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• How to build n-layered web architecture with PHP?

  - by Alex

  I have a description and design of a website and I need to redesign it to allow for new requirements. The website's purpose is the offering of government's contracts and bidding opportunities for different businesses.I'm dealing with the 3-tier architecture PHP website comprising of the user-interface tier(client's web browser),business logic layer(Apache web server with PHP engine in it and a couple of applications running within a web server as well) and a database layer(local mysql database). Now,i need to redesign it to su???rt distributed n-tier architecture and specify how I would go about it.After long hours of research i came to this solution: business logic should be separated into presentation and purely business logic tier to allow for n-layer architecture(user-interface,presentation tier,b.logic and data tier).I have decided to use ??? just for the presentation(since the original existing website is in PHP) and use it within apache web server.In the business logic i want to use J2?? implementation technology instead of implementing it in PHP(i.e using Zend app.server and smarty template) cz J2EE can provide much more essential container services which are essential for business logic,its robustness,maintainability and different critical business operations which will be carried out by the g?v?rnment's website.So,particularly,i want to use J??ss app.server with ?J? business objects in it which would provide all the b.logic in java and would interact with the database and so forth.In order to connect PHP on a web server with java on app.server i'm gonna use PHP/Java bridge API (or maybe Quercus or SOAP is better?).Finally,i have my data tier with mysql which will communicate with b.logic via JD??.Payment system application in ???.server is gonna use S??? to talk with credit card company. From your professional point of view,does it sound like a good way of redesigning the original website to allow for n-tier architecture considering the specifics of the website and the criticality of its operations?(payment system is included in it)or u would personally prefer to use PHP business objects for business logic as well instead of J2EE?If you have any wiser recommendation or some alternative,please let me know what is right or wrong in my current solution. H??? to hear your professional advice very s??n (I'm new to the area of web development) Thanks in advance

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• Small-o(n^2) implementation of Polynomial Multiplication

  - by AlanTuring

  I'm having a little trouble with this problem that is listed at the back of my book, i'm currently in the middle of test prep but i can't seem to locate anything regarding this in the book. Anyone got an idea? A real polynomial of degree n is a function of the form f(x)=a(n)x^n+?+a1x+a0, where an,…,a1,a0 are real numbers. In computational situations, such a polynomial is represented by a sequence of its coefficients (a0,a1,…,an). Assuming that any two real numbers can be added/multiplied in O(1) time, design an o(n^2)-time algorithm to compute, given two real polynomials f(x) and g(x) both of degree n, the product h(x)=f(x)g(x). Your algorithm should **not** be based on the Fast Fourier Transform (FFT) technique. Please note it needs to be small-o(n^2), which means it complexity must be sub-quadratic. The obvious solution that i have been finding is indeed the FFT, but of course i can't use that. There is another method that i have found called convolution, where if you take polynomial A to be a signal and polynomial B to be a filter. A passed through B yields a shifted signal that has been "smoothed" by A and the resultant is A*B. This is supposed to work in O(n log n) time. Of course i am completely unsure of implementation. If anyone has any ideas of how to achieve a small-o(n^2) implementation please do share, thanks.

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• How do I use Linq-to-sql to iterate db records?

  - by Seth Spearman

  I asked on SO a few days ago what was the simplest quickest way to build a wrapper around a recently completed database. I took the advice and used sqlmetal to build linq classes around my database design. Now I am having two problems. One, I don't know LINQ. And, two, I have been shocked to realize how hard it is to learn. I have a book on LINQ (Linq In Action by Manning) and it has helped some but at the end of the day it is going to take me a couple of weeks to get traction and I need to make some progress on my project today. So, I am looking for some help getting started. Click HERE To see my simple database schema. Click HERE to see the vb class that was generated for the schema. My needs are simple. I have a console app. The main table is the SupplyModel table. Most of the other tables are child tables of the SupplyModel table. I want to iterate through each of Supply Model records. I want to grab the data for a supply model and then DoStuff with the data. And I also need to iterate through the child records, for each supply model, for example the NumberedInventories and DoStuff with that as well. I need help doing this in VB rather than C# if possible. I am not looking for the whole solution...if you can supply a couple of code-snippets to get me on my way that would be great. Thanks for your help. Seth

