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• What algorithm can I use to determine points within a semi-circle?

  - by khayman218

  I have a list of two-dimensional points and I want to obtain which of them fall within a semi-circle. Originally, the target shape was a rectangle aligned with the x and y axis. So the current algorithm sorts the pairs by their X coord and binary searches to the first one that could fall within the rectangle. Then it iterates over each point sequentially. It stops when it hits one that is beyond both the X and Y upper-bound of the target rectangle. This does not work for a semi-circle as you cannot determine an effective upper/lower x and y bounds for it. The semi-circle can have any orientation. Worst case, I will find the least value of a dimension (say x) in the semi-circle, binary search to the first point which is beyond it and then sequentially test the points until I get beyond the upper bound of that dimension. Basically testing an entire band's worth of points on the grid. The problem being this will end up checking many points which are not within the bounds.

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• What is it in the CSS/DOM that prevents an input box with display: block from expanding to the size of its container

  - by Steven Xu

  Sample HTML/CSS: <div class="container"> <input type="text" /> <div class="filler"></div> </div> div.container { padding: 5px; border: 1px solid black; background-color: gray; } div.filler { background-color: red; height: 5px; } input { display: block; } http://jsfiddle.net/bPEkb/3/ Question Why doesn't the input box expand to have the same outer width as, say div.filler? That is to say, why doesn't the input box expand to fit its container like other block elements with width: auto; do? I tried checking the "User Agent CSS" in Firebug to see if I could come up with something there. No luck. I couldn't find any specific differences in CSS that I could specifically link to the input box behaving differently from the regular div.filler. Besides curiousity, I'd like to know why this is to get to the bottom of it to figure out a way to set width once and forget it. My current practice of explicitly setting the width of both input and its containing block element seems redundant and less than modular. While I'm familiar with the technique of wrapping the input element in a div then assigning to the input element negative margins, this seems quite undesirable.

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• Specifying different initial values for fields in inherited models (django)

  - by Shawn Chin

  Question : What is the recommended way to specify an initial value for fields if one uses model inheritance and each child model needs to have different default values when rendering a ModelForm? Take for example the following models where CompileCommand and TestCommand both need different initial values when rendered as ModelForm. # ------ models.py class ShellCommand(models.Model): command = models.Charfield(_("command"), max_length=100) arguments = models.Charfield(_("arguments"), max_length=100) class CompileCommand(ShellCommand): # ... default command should be "make" class TestCommand(ShellCommand): # ... default: command = "make", arguments = "test" I am aware that one can used the initial={...} argument when instantiating the form, however I would rather store the initial values within the context of the model (or at least within the associated ModelForm). My current approach What I'm doing at the moment is storing an initial value dict within Meta, and checking for it in my views. # ----- forms.py class CompileCommandForm(forms.ModelForm): class Meta: model = CompileCommand initial_values = {"command":"make"} class TestCommandForm(forms.ModelForm): class Meta: model = TestCommand initial_values = {"command":"make", "arguments":"test"} # ------ in views FORM_LOOKUP = { "compile": CompileCommandFomr, "test": TestCommandForm } CmdForm = FORM_LOOKUP.get(command_type, None) # ... initial = getattr(CmdForm, "initial_values", {}) form = CmdForm(initial=initial) This feels too much like a hack. I am eager for a more generic / better way to achieve this. Suggestions appreciated. Other attempts I have toyed around with overriding the constructor for the submodels: class CompileCommand(ShellCommand): def __init__(self, *args, **kwargs): kwargs.setdefault('command', "make") super(CompileCommand, self).__init__(*args, **kwargs) and this works when I try to create an object from the shell: >>> c = CompileCommand(name="xyz") >>> c.save() <CompileCommand: 123> >>> c.command 'make' However, this does not set the default value when the associated ModelForm is rendered, which unfortunately is what I'm trying to achieve. Update 2 (looks promising) I now have the following in forms.py which allow me to set Meta.default_initial_values without needing extra code in views. class ModelFormWithDefaults(forms.ModelForm): def __init__(self, *args, **kwargs): if hasattr(self.Meta, "default_initial_values"): kwargs.setdefault("initial", self.Meta.default_initial_values) super(ModelFormWithDefaults, self).__init__(*args, **kwargs) class TestCommandForm(ModelFormWithDefaults): class Meta: model = TestCommand default_initial_values = {"command":"make", "arguments":"test"}

