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• eBooks on iPad vs. Kindle: More Debate than Smackdown

  - by andrewbrust

  When the iPad was presented at its San Francisco launch event on January 28th, Steve Jobs spent a significant amount of time explaining how well the device would serve as an eBook reader. He showed the iBooks reader application and iBookstore and laid down the gauntlet before Amazon and its beloved Kindle device. Almost immediately afterwards, criticism came rushing forth that the iPad could never beat the Kindle for book reading. The curious part of that criticism is that virtually no one offering it had actually used the iPad yet. A few weeks later, on April 3rd, the iPad was released for sale in the United States. I bought one on that day and in the few additional weeks that have elapsed, I’ve given quite a workout to most of its capabilities, including its eBook features. I’ve also spent some time with the Kindle, albeit a first-generation model, to see how it actually compares to the iPad. I had some expectations going in, but I came away with conclusions about each device that were more scenario-based than absolute. I present my findings to you here.   Vital Statistics Let’s start with an inventory of each device’s underlying technology. The iPad has a color, backlit LCD screen and an on-screen keyboard. It has a battery which, on a full charge, lasts anywhere from 6-10 hours. The Kindle offers a monochrome, reflective E Ink display, a physical keyboard and a battery that on my first gen loaner unit can go up to a week between charges (Amazon claims the battery on the Kindle 2 can last up to 2 weeks on a single charge). The Kindle connects to Amazon’s Kindle Store using a 3G modem (the technology and network vary depending on the model) that incurs no airtime service charges whatsoever. The iPad units that are on-sale today work over WiFi only. 3G-equipped models will be on sale shortly and will command a $130 premium over their WiFi-only counterparts. 3G service on the iPad, in the U.S. from AT&T, will be fee-based, with a 250MB plan at $14.99 per month and an unlimited plan at $29.99. No contract is required for 3G service. All these tech specs aside, I think a more useful observation is that the iPad is a multi-purpose Internet-connected entertainment device, while the Kindle is a dedicated reading device. The question is whether those differences in design and intended use create a clear-cut winner for reading electronic publications. Let’s take a look at each device, in isolation, now.   Kindle To me, what’s most innovative about the Kindle is its E Ink display. E Ink really looks like ink on a sheet of paper. It requires no backlight, it’s fully visible in direct sunlight and it causes almost none of the eyestrain that LCD-based computer display technology (like that used on the iPad) does. It’s really versatile in an all-around way. Forgive me if this sounds precious, but reading on it is really a joy. In fact, it’s a genuinely relaxing experience. Through the Kindle Store, Amazon allows users to download books (including audio books), magazines, newspapers and blog feeds. Books and magazines can be purchased either on a single-issue basis or as an annual subscription. Books, of course, are purchased singly. Oddly, blogs are not free, but instead carry a monthly subscription fee, typically $1.99. To me this is ludicrous, but I suppose the free 3G service is partially to blame. Books and magazine issues download quickly. Magazine and blog subscriptions cause new issues or posts to be pushed to your device on an automated basis. Available blogs include 9000-odd feeds that Amazon offers on the Kindle Store; unless I missed something, arbitrary RSS feeds are not supported (though there are third party workarounds to this limitation). The shopping experience is integrated well, has an huge selection, and offers certain graphical perks. For example, magazine and newspaper logos are displayed in menus, and book cover thumbnails appear as well. A simple search mechanism is provided and text entry through the physical keyboard is relatively painless. It’s very easy and straightforward to enter the store, find something you like and start reading it quickly. If you know what you’re looking for, it’s even faster. Given Kindle’s high portability, very reliable battery, instant-on capability and highly integrated content acquisition, it makes reading on whim, and in random spurts of downtime, very attractive. The Kindle’s home screen lists all of your publications, and easily lets you select one, then start reading it. Once opened, publications display in crisp, attractive text that is adjustable in size. “Turning” pages is achieved through