this I mean starting the process, then when it's started closing the form and adding the process window title to a textbox on another form. I have tried to get it working but I can't. I know that the process name it is getting is right I think my problem is to do with my for loop. Basically it isn't doing anything visible right now. I feel like I am very close with my code and im hoping it just needs a couple minor tweaks. Any help would be appreciated. Sorry if my coding practices aren't that great, im pretty new to this. EDIT:I thought I found a solution but it only works now if the process has been started already. It won't start it up. Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick Dim s As String = ListView1.SelectedItems(0).Tag Dim myFile As String = Path.GetFileName(s) Dim mu As String = myFile.Replace(".exe", "").Trim() Dim f As Process Dim p As Process() = Process.GetProcessesByName(mu) For Each f In p If p.Length > 0 Then For i As Integer = 0 To p.Length - 1 ProcessID = (p(i).Id) AutoMain.Name.Text = f.MainWindowTitle Timer1.Enabled = False Me.Close() Next Else ProcessID = 0 End If If ProcessID = 0 Then Process.Start(myFile) End If Next End Sub

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• random image and its url

  - by venom

  i want to create a random image and its url, i mean not the link of the image, but in addition to image's link, i want the specified URL, so that random image was displayed and when u click on it, u go to the specified URL here is my javascript: function random_imglink(){ var myimages=new Array() //specify random images below. You can have as many as you wish myimages[1]="/documents/templates/projedepo/banner/canon.jpg" myimages[2]="/documents/templates/projedepo/banner/indigovision.jpg" var ry=Math.floor(Math.random()*myimages.length) if (ry==0) ry=1 var randomImage = '<img src="'+myimages[ry]+'" height="420" width="964" />'; document.getElementById("image2").innerHTML = randomImage; } random_imglink() Here is my HTML: <div id="slider_container"> <div id="image2"> </div> <div id="thumb2"> <a href="#" rel="/documents/templates/projedepo/banner/canon.jpg" class="image2" ><img title="Canon" class="slider_thumb" src="/documents/templates/bilgiteknolojileri/images/t_flash/t1.png" border="0"/></a> <a href="#" rel="/documents/templates/projedepo/banner/indigovision.jpg" class="image2"><img title="IndogoVision" class="slider_thumb" src="/documents/templates/bilgiteknolojileri/images/t_flash/t2.png" border="0"/></a> </div></div>

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• SQL - table alias scope.

  - by Support - multilanguage SO

  I've just learned ( yesterday ) to use "exists" instead of "in". BAD select * from table where nameid in ( select nameid from othertable where otherdesc = 'SomeDesc' ) GOOD select * from table t where exists ( select nameid from othertable o where t.nameid = o.nameid and otherdesc = 'SomeDesc' ) And I have some questions about this: 1) The explanation as I understood was: "The reason why this is better is because only the matching values will be returned instead of building a massive list of possible results". Does that mean that while the first subquery might return 900 results the second will return only 1 ( yes or no )? 2) In the past I have had the RDBMS complainin: "only the first 1000 rows might be retrieved", this second approach would solve that problem? 3) What is the scope of the alias in the second subquery?... does the alias only lives in the parenthesis? for example select * from table t where exists ( select nameid from othertable o where t.nameid = o.nameid and otherdesc = 'SomeDesc' ) AND select nameid from othertable o where t.nameid = o.nameid and otherdesc = 'SomeOtherDesc' ) That is, if I use the same alias ( o for table othertable ) In the second "exist" will it present any problem with the first exists? or are they totally independent? Is this something Oracle only related or it is valid for most RDBMS? Thanks a lot

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• Reading and writing to files simultaneously?

  - by vipersnake005

  Moved the question here. Suppose, I want to store 1,000,000,000 integers and cannot use my memory. I would use a file(which can easily handle so much data ). How can I let it read and write and the same time. Using fstream file("file.txt', ios::out | ios::in ); doesn't create a file, in the first place. But supposing the file exists, I am unable to use to do reading and writing simultaneously. WHat I mean is this : Let the contents of the file be 111111 Then if I run : - #include <fstream> #include <iostream> using namespace std; int main() { fstream file("file.txt",ios:in|ios::out); char x; while( file>>x) { file<<'0'; } return 0; } Shouldn't the file's contents now be 101010 ? Read one character and then overwrite the next one with 0 ? Or incase the entire contents were read at once into some buffer, should there not be atleast one 0 in the file ? 1111110 ? But the contents remain unaltered. Please explain. Thank you.

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• Input In Java- How does it work?