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• Stream Reuse in C#

  - by MikeD

  I've been playing around with what I thought was a simple idea. I want to be able to read in a file from somewhere (website, filesystem, ftp), perform some operations on it (compress, encrypt, etc.) and then save it somewhere (somewhere may be a filesystem, ftp, or whatever). It's a basic pipeline design. What I would like to do is to read in the file and put it onto a MemoryStream, then perform the operations on the data in the MemoryStream, and then save that data in the MemoryStream somewhere. I was thinking I could use the same Stream to do this but run into a couple of problems: Everytime I use a StreamWriter or StreamReader I need to close it and that closes the stream so that I cannot use it anymore. That seems like there must be some way to get around that. Some of these files may be big and so I may run out of memory if I try to read the whole thing in at once. I was hoping to be able to spin up each of the steps as separate threads and have the compression step begin as soon as there is data on the stream, and then as soon as the compression has some compressed data available on the stream I could start saving it (for example). Is anything like this easily possible with the C# Streams? ANyone have thoughts as to how to accomplish this best? Thanks, Mike

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• Sharepoint designer is replacing french characters with &#65533;

  - by chris

  First of all, I'm not a web designer, I'm a programmer, so I'm working a bit out of my knowledge area. However, as the person in my office who has some working knowledge of French, I'm stuck with this issue. The Problem: Sharepoint Designer is replacing all French accented characters with the &#65533; (square box or diamond-? �) character. It doesn't appear to matter if I enter the 'é' character as alt-130 (in either design or source or as &eacute; Everything works fine when editing, but when the file is saved and loaded into a browser, it replaces the characters. When reloading into designer, the file shows the 65533 symbol. EDIT: More info. I use &#233; and save, close SP designer, Reloading SP designer will show the é (instead of the code) in source. Next reload will have replaced it with &#65533; Question 1: (more important) HOW DO I STOP THIS!? Question 2: (more interesting) Why does this happen? Charset is iso-8859-1

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• How do I detect whether the sample supplied by VideoSink.OnSample() is right-side up?

  - by Ken Smith

  We're currently using the Silverlight VideoSink to capture video from users' local webcams, kinda like so: protected override void OnSample(long sampleTime, long frameDuration, byte[] sampleData) { if (FrameShouldBeSubmitted()) { byte[] resampledData = ResizeFrame(sampleData); mediaController.SetVideoFrame(resampledData); } } Now, on most of the machines that we've tested, the video sample provided in the byte[] sampleData parameter is upside-down, i.e., if you try to take the RGBA data and turn it into, say, a WriteableBitmap, the bitmap will be upside-down. That's odd, but fairly easy to correct, of course -- you just have to reverse the array as you encode it. The problem is that at least on some machines (e.g., the single Macintosh in our test environment), the video sample provided is no longer upside-down, but right-side up, and hence, flipping the image actually results in an image that's received upside-down on the far side. I reported this to MS as a bug, but their (terse) response was that it was "As Designed". Further attempts at clarification have so far been ignored. Now, I'll grant that it's kinda entertaining to imagine the discussions behind this design decision: "OK, just to make it interesting, let's play the video rightside up on a Mac, but let's turn it upside down for Windows!" "Great idea!" "Yeah, that'll keep those developers guessing!" But beyond that, I can't find this, umm, "feature" documented anywhere, nor can I find any documentation on how one is supposed to be able to tell that a given video sample is upside down or rightside up. Any thoughts on how to tell this?