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• Database schema for a library

  - by ABach

  Hi all - I'm designing a library management system for a department at my university and I wanted to enlist your eyes on my proposed schema. This post is primarily concerned with how we store multiple copies of each book; something about what I've designed rubs me the wrong way, and I'm hoping you all can point out better ways to tackle things. For dealing with users checking out books, I've devised three tables: book, customer, and book_copy. The relationships between these tables are as follows: Every book has many book_copies (to avoid duplicating the book's information while storing the fact that we have multiple copies of that book). Every user has many book_copies (the other end of the relationship) The tables themselves are designed like this: ------------------------------------------------ book ------------------------------------------------ + id + title + author + isbn + etc. ------------------------------------------------ ------------------------------------------------ customer ------------------------------------------------ + id + first_name + first_name + email + address + city + state + zip + etc. ------------------------------------------------ ------------------------------------------------ book_copy ------------------------------------------------ + id + book_id (FK to book) + customer_id (FK to customer) + checked_out + due_date + etc. ------------------------------------------------ Something about this seems incorrect (or at least inefficient to me) - the perfectionist in me feels like I'm not normalizing this data correctly. What say ye? Is there a better, more effective way to design this schema? Thanks!

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• How to disable form submit if the username is not available

  - by Rajasekar

  I have checked the user name availability. The problem is, even if the username is not available, the form is posting. Edited Code: <SCRIPT type="text/javascript"> $(document).ready(function(){ $("#emailch").change(function() { var usr = $("#emailch").val(); if(usr.length >= 3) { $("#status").html('<img src="images/loader.gif" align="absmiddle">&nbsp;Checking availability...'); $.ajax({ type: "POST", url: "includes/check.php", data: "username="+ usr, success: function(msg){ $("#status").ajaxComplete(function(event, request, settings){ if(msg == 'OK') { $("#username").removeClass('object_error'); // if necessary $("#username").addClass("object_ok"); $(this).html('&nbsp;<img src="images/tick.gif" align="absmiddle">'); } else { $("#username").removeClass('object_ok'); // if necessary $("#username").addClass("object_error"); $(this).html(msg); } }); } }); } else { $("#status").html('<font color="red">The username should have at least <strong>3</strong> characters.</font>'); $("#username").removeClass('object_ok'); // if necessary $("#username").addClass("object_error"); } }); }); </SCRIPT> What I want is that, the form should not be posted if the user name is not available. I have tried by using return false; in IF CONDITION but it fails. Please suggest any alternate method. Any help will be appreciated.

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• Google App Engine datastore encoding?

  - by sernaferna

  I'm using the GAE datastore for a Java application, and storing some text that will be in numerous languages. In my servlet, I'm first checking to see if there's any data in the data store, and, if not, I'm creating some, similar to the following: ArrayList<Lang> list = new ArrayList<Lang>(); list.add(new Lang("EN", "English", 1)); list.add(new Lang("ES", "Español", 0)); //more languages here... PersistenceManager pm = PMF.get().getPersistenceManager(); for(Lang l : list) { pm.makePersistent(l); } Since this is using JDO, I guess I should include the relevent parts of the Lang class too: @PersistenceCapable public class Lang { @PrimaryKey private String code; @Persistent private String name; @Persistent private int popularity; // getters & setters & constructors... } However, the non-ASCII characters are giving me grief. I've set my Eclipse project to use the UTF-8 encoding instead of the default Cp1252, so I think I'm okay from that perspective, but when I use the App Engine Data Viewer to look at my data, that Español entry becomes Español, and when I click on it to view it, I get a 500 Server Error. (There are some other entries with right-to-left text that don't even show up in the Data Viewer at all, but one problem at a time...) Is there anything special I can do in my code to set the character encoding, or specify to GAE that the data I'm storing is UTF-8? Or is the problem on the Eclipse side, and is there something I should be doing with my Java code?

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• Help improve this Javascript code?

