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• Help me find an appropriate ruby/python parser generator

  - by Geo

  The first parser generator I've worked with was Parse::RecDescent, and the guides/tutorials available for it were great, but the most useful feature it has was it's debugging tools, specifically the tracing capabilities ( activated by setting $RD_TRACE to 1 ). I am looking for a parser generator that can help you debug it's rules. The thing is, it has to be written in python or in ruby, and have a verbose mode/trace mode or very helpful debugging techniques. Does anyone know such a parser generator ? EDIT: when I said debugging, I wasn't referring to debugging python or ruby. I was referring to debugging the parser generator, see what it's doing at every step, see every char it's reading, rules it's trying to match. Hope you get the point. BOUNTY EDIT: to win the bounty, please show a parser generator framework, and illustrate some of it's debugging features. I repeat, I'm not interested in pdb, but in parser's debugging framework. Also, please don't mention treetop. I'm not interested in it.

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• Reference-type conversion operators: asking for trouble?

  - by Ben

  When I compile the following code using g++ class A {}; void foo(A&) {} int main() { foo(A()); return 0; } I get the following error messages: > g++ test.cpp -o test test.cpp: In function ‘int main()’: test.cpp:10: error: invalid initialization of non-const reference of type ‘A&’ from a temporary of type ‘A’ test.cpp:6: error: in passing argument 1 of ‘void foo(A&)’ After some reflection, these errors make plenty of sense to me. A() is just a temporary value, not an assignable location on the stack, so it wouldn't seem to have an address. If it doesn't have an address, then I can't hold a reference to it. Okay, fine. But wait! If I add the following conversion operator to the class A class A { public: operator A&() { return *this; } }; then all is well! My question is whether this even remotely safe. What exactly does this point to when A() is constructed as a temporary value? I am given some confidence by the fact that void foo(const A&) {} can accept temporary values according to g++ and all other compilers I've used. The const keyword can always be cast away, so it would surprise me if there were any actual semantic differences between a const A& parameter and an A& parameter. So I guess that's another way of asking my question: why is a const reference to a temporary value considered safe by the compiler whereas a non-const reference is not?

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• Flush separate Castle ActiveRecord Transaction, and refresh object in another Transaction

  - by eanticev

  I've got all of my ASP.NET requests wrapped in a Session and a Transaction that gets commited only at the very end of the request. At some point during execution of the request, I would like to insert an object and make it visible to other potential threads - i.e. split the insertion into a new transaction, commit that transaction, and move on. The reason is that the request in question hits an API that then chain hits another one of my pages (near-synchronously) to let me know that it processed, and thus double submits a transaction record, because the original request had not yet finished, and thus not committed the transaction record. So I've tried wrapping the insertion code with a new SessionScope, TransactionScope(TransactionMode.New), combination of both, flushing everything manually, etc. However, when I call Refresh on the object I'm still getting the old object state. Here's some code sample for what I'm seeing: Post outsidePost = Post.Find(id); // status of this post is Status.Old using (TransactionScope transaction = new TransactionScope(TransactionMode.New)) { Post p = Post.Find(id); p.Status = Status.New; // new status set here p.Update(); SessionScope.Current.Flush(); transaction.Flush(); transaction.VoteCommit(); } outsidePost.Refresh(); // refresh doesn't get the new status, status is still Status.Old Any suggestions, ideas, and comments are appreciated!

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• Hopping from a C++ to a Perl/Unix job

  - by rocknroll

  Hi all, I have been a C++ / Linux Developer till now and I am adept in this stack. Of late I have been getting opportunities that require Perl, Unix (with knowledge of C++,shell scripting) expertise. Organizations are showing interest even though I don't have much scripting experience to boast off. The role is more in a Support, maintenance project involving SQL as well. Off late I am in a fix whether to forgo these offers or not. I don't know the dynamics of an IT organization and thus on one hand I fear that my C++ experience will be nullified and on the positive side I am getting to work on a new technology stack which will only add to my skill set. I am sure, most of you at some point of time have encountered such dilemmas and would have taken some decision. I want you to share your perspectives on such a scenario where a person is required to change his/her technology stack when changing his/her job. What are the merits and demerits in going with either of the choices? Also I know that C++ isn't going anywhere in the near future. What about perl? I have no clue as to what the future holds for perl developer? Whether there are enough opportunities for a perl developer? I am asking this question here because most of my fellow programmers face this career choice dilemma. Thanks.