buttons dedicated to the task. Notes can be recorded, bookmarks can be saved and pages can be saved as clippings. I am not an avid book reader, and yet I found the Kindle made it really fun, convenient and soothing to read. There’s something about the easy access to the material and the simplicity of the display that makes the Kindle seduce you into chilling out and reading page after page. On the other hand, the Kindle has an awkward navigation interface. While menus are displayed clearly on the screen, the method of selecting menu items is tricky: alongside the right-hand edge of the main display is a thin column that acts as a second display. It has a white background, and a scrollable silver cursor that is moved up or down through the use of the device’s scrollwheel. Picking a menu item on the main display involves scrolling the silver cursor to a position parallel to that menu item and pushing the scrollwheel in. This navigation technique creates a disconnect, literally. You don’t really click on a selection so much as you gesture toward it. I got used to this technique quickly, but I didn’t love it. It definitely created a kind of anxiety in me, making me feel the need to speed through menus and get to my destination document quickly. Once there, I could calm down and relax. Books are great on the Kindle. Magazines and newspapers much less so. I found the rendering of photographs, and even illustrations, to be unacceptably crude. For this reason, I expect that reading textbooks on the Kindle may leave students wanting. I found that the original flow and layout of any publication was sacrificed on the Kindle. In effect, browsing a magazine or newspaper was almost impossible. Reading the text of individual articles was enjoyable, but having to read this way made the whole experience much more “a la carte” than cohesive and thematic between articles. I imagine that for academic journals this is ideal, but for consumer publications it imposes a stripped-down, low-fidelity experience that evokes a sense of deprivation. In general, the Kindle is great for reading text. For just about anything else, especially activity that involves exploratory browsing, meandering and short-attention-span reading, it presents a real barrier to entry and adoption. Avid book readers will enjoy the Kindle (if they’re not already). It’s a great device for losing oneself in a book over long sittings. Multitaskers who are more interested in periodicals, be they online or off, will like it much less, as they will find compromise, and even sacrifice, to be palpable.   iPad The iPad is a very different device from the Kindle. While the Kindle is oriented to pages of text, the iPad orbits around applications and their interfaces. Be it the pinch and zoom experience in the browser, the rich media features that augment content on news and weather sites, or the ability to interact with social networking services like Twitter, the iPad is versatile. While it shares a slate-like form factor with the Kindle, it’s effectively an elegant personal computer. One of its many features is the iBook application and integration of the iBookstore. But it’s a multi-purpose device. That turns out to be good and bad, depending on what you’re reading. The iBookstore is great for browsing. It’s color, rich animation-laden user interface make it possible to shop for books, rather than merely search and acquire them. Unfortunately, its selection is rather sparse at the moment. If you’re looking for a New York Times bestseller, or other popular titles, you should be OK. If you want to read something more specialized, it’s much harder. Unlike the awkward navigation interface of the Kindle, the iPad offers a nearly flawless touch-screen interface that seduces the user into tinkering and kibitzing every bit as much as the Kindle lulls you into a deep, concentrated read. It’s a dynamic and interactive device, whereas the Kindle is static and passive. The iBook reader is slick and fun. Use the iPad in landscape mode and you can read the book in 2-up (left/right 2-page) display; use it in portrait mode and you can read one page at a time. Rather than clicking a hardware button to turn pages, you simply drag and wipe from right-to-left to flip the single or right-hand page. The page actually travels through an animated path as it would in a physical book. The intuitiveness of the interface is uncanny. The reader also accommodates saving of bookmarks, searching of the text, and the ability to highlight a word and look it up in a dictionary. Pages display brightly and clearly. They’re easy to read. But the backlight and the glare made me less comfortable than I was with the Kindle. The knowledge that completely different