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  • twisted deferred/callbacks and asynchronous execution

    - by NetSkay
    hey guys, quick question about twisted and python... im trying to figure out how can i make my code more asynchronous using twisted and ive come to sort of a dead end, if a function of mine returns a deferred object, then i add a list of callbacks, the first callback will be called after the deferred function provides some result through deferred_obj.callback, then, in the chain of callbacks, the first callback will do something with the data and call the second callback and etc. however chained callbacks will not be considered asynchronous because they're chained and the event loop will keep firing each one of them concurrently until there is no more, right? however, if i have a deferred object, and i attach as its callback the deferred_obj.callback as in d.addCallback(deferred_obj.callback) then this will be considered asynchronous, because the deferred_obj is waiting for the data, and then the method that will pass the data is waiting on data as well, however once i d.callback 'd' object processes the data then it call deferred_obj.callback however since this object is deferred, unlike the case of chained callbacks, it will execute asynchronously... correct? meaning chained callbacks are NOT asynchronous while chained deferreds are, correct? thank you PS: assuming all of my code is non-blocking

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  • Classification: Dealing with Abstain/Rejected Class

    - by abner.ayala
    I am asking for your input and/help on a classification problem. If anyone have any references that I can read to help me solve my problem even better. I have a classification problem of four discrete and very well separated classes. However my input is continuous and has a high frequency (50Hz), since its a real-time problem. The circles represent the clusters of the classes, the blue line the decision boundary and Class 5 equals the (neutral/resting do nothing class). This class is the rejected class. However the problem is that when I move from one class to the other I activate a lot of false positives in the transition movements, since the movement is clearly non-linear. For example, every time I move from class 5 (neutral class) to 1 I first see a lot of 3's before getting to the 1 class. Ideally, I will want my decision boundary to look like the one in the picture below where the rejected class is Class =5. Has a higher decision boundary than the others classes to avoid misclassification during transition. I am currently implementing my algorithm in Matlab using naive bayes, kNN, and SVMs optimized algorithms using Matlab. Question: What is the best/common way to handle abstain/rejected classes classes? Should I use (fuzzy logic, loss function, should I include resting cluster in the training)?

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  • How to create a CGBitmapContext which works for Retina display and not wasting space for regular display?

    - by ????
    Is it true that if it is in UIKit, including drawRect, the HD aspect of Retina display is automatically handled? So does that mean in drawRect, the current graphics context for a 1024 x 768 view is actually a 2048 x 1536 pixel Bitmap context? (is there a way to print this size out to verify it). We actually enjoy the luxury of 1 point = 4 pixels automatically handled for us. However, if we use CGBitmapContextCreate, then those will really be pixels, not points? (at least if we provide a data buffer for that bitmap, the size is not for the higher resolution, but for the standard resolution, and even if we pass NULL as the buffer so that CGBitmapContextCreate handles the buffer for us, the size probably is the same as if we pass in a data buffer, and it is just standard resolution, not Retina's resolution). We can always create 2048 x 1536 for iPad 1 and iPad 2 as well as the New iPad, but it will waste memory and processor and GPU power, as it is only needed for the New iPad. So do we have to use a if () { } else { } to create such a bitmap context and how do we actually do so? And all our code CGContextMoveToPoint has to be adjusted for Retina display to use x * 2 and y * 2 vs non-retina display of just using x, y as well? That can be quite messy for the code. (or maybe we can define a local variable scaleFactor and set it to 1 for standard resolution and 2 if it is retina, so our x and y will always be x * scaleFactor, y * scaleFactor instead of just x and y.) It seems that UIGraphicsBeginImageContextWithOptions can create one for Retina automatically if the scale of 0.0 is passed in, but I don't think it can be used if I need to create the context and keep it (and using ivar or property of UIViewController to hold it). If I don't release it using UIGraphicsEndImageContext, then it stays in the graphics context stack, so it seems like I have to use CGBitmapContextCreate instead. (or do we just let it stay at the bottom of the stack and not worry about it?)

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  • Using ARIMA to model and forecast stock prices using user-friendly stats program

    - by Brian
    Hi people, Can anyone please offer some insight into this for me? I'm coming from a functional magnetic resonance imaging research background where I analyzed a lot of time series data, and I'd like to analyze the time series of stock prices (or returns) by: 1) modeling a successful stock in a particular market sector and then cross-correlating the time series of this historically successful stock with that of other newer stocks to look for significant relationships; 2) model a stock's price time series and use forecasting (e.g., exponential smoothing) to predict future values of it. I'd like to use non-linear modeling methods (ARIMA and ARCH) to do this. Several questions: How often do ARIMA and ARCH modeling methods (given that the individual who implements them does so accurately) actually fit the stock time series data they target, and what is the optimal fit I can expect? Is the extent to which this model fits the data commensurate with the extent to which it predicts this stock time series' future values? Rather than randomly selecting stocks to compare or model, if profit is my goal, what is an efficient approach, if any, to selecting the stocks I'm going to analyze? Which stats program is the most user-friendly for this? Any thoughts on this would be great and would go a long way for me. Thanks, Brian

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  • What is causing Apache2 to display PHP as plain text in this config file?

