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• Sync Vs. Async Sockets Performance in .NET

  - by Michael Covelli

  Everything that I read about sockets in .NET says that the asynchronous pattern gives better performance (especially with the new SocketAsyncEventArgs which saves on the allocation). I think this makes sense if we're talking about a server with many client connections where its not possible to allocate one thread per connection. Then I can see the advantage of using the ThreadPool threads and getting async callbacks on them. But in my app, I'm the client and I just need to listen to one server sending market tick data over one tcp connection. Right now, I create a single thread, set the priority to Highest, and call Socket.Receive() with it. My thread blocks on this call and wakes up once new data arrives. If I were to switch this to an async pattern so that I get a callback when there's new data, I see two issues The threadpool threads will have default priority so it seems they will be strictly worse than my own thread which has Highest priority. I'll still have to send everything through a single thread at some point. Say that I get N callbacks at almost the same time on N different threadpool threads notifying me that there's new data. The N byte arrays that they deliver can't be processed on the threadpool threads because there's no guarantee that they represent N unique market data messages because TCP is stream based. I'll have to lock and put the bytes into an array anyway and signal some other thread that can process what's in the array. So I'm not sure what having N threadpool threads is buying me. Am I thinking about this wrong? Is there a reason to use the Async patter in my specific case of one client connected to one server?

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• No acceleration for OpenGL and ImportError for modules that exist

  - by Aku

  I'm writing a program using wxPython and OpenGL. The program works, but without any antialiasing, and I get these error messages: (I'm using ArchLinux) INFO:OpenGL.acceleratesupport:No OpenGL_accelerate module loaded: No module named OpenGL_accelerate INFO:OpenGL.formathandler:Unable to load registered array format handler numpy: Traceback (most recent call last): File "/usr/lib/python2.6/site-packages/OpenGL/arrays/formathandler.py", line 44, in loadPlugin plugin_class = entrypoint.load() File "/usr/lib/python2.6/site-packages/OpenGL/plugins.py", line 14, in load return importByName( self.import_path ) File "/usr/lib/python2.6/site-packages/OpenGL/plugins.py", line 28, in importByName module = __import__( ".".join(moduleName), {}, {}, moduleName) File "/usr/lib/python2.6/site-packages/OpenGL/arrays/numpymodule.py", line 11, in <module> raise ImportError( """No numpy module present: %s"""%(err)) ImportError: No numpy module present: No module named numpy INFO:OpenGL.formathandler:Unable to load registered array format handler numeric: Traceback (most recent call last): File "/usr/lib/python2.6/site-packages/OpenGL/arrays/formathandler.py", line 44, in loadPlugin plugin_class = entrypoint.load() File "/usr/lib/python2.6/site-packages/OpenGL/plugins.py", line 14, in load return importByName( self.import_path ) File "/usr/lib/python2.6/site-packages/OpenGL/plugins.py", line 28, in importByName module = __import__( ".".join(moduleName), {}, {}, moduleName) File "/usr/lib/python2.6/site-packages/OpenGL/arrays/numeric.py", line 15, in <module> raise ImportError( """No Numeric module present: %s"""%(err)) ImportError: No Numeric module present: No module named Numeric However, when I look into my site-packages folder, I see those modules present there. I have a wxPython demo program that uses GLCanvas, and it works fine, without any errors. My program is quite similar to the GLCanvas demo, involving just translations, rotations, drawing quads and some basic lighting. What am I doing wrong here? (The code is over 200 lines, if necessary I'll edit this and put it here.)

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• External API function calls AS3 control timeline

