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• Real time location tracking - windows program or browser based?

  - by mawg

  I want to track a few hundred, maybe a few thousand people in real time. Let's say that the hardware aspects are sorted out and I can get the data into a database. Now, I want to get it out and show it, in real-time. Weeeell ... "real-enough" time. Let's say that I want to draw a floorplan of a building and plot everyone every 1 to 5 seconds. (I might want to show only certain "kinds" of people at the click of a button; I will need datamining, etc, but let's stick with the worse case scenario). I am comfortable enough with PHP, though not this sort of thing. I personally would be happier with a windows app coded in Delphi, but the trend seems to be to make everything browser based. So, the question, I guess is whether a browser can handle this and whether there are compelling arguments for a windows-based or browser-based solution. If browser-based can handle this (displaying a few thousand data-points a second), and there are no overwhelming arguments for windows then I guess I will go for browser-based and learn a few new tricks. The obvious advantage being that I could also re-use a large part of my code for (vehicle) tracking on Google maps.

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• Problems with video conversions through the web (local host)

  - by ron-d

  Hello, I get the following errors when I attempt video format conversions called from the local host: “An invalid media type was specified” for M4V to WMV conversions. “One or more arguments are invalid” for MP4 to WMV conversions. Here are the details of the problems: I’ve written a dll in C# that accepts videos in the formats AVI, WMV, M4V and MP4 and performs the following actions: Creates a copy of the input video in WMV format . Creates a WAV file of the input video audio portion. Creates a JPG image from a frame of the input video. I attached the dll to an ASP.NET web project that performs the dll actions. When tested through the developer studio, the actions are performed as intended for all formats. When I place the web project in place to be read when the local host is called through the web browser, the following behavior takes place: WMV format: All actions performed as intended. AVI format: Creates WMV file – OK Creates JPG image – OK Creates empty WAV file – problem. M4V format: Creates empty WAV file – problem. Does not create WMV file -problem Does not create JPG file –problem Throws me the error “An invalid media type was specified” MP4 format: Creates empty WAV file – problem. Does not create WMV file -problem Does not create JPG file –problem Throws me the error “One or more arguments are invalid” When I check their security property, all the files have the same permission access parameters (when I check their security property. Can anyone guide me as to how to solve these problems when the web project is called from the local host? Thank you.

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• Are there good reasons not to use an ORM?

  - by hangy

  During my apprenticeship, I have used NHibernate for some smaller projects which I mostly coded and designed on my own. Now, before starting some bigger project, the discussion arose how to design data access and whether or not to use an ORM layer. As I am still in my apprenticeship and still consider myself a beginner in enterprise programming, I did not really try to push in my opinion, which is that using an object relational mapper to the database can ease development quite a lot. The other coders in the development team are much more experienced than me, so I think I will just do what they say. :-) However, I do not completely understand two of the main reasons for not using NHibernate or a similar project: One can just build one’s own data access objects with SQL queries and copy those queries out of Microsoft SQL Server Management Studio. Debugging an ORM can be hard. So, of course I could just build my data access layer with a lot of SELECTs etc, but here I miss the advantage of automatic joins, lazy-loading proxy classes and a lower maintenance effort if a table gets a new column or a column gets renamed. (Updating numerous SELECT, INSERT and UPDATE queries vs. updating the mapping config and possibly refactoring the business classes and DTOs.) Also, using NHibernate you can run into unforeseen problems if you do not know the framework very well. That could be, for example, trusting the Table.hbm.xml where you set a string’s length to be automatically validated. However, I can also imagine similar bugs in a “simple” SqlConnection query based data access layer. Finally, are those arguments mentioned above really a good reason not to utilise an ORM for a non-trivial database based enterprise application? Are there probably other arguments they/I might have missed? (I should probably add that I think this is like the first “big” .NET/C# based application which will require teamwork. Good practices, which are seen as pretty normal on Stack Overflow, such as unit testing or continuous integration, are non-existing here up to now.)

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• Javascript private member on prototype...

  - by Wilq32

  Well I tried to figure out is this possible in any way. Here is code: a=function(text) { var b=text; if (!arguments.callee.prototype.get) arguments.callee.prototype.get=function() { return b; } else alert('already created!'); } var c=new a("test"); // creates prototype instance of getter var d=new a("ojoj"); // alerts already created alert(c.get()) // alerts test alert(d.get()) // alerts test from context of creating prototype function :( As you see I tried to create prototype getter. For what? Well if you write something like this: a=function(text) { var b=text; this.getText=function(){ return b} } ... everything should be fine.. but in fact every time I create object - i create getText function that uses memory. I would like to have one prototypical function lying in memory that would do the same... Any ideas? EDIT: I tried solution given by Christoph, and it seems that its only known solution for now. It need to remember id information to retrieve value from context, but whole idea is nice for me :) Id is only one thing to remember, everything else can be stored once in memory. In fact you could store a lot of private members this way, and use anytime only one id. Actually this is satisfying me :) (unless someone got better idea). someFunc = function() { var store = new Array(); var guid=0; var someFunc = function(text) { this.__guid=guid; store[guid++]=text; } someFunc.prototype.getValue=function() { return store[this.__guid]; } return someFunc; }() a=new someFunc("test"); b=new someFunc("test2"); alert(a.getValue()); alert(b.getValue());

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• Writing an auto-memoizer in Scheme. Help with macro and a wrapper.