    - by rxgx
    I am trying to run PHP and Rails in the same virtual host, however, PHP is being displayed as plain/text. When I create a test host without all the rewrites and proxy-ing, Apache2 will process the PHP as desired. Where in my config file have I gone wrong? <VirtualHost *:80> #ServerName staging.domain.com #ServerAlias www.domain.com DocumentRoot /home/demo/vhosts/domain/public <Directory /> Options FollowSymLinks AllowOverride None </Directory> <Directory /home/demo/vhosts/domain/public> Options Indexes FollowSymLinks MultiViews AllowOverride None Order allow,deny allow from all </Directory> RewriteEngine On <Proxy balancer://thinservers> BalancerMember http://127.0.0.1:5000 BalancerMember http://127.0.0.1:5001 BalancerMember http://127.0.0.1:5002 </Proxy> # Redirect all non-static requests to thin RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME} !-f RewriteRule ^/(.*)$ balancer://thinservers%{REQUEST_URI} [P,QSA,L] ProxyPass / balancer://thinservers/ ProxyPassReverse / balancer://thinservers/ ProxyPreserveHost on <Proxy *> Order deny,allow Allow from all </Proxy> # Custom log file locations ErrorLog /home/demo/vhosts/domain/log/error.log CustomLog /home/demo/vhosts/domain/log/access.log combined </VirtualHost>

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  • Why should I use Entity Framework over Linq2SQL ...

    - by Refracted Paladin
    To be clear, I am not asking for a side by side comparision which has already been asked Ad Nauseum here on SO. I am also Not asking if Linq2Sql is dead as I don't care. What I am asking is this.... I am building internal apps only for a non-profit organization. I am the only developer on staff. We ALWAYS use SQL Server as our Database backend. I design and build the Databases as well. I have used L2S successfully a couple of times already. Taking all this into consideration can someone offer me a compelling reason to use EF instead of L2S? I was at Code Camp this weekend and after an hour long demonstration on EF, all of which I could have done in L2S, I asked this same question. The speakers answer was, "L2S is dead..." Very well then! NOT! (see here) I understand EF is what MS WANTS us to use in the future(see here) and that it offers many more customization options. What I can't figure out is if any of that should, or does, matter for me in this environment. One particular issue we have here is that I inherited the Core App which was built on 4 different SQL Data bases. L2S has great difficulty with this but when I asked the aforementioned speaker if EF would help me in this regard he said "No!"

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  • Debian packaging of a Python package.

    - by chrisdew
    I need to write (or find) a script to create a Debian package (using python-support) from a Python package. The Python package will be pure Python (no C extensions). The Python package (for testing purposes) will just be a directory with an empty __init__.py file and a single Python module, package_test.py. The packaging script must use python-support to provide the correct bytecode for possible multiple installations of Python on a target platform. (i.e. v2.5 and v2.6 on Ubuntu Jaunty.) Most advice I find while googling are just examples nasty hacks that don't even use python-support or python-central. I have so far spent hours researching this, and the best I can come up with is to hack around the script from an existing open source project - but I don't know which bits are required for what I'm doing. Has anyone here made a Debian package out of a Python package in a reasonably non-hacky way? I'm starting to think that it will take me more than a week to go from no knowledge of Debian packaging and python-support to getting a working script. How long has it taken others? Any advice? Chris.

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  • java inserting special characters with preparedstatement fails