  - by giles

  I have function problem using this code (below), the embedded flash movieclip disappears or completely prevents the scrollto.js query to function in DW cs3. Communication between Flash and JavaScript is without problems, it is the call back I can't find to work and more frustratingly, should be simple, as no values are not required. So far, this has been hours of scouring the net without a workable end in sight...ahrr. What is a function for this to work? JavaScript – to call Flash event from HTML button link, placed between head tags function callExternalInterface() var flashMovie = window.document.menu; flashMovie.menu_up(value); menu_up is the string. Does anyone know of workable function for callback?? HTML <div id="btn_up"><a href="#top" name="charDev" id="charDev" onclick="">top</a></div> Pane navigation div that uses Scrollto.js query, and it's this link I need calling back to the embedded "menubtns.swf" (nested in "AS3Menu_javascript.swf") to play 5 frames of this movieclip, via a JS function. Embedded .swf code, using swfobject.js with allowScriptAccess=always <object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" name="menu"<br/> width="251" height="251" id="menu"> <param name="movie" value="../~Assets/Flash/AS3Menu_javascript.swf" /> <param name="allowScriptAccess" value="always" /> <param name="movie" value="ExternalInterfaceScript.swf" /> <param name="quality" value="high" /> <object type="application/x-shockwave-flash" data="../~Assets/Flash/AS3Menu_javascript.swf" width="250" height="250"> <p>Alternative content</p> </object> </object> AS3 / Flash import flash.external.ExternalInterface;flash.system.Security.allowDomain(/sourceDomain/); ExternalInterface.addCallBack("menu_up", this, resetmenu); function resetmenu(){ gotoAndPlay:("frame label" / "number") }

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• ASP.Net MVC Json Result: Parameters passed to controller method issue

  - by Moskie

  I'm having a problem getting a controller method that returns a JsonResult to accept parameters passed via the JQuery getJSON method. The code I’m working on works fine when the second parameter ("data") of the getJSON method call is null. But when I attempt to pass in a value there, it seems as if the controller method never even gets called. In this example case, I just want to use an integer. The getJSON call that works fine looks like this: $.getJSON(”/News/ListNewsJson/”, null, ListNews_OnReturn); The controller method is like this: public JsonResult ListNewsJson(int? id) { … return Json(toReturn); } By putting a breakpoint in the ListNewsJson method, I see that this method gets called when the data parameter of getJSON is null, but when I replace it with value, such as, say, 3: $.getJSON(”/News/ListNewsJson/”, 3, ListNews_OnReturn); … the controller method/breakpoint is never hit. Any idea what I'm doing wrong? I should also mention that the controller method works fine if I manually go to the address via my browser ("/News/ListNewsJson/3").

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• Objective-C memory model

  - by TofuBeer

  I am attempting to wrap my head around one part of the Objective-C memory model (specifically on the iPhone, so no GC). My background is C/C++/Java, and I am having an issue with the following bit of code (also wondering if I am doing this in an "Objective-C way" or not): - (NSSet *) retrieve { NSMutableSet *set; set = [NSMutableSet new]; // would normally fill the set in here with some data return ([set autorelease]); } - (void) test { NSSet *setA; NSSet *setB; setA = [self retrieve]; setB = [[self retrieve] retain]; [setA release]; [setB release]; } start EDIT Based on comments below, the updated retrieve method: - (NSSet *) retrieve { NSMutableSet *set; set = [[[NSMutableSet alloc] initWithCapacity:100] autorelease]; // would normally fill the set in here with some data return (set); } end EDIT The above code gives a warning for [setA release] "Incorrect decrement of the reference count of an object is not owned at this point by the caller". I though that the "new" set the reference count to 1. Then the "retain" call would add 1, and the "release" call would drop it by 1. Given that wouldn't setA have a reference count of 0 at the end and setB have a reference count of 1 at the end? From what I have figured out by trial and error, setB is correct, and there is no memory leak, but I'd like to understand why that is the case (what is wrong with my understanding of "new", "autorelease", "retain", and "release").

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• How can I render a list of objects using DisplayFor but from the controller in ASP.NET MVC?

  - by Darragh

  Here's the scenaio, I have an Employee object and a Company object which has a list of employees. I have Company.aspx which inherits from ViewPage<Company>. In Company.aspx I call Html.DisplayFor(m => m.Employees). I have an Employee.ascx partial view which inherits from ViewUserControl<Employee in my DisplayTemplates folder. Everything works fine and Company.aspx renders the Employee.ascx partial for each employee. Now I have two additional methods on my controller called GetEmployees and GetEmployee(Id). In the GetEmployee(Id) action I want to return the markup to display this one employee, and in GetEmployees() I want to render the markup to display all the employees (these two action methods will be called via AJAX). In the GetEmployee action I call return PartialView("DisplayTemplates\Employee", employee) This works, although I'd prefer something like return PartialViewFor(employee) which would determine the view name by convention. Anwyay, my question is how should I implement the GetEmployees() action? I don't want to create any more views, because frankly, I don't see why I should have to. I've tried the following which fails miserably :) return Content(New HtmlHelper<IList<Of DebtDto>>(null, null).DisplayFor(m => debts)); However if I could create an instance of an HtmlHelper object in my controller, I suppose I could get it to work, but it feels wrong. Any ideas? Have i missed something obvious?

