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• Using MEF with exporting project that uses resources (xml) contained in the xap.

  - by JSmyth

  I'm doing a proof of concept app in SL4 using MEF and as part of the app I am importing another xap from an existing Silverlight Project and displaying it in my host project. The problem is that the existing app uses some .xml files (as content) and it uses linq2xml to load these files which are (assumed to be) bundled in the xap. When I compose the application the initalization fails because the host app doesn't contain the xml files. If I copy these xml files into the host project and run it the composition works fine. However, I need to keep the xml files in the original project. Is there a way that I can download a xap and look at it's contents for xml files and then load them into the host xap at runtime so that after the compostion takes place the xml resources that are required can be found? Or should I work out some kind of contract with an import/export to pass the xml files to the host xap? As the people developing the imported xaps (should the project go ahead) are from a different company, I would like to keep changes to the way they develop their apps to a minimum.

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• Shortest acyclic path on directed cyclic graph with negative weights/cycles

  - by Janathan

  I have a directed graph which has cycles. All edges are weighted, and the weights can be negative. There can be negative cycles. I want to find a path from s to t, which minimizes the total weight on the path. Sure, it can go to negative infinity when negative cycles exist. But what if I disallow cycles in the path (not in the original graph)? That is, once the path leaves a node, it can not enter the node again. This surely avoids the negative infinity problem, but surprisingly no known algorithm is found by a search on Google. The closest is Floyd–Warshall algorithm, but it does not allow negative cycles. Thanks a lot in advance. Edit: I may have generalized my original problem too much. Indeed, I am given a cyclic directed graph with nonnegative edge weights. But in addition, each node has a positive reward too. I want to find a simple path which minimizes (sum of edge weights on the path) - (sum of node rewards covered by the path). This can be surely converted to the question that I posted, but some structure is lost. And some hint from submodular analysis suggests this motivating problem is not NP-hard. Thanks a lot

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• Behavior of <- NULL on lists versus data.frames for removing data

  - by Ananda Mahto

  Many R users eventually figure out lots of ways to remove elements from their data. One way is to use NULL, particularly when you want to do something like drop a column from a data.frame or drop an element from a list. Eventually, a user comes across a situation where they want to drop several columns from a data.frame at once, and they hit upon <- list(NULL) as the solution (since using <- NULL will result in an error). A data.frame is a special type of list, so it wouldn't be too tough to imagine that the approaches for removing items from a list should be the same as removing columns from a data.frame. However, they produce different results, as can be seen in the example below. ## Make some small data--two data.frames and two lists cars1 <- cars2 <- head(mtcars)[1:4] cars3 <- cars4 <- as.list(cars2) ## Demonstration that the `list(NULL)` approach works cars1[c("mpg", "cyl")] <- list(NULL) cars1 # disp hp # Mazda RX4 160 110 # Mazda RX4 Wag 160 110 # Datsun 710 108 93 # Hornet 4 Drive 258 110 # Hornet Sportabout 360 175 # Valiant 225 105 ## Demonstration that simply using `NULL` does not work cars2[c("mpg", "cyl")] <- NULL # Error in `[<-.data.frame`(`*tmp*`, c("mpg", "cyl"), value = NULL) : # replacement has 0 items, need 12 Switch to applying the same concept to a list, and compare the difference in behavior. ## Does not fully drop the items, but sets them to `NULL` cars3[c("mpg", "cyl")] <- list(NULL) # $mpg # NULL # # $cyl # NULL # # $disp # [1] 160 160 108 258 360 225 # # $hp # [1] 110 110 93 110 175 105 ## *Does* drop the `list` items while this would ## have produced an error with a `data.frame` cars4[c("mpg", "cyl")] <- NULL # $disp # [1] 160 160 108 258 360 225 # # $hp # [1] 110 110 93 110 175 105 The main questions I have are, if a data.frame is a list, why does it behave so differently in this scenario? Is there a foolproof way of knowing when an element will be dropped, when it will produce an error, and when it will simply be given a NULL value? Or do we depend on trial-and-error for this?