    - by phill
    I am using an HTML form which sends <input type=hidden name=longdesc value='SMARTNET%^" 8X5XNBD'> this is done by the following javascript code: function masinsert(id) { var currentTime=new Date(); var button = document.getElementById("m"+id); button.onclick=""; button.value="Inserting"; var itemdescription = document.getElementById("itemdescription"+id).value; function handleHttpResponse() { if (http.readyState == 4) { button.value="Item Added"; } } var http = getHTTPObject(); // We create the HTTP Object var tempUrl = "\AInsert"; tempUrl += "itemdescription="+itemdescription+"&"+"itemshortdescription="+itemdescription.substring(0,37)+; alert(tempUrl); http.open("GET", tempUrl, true); http.onreadystatechange = handleHttpResponse; http.send(null); } to a java servlet. AInsert.java in the AInsert.java file, I do a String itemdescription = request.getParameter("longdesc"); which then sends the value to a preparedstatement to run an insert query. In the query, there are sometimes special characters which throw it off. For example, when I run the following insert into itemdescription (longdesc) values ('SMARTNET%^" 8X5XNBD') here is the actual snippet: PreparedStatement ps = conn.prepareStatement("INSERT INTO itemdescription (longdesc) values(?)"); ps.setString(1, itemdescription); ps.executeUpdate(); It will produce an error saying : Cannot insert the value NULL into column 'LongDesc', table 'App.dbo.itemdescription'; column does not allow nulls. Insert fails I have tried urlencode/urldecode String encodedString = URLEncoder.encode(longdesc, "UTF-8"); String decitemdescription = URLDecoder.decode(itemdescription, "UTF-8"); and i've also tried these functions //BEGIN URL Encoder final static String[] hex = { "%00", "%01", "%02", "%03", "%04", "%05", "%06", "%07", "%08", "%09", "%0a", "%0b", "%0c", "%0d", "%0e", "%0f", "%10", "%11", "%12", "%13", "%14", "%15", "%16", "%17", "%18", "%19", "%1a", "%1b", "%1c", "%1d", "%1e", "%1f", "%20", "%21", "%22", "%23", "%24", "%25", "%26", "%27", "%28", "%29", "%2a", "%2b", "%2c", "%2d", "%2e", "%2f", "%30", "%31", "%32", "%33", "%34", "%35", "%36", "%37", "%38", "%39", "%3a", "%3b", "%3c", "%3d", "%3e", "%3f", "%40", "%41", "%42", "%43", "%44", "%45", "%46", "%47", "%48", "%49", "%4a", "%4b", "%4c", "%4d", "%4e", "%4f", "%50", "%51", "%52", "%53", "%54", "%55", "%56", "%57", "%58", "%59", "%5a", "%5b", "%5c", "%5d", "%5e", "%5f", "%60", "%61", "%62", "%63", "%64", "%65", "%66", "%67", "%68", "%69", "%6a", "%6b", "%6c", "%6d", "%6e", "%6f", "%70", "%71", "%72", "%73", "%74", "%75", "%76", "%77", "%78", "%79", "%7a", "%7b", "%7c", "%7d", "%7e", "%7f", "%80", "%81", "%82", "%83", "%84", "%85", "%86", "%87", "%88", "%89", "%8a", "%8b", "%8c", "%8d", "%8e", "%8f", "%90", "%91", "%92", "%93", "%94", "%95", "%96", "%97", "%98", "%99", "%9a", "%9b", "%9c", "%9d", "%9e", "%9f", "%a0", "%a1", "%a2", "%a3", "%a4", "%a5", "%a6", "%a7", "%a8", "%a9", "%aa", "%ab", "%ac", "%ad", "%ae", "%af", "%b0", "%b1", "%b2", "%b3", "%b4", "%b5", "%b6", "%b7", "%b8", "%b9", "%ba", "%bb", "%bc", "%bd", "%be", "%bf", "%c0", "%c1", "%c2", "%c3", "%c4", "%c5", "%c6", "%c7", "%c8", "%c9", "%ca", "%cb", "%cc", "%cd", "%ce", "%cf", "%d0", "%d1", "%d2", "%d3", "%d4", "%d5", "%d6", "%d7", "%d8", "%d9", "%da", "%db", "%dc", "%dd", "%de", "%df", "%e0", "%e1", "%e2", "%e3", "%e4", "%e5", "%e6", "%e7", "%e8", "%e9", "%ea", "%eb", "%ec", "%ed", "%ee", "%ef", "%f0", "%f1", "%f2", "%f3", "%f4", "%f5", "%f6", "%f7", "%f8", "%f9", "%fa", "%fb", "%fc", "%fd", "%fe", "%ff" }; /** * Encode a string to the "x-www-form-urlencoded" form, enhanced * with the UTF-8-in-URL proposal. This is what happens: * * <ul> * <li><p>The ASCII characters 'a' through 'z', 'A' through 'Z', * and '0' through '9' remain the same. * * <li><p>The unreserved