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• C# .NET: Descending comparison of a SortedDictionary?

  - by Rosarch

  I'm want a IDictionary<float, foo> that returns the larges values of the key first. private IDictionary<float, foo> layers = new SortedDictionary<float, foo>(new DescendingComparer<float>()); class DescendingComparer<T> : IComparer<T> where T : IComparable<T> { public int Compare(T x, T y) { return -y.CompareTo(x); } } However, this returns values in order of the smallest first. I feel like I'm making a stupid mistake here. Just to see what would happen, I removed the - sign from the comparator: public int Compare(T x, T y) { return y.CompareTo(x); } But I got the same result. This reinforces my intuition that I'm making a stupid error. This is the code that accesses the dictionary: foreach (KeyValuePair<float, foo> kv in sortedLayers) { // ... } UPDATE: This works, but is too slow to call as frequently as I need to call this method: IOrderedEnumerable<KeyValuePair<float, foo>> sortedLayers = layers.OrderByDescending(kv => kv.Key); foreach (KeyValuePair<float, ICollection<IGameObjectController>> kv in sortedLayers) { // ... } UPDATE: I put a break point in the comparator that never gets hit as I add and remove kv pairs from the dictionary. What could this mean?

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• setAttribute, onClick and cross browser compatability...

  - by Nicholas Kreidberg

  I have read a number of posts about this but none with any solid answer. Here is my code: // button creation onew = document.createElement('input'); onew.setAttribute("type", "button"); onew.setAttribute("value", "hosts"); onew.onclick = function(){fnDisplay_Computers("'" + alines[i] + "'"); }; // ie onew.setAttribute("onclick", "fnDisplay_Computers('" + alines[i] + "')"); // mozilla odiv.appendChild(onew); Now, the setAttribute() method (with the mozilla comment) works fine in mozilla but only if it comes AFTER the line above it. So in other words it seems to just default to whichever gets set last. The .onclick method (with the ie comment) does not work in either case, am I using it incorrectly? Either way I can't find a way to make this work at all in IE, let alone in both. I did change the function call when using the .onclick method and it worked fine using just a simple call to an alert function which is why I believe my syntax is incorrect. Long story short, I can't get the onclick parameter to work consistently between IE/Mozilla. -- Nicholas

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• Use of for_each on map elements

  - by Antonio

  I have a map where I'd like to perform a call on every data type object member function. I yet know how to do this on any sequence but, is it possible to do it on an associative container? The closest answer I could find was this: Boost.Bind to access std::map elements in std::for_each. But I cannot use boost in my project so, is there an STL alternative that I'm missing to boost::bind? If not possible, I thought on creating a temporary sequence for pointers to the data objects and then, call for_each on it, something like this: class MyClass { public: void Method() const; } std::map<int, MyClass> Map; //... std::vector<MyClass*> Vector; std::transform(Map.begin(), Map.end(), std::back_inserter(Vector), std::mem_fun_ref(&std::map<int, MyClass>::value_type::second)); std::for_each(Vector.begin(), Vector.end(), std::mem_fun(&MyClass::Method)); It looks too obfuscated and I don't really like it. Any suggestions?

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• FluentNHibernate Overrides: UseOverridesFromAssemblyOf non-generic version

  - by ThiagoAlves

  Hi, I have a repository class that inherits from a generic implementation: public namespace RepositoryImplementation { public class PersonRepository : Web.Generics.GenericNHibernateRepository<Person> } The generic repository implementation uses Fluent NHibernate conventions. They're working fine. One of those conventions is that all properties are not nullable. Now I need to define that specific properties may be nullable outside the conventions. Fluent NHibernate has an interesting override mechanism: public namespace RepositoryImplementation { public class PersonMappingOverride : IAutoMappingOverride<Person> { public void Override(FluentNHibernate.Automapping.AutoMapping<Funcionario> mapping) { mapping.Map(x => x.PhoneNumber).Nullable(); } } } Now I need to register the override class into Fluent NHibernate. I have the following code in the Web.Generics.GenericNHibernateRepository generic class: AutoMap.AssemblyOf<Person>() .Where(type => type.Namespace == "Entities") .UseOverridesFromAssemblyOf<PersonMappingOverride>(); The problem is: UseOverridesFromAssemblyOf is a generic method, and I can't do something like that: .UseOverridesFromAssemblyOf<PersonMappingOverride>(); Because that would cause a circular reference. I don't want the generic repository to know the either repository or the mapping override class, because they vary from project to project. I see another solution: in the GenericNHibernateRepository class I can do this.GetType() and get the repository implementation type (e.g.: PersonRepository). However I can't call UseOverridesFromAssemblyOf() passing a type. Is there another way to configure overrides in FluentNHibernate? If not, how could I call UseOverridesFromAssemblyOf<T> without making the generic repository depend upon the repository implementation or the mapping override class? (Source: http://wiki.fluentnhibernate.org/Auto_mapping#Overrides)