applications (including the Web and email and Twitter) were just a few taps away made me antsy and very tempted to task-switch. The knowledge that battery life is an issue created subtle discomfort. If the Kindle makes you feel like you’re in a library reading room, then the iPad makes you feel, at best, like you’re under fluorescent lights at a Barnes and Noble or Borders store. If you’re lucky, you’d be on a couch or at a reading table in the store, but you might also be standing up, in the aisles. Clearly, I didn’t find this conducive to focused and sustained reading. But that may have more to do with my own tendency to read periodicals far more than books, and my neurotic . And, truth be known, the book reading experience, when not explicitly compared to Kindle’s, was still pleasant. It is also important to point out that Kindle Store-sourced books can be read on the iPad through a Kindle reader application, from Amazon, specific to the device. This offered a less rich experience than the iBooks reader, but it was completely adequate. Despite the Kindle brand of the reader, however, it offered little in terms of simulating the reading experience on its namesake device. When it comes to periodicals, the iPad wins hands down. Magazines, even if merely scanned images of their print editions, read on the iPad in a way that felt similar to reading hard copy. The full color display, touch navigation and even the ability to render advertisements in their full glory makes the iPad a great way to read through any piece of work that is measured in pages, rather than chapters. There are many ways to get magazines and newspapers onto the iPad, including the Zinio reader, and publication-specific applications like the Wall Street Journal’s and Popular Science’s. The New York Times’ free Editors’ Choice application offers a Times Reader-like interface to a subset of the Gray Lady’s daily content. The completely Web-based but iPad-optimized Times Skimmer site (at www.nytimes.com/timesskimmer) works well too. Even conventional Web sites themselves can be read much like magazines, given the iPad’s ability to zoom in on the text and crop out advertisements on the margins. While the Kindle does have an experimental Web browser, it reminded me a lot of early mobile phone browsers, only in a larger size. For text-heavy sites with simple layout, it works fine. For just about anything else, it becomes more trouble than it’s worth. And given the way magazine articles make me think of things I want to look up online, I think that’s a real liability for the Kindle.   Summing Up What I came to realize is that the Kindle isn’t so much a computer or even an Internet device as it is a printer. While it doesn’t use physical paper, it still renders its content a page at a time, just like a laser printer does, and its output appears strikingly similar. You can read the rendered text, but you can’t interact with it in any way. That’s why the navigation requires a separate cursor display area. And because of the page-oriented rendering behavior, turning pages causes a flash on the display and requires a sometimes long pause before the next page is rendered. The good side of this is that once the page is generated, no battery power is required to display it. That makes for great battery life, optimal viewing under most lighting conditions (as long as there is some light) and low-eyestrain text-centric display of content. The Kindle is highly portable, has an excellent selection in its store and is refreshingly distraction-free. All of this is ideal for reading books. And iPad doesn’t offer any of it. What iPad does offer is versatility, variety, richness and luxury. It’s flush with accoutrements even if it’s low on focused, sustained text display. That makes it inferior to the Kindle for book reading. But that also makes it better than the Kindle for almost everything else. As such, and given that its book reading experience is still decent (even if not superior), I think the iPad will give Kindle a run for its money. True book lovers, and people on a budget, will want the Kindle. People with a robust amount of discretionary income may want both devices. Everyone else who is interested in a slate form factor e-reading device, especially if they also wish to have leisure-friendly Internet access, will likely choose the iPad exclusively. One thing is for sure: iPad has reduced Kindle’s market, and may have shifted its mass market potential to a mere niche play. If Amazon is smart, it will improve its iPad-based Kindle reader app significantly. It can then leverage the iPad channel as a significant market for the Kindle Store. After all, selling the eBooks themselves is what Amazon should care most about.