  - by kunjaan

  I am facing a couple of problems while writing an auto-memoizer in Scheme. I have a working memoizer function, which creats a hash table and checks if the value is already computed. If it has been computed before then it returns the value else it calls the function. (define (memoizer fun) (let ((a-table (make-hash))) (?(n) (define false-if-fail (?() #f)) (let ((return-val (hash-ref a-table n false-if-fail))) (if return-val return-val (begin (hash-set! a-table n (fun n)) (hash-ref a-table n))))))) Now I want to create a memoize-wrapper function like this: (define (memoize-wrapper function) (set! function (memoizer function))) And hopefully create a macro called def-memo which defines the function with the memoize-wrapper. eg. the macro could expand to (memoizer (define function-name arguments body ...) or something like that. So that I should be able to do : (def-memo (factorial n) (cond ((= n 1) 1) (else (* n (factorial (- n 1)))))) which should create a memoized version of the factorial instead of the normal slow one. My problem is that the The memoize-wrapper is not working properly, it doesnt call the memoized function but the original function. I have no idea how to write a define inside of the macro. How do I make sure that I can get variable lenght arguments and variable length body? How do I then define the function and wrap it around with the memoizer? Thanks a lot.

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• Django, url tag in template doesn't work: NoReverseMatch

  - by Lukasz Jocz

  I've encountered a problem with generating reverse url in templates in django. I'm trying to solve it since a few hours and I have no idea what the problem might be. URL reversing works great in models and views: # like this in models.py @models.permalink def get_absolute_url(self): return ('entry', (), { 'entry_id': self.entry.id, }) # or this in views.py return HttpResponseRedirect(reverse('entry',args=(entry_id,))) but when I'm trying to make it in template I get such an error: NoReverseMatch at /entry/1/ Reverse for ''add_comment'' with arguments '(1L,)' and keyword arguments '{}' not found. My file structure looks like this: project/ +-- frontend ¦   +-- models.py ¦   +-- urls.py ¦   +-- views.py +-- settings.py +-- templates ¦   +-- add_comment.html ¦   +-- entry.html +-- utils ¦   +-- with_template.py +-- wsgi.py My urls.py: from project.frontend.views import * from django.conf.urls import patterns, include, url urlpatterns = patterns('project.frontend.views', url(r'^entry/(?P<entry_id>\d+)/', 'entry', name="entry"), (r'^entry_list/', 'entry_list'), Then entry_list.html: {% extends "base.html" %} {% block content %} {% for entry in entries %} {% url 'entry' entry.id %} {% endfor %} {% endblock %} In views.py I have: @with_template def entry(request, entry_id): entry = Entry.objects.get(id=entry_id) entry.comments = entry.get_comments() return locals() where with_template is following decorator(but I don't think this is a case): class TheWrapper(object): def __init__(self, default_template_name): self.default_template_name = default_template_name def __call__(self, func): def decorated_func(request, *args, **kwargs): extra_context = kwargs.pop('extra_context', {}) dictionary = {} ret = func(request, *args, **kwargs) if isinstance(ret, HttpResponse): return ret dictionary.update(ret) dictionary.update(extra_context) return render_to_response(dictionary.get('template_name', self.default_template_name), context_instance=RequestContext(request), dictionary=dictionary) update_wrapper(decorated_func, func) return decorated_func if not callable(arg): return TheWrapper(arg) else: default_template_name = ''.join([ arg.__name__, '.html']) return TheWrapper(default_template_name)(arg) Do you have any idea, what may cause the problem? Great thanks in advance!

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• Solving quadratic programming using R

  - by user702846

  I would like to solve the following quadratic programming equation using ipop function from kernlab : min 0.5*x'*H*x + f'*x subject to: A*x <= b Aeq*x = beq LB <= x <= UB where in our example H 3x3 matrix, f is 3x1, A is 2x3, b is 2x1, LB and UB are both 3x1. edit 1 My R code is : library(kernlab) H <- rbind(c(1,0,0),c(0,1,0),c(0,0,1)) f = rbind(0,0,0) A = rbind(c(1,1,1), c(-1,-1,-1)) b = rbind(4.26, -1.73) LB = rbind(0,0,0) UB = rbind(100,100,100) > ipop(f,H,A,b,LB,UB,0) Error in crossprod(r, q) : non-conformable arguments I know from matlab that is something like this : H = eye(3); f = [0,0,0]; nsamples=3; eps = (sqrt(nsamples)-1)/sqrt(nsamples); A=ones(1,nsamples); A(2,:)=-ones(1,nsamples); b=[nsamples*(eps+1); nsamples*(eps-1)]; Aeq = []; beq = []; LB = zeros(nsamples,1); UB = ones(nsamples,1).*1000; [beta,FVAL,EXITFLAG] = quadprog(H,f,A,b,Aeq,beq,LB,UB); and the answer is a vector of 3x1 equals to [0.57,0.57,0.57]; However when I try it on R, using ipop function from kernlab library ipop(f,H,A,b,LB,UB,0)) and I am facing Error in crossprod(r, q) : non-conformable arguments I appreciate any comment

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• How to catch exceptions from processes in C#