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• Need advice on using Grails and Ajax to append to a div like in Rails

  - by Nate

  I'm just starting out in Grails and need some advice on using Ajax. I want to append some html to the bottom of a div inside a form. This is basically what I have: -form- -div id="listOfchildren"- childrow 1 input fields childrow 2 input fields childrow 3 input fields -/div- -form- -a-Add Child 4-/a- When I click on the "Add Child" I want to make an ajax call that results in a new childrow getting inserted into the "listOfchildren" div. So the document would look like this: -form- -div id="listOfchildren"- childrow 1 input fields childrow 2 input fields childrow 3 input fields childrow 4 input fields -/div- -form- -a-Add Child 5-/a- In Rails I would do something simple like this: render :update do |page| page.insert_html :bottom, "list_of_children", :partial = child_partial page.replace "add_link", :partial = 'add_link' end The previous code sends an javascript back to the browser with two commands. The first command tells the browser to append some html to the bottom of a div. The second command updates the "add link" counter. In grails I can only see how to replace an entire div (which would wipe out the user's existing input) and I don't see how I can call multiple functions from the ajax response. I can probably do this if I was to write some javascript functions in prototype or whatever, but I'd like to avoid that if there is a simpler way. Thanks! Nate

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• Python metaclass for enforcing immutability of custom types

  - by Mark Lehmacher

  Having searched for a way to enforce immutability of custom types and not having found a satisfactory answer I came up with my own shot at a solution in form of a metaclass: class ImmutableTypeException( Exception ): pass class Immutable( type ): ''' Enforce some aspects of the immutability contract for new-style classes: - attributes must not be created, modified or deleted after object construction - immutable types must implement __eq__ and __hash__ ''' def __new__( meta, classname, bases, classDict ): instance = type.__new__( meta, classname, bases, classDict ) # Make sure __eq__ and __hash__ have been implemented by the immutable type. # In the case of __hash__ also make sure the object default implementation has been overridden. # TODO: the check for eq and hash functions could probably be done more directly and thus more efficiently # (hasattr does not seem to traverse the type hierarchy) if not '__eq__' in dir( instance ): raise ImmutableTypeException( 'Immutable types must implement __eq__.' ) if not '__hash__' in dir( instance ): raise ImmutableTypeException( 'Immutable types must implement __hash__.' ) if _methodFromObjectType( instance.__hash__ ): raise ImmutableTypeException( 'Immutable types must override object.__hash__.' ) instance.__setattr__ = _setattr instance.__delattr__ = _delattr return instance def __call__( self, *args, **kwargs ): obj = type.__call__( self, *args, **kwargs ) obj.__immutable__ = True return obj def _setattr( self, attr, value ): if '__immutable__' in self.__dict__ and self.__immutable__: raise AttributeError( "'%s' must not be modified because '%s' is immutable" % ( attr, self ) ) object.__setattr__( self, attr, value ) def _delattr( self, attr ): raise AttributeError( "'%s' must not be deleted because '%s' is immutable" % ( attr, self ) ) def _methodFromObjectType( method ): ''' Return True if the given method has been defined by object, False otherwise. ''' try: # TODO: Are we exploiting an implementation detail here? Find better solution! return isinstance( method.__objclass__, object ) except: return False However, while the general approach seems to be working rather well there are still some iffy implementation details (also see TODO comments in code): How do I check if a particular method has been implemented anywhere in the type hierarchy? How do I check which type is the origin of a method declaration (i.e. as part of which type a method has been defined)?