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• Open the Word Application from a button on a web page

  - by Andrea

  I'm developing a proof of concept web application: A web page with a button that opens the Word Application installed on the user's PC. I'm stuck with a C# project in Visual Studio 2008 Express (Windows XP client, LAMP server). I've followed the Writing an ActiveX Control in .NET tutorial and after some tuning it worked fine. Then I added my button for opening Word. The problem is that I can reference the Microsoft.Office.Interop.Word from the project, but I'm not able to access it from the web page. The error says "That assembly does not allow partially trusted callers". I've read a lot about security in .NET, but I'm totally lost now. Disclaimer: I'm into .NET since 4 days ago. I've tried to work around this issue but I cannot see the light!! I don't even know if it will ever be possible! using System; using System.Collections.Generic; using System.ComponentModel; using System.Drawing; using System.Data; using System.Linq; using System.Text; using System.Windows.Forms; using Word = Microsoft.Office.Interop.Word; using System.IO; using System.Security.Permissions; using System.Security; [assembly: AllowPartiallyTrustedCallers] namespace OfficeAutomation { public partial class UserControl1 : UserControl { public UserControl1() { InitializeComponent(); } private void openWord_Click(object sender, EventArgs e) { try { Word.Application Word_App = null; Word_App = new Word.Application(); Word_App.Visible = true; } catch (Exception exc) { MessageBox.Show("Can't open Word application (" + exc.ToString() + ")"); } } } }

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• Why am I getting "(304) Not Modified" error on some links when using HttpWebRequest?

  - by Greg

  Hi, Any ideas why on some links that I try to access using HttpWebRequest I am getting "The remote server returned an error: (304) Not Modified." in the code? The code I'm using is from Jeff's post here. Note the concept of the code is a simple proxy server, so I'm pointing my browser at this locally running piece of code, which gets my browsers request, and then proxies it on by creating a new HttpWebRequest, as you'll see in the code. It works great for most sites/links, but for some this error comes up. You will see one key bit in the code is where it seems to copy the http header settings from the browser request to it's request out to the site, and it copies in the header attributes. Not sure if the issue is something to do with how it mimics this aspect of the request and then what happens as the result comes back? case "If-Modified-Since": request.IfModifiedSince = DateTime.Parse(listenerContext.Request.Headers[key]); break; I get the issue for example from http://en.wikipedia.org/wiki/Main_Page thanks

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• WM_NOTIFY and superclass chaining issue in Win32

  - by DasMonkeyman

  For reference I'm using the window superclass method outlined in this article. The specific issue occurs if I want to handle WM_NOTIFY messages (i.e. for custom drawing) from the base control in the superclass I either need to reflect them back from the parent window or set my own window as the parent (passed inside CREATESTRUCT for WM_(NC)CREATE to the base class). This method works fine if I have a single superclass. If I superclass my superclass then I run into a problem. Now 3 WindowProcs are operating in the same HWND, and when I reflect WM_NOTIFY messages (or have them sent to myself from the parent trick above) they always go to the outermost (most derived) WindowProc. I have no way to tell if they're messages intended for the inner superclass (base messages are supposed to go to the first superclass) or messages intended for the outer superclass (messages from the inner superclass are intended for the outer superclass). These messages are indistinguishable because they all come from the same HWND with the same control ID. Is there any way to resolve this without creating a new window to encapsulate each level of inheritance? Sorry about the wall of text. It's a difficult concept to explain. Here's a diagram. single superclass: SuperA::WindowProc() - Base::WindowProc()---\ ^--------WM_NOTIFY(Base)--------/ superclass of a superclass: SuperB::WindowProc() - SuperA::WindowProc() - Base::WindowProc()---\ ^--------WM_NOTIFY(Base)--------+-----------------------/ ^--------WM_NOTIFY(A)-----------/ The WM_NOTIFY messages in the second case all come from the same HWND and control ID, so I cannot distinguish between the messages intended for SuperA (from Base) and messages intended for SuperB (from SuperA). Any ideas?