  - by Galilyou

  Hello SO, In short, I'm dealing with Telerik's RadTreeView, and I want enable checking all the child nodes if the user checked the parent node. Simple enough! OK here's my code that handles OnClientNodeChecked event of the TreeView: function UpdateAllChildren(nodes, checked) { var i; for (i = 0; i < nodes.get_count(); i++) { var currentNode = nodes.getNode(i); currentNode.set_checked(checked); alert("now processing: " + currentNode.get_text()); if (currentNode.get_nodes().get_count() > 0) { UpdateAllChildren(currentNode.get_nodes(), checked); } } } function ClientNodeChecked(sender, eventArgs) { var node = eventArgs.get_node(); UpdateAllChildren(node.get_nodes(), node.get_checked()); } And here's the TreeView's markup: <telerik:RadTreeView ID="RadTreeView1" runat="server" CheckBoxes="True" OnClientNodeChecked="ClientNodeChecked"></telerik:RadTreeView> The tree contains quite a lot of nodes, and this is causing my targeted browser (ehm, that's IE7) to really slow down while running it. Furthermore IE7 displays an error message asking me to stop the page from running scripts as it's might make my computer not responsive (yeah, scary enough). So what do you guys propose to optimize this code? Thanks in advance

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• HTML5 or Flash?

  - by lewiguez

  I have to write a web application for a client soon. Looking at the specs, there is no reason why the project couldn't be an HTML5/CSS/Javascript project, but the client is arguing that it has to be Flash. The project has a number of dynamic elements and is web-based. It'll only be used in-house by a small number of people and all of those people use either Google Chrome or Safari 4. They are all pretty tech-savvy to boot. My question is this: what are some of the reasons (preferably technical since this is Stack Overflow) I can present to my client as to why HTML5 is better than Flash (that's assuming I'm right and it is in this case)? Is it OK to use HTML5 even though it's still a draft spec (I'm assuming it is after checking out all those Apple HTML5 demos a few days ago)? Also, would a hybrid approach be preferable for now? Something that uses Flash wherever the canvas object would've been used in the HTML5 approach and that conforms to a normal XHTML approach. Help!

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• How to check if new version of Chrome is available?

  - by serg

  I am trying to build an extension that would notify a user when new version of Chrome is available. I tried to inspect network traffic when Chrome is checking for an update and it is sending a request to http://74.125.95.113/service/update2?w=3:{long_encoded_string} page that returns XML with information I need: <?xml version="1.0" encoding="UTF-8"?> <gupdate xmlns="http://www.google.com/update2/response" protocol="2.0" server="prod"> <daystart elapsed_seconds="31272"/> <app appid="{8A69D345-D564-463C-AFF1-A69D9E530F96}" status="ok"> <updatecheck status="noupdate"/> <ping status="ok"/> </app> </gupdate> Besides sending {long_encoded_string} as URL parameter it is also sending some encoded cookie. Maybe someone familiar with Chrome build process can shed some light on those encoded strings and how to build them? Maybe there is another easier way (I have a feeling that string encoding is a dead end for me)?

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• Javascript to check if there is flash player installed and redirect to the neededn page.

  - by themajiks

  Hi. I have this script. This determines if there is a flash player installed in the browser, it redirects the browser to a flash website. if not, then it opens a non-flash website. The Code is here: <SCRIPT LANGUAGE="JavaScript"> <!-- if ((navigator.appName == "Microsoft Internet Explorer" && navigator.appVersion.indexOf("Mac") == -1 && navigator.appVersion.indexOf("3.1") == -1) || (navigator.plugins && navigator.plugins["Shockwave Flash"])|| navigator.plugins["Shockwave Flash 2.0"]){ window.location='flash/index.html'; } else { window.location='index.html'; } --> </SCRIPT> What i want is to embed this code in the non-flash index page. it should just check if there is no flash then simply go with the current index file that already has been opened, or if there is no flash player, then load the index file from within the flash website. Currently, when index.html (non-flash) is opened, it goes into loop and keeps on checking for the flash player. Can I modify the window.location='index.html'; statement no to load any file here, just go on with the file already opened.??