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• Matplotlib canvas drawing

  - by Morgoth

  Let's say I define a few functions to do certain matplotlib actions, such as def dostuff(ax): ax.scatter([0.],[0.]) Now if I launch ipython, I can load these functions and start a new figure: In [1]: import matplotlib.pyplot as mpl In [2]: fig = mpl.figure() In [3]: ax = fig.add_subplot(1,1,1) In [4]: run functions # run the file with the above defined function If I now call dostuff, then the figure does not refresh: In [6]: dostuff(ax) I have to then explicitly run: In [7]: fig.canvas.draw() To get the canvas to draw. Now I can modify dostuff to be def dostuff(ax): ax.scatter([0.],[0.]) ax.get_figure().canvas.draw() This re-draws the canvas automatically. But now, say that I have the following code: def dostuff1(ax): ax.scatter([0.],[0.]) ax.get_figure().canvas.draw() def dostuff2(ax): ax.scatter([1.],[1.]) ax.get_figure().canvas.draw() def doboth(ax): dostuff1(ax) dostuff2(ax) ax.get_figure().canvas.draw() I can call each of these functions, and the canvas will be redrawn, but in the case of doboth(), it will get redrawn multiple times. My question is: how could I code this, such that the canvas.draw() only gets called once? In the above example it won't change much, but in more complex cases with tens of functions that can be called individually or grouped, the repeated drawing is much more obvious, and it would be nice to be able to avoid it. I thought of using decorators, but it doesn't look as though it would be simple. Any ideas?

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• iPhone Objective-C service handlers

  - by Xavi Colomer

  Hello community! I am a as3 developer, I am used to use handlers everytime I launch an event and I am wondering which is the best way / practice to do that in Objective C. Let's say I want to call a diferent services from my backend. In as3 would be something like this to listent to the finish event: service.addEventListener( Event.COMPLETE, handler_serviceDidFinished ) service2.addEventListener( Event.COMPLETE, handler_serviceDidFinished2 ) But how can I do the same in Objective C? The problem is I already created the protocols and delegates, but how can I separate each response from the server? For example: -(void)callService:( NSString * )methodName withParameters:(NSMutableDictionary *) parameters { ... if (self.delegate != NULL && [self.delegate respondsToSelector:@selector(serviceDidFinishSuccessfully:)]) { [delegate serviceDidFinishSuccessfully:data]; } } Well I'm trying to create a generic delegate here, so how can I separate each response for every service? My first idea is that maybe I should return the name of the service method in the delegate call to identify each service. Maybe I should create a UID for each service and pass it the same way... Any idea?

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• Authentication problem with Wufoo

  - by fudgey

  I set up a Wufoo form with admin only portions that will only show up if I am logged in. I read through the Wufoo API documentation and I can get the authenication to work, but when I try to access the form after I authenticate, it says I need to authenticate. This is what I have so far (subdomain, api key & form id changed) <?php error_reporting(E_ALL); ini_set('display_errors', 1); $curl1 = curl_init('http://fishbowl.wufoo.com/api/v3/users.xml'); curl_setopt($curl1, CURLOPT_RETURNTRANSFER, 1); curl_setopt($curl1, CURLOPT_USERPWD, 'AOI6-LFKL-VM1Q-IEX9:footastic'); curl_setopt($curl1, CURLOPT_HTTPAUTH, CURLAUTH_ANY); curl_setopt($curl1, CURLOPT_SSL_VERIFYPEER, false); curl_setopt($curl1, CURLOPT_FOLLOWLOCATION, false); curl_setopt($curl1, CURLOPT_USERAGENT, 'Wufoo Sample Code'); $response = curl_exec($curl1); $resultStatus = curl_getinfo($curl1); if($resultStatus['http_code'] == 200) { echo 'success!<br>'; } else { echo 'Call Failed '.print_r($resultStatus); } $curl2 = curl_init("http://fishbowl.wufoo.com/api/v3/forms/w7x1p5/entries.json"); curl_setopt($curl2, CURLOPT_HEADER, 0); curl_setopt($curl2, CURLOPT_RETURNTRANSFER, 1); $response = curl_exec($curl2); curl_close ($curl2); echo $response; curl_close($curl1); ?> It doesn't matter if I close $curl1 before or after I call $curl2, I get the same message on my screen: success! You must authenticate to get at the goodies. and I know the api, subdomain and form id are all correct. And one last bonus question... can I do all of this using Ajax instead? - the page I will be displaying the form on will already be limited to admin access, so exposing the API shouldn't matter.