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• Calculate car filled up times

  - by Ivan

  Here is the question: The driving distance between Perth and Adelaide is 1996 miles. On the average, the fuel consumption of a 2.0 litre 4 cylinder car is 8 litres per 100 kilometres. The fuel tank capacity of such a car is 60 litres. Design and implement a JAVA program that prompts for the fuel consumption and fuel tank capacity of the aforementioned car. The program then displays the minimum number of times the car’s fuel tank has to be filled up to drive from Perth to Adelaide. Note that 62 miles is equal to 100 kilometres. What data will you use to test that your algorithm works correctly? Here is what I've done so far: import java.util.Scanner;// public class Ex4{ public static void main( String args[] ){ Scanner input = new Scanner( System.in ); double distance, consumption, capacity, time; distance = Math.sqrt(1996/62*100); consumption = Math.sqrt(8/100); capacity = 60; time = Math.sqrt(distance*consumption/capacity); System.out.println("The car's fuel tank need to be filled up:" + time + "times"); } } I can compile it but the problem is that the result is always 0.0, can anyone help me what's wrong with it ?

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• Building a complex view with Three20 - resources?

  - by psychotik

  I'm using three20 for most of my iPhone app. One of the views I need to create is relatively complex. It needs a top bar (under the nav bar) with some controls and label, an image view below this bar (which occupies most of the body) and another bottom bar with more controls and labels (above the tab bar control). I don't have much UI experience - my only experience with anything UI is laying stuff out using CSS, etc on websites. Apple's online doc seems to assume that the reader knows a bunch about rectangles, layouts, frames, etc or is using InterfaceBuilder. And three20 isn't too well documented either. So my question is: Is it possible to design something like what I describe in IB and then still have a three20-based app use it? If so, any tips/pointers on how would be much appreciated. Can you point me to some documentation that explain how views/controls etc are rendered. I'm pretty sure I can figure it out if I find some decent explanation/tutorial for it.

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• process of connecting RTP with SIP via SDP & land lines

  - by TacB0sS

  Hello to everyone, I have a problem with starting a media session and to combine it with my SIP client. I've designed a recursive SIP client that reuse the same request template to send the next requests to server, according to the acceptable sequences noted in the RFC's, and examples that I read. as far as I could tell the SIP part is working fine registers to server invites, and authenticates. I didn't complete any calls to clients yet because of the content header needs to be filled up (which I didn't yet so I get a 503 from the server which is OK I guess). for a long time I didn't know where to start with the media session, and slowly learned how to use the JMF and I've constructed an object that handles RTP transmitting, now I'm standing at the cross road, on the one hand I have my SIP signaling but it needs the SDP content header to complete the invite, and on the other I have the RTP which is knows how to p2p. For me to complete my design I require your help with the following questions: Is there an easy//a simple//an implemented way to convert the Audio/Video format from the JMF into SDP media headers? or even a generator that I would input all the parameters for the content header, and it would generate a content header fast, or do I have to implement this myself? Once I've finished constructing the SDK and the SIP is up and running and I get an OK response from the server (after ringing and all), how do I start the media session? do I connect p2p according to caller details I send in the SIP invite? If 2 is correct, then how does a connection to land lines would be? does land lines knows that once they send an OK back to server they listen/start RTP session on a specific port? Or did I get everything wrong? :-/ I really appreciate any help I could I get, I looked every where for answers but they are not clear, they ignore question 2 as if it was an obvious thing, but for me it just isn't. Thank in advance, Adam Zehavi.

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• Help with mysql sum and group query and managing jquery graph results.

  - by Scarface

  Hey guys, I have a system I am trying to design that will retrieve information from a database, so that it can be plotted in a jquery graph. I need to retrieve the information and somehow put it in the necessary format (for example two coordinates var d = [[1269417600000, 10],[1269504000000, 15]];). My table that I am selecting from is a table that stores user votes with fields: points_id (1=vote up ,2=vote down), user_id, timestamp, and topic_id. What I need to do is select all the votes and somehow group them into respective days and then sum the difference between 1 votes and 2 votes for each day. I then need to somehow display the data in the appropriate plotting format shown earlier. For example April 1, 4 votes. The data needs to be separated by commas, except the last plot entry, so I am not sure how to approach that. I showed an example below of the kind of thing I need but it is not correct, echo "var d=["; $query=mysql_query("SELECT *, SUM(IF(points_id = \"1\", 1,0))-SUM(IF([points_id = \"2\", 1,0)) AS 'total' FROM points LEFT JOIN topic on topic.topic_id=points.topic_id WHERE topic.creator='$user' GROUP by timestamp HAVING certain time interval"); while ($row=mysql_fetch_assoc($query)){ $timestamp=$row['timestamp']; $votes=$row['total']; echo "[$timestamp,$vote],"; } echo "];";