  - by kitofr

  I all... I have an acceptance runner program here that looks something like this: public Result Run(CommandParser parser) { var result = new Result(); var watch = new Stopwatch(); watch.Start(); try { _testConsole.Start(); parser.ForEachInput(input => { _testConsole.StandardInput.WriteLine(input); return _testConsole.TotalProcessorTime.TotalSeconds < parser.TimeLimit; }); if (TimeLimitExceeded(parser.TimeLimit)) { watch.Stop(); _testConsole.Kill(); ReportThatTestTimedOut(result); } else { result.Status = GetProgramOutput() == parser.Expected ? ResultStatus.Passed : ResultStatus.Failed; watch.Stop(); } } catch (Exception) { result.Status = ResultStatus.Exception; } result.Elapsed = watch.Elapsed; return result; } the _testConsole is an Process adapter that wraps a regular .net process into something more workable. I do however have a hard time to catch any exceptions from the started process (i.e. the catch statement is pointless here) I'm using something like: _process = new Process { StartInfo = { FileName = pathToProcess, UseShellExecute = false, CreateNoWindow = true, RedirectStandardInput = true, RedirectStandardOutput = true, RedirectStandardError = true, Arguments = arguments } }; to set up the process. Any ideas?

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• Namespace scoped aliases for generic types in C#

  - by TN

  Let's have a following example: public class X { } public class Y { } public class Z { } public delegate IDictionary<Y, IList<Z>> Bar(IList<X> x, int i); public interface IFoo { // ... Bar Bar { get; } } public class Foo : IFoo { // ... public Bar Bar { get { return null; //... } } } void Main() { IFoo foo; //= ... IEnumerable<IList<X>> source; //= ... var results = source.Select(foo.Bar); } The compiler says: The type arguments for method 'System.Linq.Enumerable.Select(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly. It's because, it cannot convert Bar to Func<IList<X>, int, IDictionary<Y, IList<Z>>>. It would be great if I could create type namespace scoped type aliases for generic types in C#. Then I would define Bar not as a delegate, but rather I would define it as an namespace scoped alias for Func<IList<X>, int, IDictionary<Y, IList<Z>>>. public alias Bar = Func<IList<X>, int, IDictionary<Y, IList<Z>>>; I could then also define namespace scoped alias for e.g. IDictionary<Y, IList<Z>>. And if used appropriately:), it will make the code more readable. Now I have inline the generic types and the real code is not well readable:( Have you find the same trouble:)? Is there any good reason why it is not in C# 3.0? Or there is no good reason, it's just matter of money and/or time? EDIT: I know that I can use using, but it is not namespace based - not so convenient for my case.

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• Detect Application Shutdown in C# NET?

  - by Michael Pfiffer

  I am writing a small console application (will be ran as a service) that basically starts a Java app when it is running, shuts itself down if the Java app closes, and shuts down the Java app if it closes. I think I have the first two working properly, but I don't know how to detect when the .NET application is shutting down so that I can shutdown the Java app prior to that happening. Google search just returns a bunch of stuff about detecting Windows shutting down. Can anyone tell me how I can handle that part and if the rest looks fine? namespace MinecraftDaemon { class Program { public static void LaunchMinecraft(String file, String memoryValue) { String memParams = "-Xmx" + memoryValue + "M" + " -Xms" + memoryValue + "M "; String args = memParams + "-jar " + file + " nogui"; ProcessStartInfo processInfo = new ProcessStartInfo("java.exe", args); processInfo.CreateNoWindow = true; processInfo.UseShellExecute = false; try { using (Process minecraftProcess = Process.Start(processInfo)) { minecraftProcess.WaitForExit(); } } catch { // Log Error } } static void Main(string[] args) { Arguments CommandLine = new Arguments(args); if (CommandLine["file"] != null && CommandLine["memory"] != null) { // Launch the Application LaunchMinecraft(CommandLine["file"], CommandLine["memory"]); } else { LaunchMinecraft("minecraft_server.jar", "1024"); } } } }

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• Attempt to use a while loop for the 'next' arg of a for loop generates #arg error

  - by JerryK

  Am attempting to teach myself to program using Tcl. The task i've set myself to motivate my learning of Tcl is to solve the 8 queens problem. My approach to creating a program is to successively 'prototype' a solution. I have asked an earlier question related to the correctly laying out the nested for loops and received a helpful answer. To my dismay I find that the next development of my code creates the same interpreter error : "wrong # args" I have been careful to have an open brace at the end of the line preceding the while loop command. I've also tried to put the arguments of the whileloop in braces. This generates a different error. I have sincerely tried to understand the Tcl syntax man page - not too successfully - suggested by the answerer of my earlier question. Here is the code set allowd 1 set notallowd 0 for {set r1p 1} {$r1p <= 8} {incr r1p } { puts "1st row q placed at $r1p" ;# re-initialize r2 'free for q placemnt' array after every change of r1 q pos: for {set i 1 } {$i <= 8} {incr i} { set r2($i) $allowd } for { set r2($r1p) $notallowd ; set r2([expr $r1p-1]) $notallowd ; set r2([expr $r1p+1]) $notallowd ; set r2p 1} {$r2p <= 8} { ;# 'next' arg of r2 forloop will be a whileloop : while r2($r2p)== $notallowd incr r2p } { puts "2nd row q placed at $r2p" ;# end of 'commnd' arg of r2 forloop } } Where am I going wrong? EDIT : to provide clear reply @slebetman As stated in my text, I did brace the arguments of the whileloop (indeed that was how i first wrote the code) below is exactly the layout of the r2 forloop tried: for { set r2($r1p) $notallowd ; set r2([expr $r1p-1]) $notallowd ; set r2([expr $r1p+1]) $notallowd ; set r2p 1} {$r2p <= 8} { ;# 'next' arg of r2 forloop will be a whileloop : while { r2($r2p)== $notallowd } { incr r2p } } { puts "2nd row q placed at $r2p" ;# end of 'commnd' arg of r2 forloop } but this generates the fatal interpreter error : "unknown math function 'r2' while compiling while { r2($r2p .... "

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• Which options do I have for Java process communication?