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• Architecting ASP.net MVC App to use repositories and services

  - by zaladane

  Hello, I recently started reading about ASP.net MVC and after getting excited about the concept, i started to migrate all my webform project to MVC but i am having a hard time keeping my controller skinny even after following all the good advices out there (or maybe i just don't get it ... ). The website i deal with has Articles, Videos, Quotes ... and each of these entities have categories, comments, images that can be associated with it. I am using Linq to sql for database operations and for each of these Entities, i have a Repository, and for each repository, i create a service to be used in the controller. so i have - ArticleRepository ArticleCategoryRepository ArticleCommentRepository and the corresponding service ArticleService ArticleCategoryService ... you see the picture. The problem i have is that i have one controller for article,category and comment because i thought that having ArticleController handle all of that might make sense, but now i have to pass all of the services needed to the Controller constructor. So i would like to know what it is that i am doing wrong. Are my services not designed properly? should i create Bigger service to encapsulate smaller services and use them in my controller? or should i have an articleCategory Controller and an articleComment Controller? A page viewed by the user is made of all of that, thee article to be viewed,the comments associated with it, a listing of the categories to witch it applies ... how can i efficiently break down the controller to keep it "skinny" and solve my headache? Thank you! I hope my question is not too long to be read ...

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• Partial Classes - are they bad design?

  - by dferraro

  Hello, I'm wondering why the 'partial class' concept even exists in .NET. I'm working on an application and we are reading a (actually very good) book relavant to the development platform we are implementing at work. In the book he provides a large code base /wrapper around the platform API and explains how he developed it as he teaches different topics about the platform development. Anyway, long story short - he uses partial classes, all over the place, as a way to fake multiple inheritence in C# (IMO). Why he didnt just split the classes up into multiple ones and use composition is beyond me. He will have 3 'partial class' files to make up his base class, each w/ 3-500 lines of code... And does this several times in his API. Do you find this justifiable? If it were me, I'd have followed the S.R.P. and created multiple classes to handle different required behaviors, then create a base class that has instances of these classes as members (e.g. composition). Why did MS even put partial class into the framework?? They removed the ability to expand/collapse all code at each scope level in C# (this was allowed in C++) because it was obviously just allowing bad habits - partial class is IMO the same thing. I guess my quetion is: Can you explain to me when there would be a legitimate reason to ever use a partial class? I do not mean this to be a rant / war thread. I'm honeslty looking to learn something here. Thanks

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• Simple encryption - Sum of Hashes in C

  - by Dogbert

  I am attempting to demonstrate a simple proof of concept with respect to a vulnerability in a piece of code in a game written in C. Let's say that we want to validate a character login. The login is handled by the user choosing n items, (let's just assume n=5 for now) from a graphical menu. The items are all medieval themed: eg: _______________________________ | | | | | Bow | Sword | Staff | |-----------|-----------|-------| | Shield | Potion | Gold | |___________|___________|_______| The user must click on each item, then choose a number for each item. The validation algorithm then does the following: Determines which items were selected Drops each string to lowercase (ie: Bow becomes bow, etc) Calculates a simple string hash for each string (ie: `bow = b=2, o=15, w=23, sum = (2+15+23=40) Multiplies the hash by the value the user selected for the corresponding item; This new value is called the key Sums together the keys for each of the selected items; this is the final validation hash IMPORTANT: The validator will accept this hash, along with non-zero multiples of it (ie: if the final hash equals 1111, then 2222, 3333, 8888, etc are also valid). So, for example, let's say I select: Bow (1) Sword (2) Staff (10) Shield (1) Potion (6) The algorithm drops each of these strings to lowercase, calculates their string hashes, multiplies that hash by the number selected for each string, then sums these keys together. eg: Final_Validation_Hash = 1*HASH(Bow) + 2*HASH(Sword) + 10*HASH(Staff) + 1*HASH(Shield) + 6*HASH(Potion) By application of Euler's Method, I plan to demonstrate that these hashes are not unique, and want to devise a simple application to prove it. in my case, for 5 items, I would essentially be trying to calculate: (B)(y) = (A_1)(x_1) + (A_2)(x_2) + (A_3)(x_3) + (A_4)(x_4) + (A_5)(x_5) Where: B is arbitrary A_j are the selected coefficients/values for each string/category x_j are the hash values for each string/category y is the final validation hash (eg: 1111 above) B,y,A_j,x_j are all discrete-valued, positive, and non-zero (ie: natural numbers) Can someone either assist me in solving this problem or point me to a similar example (ie: code, worked out equations, etc)? I just need to solve the final step (ie: (B)(Y) = ...). Thank you all in advance.