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• Correct way to trigger object clone/memento when property changes

  - by Jay

  Hi, I have a big doubt about the correct way to save an object state (clone object), if necessary to rollback the changes, when a property has changed. I know that the IEditableObject interface exists for those cases but during some tests the BeginEdit would just fire like crazy (I have a DataGrid whose values can be edited but I won't need to keep the state of the object in these cases). I'm following the MVP design pattern in my project and the view's DataContext is a wrapper of my presenter.Let's say I have a CheckBox/TextBox in my UI and when that textbox's value changes, the property bound in the wrapper gets set.Currently, before setting the new value i'm raising an event to the presenter (something like PropertyChanging) that clones my wrapper. I'm doing this because I don't think that job should be done by the wrapper itself but by the presenter.Is this a correct approach? Raising the event is an acceptable solution? I thought of other possible ideas: Interface between presenter and wrapper; Use explicit binding and trigger the binding after saving object's state; What is your opinion about the best way to do this? Should I just keep IEditableObject, is this the best way? Best Regards

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• CharField values disappearing after save (readonly field)

  - by jamida

  I'm implementing simple "grade book" application where the teacher would be able to update the grades w/o being allowed to change the students' names (at least not on the update grade page). To do this I'm using one of the read-only tricks, the simplest one. The problem is that after the SUBMIT the view is re-displayed with 'blank' values for the students. I'd like the students' names to re-appear. Below is the simplest example that exhibits this problem. (This is poor DB design, I know, I've extracted just the relevant parts of the code to showcase the problem. In the real example, student is in its own table but the problem still exists there.) models.py class Grade1(models.Model): student = models.CharField(max_length=50, unique=True) finalGrade = models.CharField(max_length=3) class Grade1OForm(ModelForm): student = forms.CharField(max_length=50, required=False) def __init__(self, *args, **kwargs): super(Grade1OForm,self).__init__(*args, **kwargs) instance = getattr(self, 'instance', None) if instance and instance.id: self.fields['student'].widget.attrs['readonly'] = True self.fields['student'].widget.attrs['disabled'] = 'disabled' def clean_student(self): instance = getattr(self,'instance',None) if instance: return instance.student else: return self.cleaned_data.get('student',None) class Meta: model=Grade1 views.py from django.forms.models import modelformset_factory def modifyAllGrades1(request): gradeFormSetFactory = modelformset_factory(Grade1, form=Grade1OForm, extra=0) studentQueryset = Grade1.objects.all() if request.method=='POST': myGradeFormSet = gradeFormSetFactory(request.POST, queryset=studentQueryset) if myGradeFormSet.is_valid(): myGradeFormSet.save() info = "successfully modified" else: myGradeFormSet = gradeFormSetFactory(queryset=studentQueryset) return render_to_response('grades/modifyAllGrades.html',locals()) template <p>{{ info }}</p> <form method="POST" action=""> <table> {{ myGradeFormSet.management_form }} {% for myform in myGradeFormSet.forms %} {# myform.as_table #} <tr> {% for field in myform %} <td> {{ field }} {{ field.errors }} </td> {% endfor %} </tr> {% endfor %} </table> <input type="submit" value="Submit"> </form>

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• Handling incremental Data Modeling Changes in Functional Programming

  - by Adam Gent

  Most of the problems I have to solve in my job as a developer have to do with data modeling. For example in a OOP Web Application world I often have to change the data properties that are in a object to meet new requirements. If I'm lucky I don't even need to programmatically add new "behavior" code (functions,methods). Instead I can declarative add validation and even UI options by annotating the property (Java). In Functional Programming it seems that adding new data properties requires lots of code changes because of pattern matching and data constructors (Haskell, ML). How do I minimize this problem? This seems to be a recognized problem as Xavier Leroy states nicely on page 24 of "Objects and Classes vs. Modules" - To summarize for those that don't have a PostScript viewer it basically says FP languages are better than OOP languages for adding new behavior over data objects but OOP languages are better for adding new data objects/properties. Are there any design pattern used in FP languages to help mitigate this problem? I have read Phillip Wadler's recommendation of using Monads to help this modularity problem but I'm not sure I understand how?

