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• Binary Search Tree - Postorder logic

  - by daveb

  I am looking at implementing code to work out binary search tree. Before I do this I was wanting to verify my input data in postorder and preorder. I am having trouble working out what the following numbers would be in postorder and preorder I have the following numbers 4, 3, 14 ,8 ,1, 15, 9, 5, 13, 10, 2, 7, 6, 12, 11, that I am intending to put into an empty binary tree in that order. The order I arrived at for the numbers in POSTORDER is 2, 1, 6, 3, 7, 11, 12, 10, 9, 8, 13, 15, 14, 4. Have I got this right? I was wondering if anyone here would be able to kindly verify if the postorder sequence I came up with is indeed the correct sequence for my input i.e doing left subtree, right subtree and then root. The order I got for pre order (Visit root, do left subtree, do right subtree) is 4, 3, 1, 2, 5, 6, 14 , 8, 7, 9, 10, 12, 11, 15, 13. I can't be certain I got this right. Very grateful for any verification. Many Thanks

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• Business entity: private instance VS single instance

  - by taoufik

  Suppose my WinForms application has a business entity Order, the entity is used in multiple views, each view handles a different domain or use-case in the application. As an example, one managing orders, the other one digging into one order and displaying additional data. If I'd use nHibernate (or any other ORM) and use one session/dataContext per view (or per db action), I'd end up getting two different instances for the same Order (let's say orderId = 1). Although functionally the same entity, they are technically two different instances. Yes, I could implement Equals/GetHashcode to make them "seem" the same. Why would you go for a single instance per entity vs private instances per view or per use-case? Having single instances has the advantage of sharing INotifyPropertyChanged events, and sharing additional (non-persistent) data. Having a private instance in each view would give you the flexibility of the undo functionality on a view level. In the example above, I'd allow the user to change order details, and give them the flexibility to not save the change. Here, synchronisation between the view/use-case happens on a data persistence level. What would your argument be?

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• Gaining information from nodes of tree

  - by jainp

  I am working with the tree data structure and trying to come up with a way to calculate information I can gain from the nodes of the tree. I am wondering if there are any existing techniques which can assign higher numerical importance to a node which appears less frequently at lower level (Distance from the root of the tree) than the same nodes appearance at higher level and high frequency. To give an example, I want to give more significance to node Book, at level 2 appearing once, then at level 3 appearing thrice. Will appreciate any suggestions/pointers to techniques which achieve something similar. Thanks, Prateek

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• Avoiding stack overflows in wrapper DLLs

  - by peachykeen

  I have a program to which I'm adding fullscreen post-processing effects. I do not have the source for the program (it's proprietary, although a developer did send me a copy of the debug symbols, .map format). I have the code for the effects written and working, no problems. My issue now is linking the two. I've tried two methods so far: Use Detours to modify the original program's import table. This works great and is guaranteed to be stable, but the user's I've talked to aren't comfortable with it, it requires installation (beyond extracting an archive), and there's some question if patching the program with Detours is valid under the terms of the EULA. So, that option is out. The other option is the traditional DLL-replacement. I've wrapped OpenGL (opengl32.dll), and I need the program to load my DLL instead of the system copy (just drop it in the program folder with the right name, that's easy). I then need my DLL to load the Cg framework and runtime (which relies on OpenGL) and a few other things. When Cg loads, it calls some of my functions, which call Cg functions, and I tend to get stack overflows and infinite loops. I need to be able to either include the Cg DLLs in a subdirectory and still use their functions (not sure if it's possible to have my DLLs import table point to a DLL in a subdirectory) or I need to dynamically link them (which I'd rather not do, just to simplify the build process), something to force them to refer to the system's file (not my custom replacement). The entire chain is: Program loads DLL A (named opengl32.dll). DLL A loads Cg.dll and dynamically links (GetProcAddress) to sysdir/opengl32.dll. I now need Cg.dll to also refer to sysdir/opengl32.dll, not DLL A. How would this be done? Edit: How would this be done easily without using GetProcAddress? If nothing else works, I'm willing to fall back to that, but I'd rather not if at all possible. Edit2: I just stumbled across the function SetDllDirectory in the MSDN docs (on a totally unrelated search). At first glance, that looks like what I need. Is that right, or am I misjudging? (off to test it now) Edit3: I've solved this problem by doing thing a bit differently. Instead of dropping an OpenGL32.dll, I've renamed my DLL to DInput.dll. Not only does it have the advantage of having to export one function instead of well over 120 (for the program, Cg, and GLEW), I don't have to worry about functions running back in (I can link to OpenGL as usual). To get into the calls I need to intercept, I'm using Detours. All in all, it works much better. This question, though, is still an interesting problem (and hopefully will be useful for anyone else trying to do crazy things in the future). Both the answers are good, so I'm not sure yet which to pick...