  - by Dmitriy Matveev

  We have a place in a code of such form: void processParam(Object param) { wrapperForComplexNativeObject result = jniCallWhichMayCrash(param); processResult(result); } processParam - method which is called with many different arguments. jniCallWhichMayCrash - a native method which is intended to do some complex processing of it's parameter and to create some complex object. It can crash in some cases. wrapperForComplexNativeObject - wrapper type generated by SWIG processResult - a method written in pure Java which processes it's parameter by creation of several kinds (by the kinds I'm not meaning classes, maybe some like hierarchies) of objects: 1 - Some non-unique objects which are referencing each other (from the same hierarchy), these objects can have duplicates created from the invocations of processParam() method with different parameter values. Since it's costly to keep all the duplicates it's necessary to cache them. 2 - Some unique objects which are referencing each other (from the same hierarchy) and some of the objects of 1st kind. After processParam is executed for each of the arguments from some set the data created in processResult will be processed together. The problem is in fact that jniCallWhichMayCrash method may crash the entire JVM and this will be very bad. The reason of crash may be such that it can happen for one argument value and not for the other. We've decided that it's better to ignore crashes inside of JVM and just skip some chunks of data when such crashes occur. In order to do this we should run processParam function inside of separate process and pass the result somehow (HOW? HOW?! This is a question) to the main process and in case of any crashes we will only lose some part of data (It's ok) without lose of everything else. So for now the main problem is implementation of transport between different processes. Which options do I have? I can think about serialization and transmitting of binary data by the streams, but serialization may be not very fast due to object complexity. Maybe I have some other options of implementing this?

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• Coldfusion 8 and HTTP PUT - is there a way to PUT an object?

  - by ciaranarcher

  Hi all We are using EHCache with CF 8 to cache stuff on a central server using a RESTful interface over HTTP. I am trying to cache a cfquery object to the cache server. I can get this to work if I call EHCache direct (i.e. store it in a local cache) but if I try to cache on a remote server over HTTP I am running into problems. The code I am using is as follows: <cfhttp url="http://localhost:8080/myCache/myKey" method="put" result="r" timeout="2" throwonerror="true" > <cfhttpparam type="body" value="#ARGUMENTS.item#" /> </cfhttp> CF doesn't like this reference to #ARGUMENTS.item# and it complains Complex object types cannot be converted to simple values. Can anyone give me an example of how to put an object over http using CF? If this is not possible with CF then a Java example would be the next best thing. Many thanks in advance! PS: I do not want to use serialization to text/JSON etc. as this approach has issues with data integrity and most importantly it's not fast enough.

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• Number of characters recommended for a statement

  - by liaK

  Hi, I have been using Qt 4.5 and so do C++. I have been told that it's a standard practice to maintain the length of each statement in the application to 80 characters. Even in Qt creator we can make a right border visible so that we can know whether we are crossing the 80 characters limit. But my question is, Is it really a standard being followed? Because in my application, I use indenting and all, so it's quite common that I cross the boundary. Other cases include, there might be a error statement which will be a bit explanatory one and which is in an inner block of code, so it too will cross the boundary. Usually my variable names look bit lengthier so as to make the names meaningful. When I call the functions of the variable names, again I will cross. Function names will not be in fewer characters either. I agree a horizontal scroll bar shows up and it's quite annoying to move back and forth. So, for function calls including multiple arguments, when the boundary is reached I will make the forth coming arguments in the new line. But besides that, for a single statement (for e.g a very long error message which is in double quotes " " or like longfun1()->longfun2()->...) if I use an \ and split into multiple lines, the readability becomes very poor. So is it a good practice to have those statement length restrictions? If this restriction in statement has to be followed? I don't think it depends on a specific language anyway. I added C++ and Qt tags since if it might. Any pointers regarding this are welcome.

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• Why null reference exception in SetMolePublicInstance?