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• Custom UIButton for Iphone.

  - by Amal

  I have an view in my App which has a number of buttons based on the number of items returned by the server. So if the server returns say 10 items, there should be 10 buttons and clicking on each button should call a different person. For the above purpose I created a custom button class deriving from UIButton. @implementation HopitalButton @synthesize index; @synthesize button_type; - (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { UIImage* img = [UIImage imageNamed:@"dr_btn.png"]; [img stretchableImageWithLeftCapWidth:10 topCapHeight:10]; [self setBackgroundImage:img forState:UIControlStateNormal]; [self setTitleColor:[UIColor colorWithRed:0.698 green:0.118 blue:0.376 alpha:1] forState:UIControlStateNormal] ; [self setFont:[UIFont fontWithName:@"Helvetica Bold" size:13]]; self.titleLabel.textColor = [UIColor colorWithRed:178 green:48 blue:95 alpha:1]; self.adjustsImageWhenHighlighted = YES; } return self; } - (void)dealloc { [super dealloc]; } @end Now the problem with the above code is that it does not create buttons that look similar to the buttons created by default in Interface builder. The borders are missing. And I create buttons of the above type by the following code: HopitalButton* hb = [[HopitalButton alloc] init]; hb.button_type = @"call"; hb.frame = CGRectMake(50, 50 + i * 67, 220, 40); [self.scroll_view addSubview:hb]; [hb setTitle:[[[self.office_full_list objectAtIndex:i] objectForKey:@"Staff" ]objectForKey:@"FullName"] forState:UIControlStateNormal]; hb.index = [NSNumber numberWithInt:[self.button_items count]]; [self.button_items insertObject:hb atIndex:[self.button_items count]]; [hb addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside]; I am not finding a way to set the button type for this custom button. Is there a way i can do it ? Or is there a better way to design the code.

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• NMock2.0 - how to stub a non interface call?

  - by dferraro

  Hello, I have a class API which has full code coverage and uses DI to mock out all the logic in the main class function (Job.Run) which does all the work. I found a bug in production where we werent doing some validation on one of the data input fields. So, I added a stub function called ValidateFoo()... Wrote a unit test against this function to Expect a JobFailedException, ran the test - it failed obviously because that function was empty. I added the validation logic, and now the test passes. Great, now we know the validation works. Problem is - how do I write the test to make sure that ValidateFoo() is actually called inside Job.Run()? ValidateFoo() is a private method of the Job class - so it's not an interface... Is there anyway to do this with NMock2.0? I know TypeMock supports fakes of non interface types. But changing mock libs right now is not an option. At this point if NMock can't support it, I will simply just add the ValidateFoo() call to the Run() method and test things manually - which obviously I'd prefer not to do considering my Job.Run() method has 100% coverage right now. Any Advice? Thanks very much it is appreciated. EDIT: the other option I have in mind is to just create an integration test for my Job.Run functionality (injecting to it true implementations of the composite objects instead of mocks). I will give it a bad input value for that field and then validate that the job failed. This works and covers my test - but it's not really a unit test but instead an integration test that tests one unit of functionality.... hmm.. EDIT2: IS there any way to do tihs? Anyone have ideas? Maybe TypeMock - or a better design?