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• web service slowdown

  - by user238591

  Hi, I have a web service slowdown. My (web) service is in gsoap & managed C++. It's not IIS/apache hosted, but speaks xml. My client is in .NET The service computation time is light (<0.1s to prepare reply). I expect the service to be smooth, fast and have good availability. I have about 100 clients, response time is 1s mandatory. Clients have about 1 request per minute. Clients are checking web service presence by tcp open port test. So, to avoid possible congestion, I turned gSoap KeepAlive to false. Until there everything runs fine : I bearly see connections in TCPView (sysinternals) New special synchronisation program now calls the service in a loop. It's higher load but everything is processed in less 30 seconds. With sysinternals TCPView, I see that about 1 thousands connections are in TIME_WAIT. They slowdown the service and It takes seconds for the service to reply, now. Could it be that I need to reset the SoapHttpClientProtocol connection ? Someone has TIME_WAIT ghosts with a web service call in a loop ?

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• My python program always brings down my internet connection after several hours running, how do I debug and fix this problem?

  - by Shane

  I'm writing a python script checking/monitoring several server/websites status(response time and similar stuff), it's a GUI program and I use separate thread to check different server/website, and the basic structure of each thread is using an infinite while loop to request that site every random time period(15 to 30 seconds), once there's changes in website/server each thread will start a new thread to do a thorough check(requesting more pages and similar stuff). The problem is, my internet connection always got blocked/jammed/messed up after several hours running of this script, the situation is, from my script side I got urlopen error timed out each time it's requesting a page, and from my FireFox browser side I cannot open any site. But the weird thing is, the moment I close my script my Internet connection got back on immediately which means now I can surf any site through my browser, so it must be the script causing all the problem. I've checked the program carefully and even use del to delete any connection once it's used, still get the same problem. I only use urllib2, urllib, mechanize to do network requests. Anybody knows why such thing happens? How do I debug this problem? Is there a tool or something to check my network status once such situation occurs? It's really bugging me for a while... By the way I'm behind a VPN, does it have something to do with this problem? Although I don't think so because my network always get back on once the script closed, and the VPN connection never drops(as it appears) during the whole process.

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• Pre-formatting text to prevent reflowing

  - by mattjn

  I've written a fairly simple script that will take elements (in this case, <p> elements are the main concern) and type their contents out like a typewriter, one by one. The problem is that as it types, when it reaches the edge of the container mid-word, it reflows the text and jumps to the next line (like word wrap in any text editor). This is, of course, expected behavior; however, I would like to pre-format the text so that this does not happen. I figure that inserting <br> before the word that will wrap would be the best solution, but I'm not quite sure what the best way to go about doing that is that supports all font sizes and container widths, while also keeping any HTML tags intact. I figure something involving a hidden <span> element, adding text to it gradually and checking its width against the container width might be on the right track, but I'm not quite sure how to actually put this together. Any help or suggestions on better methods would be appreciated.

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• PHP strtotime without leap-years

  - by Christian Sciberras

  With regards to this thread, I've developed a partial solution: function strtosecs($time,$now=null){ static $LEAPDIFF=86400; $time=strtotime($time,$now); return $time-((date('Y',$time)-1968)/4*$LEAPDIFF); } The function is supposed to get the number of seconds given a string without checking leap-years. It does this calculating the number of leap-years 1970 [(year-1986)/4], multiplying it by the difference in seconds between a leap-year and a normal year (which in the end, it's just the number of seconds in a day). Finally, I simply remove all those excess leap-year seconds from the calculated time. Here's some examples of the inputs/outputs: // test code echo strtosecs('+20 years',0).'=>'.(strtosecs('+20 years',0)/31536000); echo strtosecs('+1 years',0).'=>'.(strtosecs('+1 years',0)/31536000); // test output 630676800 => 19.998630136986 31471200 => 0.99794520547945 You will probably ask why am I doing a division on the output? It's to test it out; 31536000 is the number of seconds in a year, so that 19.99... should be 20 and 0.99... should be a 1. Sure, I could round it all and get "correct" answer, but I'm worried about the inaccuracies.