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• Using open2300 with Ubuntu

  - by Gawain

  Hello, I am currently running Ubuntu 8.10 and have been trying to use Open2300 to read data from a Lacrosse WS-2310 weather station and report it to the WUnderground server. The program compiles fine but when I try to run it, it does one of two things: usually it pauses for about 4 minutes, then prints "could not reset" to the screen. But sometimes it just hangs forever. It seems like my computer is unable to communicate with the weather station. I have set the serial port as /dev/ttyS0 in the open2300.conf file and i have also tried /dev/ttyS1, /dev/ttyS2, etc with the same result. As far as I can tell, there are no other settings regarding how Open2300 communicates with the device. Is my serial port locked somehow? It could be something as simple as an incorrect configuration for my serial port or something, but I would have no idea how to check that or change the configuration. Any help would be greatly appreciated. thanks, Gawain EDIT: I tried some tests that i found online and everything seems to be working with my serial port... gawain@gawain:~$ ls -l /dev/ttyS* crw-rw---- 1 root dialout 4, 64 2009-07-09 10:01 /dev/ttyS0 crw-rw---- 1 root dialout 4, 65 2009-07-09 08:56 /dev/ttyS1 crw-rw---- 1 root dialout 4, 66 2009-07-09 08:56 /dev/ttyS2 crw-rw---- 1 root dialout 4, 67 2009-07-09 08:56 /dev/ttyS3 gawain@gawain:~$ setserial -a /dev/ttyS0 /dev/ttyS0, Line 0, UART: 16550A, Port: 0x03f8, IRQ: 4 Baud_base: 115200, close_delay: 50, divisor: 0 closing_wait: 3000 Flags: spd_normal skip_test gawain@gawain:~$ setserial -g /dev/ttyS* /dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4 /dev/ttyS1, UART: 8250, Port: 0xd028, IRQ: 18 /dev/ttyS2, UART: 8250, Port: 0xd040, IRQ: 18 /dev/ttyS3, UART: 8250, Port: 0xd050, IRQ: 18 gawain@gawain:~$ echo 12345 > /dev/ttyS0 gawain@gawain:~$ dmesg | tail -3 [ 144.424259] ppdev0: unregistered pardevice [ 145.692199] ppdev0: registered pardevice [ 145.740052] ppdev0: unregistered pardevice I also tried changing the serial port name to /dev/ttys0 (with a lowercase S) and in that case it gave me a different error, "Unable to open serial device." This suggests to me that it is able to open /dev/ttyS0 but something else is preventing it from reading the weather station. Any ideas? thanks.

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• Idiomatic Scala way to deal with base vs derived class field names?

  - by Gregor Scheidt

  Consider the following base and derived classes in Scala: abstract class Base( val x : String ) final class Derived( x : String ) extends Base( "Base's " + x ) { override def toString = x } Here, the identifier 'x' of the Derived class parameter overrides the field of the Base class, so invoking toString like this: println( new Derived( "string" ).toString ) returns the Derived value and gives the result "string". So a reference to the 'x' parameter prompts the compiler to automatically generate a field on Derived, which is served up in the call to toString. This is very convenient usually, but leads to a replication of the field (I'm now storing the field on both Base and Derived), which may be undesirable. To avoid this replication, I can rename the Derived class parameter from 'x' to something else, like '_x': abstract class Base( val x : String ) final class Derived( _x : String ) extends Base( "Base's " + _x ) { override def toString = x } Now a call to toString returns "Base's string", which is what I want. Unfortunately, the code now looks somewhat ugly, and using named parameters to initialize the class also becomes less elegant: new Derived( _x = "string" ) There is also a risk of forgetting to give the derived classes' initialization parameters different names and inadvertently referring to the wrong field (undesirable since the Base class might actually hold a different value). Is there a better way? Edit: To clarify, I really only want the Base values; the Derived ones just seem necessary for initializing the Base ones. The example only references them to illustrate the ensuing issues. It might be nice to have a way to suppress automatic field generation if the derived class would otherwise end up hiding a base class field.