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• Why Finalize method not allowed to override

  - by somaraj

  I am new to .net ..and i am confused with the destructor mechanism in C# ..please clarify In C# destructors are converted to finalize method by CLR. If we try to override it (not using destructor ) , will get an error Error 2 Do not override object.Finalize. Instead, provide a destructor. But it seems that the Object calss implementation in mscorlib.dll has finalize defined as protected override void Finalize(){} , then why cant we override it , that what virtual function for . Why is the design like that , is it to be consistent with c++ destructor concept. Also when we go to the definition of the object class , there is no mention of the finalize method , then how does the hmscorlib.dll definition shows the finalize funtion . Does it mean that the default destructor is converted to finalize method. public class Object { public Object(); public virtual bool Equals(object obj); public static bool Equals(object objA, object objB); public virtual int GetHashCode(); public Type GetType(); protected object MemberwiseClone(); public static bool ReferenceEquals(object objA, object objB); public virtual string ToString(); }

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• Asp net aspx page and webcontrol issue

  - by Josemalive

  Hello, I have a class that inherits from Page, called APage. public abstract class APage: Page { protected Repeater ExampleRepeater; .... protected override void OnLoad(EventArgs e) { if (null != ExampleRepeater) { ExampleRepeater.DataSource = GetData(); ExampleRepeater.DataBind(); } base.OnLoad(e); } } For other hand i have an aspx page called Default that inherits from this APage: public partial class Default : APage { } on the design part of this Default page, i have a repeater: <asp:Repeater ID="ExampleRepeater" runat="server"> <ItemTemplate> <%# DataBinder.Eval(Container.DataItem, "Name") %><br/> </ItemTemplate> </asp:Repeater> This repeater is datasourced at the base APage load event, but at this level this web control is null. Do you have any idea why the control is null in the base page? Thanks in advance. Best Regards. Jose.

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• Designing bayesian networks

  - by devoured elysium

  I have a basic question about Bayesian networks. Let's assume we have an engine, that with 1/3 probability can stop working. I'll call this variable ENGINE. If it stops working, then your car doesn't work. If the engine is working, then your car will work 99% of the time. I'll call this one CAR. Now, if your car is old(OLD), instead of not working 1/3 of the time, your engine will stop working 1/2 of the time. I'm being asked to first design the network and then assign all the conditional probabilities associated with the table. I'd say the diagram of this network would be something like OLD -> ENGINE -> CAR Now, for the conditional probabilities tables I did the following: OLD |ENGINE ------------ True | 0.50 False | 0.33 and ENGINE|CAR ------------ True | 0.99 False | 0.00 Now, I am having trouble about how to define the probabilities of OLD. In my point of view, old is not something that has a CAUSE relationship with ENGINE, I'd say it is more a characteristic of it. Maybe there is a different way to express this in the diagram? If the diagram is indeed correct, how would I go to make the tables? Thanks

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• ASP.NET Event delegation between user controls

  - by Ishan

  Give the following control hierarchy on a ASP.NET page: Page HeaderControl       (User Control) TitleControl       (Server Control) TabsControl       (User Control) other controls I'm trying to raise an event (or some notification) in the TitleControl that bubbles to the Page level. Then, I'd like to (optionally) register an event handler at the Page codebehind that will take the EventArgs and modify the TabsControl in the example above. The important thing to note is that this design will allow me to drop these controls into any Page and make the entire system work seamlessly if the event handler is wired up. The solution should not involve a call to FindControl() since that becomes a strong association. If no handler is defined in the containing Page, the event is still raised by TitleControl but is not handled. My basic goal is to use event-based programming so that I can decouple the user controls from each other. The event from TitleControl is only raised in some instances, and this seemed to be (in my head) the preferred approach. However, I can't seem to find a way to cleanly achieve this. Here are my (poor) attempts: Using HttpContext.Current.Items Add the EventArgs to the Items collection on TitleControl and pick it up on the TabsControl. This works but it's fundamentally hard to decipher since the connection between the two controls is not obvious. Using Reflection Instead of passing events, look for a function on the container Page directly within TitleControl as in: Page.GetType().GetMethod("TabControlHandler").Invoke(Page, EventArgs); This will work, but the method name will have to be a constant that all Page instances will have to defined verbatim. I'm sure that I'm over-thinking this and there must be a prettier solution using delegation, but I can't seem to think of it. Any thoughts?