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• How can I visualise a "broken" hierarchical dataset?

  I have a reasonably large datatable structured something like this: StaffNo Grade Direct Boss2 Boss3 Boss4 Boss5 Boss6 ------- ----- ----- ----- ----- ----- ----- ----- 10001 1 10002 10002 10057 10094 10043 10099 10002 2 10057 NULL 10057 10094 10043 10099 10003 1 10004 10004 10057 10094 10043 10099 10004 2 10057 NULL 10057 10094 10043 10099 10057 3 10094 NULL NULL 10094 10043 10099 etc.... i.e. a unique id , their level (grade) in the hierarchy, a record of their bosses ID and the IDs of the supervisors above. (The 2,3,4, etc refers to the boss at that particular grade). The system relies on a strict hierarchy - if you are my boss (/parent) then your boss must be my grandparent. Unfortunately this rule is not enforced within the data model and the data ultimately comes from other systems which don't even know about the rule, let alone observe it. So you and I may share the same boss, but our bosses boss won't be the same. note: I cannot change the data model I cannot fix the data at source. So (for the moment) I have to fix the data once it's in place. Once a fortnight someone will do something which breaks the model and I'll need to modify the procs slightly to resolve. Not ideal, but I'm stuck with this for the next six months. Anyway, specific queries are easy to produce but I find it hard to keep track of the bigger picutre. The application which sits on this runs without complaint regardless but navigating around the system becoming extraordinarily confusing. So my question is: Can anyone recommend a tool (or technique) for generating some kind of "broken tree" diagram in this sort of circumstances? I don't want something that will fix things for me, or attempt statistical analysis but at least something that will give a visual indication of how broken it is at any one time. Note : At the moment this is in a SQL Server database but I'm open to ideas utilising C#, Perl or Python.

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• Generating easy-to-remember random identifiers

  - by Carl Seleborg

  Hi all, As all developers do, we constantly deal with some kind of identifiers as part of our daily work. Most of the time, it's about bugs or support tickets. Our software, upon detecting a bug, creates a package that has a name formatted from a timestamp and a version number, which is a cheap way of creating reasonably unique identifiers to avoid mixing packages up. Example: "Bug Report 20101214 174856 6.4b2". My brain just isn't that good at remembering numbers. What I would love to have is a simple way of generating alpha-numeric identifiers that are easy to remember. Examples would be "azil3", "ulmops", "fel2way", etc. I just made these up, but they are much easier to recognize when you see many of them at once. I know of algorithms that perform trigram analysis on text (say you feed them a whole book in German) and that can generate strings that look and feel like German words. This requires lots of data, though, and makes it slightly less suitable for embedding in an application just for this purpose. Do you know of anything else? Thanks! Carl

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• Prevent Rails link_to_remote multiple submits w Javascript

  - by Chris

  In a Rails project I need to keep a link_to_remote from getting double-clicked. It looks like :before and :after are my only choices - they get prepended/appended to the onclick Ajax call, respectively. But if I try something like: :before => "self.stopObserving()" t,he Ajax is never run. If I try it for :after the Ajax is run but the link never stops observing. The solutions I've seen rely on creating a variable and blocking the whole form, but there are multiple link_to_remote rows on this page and it is valid to click more than one of them at a time - just not the same one twice. One variable per row declared outside of link_to_remote seems very kludgey... Instead of using Prototype I originally tried plain Javascript first for this proof of concept - but it fails too: <a href="#" onclick="self.onclick = function(){alert('foo');};"click</a just puts up an alert when clicked - the lambda here does nothing? This next one is more like the desired goal and should only alert the first time. But instead it alerts every time: <a href="#" onclick="alert('bar'); self.onclick = function(){return false;};"click</a All ideas appreciated!