  - by OldGrantonian

  I get a "null reference" exception in the following line: MoleRuntime.SetMolePublicInstance(stub, receiverType, objReceiver, name, null); The program builds and compiles correctly. There are no complaints about any of the parameters to the method. Here's the specification of SetMolePublicInstance, from the object browser: SetMolePublicInstance(System.Delegate _stub, System.Type receiverType, object _receiver, string name, params System.Type[] parameterTypes) Here are the parameter values for "Locals": + stub {Method = {System.String <StaticMethodUnitTestWithDeq>b__0()}} System.Func<string> + receiverType {Name = "OrigValue" FullName = "OrigValueP.OrigValue"} System.Type {System.RuntimeType} objReceiver {OrigValueP.OrigValue} object {OrigValueP.OrigValue} name "TestString" string parameterTypes null object[] I know that TestString() takes no parameters and returns string, so as a starter to try to get things working, I specified "null" for the final parameter to SetMolePublicInstance. As already mentioned, this compiles OK. Here's the stack trace: Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.ExtendedReflection.Collections.Indexable.ConvertAllToArray[TInput,TOutput](TInput[] array, Converter`2 converter) at Microsoft.Moles.Framework.Moles.MoleRuntime.SetMole(Delegate _stub, Type receiverType, Object _receiver, String name, MoleBindingFlags flags, Type[] parameterTypes) at Microsoft.Moles.Framework.Moles.MoleRuntime.SetMolePublicInstance(Delegate _stub, Type receiverType, Object _receiver, String name, Type[] parameterTypes) at DeqP.Deq.Replace[T](Func`1 stub, Type receiverType, Object objReceiver, String name) in C:\0VisProjects\DecP_04\DecP\DeqC.cs:line 38 at DeqPTest.DecCTest.StaticMethodUnitTestWithDeq() in C:\0VisProjects\DecP_04\DecPTest\DeqCTest.cs:line 28 at Starter.Start.Main(String[] args) in C:\0VisProjects\DecP_04\Starter\Starter.cs:line 14 Press any key to continue . . . To avoid the null parameter, I changed the final "null" to "parameterTypes" as in the following line: MoleRuntime.SetMolePublicInstance(stub, receiverType, objReceiver, name, parameterTypes); I then tried each of the following (before the line): int[] parameterTypes = null; // if this is null, I don't think the type will matter int[] parameterTypes = new int[0]; object[] parameterTypes = new object[0]; // this would allow for various parameter types All three attempts produce a red squiggly line under the entire line for SetMolePublicInstance Mouseover showed the following message: The best overloaded method match for 'Microsoft.Moles.Framework.Moles.MoleRuntime.SetMolePublicInstance(System.Delegate, System.Type, object, string, params System.Type[])' has some invalid arguments. I'm assuming that the first four arguments are OK, and that the problem is with the params array.

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• Python class structure ... prep() method?

  - by Adam Nelson

  We have a metaclass, a class, and a child class for an alert system: class AlertMeta(type): """ Metaclass for all alerts Reads attrs and organizes AlertMessageType data """ def __new__(cls, base, name, attrs): new_class = super(AlertMeta, cls).__new__(cls, base, name, attrs) # do stuff to new_class return new_class class BaseAlert(object): """ BaseAlert objects should be instantiated in order to create new AlertItems. Alert objects have classmethods for dequeue (to batch AlertItems) and register (for associated a user to an AlertType and AlertMessageType) If the __init__ function recieves 'dequeue=True' as a kwarg, then all other arguments will be ignored and the Alert will check for messages to send """ __metaclass__ = AlertMeta def __init__(self, **kwargs): dequeue = kwargs.pop('dequeue',None) if kwargs: raise ValueError('Unexpected keyword arguments: %s' % kwargs) if dequeue: self.dequeue() else: # Do Normal init stuff def dequeue(self): """ Pop batched AlertItems """ # Dequeue from a custom queue class CustomAlert(BaseAlert): def __init__(self,**kwargs): # prepare custom init data super(BaseAlert, self).__init__(**kwargs) We would like to be able to make child classes of BaseAlert (CustomAlert) that allow us to run dequeue and to be able to run their own __init__ code. We think there are three ways to do this: Add a prep() method that returns True in the BaseAlert and is called by __init__. Child classes could define their own prep() methods. Make dequeue() a class method - however, alot of what dequeue() does requires non-class methods - so we'd have to make those class methods as well. Create a new class for dealing with the queue. Would this class extend BaseAlert? Is there a standard way of handling this type of situation?

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• C# Linq Select Problem in Method Chain.

  - by Gnought

  Note that the _src inherit IQueryable<U> and V inherit new(); I wrote the following statement, there is no syntax error. IQueryable<V> a = from s in _src where (s.Right - 1 == s.Left) select new V(); But if i re-wrote it as follows, the Visual Studio editor complains an error in the "Select" IQueryable<V> d = _src.Where(s => s.Right - 1 == s.Left).Select(s=> new V()); The Error is: The type arguments cannot be inferred from the usage. Try specifying the type arguments explicitly. Candidates are: System.Collections.Generic.IEnumerable<V> Select<U,V>(this System.Collections.Generic.IEnumerable<U>, System.Func<U,V>) (in class Enumerable) System.Linq.IQueryable<V> Select<U,V>(this System.Linq.IQueryable<U>, System.Linq.Expressions.Expression<System.Func<U,V>>) (in class Queryable) Could anyone explain this phenomenon, and what the solution is to fix the error?

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• Why does exec:java work and exec:exec fail?

  - by whiskerz

  Hey there, just set up a simple project to test the functionality of the maven exec plugin. I have one class containing one "Hello World" main method. I've tested two configurations of the exec plugin. <goals> <goal>exec</goal> </goals> <configuration> <executable>java</executable> <arguments> <argument>-classpath</argument> <classpath/> <argument>test.exec.HelloWorldExec</argument> </arguments> </configuration> failed miserably, giving me a ClassNotFoundException, while <goals><goal>java</goal></goals> <configuration> <mainClass>test.exec.HelloWorldExec</mainClass> </configuration> worked. However I would like to be able to start my java main class in a separate process, so I'd like to understand whats different with exec:exec and how I can get it to work? Any help appreciated cheers Whizz

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• in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

  - by Steve

  Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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• How to override part of an overload function in JavaScript

  - by Guan Yuxin

  I create a class with a function like this var Obj=function(){this.children=[];this.parent=null;}//a base class Obj.prototype.index=function(child){ // the index of current obj if(arguments.length==0){ return this.parent?this.parent.index(this):0; } // the index of a child matchs specific obj [to be override] return -1; } basically it is just an overload function composed of index() and index(child). Then I create a sub class,SubObj or whatever, inherits from Obj SubObj.prototype.prototype=Obj; Now, it's time to override the index(child) function,however, index() is also in the function an I don't want to overwrite it too. One solution is to write like this var Obj=function(){this.children=[];this.parent=null;}//a base class Obj.prototype.index=function(child){ // the index of current obj if(arguments.length==0){ return this.parent?this.parent.index(this):0; } // the index of a child matchs specific obj [to be override] return this._index(this); } Obj.prototype._index=function(this){ return -1; } SubObj.prototype._index=function(this){/* overwriteing */} But this will easily mislead other coders as _index(child) should be both private(should not be used except index() function) and public(is an overload function of index(),which is public) you guys have better idea?