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• Starting a new business with former colleagues, advice needed

  - by Sparafusile

  I was recently contacted by a former boss of mine who is thinking of starting a new business. The business will be online only it will by my job to design, build, and maintain the software going into it. I will also have to maintain the server it's running on, being the only technical person on the team. I will be one of four members of the business, the other three being the actual business know-hows and salesmen. The other three are shouldering the cost of getting the business going (incorporation, attorney fees, etc) and we will be splitting the cost of the server. I have no business knowledge at all, and don't want any part of it, I am only interested in the technical aspects. Now that we are finalizing our plans, determining roles, and getting ready to start actual work, we have come to the point where we have to determine what percentage stake each of us has. Since I have never done anything like this before, or met anyone that has, I don't know what I should expect. Can anyone give me some pointers on what to ask for in this deal?

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• Comparable and Comparator contract with regards to null

  - by polygenelubricants

  Comparable contract specifies that e.compareTo(null) must throw NullPointerException. From the API: Note that null is not an instance of any class, and e.compareTo(null) should throw a NullPointerException even though e.equals(null) returns false. On the other hand, Comparator API mentions nothing about what needs to happen when comparing null. Consider the following attempt of a generic method that takes a Comparable, and return a Comparator for it that puts null as the minimum element. static <T extends Comparable<? super T>> Comparator<T> nullComparableComparator() { return new Comparator<T>() { @Override public int compare(T el1, T el2) { return el1 == null ? -1 : el2 == null ? +1 : el1.compareTo(el2); } }; } This allows us to do the following: List<Integer> numbers = new ArrayList<Integer>( Arrays.asList(3, 2, 1, null, null, 0) ); Comparator<Integer> numbersComp = nullComparableComparator(); Collections.sort(numbers, numbersComp); System.out.println(numbers); // "[null, null, 0, 1, 2, 3]" List<String> names = new ArrayList<String>( Arrays.asList("Bob", null, "Alice", "Carol") ); Comparator<String> namesComp = nullComparableComparator(); Collections.sort(names, namesComp); System.out.println(names); // "[null, Alice, Bob, Carol]" So the questions are: Is this an acceptable use of a Comparator, or is it violating an unwritten rule regarding comparing null and throwing NullPointerException? Is it ever a good idea to even have to sort a List containing null elements, or is that a sure sign of a design error?

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• MySQL table data transformation -- how can I dis-aggregate MySQL time data?

  - by lighthouse65

  We are coding for a MySQL data warehousing application that stores descriptive data (User ID, Work ID, Machine ID, Start and End Time columns in the first table below) associated with time and production quantity data (Output and Time columns in the first table below) upon which aggregate (SUM, COUNT, AVG) functions are applied. We now wish to dis-aggregate time data for another type of analysis. Our current data table design: +---------+---------+------------+---------------------+---------------------+--------+------+ | User ID | Work ID | Machine ID | Event Start Time | Event End Time | Output | Time | +---------+---------+------------+---------------------+---------------------+--------+------+ | 080025 | ABC123 | M01 | 2008-01-24 16:19:15 | 2008-01-24 16:34:45 | 2120 | 930 | +---------+---------+------------+---------------------+---------------------+--------+------+ Reprocessing dis-aggregation that we would like to do would be to transform table content based on a granularity of minutes, rather than the current production event ("Event Start Time" and "Event End Time") granularity. The resulting reprocessing of existing table rows would look like: +---------+---------+------------+---------------------+--------+ | User ID | Work ID | Machine ID | Production Minute | Output | +---------+---------+------------+---------------------+--------+ | 080025 | ABC123 | M01 | 2010-01-24 16:19 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:20 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:21 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:22 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:23 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:24 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:25 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:26 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:27 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:28 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:29 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:30 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:31 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:22 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:33 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:34 | 133 | +---------+---------+------------+---------------------+--------+ So the reprocessing would take an existing row of data created at the granularity of production event and modify the granularity to minutes, eliminating redundant (Event End Time, Time) columns while doing so. It assumes a constant rate of production and divides output by the difference in minutes plus one to populate the new table's Output column. I know this can be done in code...but can it be done entirely in a MySQL insert statement (or otherwise entirely in MySQL)? I am thinking of a INSERT ... INTO construction but keep getting stuck. An additional complexity is that there are hundreds of machines to include in the operation so there will be multiple rows (one for each machine) for each minute of the day. Any ideas would be much appreciated. Thanks.