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• Python with Wiimote using pywiiuse module

  - by Anon

  After seeing the abilities and hackibility of wiimotes I really want to use it in my 'Intro to programming' final. Everyone must make a python program and present it to the class. I want to make a game with pygame incorporating a wiimote. I found pywiiuse which is a very basic wrapper for the wiiuse library using c types. I can NOT get anything beyond LEDs and vibrating to work. Buttons, IR, motion sensing, nothing. I've tried different versions of wiiuse, pywiiuse, even python. I can't even get the examples that came with it to run. Here's the code I made as a simple test. I copied some of the example C++ code. from pywiiuse import * from time import sleep #Init wiimotes = wiiuse_init() #Find and start the wiimote found = wiiuse_find(wiimotes,1,5) #Make the variable wiimote to the first wiimote init() found wiimote = wiimotes.contents #Set Leds wiiuse_set_leds(wiimote,WIIMOTE_LED_1) #Rumble for 1 second wiiuse_rumble(wiimote,1) sleep(1) wiiuse_rumble(wiimote,0) #Turn motion sensing on(supposedly) wiiuse_motion_sensing(wiimote,1) while 1: #Poll the wiimotes to get the status like pitch or roll if(wiiuse_poll(wiimote,1)): print 'EVENT' And here's the output when I run it. wiiuse version 0.9 wiiuse api version 8 [INFO] Found wiimote [assigned wiimote id 1]. EVENT EVENT Traceback (most recent call last): File "C:\Documents and Settings\Nick\Desktop\wiimotetext.py", line 26, in <mod ule> if(wiiuse_poll(wiimote,1)): WindowsError: exception: access violation reading 0x00000004 It seems each time I run it, it prints out EVENT 2-5 times until the trace back. I have no clue what to do at this point, I've been trying for the past two days to get it working. Thanks!

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• Android Custom Dialog NullPointerException

  - by Kyle Hughes

  I cannot for the life of me figure out why I'm getting a NullPointerException. When a user clicks on a particular image, a dialog window is supposed to pop-up and display a larger version of said image: private OnClickListener coverListener = new OnClickListener() { public void onClick(View v) { showDialog(DIALOG_COVER); } }; DIALOG_COVER is set to = 0. The associated onCreateDialog looks like this: protected Dialog onCreateDialog(int id) { Dialog dialog; switch(id) { case DIALOG_COVER: dialog = new Dialog(mContext); dialog.setContentView(R.layout.cover_dialog); dialog.setTitle(book.getTitle()); ImageView coverLarge = (ImageView)findViewById(R.id.coverLarge); coverLarge.setImageBitmap(book.getCover()); break; default: dialog = null; } return dialog; } For reference, this is cover_dialog.xml: <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/coverDialog" android:orientation="horizontal" android:layout_width="fill_parent" android:layout_height="fill_parent" android:padding="10dp"> <ImageView android:id="@+id/coverLarge" android:layout_width="wrap_content" android:layout_height="wrap_content" android:scaleType="fitStart" /></LinearLayout> Now, when the image previously described is clicked, the application immediately crashes and throws the following error through LogCat: 06-08 13:29:17.727: ERROR/AndroidRuntime(2220): Uncaught handler: thread main exiting due to uncaught exception 06-08 13:29:17.757: ERROR/AndroidRuntime(2220): java.lang.NullPointerException 06-08 13:29:17.757: ERROR/AndroidRuntime(2220): at org.kylehughes.android.brarian.AndroidBrarian.onCreateDialog(AndroidBrarian.java:259) The line in question refers to this line inside of onCreateDialog: coverLarge.setImageBitmap(book.getCover()); Basically, I don't get why coverLarge is null at that point. Any help would be much appreciated.