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• Is ADO.NET Entity framework database schema update possible ?

  - by fyasar

  Hi All I'm working on proof of concept application like crm and i need your some advice. My application's data layer completely dynamic and run onto EF 3.5. When the user update the entity, change relation or add new column to the database, first i'm planning make for these with custom classes. After I rebuild my database model layer with new changes during the application runtime. And my model layer tie with tightly coupled to my project for easy reflecting model layer changes (It connected to my project via interfaces and loading onto to application domain in the runtime). I need to create dynamic entities, create entity relations and modify them during the runtime after that i need to create change database script for updating database schema. I know ADO.NET team says "we will be able to provide this property in EF 4.0", but i don't need to wait for them. How can i update database changes during the runtime via EF 3.5 ? For example, i need to create new entity or need to change some entity schema, add new properties or change property types after than how can apply these changes on the physical database schema ? Any ideas ?

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• 'Forward-Compatible' Program Design

  - by Jeffrey Kern

  The majority of my questions I've asked here so far on StackOverflow have been how to implement individual concepts and techniques towards developing a software-based NES clone via the XNA environment. The small samples that I've thrown together on my PC work relatively great and everything. Except I hit a brick wall. How do I merge all of these samples together. Having proof-of-concept is amazing, except when you need it to go beyond just that. I now have samples strewn about that I'm trying to merge, some of them incomplete. And now I'm stuck with the chicken-and-the-egg situation of where I would like to incorporate these samples together, to make sure they work, but I cannot without test data. And I don't have tools to create test data, because they'd need to be based off of the individual pieces that need to be put together. In my mind, I'm having nightmares with circular reference. For my sample data, I am hoping to save it in XML and write a specification - and then make sample data by hand - but I'm too paranoid of manually creating an XML file full of incorrect data and blaming it on my code, or vice-versa. It doesn't help that the end-result of my work is graphic-oriented, which makes it interseting how a graphic on the screen can be visualized in XML Nodes. I guess, my question is this: What design patterns and disciplines exist in the coding world that address this type of concern? I've always relied on brute-force coding and restarting a project with a whole new code base in attempts to further along my goals, but I doubt that would be the best way to do so. Within my college career, the majority of my programming was to work on simple projects that came out of a book, or with a given correct data set and a verifyable result. I don't have that, as my own design documents that I am going by could be terribly wrong.

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• How to reuse results with a schema for end of day stock-data

  - by Vishalrix

  I am creating a database schema to be used for technical analysis like top-volume gainers, top-price gainers etc.I have checked answers to questions here, like the design question. Having taken the hint from boe100 's answer there I have a schema modeled pretty much on it, thusly: Symbol - char 6 //primary Date - date //primary Open - decimal 18, 4 High - decimal 18, 4 Low - decimal 18, 4 Close - decimal 18, 4 Volume - int Right now this table containing End Of Day( EOD) data will be about 3 million rows for 3 years. Later when I get/need more data it could be 20 million rows. The front end will be asking requests like "give me the top price gainers on date X over Y days". That request is one of the simpler ones, and as such is not too costly, time wise, I assume. But a request like " give me top volume gainers for the last 10 days, with the previous 100 days acting as baseline", could prove 10-100 times costlier. The result of such a request would be a float which signifies how many times the volume as grown etc. One option I have is adding a column for each such result. And if the user asks for volume gain in 10 days over 20 days, that would require another table. The total such tables could easily cross 100, specially if I start using other results as tables, like MACD-10, MACD-100. each of which will require its own column. Is this a feasible solution? Another option being that I keep the result in cached html files and present them to the user. I dont have much experience in web-development, so to me it looks messy; but I could be wrong ( ofc!) . Is that a option too? Let me add that I am/will be using mod_perl to present the response to the user. With much of the work on mysql database being done using perl. I would like to have a response time of 1-2 seconds.