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• Magento - Show Custom Attributes in Grouped Product table.

  - by greencoconut

  I need to find a way to show the value of a custom attribute in place of the "Product Name" shown in the image below. I'm working with /app/design/frontend/default/defaultx/template/catalog/product/view/type/grouped.php The code below doesn't work(the custom attribute is yearmade): <?php if (count($_associatedProducts)): ?> <?php foreach ($_associatedProducts as $_item): ?> <tr> <td><?php echo $this->htmlEscape($_item->getYearmade()) ?></td> Any help would be appreciated. EDIT: So the answer turned out to be quite simple. You see what I failed to mention above was that there was indeed output... but that it was just a number (eg: 52). Turns out this was the ID for that custom attribute value (It was a Dropdown type of custom attribute). So in summary This works for custom attributes of type text: echo $this->htmlEscape($_item->getYearmade()) But for all other types of custom attribute (I think), the following should be used: echo $this->htmlEscape($_item->getAttributeText('yearmade')) I would not have discovered this without the most excellent answer provided by Alan Storm, below. Thank you sir.

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• Threads, Sockets, and Designing Low-Latency, High Concurrency Servers

  - by lazyconfabulator

  I've been thinking a lot lately about low-latency, high concurrency servers. Specifically, http servers. http servers (fast ones, anyway) can serve thousands of users simultaneously, with very little latency. So how do they do it? As near as I can tell, they all use events. Cherokee and Lighttpd use libevent. Nginx uses it's own event library performing much the same function of libevent, that is, picking a platform optimal strategy for polling events (like kqueue on *bsd, epoll on linux, /dev/poll on Solaris, etc). They all also seem to employ a strategy of multiprocess or multithread once the connection is made - using worker threads to handle the more cpu intensive tasks while another thread continues to listen and handle connections (via events). This is the extent of my understanding and ability to grok the thousand line sources of these applications. What I really want are finer details about how this all works. In examples of using events I've seen (and written) the events are handling both input and output. To this end, do the workers employ some sort of input/output queue to the event handling thread? Or are these worker threads handling their own input and output? I imagine a fixed amount of worker threads are spawned, and connections are lined up and served on demand, but how does the event thread feed these connections to the workers? I've read about FIFO queues and circular buffers, but I've yet to see any implementations to work from. Are there any? Do any use compare-and-swap instructions to avoid locking or is locking less detrimental to event polling than I think? Or have I misread the design entirely? Ultimately, I'd like to take enough away to improve some of my own event-driven network services. Bonus points to anyone providing solid implementation details (especially for stuff like low-latency queues) in C, as that's the language my network services are written in.

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• How to make a good programming interview?

  - by luckyluke

  I am doing interviews with from time to time to recruit some not bad people. And I really think I AM NOT doing to correct Job. I work in a company when We have to do a lot o DB programming, .NET programming, Java programming, so we need people who are open minded and not focused on a particular tech. Afterall language is a notation, You have to understand what is going under the hood. I ask people about their project, ask them some coding questions (believe me a SQL question involving a CROSS JOIN is hard), let them write some code, ask them about oo design, ask them how they update their knowledge, and stay up to date, do they have FUN when they code (at least sometimes). Hell I even give them a coding solution for home (3 hours max) to see how they think and code. And yet my hit rate at hiring junior member (those who live over the initial 3 months) is just about 33%. So my question, how do YOU make the good interviews, because I think my hit rate is to low? Do you have any best-practices(should be at least 60-70%)? p.s. And i noticed that: the best programmers are lazy, but motivated, just being lazy is not enough:) But people who write the best code are attentive to details:)

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