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• Using Regex, how can I remove certain characters from inside angle-brackets, leaving the characters

  - by Iain Fraser

  Edit: To be clear, please understand that I am not using Regex to parse the html, that's crazy talk! I'm simply wanting to clean up a messy string of html so it will parse Edit #2: I should also point out that the control character I'm using is a special unicode character - it's not something that would ever be used in a proper tag under any normal circumstances Suppose I have a string of html that contains a bunch of control characters and I want to remove the control characters from inside tags only, leaving the characters outside the tags alone. For example Here the control character is the numeral "1". Input The quick 1<strong>orange</strong> lemming <sp11a1n 1class1='jumpe111r'11>jumps over</span> 1the idle 1frog Desired Output The quick 1<strong>orange</strong> lemming <span class='jumper'>jumps over</span> 1the idle 1frog So far I can match tags which contain the control character but I can't remove them in one regex. I guess I could perform another regex on my matches, but I'd really like to know if there's a better way. My regex Bear in mind this one only matches tags which contain the control character. <(([^>])*?`([^>])*?)*?> Thanks very much for your time and consideration. Iain Fraser

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• XNA 2D mouse picking

  - by Corndog

  I'm working on a simple 2D Real time strategy game using XNA. Right now I have reached the point where I need to be able to click on the sprite for a unit or building and be able to reference the object associated with that sprite. From the research I have done over the last three days I have found many references on how to do "Mouse picking" in 3D which does not seem to apply to my situation. I understand that another way to do this is to simply have an array of all "selectable" objects in the world and when the player clicks on a sprite it checks the mouse location against the locations of all the objects in the array. the problem I have with this approach is that it would become rather slow if the number of units and buildings grows to larger numbers. (it also does not seem very elegant) so what are some other ways I could do this. (Please note that I have also worked over the ideas of using a Hash table to associate the object with the sprite location, and using a 2 dimensional array where each location in the array represents one pixel in the world. once again they seem like rather clunky ways of doing things.)

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• 2D Ball Collisions with Corners

  - by Aaron

  I'm trying to write a 2D simulation of a ball that bounces off of fixed vertical and horizontal walls. Simulating collisions with the faces of the walls was pretty simple--just negate the X-velocity for a vertical wall or the Y-velocity for a horizontal wall. The problem is that the ball can also collide with the corners of the walls, where a horizontal wall meets with a vertical wall. I have already figured out how to detect when a collision with a corner is occurring. My question is how the ball should react to this collision--that is, how its X and Y velocities will change as a result. Here's a list of what I already know or know how to find: *The X and Y coordinates of the ball's center during the frame when a collision is detected *The X and Y components of the ball's velocity *The X and Y coordinates of the corner *The angle between the ball's center and the corner *The angle in which the ball is traveling just before the collision *The amount that the ball is overlapping the corner when the collision is detected I'm guessing that it's best to pretend that the corner is an infinitely small circle, so I can treat a collision between the ball and that circle as if the ball were colliding with a wall that runs tangent to the circles at the point of collision. It seems to me that all I need to do is rotate the coordinate system to line up with this imaginary wall, reverse the X component of the ball's velocity under this system, and rotate the coordinates back to the original system. The problem is that I have no idea how to program this. By the way, this is an ideal simulation. I'm not taking anything like friction or the ball's rotation into account. I'm using Objective-C, but I'd really just like a general algorithm or some advice. Many thanks if anyone can help!