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• Problem storing a hash in DB using Storable::nfreeze in Perl

  - by Sam

  I want to insert a hash in the db using Storable::nfreeze but the data is not inserted properly. My code is as follows: %rec=(); $rec{'name'} = 'my name'; $rec{'address'} = 'my address'; my $order1 = new Order(); $order1->set_session(\%rec); $self->createOrder($order1); sub createOrder { my $self = $_[0]; my $order = $_[1]; # Retrieve the fields to insert into the database. my $st = $dbh->prepare("insert into order (session,.......) values(?,........)"); my $session = %{$order->get_session()}; $st->execute(&Storable::nfreeze(\%session),.....); $st->finish(); } sub getOrder { ... my $session = &Storable::thaw( $ref->{'session'} ); ..... } The thaw is working fine because I tested it withe some rows that have been inserted correctly, but when I try to get a row that was inserted using the createOrder subroutine, I get an error saying: Storable binary image v36.65 more recent than I am (v2.7) at blib/lib/Storable.pm (autosplit into blib/lib/auto/Storable/thaw.al) line 415 The error comes from the line that have thaw. The nfreeze did not store the hash properly. Can someone point me to what I'm doing wrong in the createOrder subroutine? I know the module version have nothing to do with the problem.

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• Arduino (processing) Library in Netbeans and control

  - by Casper Marcussen

  Hello everyone I am trying to control 4 LEDs and getting analog input from 4 contacts. The program is written in java, so to gain acces to the functions of arduino, such as AnalogRead() and setting an LED to high or low, would importing the processing library let the program use those functions? I was also wondering, if the program, will be transferred to the arduino it self, or the java program will just pull the data from the pins?

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• Showing Live Wallpaper in a 1.6 target app by detecting if it's a 2.1 device?

  - by itamarw

  We're building an Android app with target SDK 1.6, so it will run on 1.6 devices and higher. We'd like to support Live Wallpapers, which we know is 2.1+ only. Is there a way to build one app with 1.6 SDK as the target, but detect if the device it's running on is 2.1, and only in that scenario call the live wallpaper API. We're trying to avoid having to build a separate 1.6 and 2.1 versions, and would like to be able to support Live Wallpapers for only 2.1 devices. So to be clear- 1 app, that can support 1.6 and higher, and support live wallpapers for 2.1 devices. Any way of doing this?

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• Better way to clean this messy bool method

  - by Luís Custódio

  I'm reading Fowler Clean Code book and I think that my code is a little messy, I want some suggestions: I have a simple business requirement that is return the date of new execution of my Thread. I've two class fields: _hour and _day. If actual day is higher than my _day field I must return true, so I'll add a month to "executionDate" If the day is the same, but the actual hour is higher than _hour I should return true too. So I did this simple method: private bool ScheduledDateGreaterThanCurrentDate (DateTime dataAtual) { if (dateActual.Day > _day) { return true; } if (dateActual.Day == _day && dateActual.Hour > _hour) { return true; } if (dateActual.Day == _day && dateActual.Hour == _hour) if (dateActual.Minute>0 || dateActual.Second>0) return true; return false; } I'm programming with TDD, so I know that the return is correct, but this is bad maintain code right?