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• Asynchronous Streaming in ASP.NET WebApi

  - by andresv

   Hi everyone, if you use the cool MVC4 WebApi you might encounter yourself in a common situation where you need to return a rather large amount of data (most probably from a database) and you want to accomplish two things: Use streaming so the client fetch the data as needed, and that directly correlates to more fetching in the server side (from our database, for example) without consuming large amounts of memory. Leverage the new MVC4 WebApi and .NET 4.5 async/await asynchronous execution model to free ASP.NET Threadpool threads (if possible).  So, #1 and #2 are not directly related to each other and we could implement our code fulfilling one or the other, or both. The main point about #1 is that we want our method to immediately return to the caller a stream, and that client side stream be represented by a server side stream that gets written (and its related database fetch) only when needed. In this case we would need some form of "state machine" that keeps running in the server and "knows" what is the next thing to fetch into the output stream when the client ask for more content. This technique is generally called a "continuation" and is nothing new in .NET, in fact using an IEnumerable<> interface and the "yield return" keyword does exactly that, so our first impulse might be to write our WebApi method more or less like this:           public IEnumerable<Metadata> Get([FromUri] int accountId)         {             // Execute the command and get a reader             using (var reader = GetMetadataListReader(accountId))             {                 // Read rows asynchronously, put data into buffer and write asynchronously                 while (reader.Read())                 {                     yield return MapRecord(reader);                 }             }         }   While the above method works, unfortunately it doesn't accomplish our objective of returning immediately to the caller, and that's because the MVC WebApi infrastructure doesn't yet recognize our intentions and when it finds an IEnumerable return value, enumerates it before returning to the client its values. To prove my point, I can code a test method that calls this method, for example:        [TestMethod]         public void StreamedDownload()         {             var baseUrl = @"http://localhost:57771/api/metadata/1";             var client = new HttpClient();             var sw = Stopwatch.StartNew();             var stream = client.GetStreamAsync(baseUrl).Result;             sw.Stop();             Debug.WriteLine("Elapsed time Call: {0}ms", sw.ElapsedMilliseconds); } So, I would expect the line "var stream = client.GetStreamAsync(baseUrl).Result" returns immediately without server-side fetching of all data in the database reader, and this didn't happened. To make the behavior more evident, you could insert a wait time (like Thread.Sleep(1000);) inside the "while" loop, and you will see that the client call (GetStreamAsync) is not going to return control after n seconds (being n == number of reader records being fetched).Ok, we know this doesn't work, and the question would be: is there a way to do it?Fortunately, YES!  and is not very difficult although a little more convoluted than our simple IEnumerable return value. Maybe in the future this scenario will be automatically detected and supported in MVC/WebApi.The solution to our needs is to use a very handy class named PushStreamContent and then our method signature needs to change to accommodate this, returning an HttpResponseMessage instead of our previously used IEnumerable<>. The final code will be something like this: public HttpResponseMessage Get([FromUri] int accountId)         {             HttpResponseMessage response = Request.CreateResponse();             // Create push content with a delegate that will get called when it is time to write out              // the response.             response.Content = new PushStreamContent(                 async (outputStream, httpContent, transportContext) =>                 {                     try                     {                         // Execute the command and get a reader                         using (var reader = GetMetadataListReader(accountId))                         {                             // Read rows asynchronously, put data into buffer and write asynchronously                             while (await reader.ReadAsync())                             {                                 var rec = MapRecord(reader);                                 var str = await JsonConvert.SerializeObjectAsync(rec);                                 var buffer = UTF8Encoding.UTF8.GetBytes(str);                                 // Write out data to output stream                                 await outputStream.WriteAsync(buffer, 0, buffer.Length);                             }                         }                     }                     catch(HttpException ex)                     {                         if (ex.ErrorCode == -2147023667) // The remote host closed the connection.                          {                             return;                         }                     }                     finally                     {                         // Close output stream as we are done                         outputStream.Close();                     }                 });             return response;         } As an extra bonus, all involved classes used already support async/await asynchronous execution model, so taking advantage of that was very easy. Please note that the PushStreamContent class receives in its constructor a lambda (specifically an Action) and we decorated our anonymous method with the async keyword (not a very well known technique but quite handy) so we can await over the I/O intensive calls we execute like reading from the database reader, serializing our entity and finally writing to the output stream.  Well, if we execute the test again we will immediately notice that the a line returns immediately and then the rest of the server code is executed only when the client reads through the obtained stream, therefore we get low memory usage and far greater scalability for our beloved application serving big chunks of data.Enjoy!Andrés.        

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• How to Convert News Feeds to Ebooks with Calibre

  - by Jason Fitzpatrick

  Setting up your ebook reader to receive bundles of articles from web sites that interest you is a great way to add functionality and great content. Read on as we show you how to turn the RSS feeds from your favorite sites into ebooks. If you’re a fan of the easy-on-the-eyes digital reading experience provided by your ebook reader, it only seems natural to set up your ebook reader to receive feeds from your favorite news sources so you can enjoy even more content. In this tutorial we’ll be walking you through a simple way to shuttle hand picked content to your ebook reader. HTG Explains: Why Linux Doesn’t Need Defragmenting How to Convert News Feeds to Ebooks with Calibre How To Customize Your Wallpaper with Google Image Searches, RSS Feeds, and More

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• Why won't my Western Digital My Book Home 500GB drive mount on my Macbook Pro via Firewire?

  - by Ryan O

  I can connect the drive via USB and it mounts correctly. However, when I connect via FireWire, the drive powers down. The drive realizes that it is plugged in. When I plug in via FireWire, the lights on the front of the drive flash the same as when it it mounting via USB, but then the drive powers down. I've upgraded the firmware on the drive, but it still won't mount via FireWire.