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• Should I store generated code in source control

  - by Ron Harlev

  This is a debate I'm taking a part in. I would like to get more opinions and points of view. We have some classes that are generated in build time to handle DB operations (in This specific case, with SubSonic, but I don't think it is very important for the question). The generation is set as a pre-build step in Visual Studio. So every time a developer (or the official build process) runs a build, these classes are generated, and then compiled into the project. Now some people are claiming, that having these classes saved in source control could cause confusion, in case the code you get, doesn't match what would have been generated in your own environment. I would like to have a way to trace back the history of the code, even if it is usually treated as a black box. Any arguments or counter arguments? UPDATE: I asked this question since I really believed there is one definitive answer. Looking at all the responses, I could say with high level of certainty, that there is no such answer. The decision should be made based on more than one parameter. Reading the answers below could provide a very good guideline to the types of questions you should be asking yourself when having to decide on this issue. I won't select an accepted answer at this point for the reasons mentioned above.

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• How can I load file into web app through certain periods?

  - by Elena

  Hi all! I have next task: I need to load the same file into my web app several times, for example - twice a day! Suppose in that file I have information, that changes, and I need to load this info into my app to change the statistics for example. How can I load file several times (twice an hour, or twice a day)? What should I use? Is any algorithm to do that? I am not allowed to use external libraries like Quartz Scheduler. So I need to do it with Thread and/or Timer. Can anybody give me some example or algorithm how to do it. Where can I create the entry point to my Thread, can I do it in managed bean or I need some sort of filter/listener/servlet. I works with jsf and richFaces. Maybe in this technologies there are some algorithms to solve my problem. Any ideas? Thanks very much for help!

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• Converting UnicodeString to PAnsiChar in Delphi XE

  - by moodforaday

  In Delphi XE I am using the BASS audio library, which contains this function: function BASS_StreamCreateURL(url: PAnsiChar; offset: DWORD; flags: DWORD; proc: DOWNLOADPROC; user: Pointer):HSTREAM; stdcall; external bassdll; The 'url' parameter is of type PAnsiChar, so in my code I do a cast: FStreamHandle := BASS_StreamCreateURL(PAnsiChar( url ) [...] The compiler emits a warning on this line: "suspicious typecast of string to PAnsiChar". In trying to eliminate the warning, I found that the recommended way is to use a double cast: FStreamHandle := BASS_StreamCreateURL(PAnsiChar( AnsiString( url )) [...] This does eliminate the warning, but the BASS function now returns error code 2 ("cannot open file"), which tells me the URL string it receives is somehow broken. I cannot see what the bass DLL actually receives, but using a breakpoint in the debugger the string looks good: var s : PAnsiChar; begin s := PAnsiChar( AnsiString( url )); At this point string s appears fine, but the BASS function fails when I pass it. My initial code: PAnsiChar( url ) works well with BASS, but emits a warning. So what's the correct way of getting from UnicodeString to PAnsiChar without a warning?

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• Manipulate score/rank on query results from NHibernate.Search

  - by Fernando Figueiredo

  I've been working with NHibernate, NHibernate.Search and Lucene.Net to improve the search engine used on the website I develop. Basically, I use it to search contents of corporations specification documents. This is not to be confused with Lucene's notion of documents: in my case, a specification document (which I'll hereafter call a "specdoc") can contain many pages, and the content of these pages are the ones that are actually indexed (thus, the pages themselves are the ones that fall into Lucene's concept of documents). So, the pages belong to a specdoc, that in turn belong to a corporation (so, a corporation can have many specdocs). I'm using NHibernate.Search "IndexEmbedded" and "ContainedIn" attributes to associate the pages with their specdoc and the specdocs to their corporations, so I can query for terms in specdoc pages and have Lucene/NH.Search return either the pages themselves, the specdocs, or the corporations that match the query on the pages. I can query this way and get ranked results, thus presenting results (that is, corporations, specdocs or pages) by relevance, which is great. But now I need something more. Specifically in the case where I query terms and have NH.Search return the corporations that match, I need to manually/artificially tune the score of some of the results, because there are corporations that I want to show up on the top of the result set - think of "sponsored results". I'm thinking of doing it on my application, maybe creating an entity/database table that contain an association to the corporation entity, and a score boost value. But I don't know how to feed this to Lucene and have it boost the results accordingly at search time. Initially I thought about deriving a Similarity class to do this, but it doesn't look like Similarity can be used to modify result sets at search time. As per this page, it looks like what I need is to mess around with weight or scoring. But the docs are a little superficial in that there are no examples on how to implement a custom scoring, let alone integrate it with NH.Search. So, does anyone know how to do this, or point me to some documentation or working example on how to do something similar? Thanks!