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• Adding and sorting a linked list in C

  - by user1202963

  In my assignment, I have to write a function that takes as arguments a pointer to a "LNode" structure and an integer argument. Then, I have to not only add that integer into the linked list, but also put place it so that the list is in proper ascending order. I've tried several various attempts at this, and this is my code as of posting. LNode* AddItem(LNode *headPtr, int newItem) { auto LNode *ptr = headPtr; ptr = malloc(sizeof(LNode)); if (headPtr == NULL) { ptr->value = newItem; ptr->next = headPtr; return ptr; } else { while (headPtr->value > newItem || ptr->next != NULL) { printf("While\n"); // This is simply to let me know how many times the loop runs headPtr = headPtr->next; } ptr->value = newItem; ptr->next = headPtr; return ptr; } } // end of "AddItem" When I run it, and try to insert say a 5 and then a 3, the 5 gets inserted, but then the while loop runs once and I get a segmentation fault. Also I cannot change the arguments as it's part of a skeletal code for this project. Thanks to anyone who can help. If it helps this is what the structure looks like typedef struct LNode { int value; struct LNode *next; } LNode;

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• Adding functions to Java class libraries

  - by Eric

  I'm using a Java class library that is in many ways incomplete: there are many classes that I feel ought to have additional member functions built in. However, I am unsure of the best practice of adding these member functions. Lets call the insufficient base class A. class A { public A(/*long arbitrary arguments*/) { //... } public A(/*long even more arbitrary arguments*/) { //... } public int func() { return 1; } } Ideally, I would like to add a function to A. However, I can't do that. My choice is between: class B extends A { //Implement ALL of A's constructors here public int reallyUsefulFunction() { return func()+1; } } and class AddedFuncs { public int reallyUsefulFunction(A a) { return a.func()+1; } } The way I see it, they both have advantages and disadvantages. The first choice gives a cleaner syntax than the second, and is more logical, but has problems: Let's say I have a third class, C, within the class library. class C { public A func() { return new A(/*...*/); } } As I see it, there is no easy way of doing this: C c; int useful = c.func().reallyUsefulFunction(); as the type returned by C.func() is an A, not a B, and you can't down-cast. So what is the best way of adding a member function to a read-only library class?

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• C++ Inheritance and Constructors

  - by DizzyDoo

  Hello, trying to work out how to use constructors with an inherited class. I know this is very much wrong, I've been writing C++ for about three days now, but here's my code anyway: clientData.h, two classes, ClientData extends Entity : #pragma once class Entity { public: int x, y, width, height, leftX, rightX, topY, bottomY; Entity(int x, int y, int width, int height); ~Entity(); }; class ClientData : public Entity { public: ClientData(); ~ClientData(); }; and clientData.cpp, which contains the functions: #include <iostream> #include "clientData.h" using namespace std; Entity::Entity(int x, int y, int width, int height) { this->x = x; this->y = y; this->width = width; this->height = height; this->leftX = x - (width/2); this->rightX = x + (width/2); this->topY = y - (height/2); this-bottomY = y + (height/2); } Entity::~Entity() { cout << "Destructing.\n"; } ClientData::ClientData() { cout << "Client constructed."; } ClientData::~ClientData() { cout << "Destructing.\n"; } and finally, I'm creating a new ClientData with: ClientData * Data = new ClientData(32,32,32,16); Now, I'm not surprised my compiler shouts errors at me, so how do I pass the arguments to the right classes? The first error (from MVC2008) is error C2661: 'ClientData::ClientData' : no overloaded function takes 4 arguments and the second, which pops up whatever changes I seem to make is error C2512: 'Entity' : no appropriate default constructor available Thanks.

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• Drupal 7 - I can't pass post data in module function

  - by user2603290

  I can't pass post data in my custom module. filenames: mymodule.info mymodule.mod .info name = My Module description = My custom module. package = DEV version = 1.0 core = 7.x .module <?php function mymodule_menu() { $items = array(); $items['getcountries'] = array( 'title' => 'Get Countries', 'page callback' => 'getcountries', 'access arguments' => array('access content'), 'type' => MENU_CALLBACK, ); $items['getstates'] = array( 'title' => 'Get States', 'page callback' => 'getstates', 'access arguments' => array('access content'), 'type' => MENU_CALLBACK, ); return $items; } function getcountries() { $result = db_query("select distinct(country) from region"); $jsonarray = Array(); foreach ($result as $record) { $jsonarray[] = array( 'item' => $record->country, 'value' => $record->country ); } $json = json_encode($jsonarray); echo $json; } function getstates() { echo $_POST["test"]; } Ajax call $(document).ready(function(){ $.ajax({ url: '/getstates', type: 'POST', data: '{"test":"1"}', success : function () { alert('ok'); }, error : function (jqXHR, textStatus, errorThrown) { alert('error'); } }); }); The first item "getcountries" is working fine however the second one is not. I can browse to http://mysite.com/getstates ok but when I call this function using ajax it is not passing the value of "test" which is "1" to $_POST["test"]. I am new to Drupal so I am positive that I miss something here. I thought I need a new set of eyes.