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• boost::binding that which is already bound

  - by PaulH

  I have a Visual Studio 2008 C++ application that does something like this: template< typename Fcn > inline void Bar( Fcn fcn ) // line 84 { fcn(); }; template< typename Fcn > inline void Foo( Fcn fcn ) { // this works fine Bar( fcn ); // this fails to compile boost::bind( Bar, fcn )(); }; void main() { SYSTEM_POWER_STATUS_EX status = { 0 }; Foo( boost::bind( ::GetSystemPowerStatusEx, &status, true ) ); // line 160 } *The call to GetSystemPowerStatusEx() is just for demonstration. Insert your favorite call there and the behavior is the same. When I go to compile this, I get 84 errors. I won't post them all unless asked, but they start with this: 1>.\MyApp.cpp(99) : error C2896: 'boost::_bi::bind_t<_bi::dm_result<MT::* ,A1>::type,boost::_mfi::dm<M,T>,_bi::list_av_1<A1>::type> boost::bind(M T::* ,A1)' : cannot use function template 'void Bar(Fcn)' as a function argument 1> .\MyApp.cpp(84) : see declaration of 'Bar' 1> .\MyApp.cpp(160) : see reference to function template instantiation 'void Foo<boost::_bi::bind_t<R,F,L>>(Fcn)' being compiled 1> with 1> [ 1> R=BOOL, 1> F=BOOL (__cdecl *)(PSYSTEM_POWER_STATUS_EX,BOOL), 1> L=boost::_bi::list2<boost::_bi::value<_SYSTEM_POWER_STATUS_EX *>,boost::_bi::value<bool>>, 1> Fcn=boost::_bi::bind_t<BOOL,BOOL (__cdecl *)(PSYSTEM_POWER_STATUS_EX,BOOL),boost::_bi::list2<boost::_bi::value<_SYSTEM_POWER_STATUS_EX *>,boost::_bi::value<bool>>> 1> ] If anybody can point out what I may be doing wrong, I would appreciate it. Thanks, PaulH

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• calling asp.net mvc action method using jquery post method expires the session

  - by nccsbim071

  hi, i have a website where i provicde a link. On clicking the link a controller action method is called to generate a zip file after creation of zip file is done, i show the link to download the zip file by replacing the link to create a zip with the link to download the zip. the problem is that after zip file creation is over and link is shown, when user clicks on the link to download the zip file, they are sent to login. After providing correct credentials in the login page they are prompted to download the zip file. they sould not be sent to the login page. In the action to generate zip file i haven't abondoned the session or haven't not done anything that abondons the session. the user should not be sen't to login page after successful creation of zip file user should be able to download the file without login. i search internet on this problem, but i did not find any solution. In one of the blog written by hanselman i found this statement that creates the problem with the session: Is some other thing like an Ajax call or IE's Content Advisor simultaneously hitting the default page or login page and causing a race condition that calls Session.Abandon? (It's happened before!) so i thought there might be some problem with ajax call that causes the session to expire, but i don't know what is happening? any help please thanks

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• WCF: How can I send data while gracefully closing a connection?

  - by mafutrct

  I've got a WCF service that offers a Login method. A client is required to call this method (due to it being the only IsInitiating=true). This method should return a string that describes the success of the call in any case. If the login failed, the connection should be closed. The issue is with the timing of the close. I'd like to send the return value, then immediately close the connection. string Login (string name, string pass) { if (name != pass) { OperationContext.Current.Channel.Close (); return "fail"; } else { return "yay"; } } The MSDN states that calling Close on the channel causes an ICommunicationObject to gracefully transition from the Opened state to the Closed state. The Close method allows any unfinished work to be completed before returning. For example, finish sending any buffered messages). This did not work for me (or my understanding is wrong), as the close is executed immediately - WCF does not wait for the Login method to finish executing and return a string but closes the connection earlier. Therefore I assume that calling Close does not wait for the running method to finish. Now, how can I still return a value, then close?

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• Which is faster in Python: x**.5 or math.sqrt(x)?

  - by Casey

  I've been wondering this for some time. As the title say, which is faster, the actual function or simply raising to the half power? UPDATE This is not a matter of premature optimization. This is simply a question of how the underlying code actually works. What is the theory of how Python code works? I sent Guido van Rossum an email cause I really wanted to know the differences in these methods. My email: There are at least 3 ways to do a square root in Python: math.sqrt, the '**' operator and pow(x,.5). I'm just curious as to the differences in the implementation of each of these. When it comes to efficiency which is better? His response: pow and ** are equivalent; math.sqrt doesn't work for complex numbers, and links to the C sqrt() function. As to which one is faster, I have no idea...