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• Should I be relying on WebTests for data validation?

  - by Alexander Kahoun

  I have a suite of web tests created for a web service. I use it for testing a particular input method that updates a SQL Database. The web service doesn't have a way to retrieve the data, that's not its purpose, only to update it. I have a validator that validates the response XML that the web service generates for each request. All that works fine. It was suggested by a teammate that I add data validation so that I check the database to see the data after the initial response validator runs and compare it with what was in the input request. We have a number of services and libraries that are separate from the web service I'm testing that I can use to get the data and compare it. The problem is that when I run the web test the data validation always fails even when the request succeeds. I've tried putting the thread to sleep between the response validation and the data validation but to no avail; It always gets the data from before the response validation. I can set a break point and visually see that the data has been updated in the DB, funny thing is when I step through it in debug with the breakpoint it does validate successfully. Before I get too much more into this issue I have to ask; Is this the purpose of web tests? Should I be able to validate data through service calls in this manner or am I asking too much of a web test and the response validation is as far as I should go?

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• Activate a python virtual environment using activate_this.py in a fabfile on Windows

  - by Rudy Lattae

  I have a Fabric task that needs to access the settings of my Django project. On Windows, I'm unable to install Fabric into the project's virtualenv (issues with Paramiko + pycrypto deps). However, I am able to install Fabric in my system-wide site-packages, no problem. I have installed Django into the project's virtualenv and I am able to use all the " python manage.py" commands easily when I activate the virtualenv with the "VIRTUALENV\Scripts\activate.bat" script. I have a fabric tasks file (fabfile.py) in my project that provides tasks for setup, test, deploy, etc. Some of the tasks in my fabfile need to access the settings of my django project through "from django.conf import settings". Since the only usable Fabric install I have is in my system-wide site-packages, I need to activate the virtualenv within my fabfile so django becomes available. To do this, I use the "activate_this" module of the project's virtualenv in order to have access to the project settings and such. Using "print sys.path" before and after I execute activate_this.py, I can tell the python path changes to point to the virtualenv for the project. However, I still cannot import django.conf.settings. I have been able to successfully do this on *nix (Ubuntu and CentOS) and in Cygwin. Do you use this setup/workflow on Windows? If so Can you help me figure out why this wont work on Windows or provide any tips and tricks to get around this issue? Thanks and Cheers. REF: http://virtualenv.openplans.org/#id9 | Using Virtualenv without bin/python Local development environment: Python 2.5.4 Virtualenv 1.4.6 Fabric 0.9.0 Pip 0.6.1 Django 1.1.1 Windows XP (SP3)

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• How does Java handle ArrayList refrerences and assignments?

  - by Jonathan

  Hey all- I mostly write in C but am using Java for this project. I want to know what Java is doing here under the hood. ArrayList<Integer> prevRow, currRow; currRow = new ArrayList<Integer>(); for(i =0; i < numRows; i++){ prevRow = currRow; currRow.clear(); currRow.addAll(aBunchOfItems); } Is the prevRow = currRow line copying the list or does prevRow now point to the same list as currRow? If prevRow points to the same list as currRow, I should create a new ArrayList instead of clearing.... private ArrayList<Integer> someFunction(ArrayList<Integer> l){ Collections.sort(l); return l; } main(){ ArrayList<Integer> list = new ArrayList<Integer>(Integer(3), Integer(2), Integer(1)); list = someFunction(list); //Option 1 someFunction(list); //Option 2 } In a similar question, do Option 1 and Option 2 do the same thing in the above code? Thanks- Jonathan