  - by Nir Avnon

  Hey guys, with a lot of help from you i was managed to write this nice code (I'm new in it, so kind of exciting.. :) ) And still I have not understand how can I input this code. first of all, I get an this error in the console line (I'm using Eclipse): Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 at NumberConverter.main(NumberConverter.java:5). What does that mean? I just want to chack whether it works, and I can't call the function/program any how. I used to call in an "old fashion way", like in scheme, to the function that I wrote and see if something happens. How does it work in java? Do we call the program itself? function? what and where do we write? -I want to chack if it works, doesn't matter how, and I'll be glad to know how can I plugin input. Thank you so much! public class NumberConverter{ public static void main(String[] args) { int i = Integer.parseInt(args[0]); toBinary(i); toOctal(i); toHex(i); } public static void toBinary(int int1){ System.out.println(int1 + " in binary is"); System.out.println(Integer.toBinaryString(int1)); } public static void toOctal(int int1){ System.out.println(int1 + " in octal is"); System.out.println(Integer.toOctalString(int1)); } public static void toHex(int int1){ System.out.println(int1 + " in hex is"); System.out.println(Integer.toHexString(int1)); } }

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• Implementing a Version check between an Abstract class and it's implementation

  - by Michael Stum

  I have this abstract class and concrete implementation (they are in different assemblies): public abstract class MyAbstractClass { private static readonly int MyAbstractClassVersion = 1; public abstract int ImplementedVersion { get; } protected MyAbstractClass() { CheckVersion(); } private void CheckVersion() { var message = string.Format( "MyAbstractClass implements Version {0}, concrete is Version {1}", RepositoryVersion, ImplementedVersion); if (!MyAbstractClassVersion.Equals(ImplementedVersion)) throw new InvalidOperationException(message); } } public class ConcreteClass : MyAbstractClass { public ConcreteClass() : base() { // ConcreteClass is guaranteed to have // a constructor that calls the base constructor // I just simplified the example } public override int ImplementedVersion { get { return 2; } } } As you see, I call CheckVersion() from the abstract constructor, to get rid of the "virtual member call in base constructor" message, but I am not sure if that's really the way to do it. Sure, it works, but that doesn't mean it will always work, will it? Also, I wonder if I can get the name of the Concrete Type from the CheckVersion() function? I know that adding new abstract members will force an error anyway (System.TypeLoadException) and I'm not sure if I want this type of strict Versioning, but I'm just curious how it would be done properly given only the abstract class and an implementation (I know I could do it by using interfaces and/or a Factory pattern).

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• get_browser not working

  - by tazphoenix

  it's not working.i mean i have many scripts to get ip and os but anyway get_browser is internal function and should work but its not.when i try to get a print_r on the function i get. Array ( [browser_name_regex] => §^.*$§ [browser_name_pattern] => * [browser] => Default Browser [version] => 0 [majorver] => 0 [minorver] => 0 [platform] => unknown [alpha] => [beta] => [win16] => [win32] => [win64] => [frames] => 1 [iframes] => [tables] => 1 [cookies] => [backgroundsounds] => [cdf] => [vbscript] => [javaapplets] => [javascript] => [activexcontrols] => [isbanned] => [ismobiledevice] => [issyndicationreader] => [crawler] => [cssversion] => 0 [supportscss] => [aol] => [aolversion] => 0 ) I'm using win7 and firefox.

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• Interview Q: sorting an almost sorted array (elements misplaced by no more than k)

  - by polygenelubricants

  I was asked this interview question recently: You're given an array that is almost sorted, in that each of the N elements may be misplaced by no more than k positions from the correct sorted order. Find a space-and-time efficient algorithm to sort the array. I have an O(N log k) solution as follows. Let's denote arr[0..n) to mean the elements of the array from index 0 (inclusive) to N (exclusive). Sort arr[0..2k) Now we know that arr[0..k) are in their final sorted positions... ...but arr[k..2k) may still be misplaced by k! Sort arr[k..3k) Now we know that arr[k..2k) are in their final sorted positions... ...but arr[2k..3k) may still be misplaced by k Sort arr[2k..4k) .... Until you sort arr[ik..N), then you're done! This final step may be cheaper than the other steps when you have less than 2k elements left In each step, you sort at most 2k elements in O(k log k), putting at least k elements in their final sorted positions at the end of each step. There are O(N/k) steps, so the overall complexity is O(N log k). My questions are: Is O(N log k) optimal? Can this be improved upon? Can you do this without (partially) re-sorting the same elements?

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• Why is function's length information of other shared lib in ELF?