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• Going by the eBook

  - by Tony Davis

  The book and magazine publishing world is rapidly going digital, and the industry is faced with making drastic changes to their ways of doing business. The sudden take-up of digital readers by the book-buying public has surprised even the most technological-savvy of the industry. Printed books just aren't selling like they did. In contrast, eBooks are doing well. The ePub file format is the standard around which all publishers are converging. ePub is a standard for formatting book content, so that it can be reflowed for various devices, with their widely differing screen-sizes, and can be read offline. If you unzip an ePub file, you'll find familiar formats such as XML, XHTML and CSS. This is both a blessing and a curse. Whilst it is good to be able to use familiar technologies that have been developed to a level of considerable sophistication, it doesn't get us all the way to producing a viable publication. XHTML is a page-description language, not a book-description language, as we soon found out during our initial experiments, when trying to specify headers, footers, indexes and chaptering. As a result, it is difficult to predict how any particular eBook application will decide to render a book. There isn't even a consensus as to how the cover image is specified. All of this is awkward for the publisher. Each book must be created and revised in a form from which can be generated a whole range of 'printed media', from print books, to Mobi for kindles, ePub for most Tablets and SmartPhones, HTML for excerpted chapters on websites, and a plethora of other formats for other eBook readers, each with its own idiosyncrasies. In theory, if we can get our content into a clean, semantic XML form, such as DOCBOOKS, we can, from there, after every revision, perform a series of relatively simple XSLT transformations to output anything from a HTML article, to an ePub file for reading on an iPad, to an ICML file (an XML-based file format supported by the InDesign tool), ready for print publication. As always, however, the task looks bigger the closer you get to the detail. On the way to the utopian world of an XML-based book format that encompasses all the diverse requirements of the different publication media, ePub looks like a reasonable format to adopt. Its forthcoming support for HTML 5 and CSS 3, with ePub 3.0, means that features, such as widow-and-orphan controls, multi-column flow and multi-media graphics can be incorporated into eBooks. This starts to make it possible to build an "app-like" experience into the eBook and to free publishers to think of putting context before container; to think of what content is required, be it graphical, textual or audio, from the point of view of the user, rather than what's possible in a given, traditional book "Container". In the meantime, there is a gap between what publishers require and what current technology can provide and, of course building this app-like experience is far from plain sailing. Real portability between devices is still a big challenge, and achieving the sort of wizardry seen in the likes of Theodore Grey's "Elements" eBook will require some serious device-specific programming skills. Cheers, Tony.

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• Decorator Pattern (A Layman to Laymen)

  This article takes a scenario based approach to make the reader understand Decorator pattern

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• Strategy pattern primer (A layman to laymen)

  This article takes a scenario based approach to make reader understand this pattern

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• How to setup exchange server mail and address book accounts on mac - Snow Lepord?

  - by Abhishek

  I just got myself a mac, and I've been a long time windows user. So I'm exploring the built in apps, and I wanna setup my 3 mail accounts (1x gmail, 1x hotmail, and 1x corporate using google apps), but I want them to work the way they work on my iphone and my ipad - Using exchange... It really makes life easy to be able to receive and respond to mail instantly, not to mention the contact and calendar syncing... Any ideas? I have found the 'Exchange 2007' and 'Exchange IMAP' options when setting up the account, but things like the server address and all?

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• Decorator Pattern (A Layman to Laymen)

  This article takes a scenario based approach to make the reader understand Decorator pattern

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• What's a good web-based application for storing your book collection?

  - by JJarava

  Hi all! I'm looking for a (better if web-based; i.e., something I can install in my home server on my LAN) software to keep track of my books/DVDs/etc. I already know of Readerware offerings, which I find quite interesting, but I'd like something that is Web-based, so I can run it on my MacMini on the living room, and access it from any of the comuputers in the house. I've been googling around, and I've been quite surprised to NOT find any clear option. Alternatively, good "native" software for Windows/MacOSX will be more than welcome. Thanks a lot PS: Given the # of interesting suggestions for Web 2.0, ASP-Hosted type sites, I've clarified the question a bit: I'd prefer some software that I can install and use in my systems, not something "in the cloud" (although I'll check the suggestions out!)

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• Which version of Grady Booch's OOA/D book should I buy?

  - by jackj

  Grady Booch's "Object-Oriented Analysis and Design with Applications" is available brand new in both the 2nd edition (1993) and the 3rd edition (2007), while many used copies of both editions are available. Here are my concerns: 1) The 2nd edition uses C++: given that I just finished reading my first two C++ books (Accelerated C++ and C++ Primer) I guess practical tips can only help, so the 2nd edition is probably best (I think the 3rd edition has absolutely no code). On the other hand, the C++ books I read insist on the importance of using standard C++, whereas Booch's 2nd edition was published before the 1998 standard. 2) The 2nd edition is shorter (608 pages vs. 720) so, I guess, it will be slightly easier to get through. 3) The 3rd edition uses UML 2.0, whereas the 2nd edition is pre-UML. Some reviews say that the notation in the 2nd edition is close enough to UML, so it doesn't matter, but I don't know if I should be worrying about this or not. 4) The 2nd edition is available in good-shape used copies for considerably less than what the 3rd one goes for. Given all the above factors, do you think I should buy the 2nd or the 3rd edition? Recommendations on other books are also welcome but I would prefer it if whoever answers has read at least one of the versions of Booch's book (preferably both!). I have already bought but not read GoF and Riel's books. I also know that I should practice a lot with real-life code. Thanks.