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• .NET XML serialization

  - by ShdNx

  I would like to serialize and deserialize mixed data into XML. After some searches I found out that there were two ways of doing it: System.Runtime.Serialization.Formatters.Soap.SoapFormatter and System.Xml.Serialization.XmlSerializer. However, neither turned out to match my requirements, since: SoapFormatter doesn't support serialization of generic types XmlSerializer refuses to serialize types that implement IDictionary, not to mention that it's far less easy-to-use than "normal" serialization (e.g. see this SO question) I'm wondering if there exists an implementation that doesn't have these limitations? I have found attempts (for example CustomXmlSerializer and YAXLib as suggested in a related SO question), but they don't seem to work either. I was thinking about writing such serializer myself (though it certainly doesn't seem to be a very easy task), but then I find myself limited by the CLR, as I cannot create object instances of types that won't have a paramaterless constructor, even if I'm using reflection. I recall having read somewhere that implementations in System.Runtime.Serialization somehow bypass the normal object creation mechanism when deserializing objects, though I'm not sure. Any hints of how could this be done? Could somebody please point me to the right direction with this?

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• Is there an easier way with jQuery accordions?

  - by Josh

  I've been struggling with a feature I've been trying to create for sometime. The idea here is that the user sees the little thumbnail + headline, as well as the Posted By information. They can then click on the headline to expand to the article or click on the "Comments" link to expand directly to the comments made on the article. Or, if they want they can view comments by clicking on the headline(to expand to the article), then click on View Comments (to expand to the comments). In the end, a modular yet flexible and functional open/close system to view latest news. Here is what I've been working on: (I put all my code in one place so its easier on whomever may look at this to view) http://notedls.com/pointtest.html This is what I'm shooting for, but it's far from what I want ;( It's using the jQuery 1.6 plugin, which 1.8 is out but I'm far from being a master or expert at this and I don't think I could build from the ground up. I've already edited this plugin to get it to work like this, but as you can see, the AUTHOR and Comments start making shit hit the fan ;; It's because the code is calling the "A TAG" for the header; which is the headline. Does anyone know any easier way to achieve what I'm envisioning or possible a way to fix this current code? I'm pretty desperate at this point ;;

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• how to implement login and service features as in skype or msn chat in a wpf application

  - by black sensei

  Hello Good people! I'm building an WPF application that connect to web services for its operations.Things that i needed to be working are so far fine.Now i'll like to improve use experience by adding features like username editable combobox, sign me in when skype start and start when computer start. I have a fair idea about each feature but very small knowledge about their implementation. Question 1 username combobox : i use a combobox with isEditable set to true but i think it doesnt have the previous username, would that mean that i have to store every successful login username in a sqlite for example? Question 2 sign me in when skype start : i think about using sqlite after all to store the credentials and store the value (as in true or false) if autologin has to be performed. Question 3 start when computer start : i know it's about having is as service.but the process of using it as a service and removing its service when checkbox is checked or unckecked is a bit confusing to me. Question 4 Please wait(signing in) of skype if i want to do things like please wait at login(login is over webservice) in a WPF application should i use a animated gif in a grid that i can show when hiding the login combobox and passwordbox grid or i should use an animated object(for which i have no knowledge about for now) ? This post in mainly for you experts to either point me to the right resource and tell me what is done as best practice. things like dos and dons.Thanks for reading this and please let me have a clair idea about how to start implementing those features. thanks again

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• After Navigate2 Method returns S_OK Stuck at READYSTATE of READYSTATE_LOADING