characters - _ . ! ~ * ' ( ) remain the same. * * <li><p>The space character ' ' is converted into a plus sign '+'. * * <li><p>All other ASCII characters are converted into the * 3-character string "%xy", where xy is * the two-digit hexadecimal representation of the character * code * * <li><p>All non-ASCII characters are encoded in two steps: first * to a sequence of 2 or 3 bytes, using the UTF-8 algorithm; * secondly each of these bytes is encoded as "%xx". * </ul> * * @param s The string to be encoded * @return The encoded string */ public static String encode(String s) { StringBuffer sbuf = new StringBuffer(); int len = s.length(); for (int i = 0; i < len; i++) { int ch = s.charAt(i); if ('A' <= ch && ch <= 'Z') { // 'A'..'Z' sbuf.append((char)ch); } else if ('a' <= ch && ch <= 'z') { // 'a'..'z' sbuf.append((char)ch); } else if ('0' <= ch && ch <= '9') { // '0'..'9' sbuf.append((char)ch); } else if (ch == ' ') { // space sbuf.append('+'); } else if (ch == '-' || ch == '_' // unreserved || ch == '.' || ch == '!' || ch == '~' || ch == '*' || ch == '\'' || ch == '(' || ch == ')') { sbuf.append((char)ch); } else if (ch <= 0x007f) { // other ASCII sbuf.append(hex[ch]); } else if (ch <= 0x07FF) { // non-ASCII <= 0x7FF sbuf.append(hex[0xc0 | (ch >> 6)]); sbuf.append(hex[0x80 | (ch & 0x3F)]); } else { // 0x7FF < ch <= 0xFFFF sbuf.append(hex[0xe0 | (ch >> 12)]); sbuf.append(hex[0x80 | ((ch >> 6) & 0x3F)]); sbuf.append(hex[0x80 | (ch & 0x3F)]); } } return sbuf.toString(); } //end encode and //decode url private static String unescape(String s) { StringBuffer sbuf = new StringBuffer () ; int l = s.length() ; int ch = -1 ; int b, sumb = 0; for (int i = 0, more = -1 ; i < l ; i++) { /* Get next byte b from URL segment s */ switch (ch = s.charAt(i)) { case '%': ch = s.charAt (++i) ; int hb = (Character.isDigit ((char) ch) ? ch - '0' : 10+Character.toLowerCase((char) ch) - 'a') & 0xF ; ch = s.charAt (++i) ; int lb = (Character.isDigit ((char) ch) ? ch - '0' : 10+Character.toLowerCase ((char) ch)-'a') & 0xF ; b = (hb << 4) | lb ; break ; case '+': b = ' ' ; break ; default: b = ch ; } /* Decode byte b as UTF-8, sumb collects incomplete chars */ if ((b & 0xc0) == 0x80) { // 10xxxxxx (continuation byte) sumb = (sumb << 6) | (b & 0x3f) ; // Add 6 bits to sumb if (--more == 0) sbuf.append((char) sumb) ; // Add char to sbuf } else if ((b & 0x80) == 0x00) { // 0xxxxxxx (yields 7 bits) sbuf.append((char) b) ; // Store in sbuf } else if ((b & 0xe0) == 0xc0) { // 110xxxxx (yields 5 bits) sumb = b & 0x1f; more = 1; // Expect 1 more byte } else if ((b & 0xf0) == 0xe0) { // 1110xxxx (yields 4 bits) sumb = b & 0x0f; more = 2; // Expect 2 more bytes } else if ((b & 0xf8) == 0xf0) { // 11110xxx (yields 3 bits) sumb = b & 0x07; more = 3; // Expect 3 more bytes } else if ((b & 0xfc) == 0xf8) { // 111110xx (yields 2 bits) sumb = b & 0x03; more = 4; // Expect 4 more bytes } else /*if ((b & 0xfe) == 0xfc)*/ { // 1111110x (yields 1 bit) sumb = b & 0x01; more = 5; // Expect 5 more bytes } /* We don't test if the UTF-8 encoding is well-formed */ } return sbuf.toString() ; } but the decoding doesn't change it back to the original special characters. Any ideas? thanks in advance UPDATE: I tried adding these two statements to grab the request String itemdescription = URLDecoder.decode(request.getParameter("itemdescription"), "UTF-8"); String itemshortdescription = URLDecoder.decode(request.getParameter("itemshortdescription"), "UTF-8"); System.out.println("processRequest | short descrip "); and this is failing as well if that helps. UPDATE2: I created an html form and did a direct insert with the encoded itemdescription such as and the insertion works correctly with the special charaters and everything. I guess there is something going on with my javascript submit. Any ideas on this?