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• COM Dual Interfaces

  - by Tony

  A dual interface in COM is one that is able to be accessed via a DispInterface or via VTable methods. Now can someone tell me what is exactly what the difference is between the two methods? I thought that a VTable is a virtual table which holds the pointers to the different functions when implementing a class hierarchy which has virtual functions that can be overridden in child classes. However I do not see how this is related to a dual interface in COM?

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• ConcurrentLinkedQueue$Node remains in heap after remove()

  - by action8

  I have a multithreaded app writing and reading a ConcurrentLinkedQueue, which is conceptually used to back entries in a list/table. I originally used a ConcurrentHashMap for this, which worked well. A new requirement required tracking the order entries came in, so they could be removed in oldest first order, depending on some conditions. ConcurrentLinkedQueue appeared to be a good choice, and functionally it works well. A configurable amount of entries are held in memory, and when a new entry is offered when the limit is reached, the queue is searched in oldest-first order for one that can be removed. Certain entries are not to be removed by the system and wait for client interaction. What appears to be happening is I have an entry at the front of the queue that occurred, say 100K entries ago. The queue appears to have the limited number of configured entries (size() == 100), but when profiling, I found that there were ~100K ConcurrentLinkedQueue$Node objects in memory. This appears to be by design, just glancing at the source for ConcurrentLinkedQueue, a remove merely removes the reference to the object being stored but leaves the linked list in place for iteration. Finally my question: Is there a "better" lazy way to handle a collection of this nature? I love the speed of the ConcurrentLinkedQueue, I just cant afford the unbounded leak that appears to be possible in this case. If not, it seems like I'd have to create a second structure to track order and may have the same issues, plus a synchronization concern.

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• displaying data between date ranges mysql

  - by Kyle Hudson

  Hi Guys, I need to work out a period of 6 months (backwards) from a given date. Example date: 07/06/2010 00:00:00 needs to count back 6 months and display: 07/12/2009 00:00:00 I have been scanning through: http://dev.mysql.com/doc/refman/5.1/en/date-and-time-functions.html and non of these functions make sense to me :( Hope this makes sense and any help would be appriciated. Kyle

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• Improving field get and set performance with ASM or Javassist

  - by ng

  I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM and Javasist examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and one with Javassist? Any help would be greatly appreciated.

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• GLOBALS ARE BAAAAAAADDDD!!!!!

  - by Matt

  HOWEVER! would setting the $link to my database be one thing that I prolly should use a GLOBAL scope for? In my setting of (lots of functions)...it seems as though having only one variable that is on the global scope would be wise. I am currently using the functions to transfer it back and forth so that way I do not have it on global...but it is a bit of a hinder to my script. Please Advise, Thank you. Matt

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• Java - Virtual Methods

  - by Gogi

  How does virtual functions work behind the scenes in Inheritance ? Does the compiler treat virtual functions specially ?

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• What industries develop the highest quality software? Lowest quality? Why?

  - by Derek Mahar

  From your experience, of those industries that develop custom software for internal use such as financial services companies, which ones produce higher quality software measured in defect rates and, more qualitatively, ease of maintenance over the long term? What contributes the most to this achievement of higher quality? Is it due to better software development practices such as greater emphasis on testing or specification? Developers who better understand the tools or who are strong problem solvers? Better communication between team members? On the flip-side, which industries do you think produce the lowest quality software? Why?