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• Which to use, XMP or RDF?

  - by zotty

  What's the difference between RDF and XMP? From what I can tell, XMP is derived from RDF... so what does it offer that RDF doesn't? My particular situation is this: I've got some images which need tagging with details of how an experiment was performed, and what sort of data analysis has been performed on the images. A colleague of mine is pushing for XMP, but he's thinking of the images as photos - they're not really, they're just bits of data. From what I've seen (mainly by opening images in notepad++) the XMP data looks very similar to RDF - even so far as using RDF in the tag names (e.g. <rdf:Seq>). I'd like this data to be usable by other people who use similar instruments for similar experiments, so creating a mini standard (schema?) seems like the way to go. Apologies for the lack of fundemental understanding - I'm a Doctor, not a programmer! If it makes any difference, the language of choice will be C#. Edit for more information: First off, thanks for the excellent replies - thinking of XMP as a vocabulary for RDF makes things a lot clearer. The sort of data I'll be storing wont be avaliable in any of the pre-defined sets. It'll detail experimental set ups, locations and results. I think using RDF is the way to go.

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• Is ADO.NET Entity framework database schema update possible?

  - by fyasar

  I'm working on proof of concept application like crm and i need your some advice. My application's data layer completely dynamic and run onto EF 3.5. When the user update the entity, change relation or add new column to the database, first i'm planning make for these with custom classes. After I rebuild my database model layer with new changes during the application runtime. And my model layer tie with tightly coupled to my project for easy reflecting model layer changes (It connected to my project via interfaces and loading onto to application domain in the runtime). I need to create dynamic entities, create entity relations and modify them during the runtime after that i need to create change database script for updating database schema. I know ADO.NET team says "we will be able to provide this property in EF 4.0", but i don't need to wait for them. How can i update database changes during the runtime via EF 3.5 ? For example, i need to create new entity or need to change some entity schema, add new properties or change property types after than how can apply these changes on the physical database schema ? Any ideas ?

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• Diamond problem in C++

  - by Jack

  I know the diamond problem. I am using gcc compiler. I have some scenarios I need explanation about. 1) class A{ public: virtual void eat(){cout<<"A eat\n";} }; class B:public A{ public: void eat(){ cout<<"B eat\n";}}; class C:public A{ public: void eat(){ cout<<"C eat\n";}}; class D:public B,C{ public: void eat(){ cout<<"D eat\n";}}; int main() { A * a = new D(); a->eat(); getch(); return 0; } Why doesn't this work? 2) class A{ public: void eat(){cout<<"A eat\n";} }; class B:virtual public A{ public: void eat(){ cout<<"B eat\n";}}; class C:virtual public A{ public: void eat(){ cout<<"C eat\n";}}; class D: public B,C{ public: void eat(){ cout<<"D eat\n";}}; int main() { A * a = new D(); a->eat(); getch(); return 0; } When I do this what happens in the background. How does the ambiguity get removed. Is the concept of vtables involved here?

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• Webcrawler, feedback?

  - by Jan Kuboschek

  Hey folks, every once in a while I have the need to automate data collection tasks from websites. Sometimes I need a bunch of URLs from a directory, sometimes I need an XML sitemap (yes, I know there is lots of software for that and online services). Anyways, as follow up to my previous question I've written a little webcrawler that can visit websites. Basic crawler class to easily and quickly interact with one website. Override "doAction(String URL, String content)" to process the content further (e.g. store it, parse it). Concept allows for multi-threading of crawlers. All class instances share processed and queued lists of links. Instead of keeping track of processed links and queued links within the object, a JDBC connection could be established to store links in a database. Currently limited to one website at a time, however, could be expanded upon by adding an externalLinks stack and adding to it as appropriate. JCrawler is intended to be used to quickly generate XML sitemaps or parse websites for your desired information. It's lightweight. Is this a good/decent way to write the crawler, provided the limitations above? http://pastebin.com/VtgC4qVE - Main.java http://pastebin.com/gF4sLHEW - JCrawler.java http://pastebin.com/VJ1grArt - HTMLUtils.java Thanks for your feedback in advance! :)

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• How do I get started designing and implementing a script interface for my .NET application?