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  • MVC2 Areas not Registering Correctly

    - by Geoffrey
    I believe I have my Areas setup correctly (they were working in MVC1 fine). I followed the guide here: http://odetocode.com/Blogs/scott/archive/2009/10/13/asp-net-mvc2-preview-2-areas-and-routes.aspx I've also used Haacked's Route Debugger. Which shows the correct Area/Controller registration when I run it. However when I try to go to my (AreaName)/(Controller) I get this error: "The resource cannot be found." I believe this indicates there's a problem with the routing, but I'm having trouble debugging this. Where should I set my breakpoints to catch routing errors in MVC2? I'm also using SparkViewEngine compiled against MVC2 references. Could this possibly be causing this error? I've set breakpoints on the controller in the area and it never fires off, I assumed the view engine doesn't kick in until after the controller has been initiated, but I could be wrong. The non-area landing page works fine, and I've stripped my project of all areas except one, to avoid any sort of naming conflicts. Any ideas where I can try to look next?

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  • Http Digest Authentication, Handle different browser char-sets...

    - by user160561
    Hi all, I tried to use the Http Authentication Digest Scheme with my php (apache module) based website. In general it works fine, but when it comes to verification of the username / hash against my user database i run into a problem. Of course i do not want to store the user´s password in my database, so i tend to store the A1 hashvalue (which is md5($username . ':' . $realm . ':' . $password)) in my db. This is just how the browser does it too to create the hashes to send back. The Problem: I am not able to detect if the browser does this in ISO-8859-1 fallback (like firefox, IE) or UTF-8 (Opera) or whatever. I have chosen to do the calculation in UTF-8 and store this md5 hash. Which leads to non-authentication in Firefox and IE browsers. How do you solve this problem? Just do not use this auth-scheme? Or Store a md5 Hash for each charset? Force users to Opera? (Terms of A1 refer to the http://php.net/manual/en/features.http-auth.php example.) (for digest access authentication read the according wikipedia entry)

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  • DataGrid - Edit the selected row when a button is clicked.

    - by Chepech
    Hi all. I have a very simple DataGrid with 2 columns, some thing like this: <mx:DataGrid id="grid" > <mx:columns> <mx:DataGridColumn dataField="name" headerText="Name"/> <mx:DataGridColumn dataField="date" headerText="Date"/> </mx:columns> </mx:DataGrid> What Im trying to do is to activate the edition of the selected row when the user clicks a button. So far I've been unable to find any example of how to do this. I already tried 6 or 7 different approaches but non works. Does any one has a clue how to do this? How do you get the selected row (NOT selectedItem) of a DataGrid and how can you: Change the ItemRenderEditor or ItemRenderer on the fly of just that row. Or enable the edition of that specific row without clicking it. This are the questions that I've been unable to answer Help will be greatly appreciated.

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  • Why boost property tree write_json saves everything as string? Is it possible to change that?

    - by pprzemek
    I'm trying to serialize using boost property tree write_json, it saves everything as strings, it's not that data are wrong, but I need to cast them explicitly every time and I want to use them somewhere else. (like in python or other C++ json (non boost) library) here is some sample code and what I get depending on locale: boost::property_tree::ptree root, arr, elem1, elem2; elem1.put<int>("key0", 0); elem1.put<bool>("key1", true); elem2.put<float>("key2", 2.2f); elem2.put<double>("key3", 3.3); arr.push_back( std::make_pair("", elem1) ); arr.push_back( std::make_pair("", elem2) ); root.put_child("path1.path2", arr); std::stringstream ss; write_json(ss, root); std::string my_string_to_send_somewhare_else = ss.str(); and my_string_to_send_somewhere_else is sth. like this: { "path1" : { "path2" : [ { "key0" : "0", "key1" : "true" }, { "key2" : "2.2", "key3" : "3.3" } ] } } Is there anyway to save them as the values, like: "key1" : true or "key2" : 2.2 ?

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  • Broken ssl, what to do

    - by TIT
    I have a site and i implemented ssl there. but when i browse it, the security seals dont come. i asked to godaddy, they replaid: Thank you for contacting online support. I cannot replicate the issue you have described. The error you described is caused by the way your site has been designed. If you receive this error, you have a combination of secure and non-secure objects on the page. For example, if your secure website was https://www.domain.tld and you added an object (an image, script, flash file, etc.) to that page that was located at http://www.domain.tld/image.jpg, you would break the seal. You will need to change your design to link to objects using https (ie https://www.domain.tld/image.jpg) or modify your site design to use relative paths (/image.jpg). This error can only be corrected by modifying your site design. Please contact your web designer or the manufacturer of your web design software if you require additional assistance modifying your site design. but the problem is i made everything,all my images javascripts are unders https, but the seal still not coming, saying: some content insecure. what is the problem.

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  • MongoDB - proper use of collections?

    - by zmg
    In Mongo my understanding is that you can have databases and collections. I'm working on a social-type app that will have blogs and comments (among other things) and had previously be using MySQL and pretty heavy partitioning in an attempt to limit possible concurrency issues. With MySQL I've stuffed all my user data into a _user database with several tables to further partition the data (blogs, pages, etc). My immediate reaction with Mongo would be to create a 'users' database with one collection per user. In this way user 'zach' blog entries would go into the 'zach' collection with associated comments and such becoming sub-objects in the same collection. Basically like dynamically creating one table per user in MySQL, but apparently without the complexity and limitations that might impose. Of course since I haven't really used Mongo before I'm having trouble gauging the (ahem..) quality of this idea and the potential problems it might cause down the road. I'd like user data to be treated a lot like a users directory in a *nix environment where user created/non-shared (mostly) gets put into one place (currently with MySQL that would be the appname_users as mentioned above). Most of the users data will be specific to the users page(s). Some of the user data which is queried across all site users (searchable user profiles) is currently kept in a separate database/table and I expect things like this could be put into a appname_system database and be broken up into collections and/or application specific databases (appname_profiles). Anyway, since the available documentation on this is currently a little thin and my experience is extremely limited I thought I might find a little guidance from someone with a better working understanding of the system. On the plus side I'd really already been attempting to treat MySQL as a schema-less document-store and doing this with Mongo seems much more intuitive/sane/rational so I'm really looking forward to getting started. Thanks, Zach

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  • Business entity: private instance VS single instance