  - by Stone Free

  I am working on a MFC Document View architecture application which has multiple documents and views and a tabbed window interface. I have been tasked with making an automatic switch to another tab on the press of the OK button in one of the other tabs. When the other tab is clicked on it uses a C++ wrapper over IWebBrowser2 to navigate to a specific web page. When this is done manually by clicking on the tab everything is fine and the webpage within the view loads successfully. In my first attempt at doing this the tab successfully switched in response to a call to AfxGetMainWnd()->SendMessageToDescendants(SOME_MESSAGE, ...); however by sending this windows message at the wrong point the application would crash once control returned because the chain of events caused the (modeless) dialog (*) that sent the message, to no longer exist. I then found the correct place to make the call, but now when the other tab is activated, it no longer displays the webpage as it should. To debug this problem I added code to check the READYSTATE in both the situation where it works and the situation where it does not. When the page fails to load (despite the call to Navigate2 returning S_OK), the READYSTATE just stays at READYSTATE_LOADING. Unfortunately now I am to many edits away from when I had it partially working. I have added TRACE statements to the most obvious events such as OnSetFocus, CView::OnActivateView but all traces come out in the same order despite the behaviour being different * hosted in the view

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• Draw LINE_STRIP with Unity

  - by Boozzz

  For a new project I am thinking about whether to use OpenGL or Unity3d. I have a bit of experience with OpenGL, but I am completely new to Unity. I already read through the Unity documentation and tutorials on the Unity Website. However, I could not find a way to draw a simple Line-Strip with Unity. In the following example (C#, OpenGL/SharpGL) I draw a round trajectory from a predifined point to an obstacle, which can be imagined as a divided circle with midpoint [cx,cy] and radius r. The position (x-y coordinates) of the obstacle is given by obst_x and obst_y. Question 1: How could I do the same with Unity? Question 2: In my new project, I will have to draw quite a lot of such geometric primitives. Does it make any sense to use Unity for those things? void drawCircle(float cx, float cy, float r, const float obst_x, const float obst_y) { float theta = 0.0f, pos_x, pos_y, dist; const float delta = 0.1; glBegin(GL_LINE_STRIP); while (theta < 180) { theta += delta; //get the current angle float x = r * cosf(theta); //calculate the x component float y = r * sinf(theta); //calculate the y component pos_x = x + cx; //calculate current x position pos_y = y + cy; //calculate current y position //calculate distance from current vertex to obstacle dist = sqrt(pow(pos_x - obst_x) + pow(pos_y - obst_y)); //check if current vertex intersects with obstacle if dist <= 0 { break; //stop drawing circle } else { glVertex2f(pos_x, pos_y); //draw vertex } } glEnd(); }

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• Looking for examples of "real" uses of continuations

  - by Sébastien RoccaSerra

  I'm trying to grasp the concept of continuations and I found several small teaching examples like this one from the Wikipedia article: (define the-continuation #f) (define (test) (let ((i 0)) ; call/cc calls its first function argument, passing ; a continuation variable representing this point in ; the program as the argument to that function. ; ; In this case, the function argument assigns that ; continuation to the variable the-continuation. ; (call/cc (lambda (k) (set! the-continuation k))) ; ; The next time the-continuation is called, we start here. (set! i (+ i 1)) i)) I understand what this little function does, but I can't see any obvious application of it. While I don't expect to use continuations all over my code anytime soon, I wish I knew a few cases where they can be appropriate. So I'm looking for more explicitely usefull code samples of what continuations can offer me as a programmer. Cheers!