  - by Peter Mortensen

  How do I get started designing and implementing a script interface for my .NET application? There is VSTA (the .NET equivalent of VBA for COM), but as far as I understand I would have to pay a license fee for every installation of my application. It is an open source application so this will not work. There is also e.g. the embedding of interpreters (IronPython?), but I don't understand how this would allow exposing an "object model" (see below) to external (or internal) scripts. What is the scripting interface story in .NET? Is it somehow trivial in .NET to do this? Background: I have once designed and implemented a fairly involved script interface for a Macintosh application for acquisition and analysis of data from a mass spectrometer (Mac OS, System 7) and later a COM interface for a Windows application. Both were designed with an "object model" and classes (that can have properties). These are overloaded words, but in a scripting interface context object model is essentially a containment hiarchy of objects of specific classes. Classes have properties and lists of contained objects. E.g. like in the COM interfaces exposed in Microsoft Office applications, where the application object can be used to add to its list of documents (with the side effect of creating the GUI representation of a document). External scripts can create new objects in a container and navigate through the content of the hiarchy at any given time. In the Macintosh case scripts could be written in e.g. AppleScript or Frontier. On the Macintosh the implementation of a scripting interface was very complicated. Support for it in Metroworks' C++ class library (the name escapes me right now) made it much simpler.

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• What is the the relation between programming and mathematics?

  - by Math Grad

  Programmers seem to think that their work is quite mathematical. I understand this when you try to optimize something in performance, find the most efficient alogithm, etc.. But it patently seems false when you look at a billing application for a shop, or a systems software riddled with I/O calls. So what is it exactly? Is computation and associated programming really mathematical? Here I have in mind particularly the words of the philosopher Schopenhauer in mind: That arithmetic is the basest of all mental activities is proved by the fact that it is the only one that can be accomplished by means of a machine. Take, for instance, the reckoning machines that are so commonly used in England at the present time, and solely for the sake of convenience. But all analysis finitorum et infinitorum is fundamentally based on calculation. Therefore we may gauge the “profound sense of the mathematician,” of whom Lichtenberg has made fun, in that he says: “These so-called professors of mathematics have taken advantage of the ingenuousness of other people, have attained the credit of possessing profound sense, which strongly resembles the theologians’ profound sense of their own holiness.” I lifted the above quote from here. It seems that programmers are doing precisely the sort of mechanized base mental activity the grand old man is contemptuous about. So what exactly is the deal? Is programming really the "good" kind of mathematics, or just the baser type, or altogether something else just meant for business not to be confused with a pure discipline?

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• Hadoop/MapReduce: Reading and writing classes generated from DDL

  - by Dave

  Hi, Can someone walk me though the basic work-flow of reading and writing data with classes generated from DDL? I have defined some struct-like records using DDL. For example: class Customer { ustring FirstName; ustring LastName; ustring CardNo; long LastPurchase; } I've compiled this to get a Customer class and included it into my project. I can easily see how to use this as input and output for mappers and reducers (the generated class implements Writable), but not how to read and write it to file. The JavaDoc for the org.apache.hadoop.record package talks about serializing these records in Binary, CSV or XML format. How do I actually do that? Say my reducer produces IntWritable keys and Customer values. What OutputFormat do I use to write the result in CSV format? What InputFormat would I use to read the resulting files in later, if I wanted to perform analysis over them?