    - by taoufik
    Suppose my WinForms application has a business entity Order, the entity is used in multiple views, each view handles a different domain or use-case in the application. As an example, one managing orders, the other one digging into one order and displaying additional data. If I'd use nHibernate (or any other ORM) and use one session/dataContext per view (or per db action), I'd end up getting two different instances for the same Order (let's say orderId = 1). Although functionally the same entity, they are technically two different instances. Yes, I could implement Equals/GetHashcode to make them "seem" the same. Why would you go for a single instance per entity vs private instances per view or per use-case? Having single instances has the advantage of sharing INotifyPropertyChanged events, and sharing additional (non-persistent) data. Having a private instance in each view would give you the flexibility of the undo functionality on a view level. In the example above, I'd allow the user to change order details, and give them the flexibility to not save the change. Here, synchronisation between the view/use-case happens on a data persistence level. What would your argument be?

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  • Examples of monoids/semigroups in programming

    - by jkff
    It is well-known that monoids are stunningly ubiquitous in programing. They are so ubiquitous and so useful that I, as a 'hobby project', am working on a system that is completely based on their properties (distributed data aggregation). To make the system useful I need useful monoids :) I already know of these: Numeric or matrix sum Numeric or matrix product Minimum or maximum under a total order with a top or bottom element (more generally, join or meet in a bounded lattice, or even more generally, product or coproduct in a category) Set union Map union where conflicting values are joined using a monoid Intersection of subsets of a finite set (or just set intersection if we speak about semigroups) Intersection of maps with a bounded key domain (same here) Merge of sorted sequences, perhaps with joining key-equal values in a different monoid/semigroup Bounded merge of sorted lists (same as above, but we take the top N of the result) Cartesian product of two monoids or semigroups List concatenation Endomorphism composition. Now, let us define a quasi-property of an operation as a property that holds up to an equivalence relation. For example, list concatenation is quasi-commutative if we consider lists of equal length or with identical contents up to permutation to be equivalent. Here are some quasi-monoids and quasi-commutative monoids and semigroups: Any (a+b = a or b, if we consider all elements of the carrier set to be equivalent) Any satisfying predicate (a+b = the one of a and b that is non-null and satisfies some predicate P, if none does then null; if we consider all elements satisfying P equivalent) Bounded mixture of random samples (xs+ys = a random sample of size N from the concatenation of xs and ys; if we consider any two samples with the same distribution as the whole dataset to be equivalent) Bounded mixture of weighted random samples Which others do exist?

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  • Is this a clean way to manage AsyncResults with Generic Methods?

    - by Michael Stum
    I've contributed Async Support to a Project I'm using, but I made a bug which I'm trying to fix. Basically I have this construct: private readonly Dictionary<WaitHandle, object> genericCallbacks = new Dictionary<WaitHandle, object>(); public IAsyncResult BeginExecute<T>(RestRequest request, AsyncCallback callback, object state) where T : new() { var genericCallback = new RequestExecuteCaller<T>(this.Execute<T>); var asyncResult = genericCallback.BeginInvoke(request, callback, state); genericCallbacks[asyncResult.AsyncWaitHandle] = genericCallback; return asyncResult; } public RestResponse<T> EndExecute<T>(IAsyncResult asyncResult) where T : new() { var cb = genericCallbacks[asyncResult.AsyncWaitHandle] as RequestExecuteCaller<T>; genericCallbacks.Remove(asyncResult.AsyncWaitHandle); return cb.EndInvoke(asyncResult); } So I have a generic BeginExecute/EndExecute method pair. As I need to store the delegate that is called on EndExecute somewhere I created a dictionary. I'm unsure about using WaitHandles as keys though, but that seems to be the only safe choice. Does this approach make sense? Are WaitHandles unique or could I have two equal ones? Or should I instead use the State (and wrap any user provided state into my own State value)? Just to add, the class itself is non-generic, only the Begin/EndExecute methods are generic.

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  • Java: Initializing a public static field in superclass that needs a different value in every subclas

    - by BinaryMuse
    Good evening, I am developing a set of Java classes so that a container class Box contains a List of a contained class Widget. A Widget needs to be able to specify relationships with other Widgets. I figured a good way to do this would be to do something like this: public abstract class Widget { public static class WidgetID { // implementation stolen from Google's GWT private static int nextHashCode; private final int index; public WidgetID() { index = ++nextHashCode; } public final int hashCode() { return index; } } public abstract WidgetID getWidgetID(); } so sublcasses of Widget could: public class BlueWidget extends Widget { public static final WidgetID WIDGETID = new WidgetID(); @Override public WidgetID getWidgetID() { return WIDGETID; } } Now, BlueWidget can do getBox().addWidgetRelationship(RelationshipTypes.SomeType, RedWidget.WIDGETID, and Box can iterate through it's list comparing the second parameter to iter.next().getWidgetID(). Now, all this works great so far. What I'm trying to do is keep from having to declare the public static final WidgetID WIDGETID in all the subclasses and implement it instead in the parent Widget class. The problem is, if I move that line of code into Widget, then every instance of a subclass of Widget appears to get the same static final WidgetID for their Subclassname.WIDGETID. However, making it non-static means I can no longer even call Subclassname.WIDGETID. So: how do I create a static WidgetID in the parent Widget class while ensuring it is different for every instance of Widget and subclasses of Widget? Or am I using the wrong tool for the job here? Thanks!