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• What would you write in a consitution (law book) for a programmers' country?

  - by Developer Art

  After we have got our great place to talk about professional matters and sozialize online - on SO, I believe the next logical step would be to found our own country! I invite you all to participate and bring together your available resources. We will buy an island, better even a group of island so that we could establish states like .NET territories, Java land, Linux republic etc. We will build a society of programmers (girls - we need you too). To the organizational side, we're going to need some constitution or a law book. I suggest we write it together. I make it a wiki as it should be a cooperative effort. I'll open the work. Section 1. Programmers' rights. Every citizen has a right to an Internet connection 24/7. Every citizen can freely choose the field of interest Section 2. Programmers' obligations. Every citizen must embrace the changing nature of the profession and constanly educate himself Section 3. Law enforcement. Code duplication when can be avoided is punished by limiting the bandwith speed to 64Kbit for a period of one week. Using ugly hacks instead of refactoring code is punished by cutting the Internet connection for a period of one month. Usage of technologies older than 5/10 years is punished by restricting the web access to the sites last updated 5/10 years ago for a period of one month. Please feel free to modify and extend the list. We'll need to have it ready before we proceed formally with the country foundation. A purchase fund will be established shortly. Everyone is invited to participate.

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• ISBNs are used as primary key, now I want to add non-book things to the DB - should I migrate to EAN

  - by fish2000

  I built an inventory database where ISBN numbers are the primary keys for the items. This worked great for a while as the items were books. Now I want to add non-books. some of the non-books have EANs or ISSNs, some do not. It's in PostgreSQL with django apps for the frontend and JSON api, plus a few supporting python command-line tools for management. the items in question are mostly books and artist prints, some of which are self-published. What is nice about using ISBNs as primary keys is that in on top of relational integrity, you get lots of handy utilities for validating ISBNs, automatically looking up missing or additional information on the book items, etcetera, many of which I've taken advantage. some such tools are off-the-shelf (PyISBN, PyAWS etc) and some are hand-rolled -- I tried to keep all of these parts nice and decoupled, but you know how things can get. I couldn't find anything online about 'private ISBNs' or 'self-assigned ISBNs' but that's the sort of thing I was interested in doing. I doubt that's what I'll settle on, since there is already an apparent run on ISBN numbers. should I retool everything for EAN numbers, or migrate off ISBNs as primary keys in general? if anyone has any experience with working with these systems, I'd love to hear about it, your advice is most welcome.

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• What would you write in a Constitution (law book) for a programmers' country? [closed]

  - by Developer Art

  After we have got our great place to talk about professional matters and sozialize online - on SO, I believe the next logical step would be to found our own country! I invite you all to participate and bring together your available resources. We will buy an island, better even a group of islands so that we could establish states like .NET territories, Java land, Linux republic etc. We will build a society of programmers (girls - we need you too). To the organizational side, we're going to need some sort of a Constitution or a law book. I suggest we write it together. I make it a wiki as it should be a cooperative effort. I'll open the work. Section 1. Programmers' rights. Every citizen has a right to an Internet connection 24/7. Every citizen can freely choose the field of interest Section 2. Programmers' obligations. Every citizen must embrace the changing nature of the profession and constanly educate himself Section 3. Law enforcement. Code duplication when can be avoided is punished by limiting the bandwith speed to 64Kbit for a period of one week. Using ugly hacks instead of refactoring code is punished by cutting the Internet connection for a period of one month. Usage of technologies older than 5/10 years is punished by restricting the web access to the sites last updated 5/10 years ago for a period of one month. Please feel free to modify and extend the list. We'll need to have it ready before we proceed formally with the country foundation. A purchase fund will be established shortly. Everyone is invited to participate.

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• Best (Java) book for understanding 'under the bonnet' for programming?

  - by Ben

  What would you say is the best book to buy to understand exactly how programming works under the hood in order to increase performance? I've coded in assembly at university, I studied computer architecture and I obviously did high level programming, but what I really dont understand is things like: -what is happening when I perform a cast -whats the difference in performance if I declare something global as opposed to local? -How does the memory layout for an ArrayList compare with a Vector or LinkedList? -Whats the overhead with pointers? -Are locks more efficient than using synchronized? -Would creating my own array using int[] be faster than using ArrayList -Advantages/disadvantages of declaring a variable volatile I have got a copy of Java Performance Tuning but it doesnt go down very low and it contains rather obvious things like suggesting a hashmap instead of using an ArrayList as you can map the keys to memory addresses etc. I want something a bit more Computer Sciencey, linking the programming language to what happens with the assembler/hardware. The reason im asking is that I have an interview coming up for a job in High Frequency Trading and everything has to be as efficient as possible, yet I cant remember every single possible efficiency saving so i'd just like to learn the fundamentals. Thanks in advance