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• C++ Constructor initialization list strangeness

  - by Andy

  I have always been a good boy when writing my classes, prefixing all member variables with m_: class Test { int m_int1; int m_int2; public: Test(int int1, int int2) : m_int1(int int1), m_int2(int int2) {} }; void main() { Test t(10, 20); // Just an example } However, recently I forgot to do that and ended up writing: class Test { int int1; int int2; public: // Very questionable, but of course I meant to assign ::int1 to this->int1! Test(int int1, int int2) : int1(int1), int2(int2) {} }; Believe it or not, the code compiled with no errors/warnings and the assignments took place correctly! It was only when doing the final check before checking in my code when I realised what I had done. My question is: why did my code compile? Is something like that allowed in the C++ standard, or is it simply a case of the compiler being clever? In case you were wondering, I was using Visual Studio 2008 Thank you.

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• Need a VB Script to check if service exist

  - by Shorabh Upadhyay

  I want to write a VBS script which will check if specific service is installed/exist or not locally. If it is not installed/exist, script will display message (any text) and disabled the network interface i.e. NIC. If service exist and running, NO Action. Just exit. If service exist but not running, same action, script will display message (any text) and disabled the network interface i.e. NIC. i have below given code which is displaying a message in case one service is stop but it is not - Checking if service exist or not Disabling the NIC strComputer = "." Set objWMIService = Getobject("winmgmts:"_ & "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2") Set colRunningServices = onjWMIService.ExecQuery _ ("select State from Win32_Service where Name = 'dhcp'") For Each objService in colRunningServices If objService.State <> "Running" Then errReturn = msgbox ("Stopped") End If Next Please help. Thanks in advance.

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• The question about the basics of LINQ to SQL working

  - by Alex

  I just started learning LINQ to SQL, and so far I'm impressed with the easy of use and good performance. I used to think that when doing LINQ queries like from Customer in DB.Customers where Customer.Age > 30 select Customer Get all customers from the database ("SELECT * FROM Customers"), move them to the Customers array and then make a search in that Array using .NET methods. This is very inefficient, what if there are hundreds of thousands of customers in the database? Making such big SELECT queries would kill the web application. Now after experiencing how actually fast LINQ to SQL is, I start to suspect that when doing that query I just wrote, LINQ somehow converts it to a SQL Query string SELECT * FROM Customers WHERE Age > 30 And only when necessary it will run the query. So my question is: am I right? And when is the query actually run? The reason why I'm asking is not only because I want to understand how it works in order to build good optimized applications, but because I came across the following problem. I have 2 tables, one of them is Books, the other has information on how many books were sold on certain days. My goal is to select books that had at least 50 sales/day in past 10 days. It's done with this simple query: from Book in DB.Books where (from Sale in DB.Sales where Sale.SalesAmount >= 50 and Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID).Contains(Book.ID) select Book The point is, I have to use the checking part in several queries and I decided to create an array with IDs of all popular books: var popularBooksIDs = from Sale in DB.Sales where Sale.SalesAmount >= 50 and Sale.DateOfSale >= DateTime.Now.AddDays(-10) select Sale.BookID; BUT when I try to do the query now: from Book in DB.Books where popularBooksIDs.Contains(Book.ID) select Book It doesn't work! That's why I think that we can't use thins kinds of shortcuts in LINQ to SQL queries, like we can't use them in real SQL. We have to create straightforward queries, am I right?

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• MAC : How to check if the file is still being copied in cpp?

  - by Peda Pola

  In my current project, we had a requirement to check if the file is still copying. We have already developed a library which will give us OS notification like file_added , file_removed , file_modified, file_renamed on a particular folder along with the corresponding file path. The problem here is that, lets say if you add 1 GB file, it is giving multiple notification such as file_added , file_modified, file_modified as the file is being copied. Now i decided to surpass these notifications by checking if the file is copying or not. Based on that i will ignore events. I have written below code which tells if the file is being copied or not which takes file path as input parameter. Details:- In Mac, while file is being copied the creation date is set as some date less than 1970. Once it is copied the date is set to current date. Am using this technique. Based on this am deciding that file is being copied. Problem:- when we copy file in the terminal it is failing. Please advice me any approach. bool isBeingCopied(const boost::filesystem::path &filePath) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; bool isBeingCopied = false; if([[[[NSFileManager defaultManager] attributesOfItemAtPath:[NSString stringWithUTF8String:filePath.string().c_str()] error:nil] fileCreationDate] timeIntervalSince1970] < 0) { isBeingCopied = true; } [pool release]; return isBeingCopied; }