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• python: how to design a container with elements that must reference their container

  - by Luke404

  (the title is admittedly not that great. Please forgive my English, this is the best I could think of) I'm writing a python script that will manage email domains and their accounts, and I'm also a newby at OOP design. My two (related?) issues are: the Domain class must do special work to add and remove accounts, like adding/removing them to the underlying implementation how to manage operations on accounts that must go through their container To solve the former issue I'd add a factory method to the Domain class that'll build an Account instance in that domain, and a 'remove' (anti-factory?) method to handle deletions. For the latter this seems to me "anti-oop" since what would logically be an operation on an Account (eg, change password) must always reference the containing Domain. Seems to me that I must add to the Account a reference back to the Domain and use that to get data (like the domain name) or call methods on the Domain class. Code example (element uses data from the container) that manages an underlying Vpopmail system: class Account: def __init__(self, name, password, domain): self.name = name self.password = password self.domain = domain def set_password(self, password): os.system('vpasswd %s@%s %s' % (self.name, self.domain.name, password) self.password = password class Domain: def __init__(self, domain_name): self.name = domain_name self.accounts = {} def create_account(self, name, password): os.system('vadduser %s@%s %s' % (name, self.name, password)) account = Account(name, password, self) self.accounts[name] = account def delete_account(self, name): os.system('vdeluser %s@%s' % (name, self.name)) del self.accounts[name] another option would be for Account.set_password to call a Domain method that would do the actual work - sounds equally ugly to me. Also note the duplication of data (account name also as dict key), it sounds logical (account names are "primary key" inside a domain) but accounts need to know their own name.

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• IoC & Interfaces Best Practices

  - by n8wrl

  I'm experimenting with IoC on my way to TDD by fiddling with an existing project. In a nutshell, my question is this: what are the best practices around IoC when public and non-public methods are of interest? There are two classes: public abstract class ThisThingBase { public virtual void Method1() {} public virtual void Method2() {} public ThatThing GetThat() { return new ThatThing(this); } internal virtual void Method3() {} internal virtual void Method4() {} } public class Thathing { public ThatThing(ThisThingBase thing) { m_thing = thing; } ... } ThatThing does some stuff using its ThisThingBase reference to call methods that are often overloaded by descendents of ThisThingBase. Method1 and Method2 are public. Method3 and Method4 are internal and only used by ThatThings. I would like to test ThatThing without ThisThing and vice-versa. Studying up on IoC my first thought was that I should define an IThing interface, implement it by ThisThingBase and pass it to the ThatThing constructor. IThing would be the public interface clients could call but it doesn't include Method3 or Method4 that ThatThing also needs. Should I define a 2nd interface - IThingInternal maybe - for those two methods and pass BOTH interfaces to ThatThing?

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• JQueryUI with Google's CDN help

  - by TenaciousImpy

  Hi, I'm having trouble loading JQueryUI from Google's CDN. I've got an ASP.NET application that and am using this to call the scripts: <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js" type="text/javascript"></script> <script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.7.2/jquery-ui.js" type="text/javascript"></script> <link href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/ui-darkness/jquery-ui.css" rel="stylesheet" type="text/css" /> <script type="text/javascript"> $(function() { $("#accordion").accordion(); }); </script> </asp:Content> I then have a test accordion: <div id="accordion"> <h3><a href="#">First header</a></h3> <div>First content</div> <h3><a href="#">Second header</a></h3> <div>Second content</div> </div> However, this doesn't work. I used Chrome's Dev tool and I get this error: Uncaught Error: The 'accordion' plugin requires Sys.scripts.ExtendedAccordion to be loaded with a call to Sys.require() first I'm also using MS' Ajax CDN in my masterpage, so could that be causing a problem? Thanks

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• Shark was unable to find symbol information for this address range - iPhone

  - by Elliot

  I'm trying to use Shark to determine which method(s) are taking the most time in my iPhone app. After sampling, I get this: Clicking the "!" button yields: Shark was unable to find symbol information for this address range. Typically this happens because the application was compiled without symbols or they have been subsequently stripped away. In Xcode, make sure the "Generate Debug Symbols" checkbox is selected (passes the -g flag to the compiler). Note that this does not affect code optimization, and does not typically alter performance significantly. However, the extra symbol information does consume significantly more space and may bloat the size of the executable. But I AM using the Debug option, and I am running on my Device. And Generate Debug Symbols IS checked. So what's wrong?

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