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  • How to use DLL reference with an ActiveX <object> via JavaScript

    - by John Factorial
    My question: how can I set an ActiveX object's property via JavaScript to an enum value found in a non-ActiveX DLL? Problem description: I am instantiating an ActiveX object with the following object tag: <object classid="clsid:F338193D-2491-4D7B-80CE-03487041A278" id="VideoCapture1" width="500" height="500"></object> (This is the guid for the 3rd party ActiveX I'm using, "VisioForge_Video_Capture_4.VFVideoCapture4X") I have example C# code for using this ActiveX, which I am porting to JavaScript. Code like this works just fine: VideoCapture1.Debug_Mode = true; var devcount = VideoCapture1.Video_CaptureDevices_GetCount(); var devs = []; for (var i =0; i < devcount; ++i) { devs[devs.length] = VideoCapture1.Video_CaptureDevices_GetItem(i); } ... etc ... However, VideoCapture1 has some settings which refer to a DLL enum, like so (C# code): VideoCapture1.Mode = VisioForge_Video_Capture_4.TxVFMode.Mode_Video_Preview; I can see in Visual Web Developer that TxVFMode.Mode_Video_Preview is value 1 in the enum. However, the following JS does not appear to set the Mode properly: VideoCapture1.Mode = 1; Does anyone know how I can set VideoCapture1.Mode to the enum value found in the TxVFMode? PS: In Visual Web Developer, when I "Go to definition" on TxVFMode, I get the Guid for the enum. I thought I could create an with this Guid or instantiate a VisioForge_Video_Capture_4.TxVFMode in JS, but neither gives me a usable object.

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  • “Could not find type” error loading a form in the Designer

    - by Vaccano
    This is the exact same question as this one: “Could not find type” error loading a form in the Designer Before anyone goes closing my question please read that one. You will realize that it did not get a real answer. I hope to get a full answer (rather than a workaround) from this question. When I create a class that descends from Control and uses generics, that class fails to load in the designer. Here is and example: class OwnerDrawnListBox<T> : System.Windows.Forms.Control { private readonly List<T> _items; // Other list box private stuff here public OwnerDrawnListBox() { _items = new List<T>(); } // More List box code } I then use this in my designer: private OwnerDrawnListBox<Bag> lstAvailable; private void InitializeComponent() { // Used to be System.Windows.Forms.ListBox(); this.lstAvailable = new ARUP.ScanTrack.Mobile.OwnerDrawnListBox<Bag>(); // Other items } If the generic class is subclassed (to a non-generic) then the referenced question says that it works fine (ie if I made Class BagOwnerDrawListBox: OwnerDrawnListBox<Bag>). What I want to know is there a way to "fix" this so that the generic item is accepted by the designer? Side Note: I am using the Compact Framework.

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  • VS2010 express beta2 - no add reference dialog, no open file/project dialogs

    - by David
    Just installed VS2010 express for Windows Phone last night. Install went smoothly. It creates a project, compiles, and deploys the app to the emulator. Here's the problem: When I try to "Add Reference" through the Project menu, I do not get the Add Reference dialog box. Same thing if I right click References in the solution explorer and click Add Reference. That's not all. "File...Open" and "File...Open Project" also fail to throw up an open file dialog box. When attempting any of these actions, the IDE quickly loses and regains focus. Even pressing a keyboard shortcut (Ctrl+O) causes the IDE to quickly lose and regain focus, but no open file dialog box appears. This is what I have tried, not particularly in this order: 1. Turned off UAC 2. Monitored file and registry access using Process Monitor during a File...Open operation. File activity showed mostly "SUCCESS" with a few "FAST IO DISALLOWED" and a few "INVALID DEVICE REQUEST" results. Registry activity showed mostly "SUCCESS" with some "NAME NOT FOUND" and a few "BUFFER OVERFLOW" results. 3. Created a new, clean Windows account to run the IDE from 4. Forced a test project to add a reference to "System.Xml.Linq" by editing the ".csproj" project file. Project failed to load in the IDE. I don't have these problems at all on 2 other Windows 7 computers with VS2010 C# express beta 2 installed. One machine is 32bit and the other 64bit, both Home Premium edition. My system: Windows 7 Home Premium, 64bit Other Visual Studio products installed: VS2008 C# express, VS2008 C++ express One other thing to note: Several months ago I installed the non-phone distribution of VS2010 C# express beta 2, and I had the same exact problems. Back then I chalked it up to being beta and went back to VS2008 C# express, where I do not have these issues.