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• Cisco VPN Client Behind ASA 5505

  - by fdf33

  I'm trying to get connected to another ASA via Cisco VPN Client. I am behind an ASA 5505 myself and I am tryihng to VPN to a 5510. I get the message: Secure VPN Connection terminated locally by the Client. Reason 412: The remote peer is no longer responding. I can connect to the other ASA if I use a normal cheap Linksys. Here's the version of my ASA: Result of the command: "sh ver" Cisco Adaptive Security Appliance Software Version 8.4(1) Any help would be great. Thanks running-config : Saved : Written by enable_15 at 23:12:32.378 UTC Fri Jul 1 2011 ! ASA Version 8.4(1) ! hostname aaaasa domain-name aaa.local enable password xxxxxxxxxxxxxxx encrypted passwd xxxxxxxxxxxxxxxxxxxx encrypted names ! interface Vlan1 nameif inside security-level 100 ip address 192.168.1.254 255.255.255.0 ! interface Vlan2 nameif outside security-level 0 ip address xxx.xxx.xxx.xxx 255.255.254.0 ! interface Vlan5 no nameif security-level 50 ip address 172.16.0.254 255.255.255.0 ! interface Vlan500 no nameif security-level 100 ip address 10.10.10.1 255.255.255.0 ! interface Ethernet0/0 switchport access vlan 2 ! interface Ethernet0/1 ! interface Ethernet0/2 ! interface Ethernet0/3 ! interface Ethernet0/4 ! interface Ethernet0/5 ! interface Ethernet0/6 ! interface Ethernet0/7 ! boot system disk0:/asa841-k8.bin ftp mode passive dns domain-lookup inside dns domain-lookup outside dns server-group DefaultDNS name-server 4.2.2.2 domain-name aaa.local same-security-traffic permit inter-interface same-security-traffic permit intra-interface object network obj_any subnet 0.0.0.0 0.0.0.0 object network A_93.97.168.1 host 93.97.168.1 object network rdp host 192.168.1.2 object network NETWORK_OBJ_192.168.1.0_24 subnet 192.168.1.0 255.255.255.0 access-list 101 extended permit tcp any host 192.168.1.2 eq 3389 access-list 101 extended permit icmp any any echo-reply access-list 101 extended permit icmp any any source-quench access-list 101 extended permit icmp any any time-exceeded access-list 101 extended permit icmp any any unreachable access-list 102 extended permit ip any any pager lines 24 logging enable logging asdm informational mtu inside 1500 mtu outside 1492 ip local pool VPNPool 192.168.2.200-192.168.2.210 mask 255.255.255.0 icmp unreachable rate-limit 1 burst-size 1 asdm image disk0:/asdm-641.bin no asdm history enable arp timeout 14400 ! object network rdp nat (inside,outside) static interface service tcp 3389 3389 ! nat (inside,outside) after-auto source dynamic any interface access-group 101 in interface outside access-group 102 out interface outside ! router ospf 1 network 192.168.1.0 255.255.255.0 area 0 log-adj-changes ! route outside 0.0.0.0 0.0.0.0 93.97.168.1 1 timeout xlate 3:00:00 timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02 timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00 timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00 timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute timeout tcp-proxy-reassembly 0:01:00 dynamic-access-policy-record DfltAccessPolicy http server enable http 192.168.1.0 255.255.255.0 inside no snmp-server location no snmp-server contact snmp-server enable traps snmp authentication linkup linkdown coldstart crypto ipsec ikev2 ipsec-proposal DES protocol esp encryption des protocol esp integrity sha-1 md5 crypto ipsec ikev2 ipsec-proposal 3DES protocol esp encryption 3des protocol esp integrity sha-1 md5 crypto ipsec ikev2 ipsec-proposal AES protocol esp encryption aes protocol esp integrity sha-1 md5 crypto ipsec ikev2 ipsec-proposal AES192 protocol esp encryption aes-192 protocol esp integrity sha-1 md5 crypto ipsec ikev2 ipsec-proposal AES256 protocol esp encryption aes-256 protocol esp integrity sha-1 md5 crypto dynamic-map SYSTEM_DEFAULT_CRYPTO_MAP 65535 set ikev2 ipsec-proposal AES256 AES192 AES 3DES DES crypto map outside_map 65535 ipsec-isakmp dynamic SYSTEM_DEFAULT_CRYPTO_MAP crypto map outside_map interface outside crypto ca trustpoint ASDM_TrustPoint0 enrollment self subject-name CN=ciscoasa proxy-ldc-issuer crl configure crypto ca certificate chain ASDM_TrustPoint0 certificate 8877d64d 30820248 308201b1 a0030201 02020488 77d64d30 0d06092a 864886f7 0d010105 05003036 3111300f 06035504 03130863 6973636f 61736131 21301f06 092a8648 86f70d01 09021612 63697363 6f617361 2e6e6a64 2e6c6f63 616c301e 170d3131 30353231 30383533 34325a17 0d323130 35313830 38353334 325a3036 3111300f 06035504 03130863 6973636f 61736131 21301f06 092a8648 86f70d01 09021612 63697363 6f617361 