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• Creating Domain Model

  - by Zai

  Hi, I have created a use case of a small application and now I have to create a Domain Model of that use cases of the application and which functions will be implemented in this application. I have no previous experience in Domain Modeling and UML, please suggest me steps to create the domain model or any suggestions, Do I have to have a very solid understanding of Object oriented concepts for creating domain model? The application is simple and creates online poll/voting system and have functions like Register Account, Confirmation Email of account, Membership, Create Poll, Send Poll etc

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• JLayeredPane versus Container layering

  - by Gili

  JLayeredPane allows one to stack multiple Components on top of one another using JLayeredPane.add(Component, Integer). Components in higher "layers" display on top of Components in lower "layers". Container.add(Component, int) provides a similar mechanism whereby Components with lower indexes display on top of Components with higher indexes. Please note that the first mechanism uses Integer and the second mechanism uses int. Also, one renders high values on top of low ones, and the other does the opposite. Do not mix the two :) My question is: what's the point of using JLayeredPane when Container already provides the same mechanism? Does one layer components better than the another? UPDATE: There is also Container.setComponentZOrder(Component, int) to consider.

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• Call private method in Flex, Actionscript.

  - by core07

  I need it in FlexUnit to test private methods. Is there any possibility to do this via reflection by using describeType or maybe flexUnit has some build in facility? I dislike artificial limitation that i cannot test private functions, it greatly reduces flexibility. Yes it is good design for me to test private functions, so please do not advise me to refactor my code. I do not want to break the encapsulation for the sake of unit testing.

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• PHP custom class and function autocompletion in TextMate project

  - by Koen.

  Is there a bundle which completes my custom classes and functions in a TextMate project? Like the code hints with PHP core functions?

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• How does PHP work - literature

  - by Ondrej Slinták

  I'm interested in literature (articles on internet, in magazines, books, podcasts - I don't really mind anything) that describes how PHP works internally, about its gotchas and perhaps some advanced functions. Is there anything like this out there? I tried to search on Google, but majority of articles were about starting with PHP and its basic functions. Any input is really welcome as I'm trying to understand the language internally - I'm tired of my mindless typing of code without understanding its essence.

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• problem storing a hash in DB using Storage::nfreeze Perl

  - by Sam

  Hello, I want to insert a hash in the db using Storage::nfreeze but the data is not inserted properly. the code is as follow: %rec=(); $rec{'name'} = 'my name'; $rec{'address'} = 'my address'; my $order1 = new Order(); $order1->set_session(\%rec); $self->createOrder($order1); sub createOrder { my $self = $_[0]; my $order = $_[1]; # Retrieve the fields to insert into the database. my $st = $dbh->prepare("insert into order (session,.......) values(?,........)"); my $session = %{$order->get_session()}; $st->execute(&Storable::nfreeze(\%session),.....); $st->finish(); } sub getOrder { ... my $session = &Storable::thaw( $ref->{'session'} ); ..... } the thaw is working fine because I tested it withe some rows that have been inserted correctly. but when I try to get a row that was inserted using the createOrder subroutine, I get an error saying" Storable binary image v36.65 more recent than I am (v2.7) at blib/lib/Storable.pm (autosplit into blib/lib/auto/Storable/thaw.al) line 415 the error comes from the line that have thaw. the nfreeze did not store the hash properly. Can someone point me to what i m doing wrong in the createOrder subroutine? Thanks in advance. I know the module version have nothing to do with the problem.

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• non-latin email address validation

  - by Eric Di Bari

  Now that ICann is allowing non-latin-character domain names, should I be concerned about e-mail validation? Currently, my sites are using php functions to ensure some alpha-numeric character set in each segment of an email address. Will these other character sets, such as Cyrillic, Arabic, and Chinese, pass validation? Are there recommended php functions to utilize for this?

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• Oracle command hangs when using view for "WHILE x IN..." subquery