  - by minastaros

  Our project (C++, Linux, gcc, PowerPC) consists of several shared libraries. When releasing a new version of the package, only those libs should change whose source code was actually affected. With "change" I mean absolute binary identity (the checksum over the file is compared. Different checksum - different version according to the policy). (I should mention that the whole project is always built at once, no matter if any code has changed or not per library). Usually this can by achieved by hiding private parts of the included Header files and not changing the public ones. However, there was a case where just a delete was added to the destructor of a class TableManager (in the TableManager.cpp file!) of library libTableManager.so, and yet the binary/checksum of library libB.so (which uses class TableManager ) has changed. TableManager.h: class TableManager { public: TableManager(); ~TableManager(); private: int* myPtr; } TableManager.cpp: TableManager::~TableManager() { doSomeCleanup(); delete myPtr; // this delete has been added } By inspecting libB.so with readelf --all libB.so, looking at the .dynsym section, it turned out that the length of all functions, even the dynamically used ones from other libraries, are stored in libB! It looks like this (length is the 668 in the 3rd column): 527: 00000000 668 FUNC GLOBAL DEFAULT UND _ZN12TableManagerD1Ev So my questions are: Why is the length of a function actually stored in the client lib? Wouldn't a start address be sufficient? Can this be suppressed somehow when compiling/linking of libB.so (kind of "stripping")? We would really like to reduce this degree of dependency...

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• What should a hobbyist do to develop good programming skills after basics?

  - by thyrgle

  So I'll say right here that I'm no professional coder. I'm a hobbyist. And pretty much like other people I feel like I'm doing it wrong. Like this question A feeling that I'm not a good programmer if have began to feel like that. Now I know basically that they say you shouldn't worry and that your good even if you continuously doubt yourself. But, they are talking to him. I'm not like him (in the sense I'm more of a newbie)... I've been coding as a hobbyist for 3 years (3 hobbyist years mind you!) unlike his 10-11 years that he states. Also, the only thing I've probably read in-depth is Teach Yourself C++ in 21 Days. And before I continue, just so your not confused about the various questions I've posted on (mostly) iPhone and OpenGL, I have poked and prodded at those two things for a few months each and finally sort of got a hang of both of them. But, from what I've noticed, is that I suck at making good code. For me its not even a debate of whether I'm doing it wrong or not: I can tell (from the various spaghetti code I create and other various discrepancies I, and others, can see and have noted in my code). What is a good way to get rid of these awful habits of mine and do it in a more correct, or if there is no "correct way" then I mean "typical", way?

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• Should I put actors in the Domain-Model/Class-Diagram?

  - by devoured elysium

  When designing both the domain-model and class-diagrams I am having some trouble understanding what to put in them. I'll give an example of what I mean: I am doing a vacations scheduler program, that has an Administrator and End-Users. The Administrator does a couple of things like registering End-Users in the program, changing their previleges, etc. The End-User can choose his vacations days, etc. I initially defined an Administrator and End-User as concepts in the domain-model, and later as classes in the class-diagram. In the class-diagram, both classes ended up having a couple of methods like Administrator.RegisterNewUser(); Administrator.UnregisterUser(int id); etc. Only after some time I realised that actually both Administrator and End-User are actors, and maybe I got this design totally wrong. Instead of filling Administrator and End-User classes with methods to do what my Use-Cases request, I could define other classes from the domain to do them, and have controllers handle the Use-Cases(actually, I decided to do one for each Use-Case). I could have a UserDatabase.RegisterNewUser() and UserDatabase.UnregisterUser(int id);, for example, instead of having those methods on the Administrator class. The idea would be to try to think of the whole vacation-scheduler as a "closed-program" that has a set of features and doesn't bother with things such as authentication, that should be internal/protected, being that the only public things I'd let the outside world see would be its controllers. Is this the right approach? Or am I getting this totally wrong? Is it generally bad idea to put Actors in the domain-model/class-diagrams? What are good rules of thumb for this? My lecturer is following Applying UML and Patterns, which I find awful, so I'd like to know where I could look up more info on this described actor-models situation. I'm still a bit confused about all of this, as this new approach is radically different from anything I've done before.

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• understanding the ORM models in MVC

  - by fayer

  i cant fully understand the ORM models in MVC. so i am using symfony with doctrine. the doctrine models are created. does this mean that i don't have to create any models? are the doctrine models the only models i need? where should i put the code that uses the doctrine models: eg. $phoneIds = array(); $phone1 = new Phonenumber(); $phone1['phonenumber'] = '555 202 7890'; $phone1->save(); $phoneIds[] = $phone1['id']; $phone2 = new Phonenumber(); $phone2['phonenumber'] = '555 100 7890'; $phone2->save(); $phoneIds[] = $phone2['id']; $user = new User(); $user['username'] = 'jwage'; $user['password'] = 'changeme'; $user->save(); $user->link('Phonenumbers', $phoneIds); should this code be in the controller or in another model? and where should i validate these fields (check if it exists in database, that email is email etc)? could someone please shed a light on this. thanks.

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