2e6e6a64 2e6c6f63 616c3081 9f300d06 092a8648 86f70d01 01010500 03818d00 30818902 818100ea 1aa95141 480e616c efee6816 a96d6511 313b6776 cd3dd57b cd84b4d2 5e108aee 7c980086 4d92e2eb b6c7bf66 4585af0a ccbf153a db9270be c6f5c67b db9dd8d1 2f78d033 3348b056 df4be0da 70e08953 53adf294 9db6c020 597d250f bf448b43 b90179c8 ff0b15d8 744632d9 31c1945f 0b11e258 b4c1d224 692efff4 7b2f5102 03010001 a3633061 300f0603 551d1301 01ff0405 30030101 ff300e06 03551d0f 0101ff04 04030201 86301f06 03551d23 04183016 8014493c 19db183a ab1af9e9 b1e44ad4 2a408b3c 89d1301d 0603551d 0e041604 14493c19 db183aab 1af9e9b1 e44ad42a 408b3c89 d1300d06 092a8648 86f70d01 01050500 03818100 1dd1760a fdd15941 4803fb9a cd6f44a7 2e275854 a1c0fbe1 d19f2cc9 182d43ef a547f854 8df96d15 3ea79c62 cf3fcb1c 5820360b c607dbfc 4de8bb16 19f727e9 b928a085 665816d8 138e4a35 ed610950 7910dd4a 0b1a9dd9 0e26f1c8 b78bc0cc cbf19eb2 4c4c3931 45199ea5 249e3266 661e44fd 7a00d376 dcfc6e4e d43f10b8 quit crypto isakmp nat-traversal 30 crypto ikev2 policy 1 encryption aes-256 integrity sha group 5 prf sha lifetime seconds 86400 crypto ikev2 policy 10 encryption aes-192 integrity sha group 5 prf sha lifetime seconds 86400 crypto ikev2 policy 20 encryption aes integrity sha group 5 prf sha lifetime seconds 86400 crypto ikev2 policy 30 encryption 3des integrity sha group 5 prf sha lifetime seconds 86400 crypto ikev2 policy 40 encryption des integrity sha group 5 prf sha lifetime seconds 86400 crypto ikev2 enable outside client-services port 443 crypto ikev2 remote-access trustpoint ASDM_TrustPoint0 telnet timeout 5 ssh 192.168.1.0 255.255.255.0 inside ssh timeout 5 console timeout 0 dhcpd auto_config outside ! dhcpd address 192.168.1.5-192.168.1.36 inside dhcpd dns 4.2.2.2 interface inside dhcpd enable inside ! threat-detection basic-threat threat-detection statistics host number-of-rate 3 threat-detection statistics port threat-detection statistics protocol threat-detection statistics access-list threat-detection statistics tcp-intercept rate-interval 30 burst-rate 400 average-rate 200 ntp server 82.219.4.31 source outside prefer ssl trust-point ASDM_TrustPoint0 outside webvpn enable outside anyconnect image disk0:/anyconnect-win-2.4.1012-k9.pkg 1 anyconnect profiles AnyConnectVPN_client_profile disk0:/AnyConnectVPN_client_profile.xml anyconnect profiles SSLAnyConnectVPN_client_profile disk0:/SSLAnyConnectVPN_client_profile.xml anyconnect enable tunnel-group-list enable group-policy GroupPolicy_AnyConnectVPN internal group-policy GroupPolicy_AnyConnectVPN attributes wins-server none dns-server value 4.2.2.2 vpn-tunnel-protocol ikev2 ssl-client ssl-clientless default-domain value aaa.local webvpn url-list none anyconnect profiles value AnyConnectVPN_client_profile type user group-policy GroupPolicy_SSLAnyConnectVPN internal group-policy GroupPolicy_SSLAnyConnectVPN attributes wins-server none dns-server value 4.2.2.2 vpn-tunnel-protocol ikev2 ssl-client default-domain value aaa.local webvpn anyconnect profiles value SSLAnyConnectVPN_client_profile type user username testuser password xxxxxxxxxxxxxxxxx encrypted privilege 0 username testuser attributes vpn-group-policy GroupPolicy_AnyConnectVPN tunnel-group SSLPOL type remote-access tunnel-group SSLPOL general-attributes default-group-policy GroupPolicy_AnyConnectVPN tunnel-group SSLAnyConnectVPN type remote-access tunnel-group SSLAnyConnectVPN general-attributes address-pool VPNPool default-group-policy GroupPolicy_SSLAnyConnectVPN tunnel-group SSLAnyConnectVPN webvpn-attributes group-alias SSLAnyConnectVPN enable ! class-map inspection_default match default-inspection-traffic ! ! policy-map type inspect dns preset_dns_map parameters message-length maximum 512 policy-map global_policy class inspection_default inspect dns preset_dns_map inspect esmtp inspect ftp inspect h323 h225 inspect h323 ras inspect ip-options inspect netbios inspect rsh inspect rtsp inspect sip inspect skinny inspect sqlnet inspect sunrpc inspect tftp inspect xdmcp ! service-policy global_policy global prompt hostname context call-home profile CiscoTAC-1 no active destination address http https://tools.cisco.com/its/service/oddce/services/DDCEService destination address email [email protected] destination transport-method http subscribe-to-alert-group diagnostic subscribe-to-alert-group environment subscribe-to-alert-group inventory periodic monthly subscribe-to-alert-group configuration periodic monthly subscribe-to-alert-group telemetry periodic daily Cryptochecksum:94a65341aa27d3929d5e92a32ba22120 : end

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