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• Independence Day for Software Components &ndash; Loosening Coupling by Reducing Connascence

  - by Brian Schroer

  Today is Independence Day in the USA, which got me thinking about loosely-coupled “independent” software components. I was reminded of a video I bookmarked quite a while ago of Jim Weirich’s “Grand Unified Theory of Software Design” talk at MountainWest RubyConf 2009. I finally watched that video this morning. I highly recommend it. In the video, Jim talks about software connascence. The dictionary definition of connascence (con-NAY-sense) is: 1. The common birth of two or more at the same time 2. That which is born or produced with another. 3. The act of growing together. The brief Wikipedia page about Connascent Software Components says that: Two software components are connascent if a change in one would require the other to be modified in order to maintain the overall correctness of the system. Connascence is a way to characterize and reason about certain types of complexity in software systems. The term was introduced to the software world in Meilir Page-Jones’ 1996 book “What Every Programmer Should Know About Object-Oriented Design”. The middle third of that book is the author’s proposed graphical notation for describing OO designs. UML became the standard about a year later, so a revised version of the book was published in 1999 as “Fundamentals of Object-Oriented Design in UML”. Weirich says that the third part of the book, in which Page-Jones introduces the concept of connascence “is worth the price of the entire book”. (The price of the entire book, by the way, is not much – I just bought a used copy on Amazon for $1.36, so that was a pretty low-risk investment. I’m looking forward to getting the book and learning about connascence from the original source.) Meanwhile, here’s my summary of Weirich’s summary of Page-Jones writings about connascence: The stronger the form of connascence, the more difficult and costly it is to change the elements in the relationship. Some of the connascence types, ordered from weak to strong are: Connascence of Name Connascence of name is when multiple components must agree on the name of an entity. If you change the name of a method or property, then you need to change all references to that method or property. Duh. Connascence of name is unavoidable, assuming your objects are actually used. My main takeaway about connascence of name is that it emphasizes the importance of giving things good names so you don’t need to go changing them later. Connascence of Type Connascence of type is when multiple components must agree on the type of an entity. I assume this is more of a problem for languages without compilers (especially when used in apps without tests). I know it’s an issue with evil JavaScript type coercion. Connascence of Meaning Connascence of meaning is when multiple components must agree on the meaning of particular values, e.g that “1” means normal customer and “2” means preferred customer. The solution to this is to use constants or enums instead of “magic” strings or numbers, which reduces the coupling by changing the connascence form from “meaning” to “name”. Connascence of Position Connascence of positions is when multiple components must agree on the order of values. This refers to methods with multiple parameters, e.g.: eMailer.Send("[email protected]", "[email protected]", "Your order is complete", "Order completion notification"); The more parameters there are, the stronger the connascence of position is between the component and its callers. In the example above, it’s not immediately clear when reading the code which email addresses are sender and receiver, and which of the final two strings are subject vs. body. Connascence of position could be improved to connascence of type by replacing the parameter list with a struct or class. This “introduce parameter object” refactoring might be overkill for a method with 2 parameters, but would definitely be an improvement for a method with 10 parameters. This points out two “rules” of connascence:  The Rule of Degree: The acceptability of connascence is related to the degree of its occurrence. The Rule of Locality: Stronger forms of connascence are more acceptable if the elements involved are closely related. For example, positional arguments in private methods are less problematic than in public methods. Connascence of Algorithm Connascence of algorithm is when multiple components must agree on a particular algorithm. Be DRY – Don’t Repeat Yourself. If you have “cloned” code in multiple locations, refactor it into a common function.   Those are the “static” forms of connascence. There are also “dynamic” forms, including… Connascence of Execution Connascence of execution is when the order of execution of multiple components is important. Consumers of your class shouldn’t have to know that they have to call an .Initialize method before it’s safe to call a .DoSomething method. Connascence of Timing Connascence of timing is when the timing of the execution of multiple components is important. I’ll have to read up on this one when I get the book, but assume it’s largely about threading. Connascence of Identity Connascence of identity is when multiple components must reference the entity. The example Weirich gives is when you have two instances of the “Bob” Employee class and you call the .RaiseSalary method on one and then the .Pay method on the other does the payment use the updated salary?   Again, this is my summary of a summary, so please be forgiving if I misunderstood anything. Once I get/read the book, I’ll make corrections if necessary and share any other useful information I might learn.   See Also: Gregory Brown: Ruby Best Practices Issue #24: Connascence as a Software Design Metric (That link is failing at the time I write this, so I had to go to the Google cache of the page.)