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  • Getting exception when trying to monkey patch pymongo.connection._Pool

    - by Creotiv
    I use pymongo 1.9 on Ubuntu 10.10 with python 2.6.6 When i trying to monkey patch pymongo.connection._Pool i'm getting error on connection: AutoReconnect: could not find master/primary But when i change _Pool class in pymongo.connection module, it work pretty fine. Even if i copy _Pool implementation from pymongo.connection module and will try to monkey patch by the same code, it still giving same exception. I need to remove threading.local from _Pool class, because i use gevent and i need to implement Pool for all mongo connections(for all threads). I use this code: import pymongo class GPool: """A simple connection pool. Uses thread-local socket per thread. By calling return_socket() a thread can return a socket to the pool. Right now the pool size is capped at 10 sockets - we can expose this as a parameter later, if needed. """ # Non thread-locals __slots__ = ["sockets", "socket_factory", "pool_size","sock"] #sock = None def __init__(self, socket_factory): self.pool_size = 10 if not hasattr(self,"sock"): self.sock = None self.socket_factory = socket_factory if not hasattr(self, "sockets"): self.sockets = [] def socket(self): # we store the pid here to avoid issues with fork / # multiprocessing - see # test.test_connection:TestConnection.test_fork for an example # of what could go wrong otherwise pid = os.getpid() if self.sock is not None and self.sock[0] == pid: return self.sock[1] try: self.sock = (pid, self.sockets.pop()) except IndexError: self.sock = (pid, self.socket_factory()) return self.sock[1] def return_socket(self): if self.sock is not None and self.sock[0] == os.getpid(): # There's a race condition here, but we deliberately # ignore it. It means that if the pool_size is 10 we # might actually keep slightly more than that. if len(self.sockets) < self.pool_size: self.sockets.append(self.sock[1]) else: self.sock[1].close() self.sock = None pymongo.connection._Pool = GPool

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  • I Need a Human Readable, Yet Parse-able Document Format

    - by macinjosh
    I'm working on one of those projects where there are a million better ways to accomplish what I need but I have no choice and I have to do it this way. Here it is: There is a web form, when the user fills it out and hits a submit a human readable text file is created using the form data. It looks like this: field_1: value for field one field_2: value for field two more data for field two (field two has a newline in it!) field3: some more data My problem is this: I need to parse this text file back into the web form so that the user can edit it. How could I, in a foolproof way, accomplish this? A database is not an option, I have to use these text files. My Questions: Is there a foolproof way to do this using the format in the example above? What human readable format would work better (in other words I can change the format) Human readable means that a non programmer could read it and know what is what. This project uses PHP.

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  • Two divs with wrapping text sharing the same line

    - by Jerad Rose
    Simple problem - How do I get these two divs to share the same line: <div style="width: 200px; padding: 0; background-color: #f00; float: left; display: inline; ">Lorem ipsum dolor sit</div> <div style="margin-left: 200px; padding: 0; background-color: #0f0; float: right; display: inline; ">Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Duis interdum leo nec purus eleifend ut laoreet metus varius. Praesent lobortis risus sem. Duis gravida risus convallis purus dapibus fermentum. Nulla nec arcu pellentesque justo hendrerit pulvinar id ac velit. Nulla cursus volutpat risus, id volutpat metus tempus eget. Morbi rhoncus, diam sed vestibulum elementum, odio nulla faucibus ligula, ut dapibus lorem nunc vitae purus. Nam commodo iaculis ultricies. Etiam in velit dolor, vel convallis tellus. Aliquam tincidunt, erat ac dictum varius, sapien mi faucibus est, sit amet venenatis nisl massa non turpis. Donec eget libero mauris. Cras ac magna est, id hendrerit est.</div> Thanks in advance.

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  • casting Collection<SomeClass> to Collection<SomeSuperClass>

    - by skrebbel
    Hi all, I'm sure this has been answered before, but I really cannot find it. I have a java class SomeClass and an abstract class SomeSuperClass. SomeClass extends SomeSuperClass. Another abstract method has a method that returns a Collection<SomeSuperClass>. In an implementation class, I have a Collection<SomeClass> myCollection I understand that I cannot just return myCollection, because Collection<SomeClass> does not inherit from Collection<SomeSuperClass>. Nevertheless, I know that everything in myCollection is a SomeSuperClass because after all, they're SomeClass objects which extend SomeSuperClass. How can I make this work? I.e. I want public class A { private Collection<SomeClass> myCollection; public Collection<SomeSuperClass> getCollection() { return myCollection; //compile error! } } The only way I've found is casting via a non-generic type and getting unchecked warnings and whatnot. There must be a more elegant way, though? I feel that also using Collections.checkedSet() and friends are not needed, since it is statically certain that the returned collection only contains SomeClass objects (this would not be the case when downcasting instead of upcasting, but that's not what I'm doing). What am I missing? Thanks!

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