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• Working with ieee format numbers in ARM

  - by Jake Sellers

  I'm trying to write an ARM program that will convert an ieee number to a TNS format number. TNS is a format used by some super computers, and is similar to ieee but different. I'm trying to use several masks to place the three different "part" of the ieee number in separate registers so I can move them around accordingly. Here is my unpack subroutine: UnpackIEEE LDR r1, SMASK ;load the sign bit mask into r1 LDR r2, EMASK ;load the exponent mask into r2 LDR r3, GMASK ;load the significand mask into r3 AND r4, r0, r1 ;apply sign mask to IEEE and save into r4 AND r5, r0, r2 ;apply exponent mask to IEEE and save into r5 AND r6, r0, r3 ;apply significand mask to IEEE and save into r6 MOV pc, r14 ;return And here are the masks and number declarations so you can understand: IEEE DCD 0x40300000 ;2.75 decimal or 01000000001100000000000000000000 binary SMASK DCD 0x80000000 ;Sign bit mask EMASK DCD 0x7F800000 ;Exponent mask GMASK DCD 0x007FFFFF ;Significand mask When I step through with the debugger, the results I get are not what I expect after working through it on paper. EDIT: What I mean, is that after the subroutine runs, registers 4, 5, and 6 all remain 0. I can't figure out why the masks are not working. I think I do not fully understand how the number is being stored in the register or using the masks wrong. Any help appreciated. If you need more info just ask. EDIT: entry point: Very simple, just trying to get these subroutines working. ENTRY LDR r1, IEEE ;load IEEE num into r1 BL UnpackIEEE ;call unpack sub SWI SWI_Exit ;finish

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• Question about mixing MEF and Unity

  - by Dave

  I'm finally diving into Unity head first, and have run into my first real problem. I've been gradually changing some things in my app from being MEF-resolved to Unity-resolved. Everything went fine on the application side, but then I realized that my plugins were not being loaded. I started to look into this issue, and I believe it's a case where MEF and Unity don't mix. Plugins are loaded by MEF, but each plugin needs to get access to the shared libraries in my application, like app preferences, logging, etc. Initially, my plugin constructor had the ImportingConstructor attribute. I then replaced it with InjectionConstructor so that Unity could resolve its shared library dependencies. But because I did that, MEF no longer loaded it! Then I used both attributes, which compiled, but then I got a composition error (MEF). I figured that this was because the constructor takes a parameter that was once resolved by a MEF Import, so I removed all parameters. As expected, now MEF was able to load my plugin, but because the constructor needs to call into the interface that was once passed in, construction fails. So now I'm at a point where I can get MEF to start to load my plugin, but can't do anything with it because the plugin relies on shared libraries that are registered with Unity. For those of you that have successfully mixed MEF and Unity, how do you go about resolving the references to the shared libraries with Unity? It seems like a catch-22, where in order to have Unity work with the plugin, I'd have to create the plugin via Resolve, but then it's impossible to use MEF. UPDATE I can work around this problem by using an ImportingConstructor for the plugin that takes an IUnityContainer, and then call Resolve for each interface that I need, but although it works, it is incredibly lame to do it this way, as this would require all plugin authors to remember to save a reference to the passed in IUnityContainer...

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• BDD on Rails - Is the community more behind Shoulda or RSpec?

  - by Wayne M

  For a new application I want to start dabbling in BDD and I'm trying to decide between using RSpec or Thoughtbot's Shoulda. I like the macros that Shoulda uses, and the fact that it doesn't seem to reinvent the way Ruby/Rails does testing, but simply provides an add-on. On the other hand, the macros seem like a bit too much "magic" instead of being explicit about what you're testing (however I know from dabbling that it's annoying to write a dozen "should be invalid without xxx" two-liners on a model). To be honest I find writing specifications/tests for models to be trivially and almost boringly easy, but I find writing them for controllers to be insanely difficult because I'm never sure exactly what I should be testing or how to write it. I'm iffy on the subject of mocking and stubbing since I think they give you false assumptions (since you can just tell it to think it has whatever data you need or to pretend that Method X was called) and I know that RSpec makes heavy use of both of them. I like the documentation that RSPec produces but I'm creating an application for sale, not to give to a client so the pretty documentation isn't that useful. I like Cucumber but it seems like overkill (and yes I know it can be used with Shoulda). At this point is the Rails community in favor of RSpec or Shoulda?

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