  - by Calvin Fisher

  I'm working on a web service that fetches data from an oracle data source in chunks and passes it back to an indexing/search tool in XML format. I'm the C#/.NET guy, and am kind of fuzzy on parts of Oracle. Our Oracle team gave us the following script to run, and it works well: SELECT ROWID, [columns] FROM [table] WHERE ROWID IN ( SELECT ROWID FROM ( SELECT ROWID FROM [table] WHERE ROWID > '[previous_batch_last_rowid]' ORDER BY ROWID ) WHERE ROWNUM <= 10000 ) ORDER BY ROWID 10,000 rows is an arbitrary but reasonable chunk size and ROWID is sufficiently unique for our purposes to use as a UID since each indexing run hits only one table at a time. Bracketed values are filled in programmatically by the web service. Now we're going to start adding views to the indexing, each of which will union a few separate tables. Since ROWID would no longer function as a unique identifier, they added a column to the views (VIEW_UNIQUE_ID) that concatenates the ROWIDs from the component tables to construct a UID for each union. But this script does not work, even though it follows the same form as the previous one: SELECT VIEW_UNIQUE_ID, [columns] FROM [view] WHERE VIEW_UNIQUE_ID IN ( SELECT VIEW_UNIQUE_ID FROM ( SELECT VIEW_UNIQUE_ID FROM [view] WHERE ROWID > '[previous_batch_last_view_unique_id]' ORDER BY VIEW_UNIQUE_ID ) WHERE ROWNUM <= 10000 ) ORDER BY VIEW_UNIQUE_ID It hangs indefinitely with no response from the Oracle server. I've waited 20+ minutes and the SQLTools dialog box indicating a running query remains the same, with no progress or updates. I've tested each subquery independently and each works fine and takes a very short amount of time (<= 1 second), so the view itself is sound. But as soon as the inner two SELECT queries are added with "WHERE VIEW_UNIQUE_ID IN...", it hangs. Why doesn't this query work for views? In what important way are they not interchangeable here?

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• Good Starting Points for Optimizing Database Calls in Ruby on Rails?

  - by viatropos

  I have a menu in Rails which grabs a nested tree of Post models, each which have a Slug model associated via a polymorphic association (using the friendly_id gem for slugs and awesome_nested_set for the tree). The database output in development looks like this (here's the full gist): SQL (0.4ms) SELECT COUNT(*) AS count_id FROM "posts" WHERE ("posts".parent_id = 39) CACHE (0.0ms) SELECT "posts".* FROM "posts" WHERE ("posts"."id" = 13) LIMIT 1 CACHE (0.0ms) SELECT "slugs".* FROM "slugs" WHERE ("slugs".sluggable_id = 13 AND "slugs".sluggable_type = 'Post') ORDER BY id DESC LIMIT 1 Slug Load (0.4ms) SELECT "slugs".* FROM "slugs" WHERE ("slugs".sluggable_id = 40 AND "slugs".sluggable_type = 'Post') ORDER BY id DESC LIMIT 1 SQL (0.3ms) SELECT COUNT(*) AS count_id FROM "posts" WHERE ("posts".parent_id = 40) CACHE (0.0ms) SELECT "posts".* FROM "posts" WHERE ("posts"."id" = 13) LIMIT 1 CACHE (0.0ms) SELECT "slugs".* FROM "slugs" WHERE ("slugs".sluggable_id = 13 AND "slugs".sluggable_type = 'Post') ORDER BY id DESC LIMIT 1 Slug Load (0.4ms) SELECT "slugs".* FROM "slugs" WHERE ("slugs".sluggable_id = 41 AND "slugs".sluggable_type = 'Post') ORDER BY id DESC LIMIT 1 ... Rendered shared/_menu.html.haml (907.6ms) What are some quick things I should always do to optimize this from the start (easy things)? Some things I'm thinking now are: Can Rails 3 eager load the whole Post tree + associated Slugs in one DB call? Can I do that easily with named scopes or custom SQL? What is best practice in this situation? Not really thinking about memcached in this situation as that can be applied to much more than just this.

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• Insight into how things get printed onto the screen (cout,printf) and origin of really complex stuff

  - by sil3nt

  I've always wondered this, and still haven't found the answer. Whenever we use "cout" or "printf" how exactly is that printed on the screen?. How does the text come out as it does...(probably quite a vague question here, ill work with whatever you give me.). So basically how are those functions made?..is it assembly?, if so where does that begin?. This brings on more questions like how on earth have they made openGl/directx functions.. break it down people break it down.:)

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