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• Text message intent - catch and send

  - by Espen

  Hi! I want to be able to control incoming text messages. My application is still on a "proof of concept" version and I'm trying to learn Android programming as I go. First my application need to catch incomming text messages. And if the message is from a known number then deal with it. If not, then send the message as nothing has happened to the default text message application. I have no doubt it can be done, but I still have some concern and I see some pitfalls at how things are done on Android. So getting the incomming text message could be fairly easy - except when there are other messaging applications installed and maybe the user wants to have normal text messages to pop up on one of them - and it will, after my application has had a look at it first. How to be sure my application get first pick of incomming text messages? And after that I need to send most text messages through to any other text message application the user has chosen so the user can actually read the message my application didn't need. Since Android uses intents that are relative at best, I don't see how I can enforce my application to get a peek at all incomming text messages, and then stop it or send it through to the default text messaging application...

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• How can I superimpose modified loess lines on a ggplot2 qplot?

  - by briandk

  Background Right now, I'm creating a multiple-predictor linear model and generating diagnostic plots to assess regression assumptions. (It's for a multiple regression analysis stats class that I'm loving at the moment :-) My textbook (Cohen, Cohen, West, and Aiken 2003) recommends plotting each predictor against the residuals to make sure that: The residuals don't systematically covary with the predictor The residuals are homoscedastic with respect to each predictor in the model On point (2), my textbook has this to say: Some statistical packages allow the analyst to plot lowess fit lines at the mean of the residuals (0-line), 1 standard deviation above the mean, and 1 standard deviation below the mean of the residuals....In the present case {their example}, the two lines {mean + 1sd and mean - 1sd} remain roughly parallel to the lowess {0} line, consistent with the interpretation that the variance of the residuals does not change as a function of X. (p. 131) How can I modify loess lines? I know how to generate a scatterplot with a "0-line,": # First, I'll make a simple linear model and get its diagnostic stats library(ggplot2) data(cars) mod <- fortify(lm(speed ~ dist, data = cars)) attach(mod) str(mod) # Now I want to make sure the residuals are homoscedastic qplot (x = dist, y = .resid, data = mod) + geom_smooth(se = FALSE) # "se = FALSE" Removes the standard error bands But does anyone know how I can use ggplot2 and qplot to generate plots where the 0-line, "mean + 1sd" AND "mean - 1sd" lines would be superimposed? Is that a weird/complex question to be asking?

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• JMF microphone volume controller

  - by TacB0sS

  How to obtain the Microphone volume controller in JMF? this is what I have: I tried this implementation concept of yours, but I keep getting a null from the first volume processor when I try to get the stream, here is how I do it: // the device is the media device specifically audio Processor processorForVolume = Manager.createProcessor(device.getLocator()); // wait until configured ProcessorStates newState = new ProcessorStateListener(Processor.Configured).waitForProcessorState(processorForVolume); System.out.println("volumeProcessorState: "+newState); // setting the content descriptor to null - read in another thread this allows to get the gain control processorForVolume.setContentDescriptor(null); // set the track control format to one supported by the device and the track control. // I didn't match it to an RTP allowed format, but I don't think this has anything to do with it... TrackControl[] trackControls = processorForVolume.getTrackControls(); if (trackControls.length == 0) throw new MC_Exception("No track controls where found for this device:", new Object[]{device}); for (TrackControl control : trackControls) trackManipulator.manipulateTrackControls(control); // wait until the processor is realized newState = new ProcessorStateListener(Controller.Realized).waitForProcessorState(processorForVolume); System.out.println("volumeProcessorState: "+newState); // receives the gain control micVolumeController = processorForVolume.getGainControl(); // cannot get the output stream to process further... any suggestions? processor = Manager.createProcessor(processorForVolume.getDataOutput()); new ProcessorStateListener(Processor.Configured).waitForProcessorState(processor); processor.setContentDescriptor(DeviceCapturingManager.RAW_RTP); new ProcessorStateListener(Controller.Realized).waitForProcessorState(processor); this is the output It generates: volumeProcessorState: Configured format set to track control - com.sun.media.ProcessEngine$ProcTControl@1627c16: LINEAR, 48000.0 Hz, 16-bit, Stereo, LittleEndian, Signed volumeProcessorState: Realized and the data output from the processor is Null. I should make clear that when the content descriptor != null I do get an output stream but not the volume controller, and the when it is null I get the controller, but no stream. I try to connect to an audio microphone device Adam.

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