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• Calculating collision for a moving circle, without overlapping the boundaries

  - by Robert Vella

  Let's say I have circle bouncing around inside a rectangular area. At some point this circle will collide with one of the surfaces of the rectangle and reflect back. The usual way I'd do this would be to let the circle overlap that boundary and then reflect the velocity vector. The fact that the circle actually overlaps the boundary isn't usually a problem, nor really noticeable at low velocity. At high velocity it becomes quite clear that the circle is doing something it shouldn't. What I'd like to do is to programmatically take reflection into account and place the circle at it's proper position before displaying it on the screen. This means that I have to calculate the point where it hits the boundary between it's current position and it's future position -- rather than calculating it's new position and then checking if it has hit the boundary. This is a little bit more complicated than the usual circle/rectangle collision problem. I have a vague idea of how I should do it -- basically create a bounding rectangle between the current position and the new position, which brings up a slew of problems of it's own (Since the rectangle is rotated according to the direction of the circle's velocity). However, I'm thinking that this is a common problem, and that a common solution already exists. Is there a common solution to this kind of problem? Perhaps some basic theories which I should look into?

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• Is there an equivalent for ActiveRecord#find_by equivalent for C#?

  - by Benjamin Manns

  I'm originally a C# developer (as a hobby), but as of late I have been digging into Ruby on Rails and I am really enjoying it. Right now I am building an application in C# and I was wondering if there is any collection implementation for C# that could match (or "semi-match") the find_by method of ActiveRecord. What I am essentially looking for is a list that would hold Rectangles: class Rectangle { public int Width { get; set; } public int Height { get; set; } public String Name { get; set; } } Where I could query this list and find all entries with Height = 10, Width = 20, or name = "Block". This was done with ActiveRecord by doing a call similar to Rectangle.find_by_name('Block'). The only way I can think of doing this in C# is to create my own list implementation and iterate through each item manually checking each item against the criteria. I fear I would be reinventing the wheel (and one of poorer quality). Any input or suggestions is much appreciated.

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• JQuery Post caused permission denied warning in IE 6 and IE 7

  - by kwokwai

  Hi all, I am using firefox 3 and IE 6, 7 to test if a simple php web page using JQuery Post to pass some data to and from another server web page. $(document).ready(function(){ $("#data\\[User\\]\\[name\\]").click(function(){ var usr=$("#data\\[User\\]\\[name\\]").val(); if(usr.length >= 4){ $("#username").append('<span id="loaderimg" name="loaderimg"><img align="absmiddle" src="loader.gif"/> Checking data availability,&nbsp;please wait.</span>'); var url = "http://mysite.com/site1/toavail/"+usr; $.post( url, function(data) {alert(data);}); }); }); //--> </script> <table border=0 width="100%"> <tr> <td>Username</td> <td> <div id="username"> <input type="text" name="data[User][name]" id="data[User][name]"> </div> </td> </tr> </table> In Firefox 3, the alert box showed empty message. In IE 6 and IE 7, I got an error message saying "Permssion denied"

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• Compare Properties automatically

  - by juergen d

  I want to get the names of all properties that changed for matching objects. I have these (simplified) classes: public enum PersonType { Student, Professor, Employee } class Person { public string Name { get; set; } public PersonType Type { get; set; } } class Student : Person { public string MatriculationNumber { get; set; } } class Subject { public string Name { get; set; } public int WeeklyHours { get; set; } } class Professor : Person { public List<Subject> Subjects { get; set; } } Now I want to get the objects where the Property values differ: List<Person> oldPersonList = ... List<Person> newPersonList = ... List<Difference> = GetDifferences(oldPersonList, newPersonList); public List<Difference> GetDifferences(List<Person> oldP, List<Person> newP) { //how to check the properties without casting and checking //for each type and individual property?? //can this be done with Reflection even in Lists?? } In the end I would like to have a list of Differences like this: class Difference { public List<string> ChangedProperties { get; set; } public Person NewPerson { get; set; } public Person OldPerson { get; set; } } The ChangedProperties should contain the name of the changed properties.

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• How can I tell if a byte array has already been compressed?

  - by MikeG

  Hi, Can I rely on the first few bytes of data compressed using the System.IO.Compression.DeflateStream in .NET always being the same? These bytes seem to always be the 1st bytes: 237, 189, 7, 96, 28, 73, 150, 37, 38, 47 , ... I'm assuming this is some kind of header, I'd like to assume that this header is fixed and isn't going to change. Has anyone got any extra info about this? Background info (The reason I want to know this info is...) I have a load of data in a database table that could do with being made smaller. I've decided I'm going to start compressing the data and not going to bother compressing the existing data. When the data gets into my .NET code the data is a String. I'd like to be able to look at the 1st few bytes of the string and see if it has been compressed, if it has then I need to de-compress it. I was originally thinking I could convert the string to bytes and just try de-compressing the data. Then if an exception happens, I could just assume it wasn't compressed. But I think checking the header bytes would give me much better performance. Many thanks, Mike G

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• Implementing a scrabble trainer (cheater)

  - by bstullkid

  Hello, I've recently been playing alot of online scrabble so I decided to make a program that quickly searches through a dictionary of 200,000+ words with an input of up to any 26 letters. My first attempt was fail as it took a while when you input 8 or more letters (just a basic look through dictionary and cancel out a letter if its found kind of thing), so I made a tree like structure containing only an array of 26 of the same structure and a flag to indicate the end of a word, doing that It can output all possible words in under a second even with an input of 26 characters. But it seems that when I input 12 or more letters with some of the same characters repeated i get duplicates; can anyone see why I would be getting duplicates with this code? (ill post my program at the bottom) Also, the next step once the duplicates are weeded out is to actually be able to input the letters on the game board and then have it calculate the best word you can make on a given board. I am having trouble trying to figure out a good algorithm that can analyze a scrabble board and an input of letters and output a result; the possible words that could be made I have no problem with but actually checking a board efficiently (ie can this word fit here, or here etc... without creating a non dictionary word in the process on some other string of letters) Anyone have a idea for an approach at that? (given a scrabble board, and an input of 7 letters, find all possible valid words or word sets that you can make) lol crap i forgot to email myself the code from my other computer thats in another state... ill post it on monday when I get back there! btw the dictionary im using is sowpods (http://www.calvin.edu/~rpruim/scrabble/ospd3.txt)

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• Delphi: How to avoid EIntOverflow underflow when subtracting?

  - by Ian Boyd

  Microsoft already says, in the documentation for GetTickCount, that you could never compare tick counts to check if an interval has passed. e.g.: Incorrect (pseudo-code): DWORD endTime = GetTickCount + 10000; //10 s from now ... if (GetTickCount > endTime) break; The above code is bad because it is suceptable to rollover of the tick counter. For example, assume that the clock is near the end of it's range: endTime = 0xfffffe00 + 10000 = 0x00002510; //9,488 decimal Then you perform your check: if (GetTickCount > endTime) Which is satisfied immediatly, since GetTickCount is larger than endTime: if (0xfffffe01 > 0x00002510) The solution Instead you should always subtract the two time intervals: DWORD startTime = GetTickCount; ... if (GetTickCount - startTime) > 10000 //if it's been 10 seconds break; Looking at the same math: if (GetTickCount - startTime) > 10000 if (0xfffffe01 - 0xfffffe00) > 10000 if (1 > 10000) Which is all well and good in C/C++, where the compiler behaves a certain way. But what about Delphi? But when i perform the same math in Delphi, with overflow checking on ({Q+}, {$OVERFLOWCHECKS ON}), the subtraction of the two tick counts generates an EIntOverflow exception when the TickCount rolls over: if (0x00000100 - 0xffffff00) > 10000 0x00000100 - 0xffffff00 = 0x00000200 What is the intended solution for this problem? Edit: i've tried to temporarily turn off OVERFLOWCHECKS: {$OVERFLOWCHECKS OFF}] delta = GetTickCount - startTime; {$OVERFLOWCHECKS ON} But the subtraction still throws an EIntOverflow exception. Is there a better solution, involving casts and larger intermediate variable types?

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