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• How to add a blank page to a pdf using iTextSharp?

  - by Russell

  I am trying to do something I thought would be quite simple, however it is not so straight forward and google has not helped. I am using iTextSharp to merge PDF documents (letters) together so they can all be printed at once. If a letter has an odd number of pages I need to append a blank page, so we can print the letters double-sided. Here is the basic code I have at the moment for merging all of the letters: // initiaise MemoryStream pdfStreamOut = new MemoryStream(); Document document = null; MemoryStream pdfStreamIn = null; PdfReader reader = null; int numPages = 0; PdfWriter writer = null; for int(i = 0;i < letterList.Count; i++) { byte[] myLetterData = ...; pdfStreamIn = new MemoryStream(myLetterData); reader = new PdfReader(pdfStreamIn); numPages = reader.NumberOfPages; // open the streams to use for the iteration if (i == 0) { document = new Document(reader.GetPageSizeWithRotation(1)); writer = PdfWriter.GetInstance(document, pdfStreamOut); document.Open(); } PdfContentByte cb = writer.DirectContent; PdfImportedPage page; int importedPageNumber = 0; while (importedPageNumber < numPages) { importedPageNumber++; document.SetPageSize(reader.GetPageSizeWithRotation(importedPageNumber)); document.NewPage(); page = writer.GetImportedPage(reader, importedPageNumber); cb.AddTemplate(page, 1f, 0, 0, 1f, 0, 0); } } I have tried using: document.SetPageSize(reader.GetPageSizeWithRotation(1)); document.NewPage(); at the end of the for loop for an odd number of pages without success. Any help would be much appreciated!

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• How to not persist NSManagedObjects retrieved from NSManagedObjectContext

  - by RickiG

  Hi I parse an xml file containing books, for each new node I go: Book *book = (Book*)[NSEntityDescription insertNewObjectForEntityForName:@"Book" inManagedObjectContext:managedObjectContext]; To obtain an NSManagedObject of my Core Data Book Entity, I then proceed to populate the managed Book object with data, add it to an array, rinse, repeat. When I am done, I present the list of books to the user. I have not yet executed the save: NSError *error; if (![managedObjectContext save:&error]) { NSLog(@"%@", [error domain]); } The user now selects one of the books, this one I would like to persist, but only this one, all the other books are of no interest to me any more. The Book Entity does not have/or is part of any relationships. It is just a "single" Entity. If I pull the "save lever" every Book object will be persisted and I will have to delete everything but my desired one. How would I get around this challenge, I can't really seem to find that particular use-case in the Core Data Programming Guide, which sort of also bugs me a bit, am I going against best practice here? Thanks for any help given.

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• C# - InvalidCastException when fetching double from sqlite

  - by Irro

  I keep getting a InvalidCastException when I'm fetching any double from my SQLite database in C#. The exception says "Specified cast is not valid." I am able to see the value in a SQL manager so I know it exists. It is possible to fetch Strings (VARCHARS) and ints from the database. I'm also able to fetch the value as an object but then I get "66.0" when it's suppose to be "66,8558604947586" (latitude coordination). Any one who knows how to solve this? My code: using System.Data.SQLite; ... SQLiteConnection conn = new SQLiteConnection(@"Data Source=C:\\database.sqlite; Version=3;"); conn.Open(); SQLiteDataReader reader = getReader(conn, "SELECT * FROM table"); //These are working String name = reader.GetString(1); Int32 value = reader.GetInt32(2); //This is not working Double latitude = reader.getDouble(3); //This gives me wrong value Object o = reader[3]; //or reader["latitude"] or reader.getValue(3)

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• How to avoid saving a blank model which attributes can be blank

  - by auralbee

  Hello people, I have two models with a HABTM association, let´s say book and author. class Book has_and_belongs_to_many :authors end class Author has_and_belongs_to_many :books end The author has a set of attributes (e.g. first-name,last-name,age) that can all be blank (see validation). validates_length_of :first_name, :maximum => 255, :allow_blank => true, :allow_nil => false In the books_controller, I do the following to append all authors to a book in one step: @book = Book.new(params[:book]) @book.authors.build(params[:book][:authors].values) My question: What would be the easiest way to avoid the saving of authors which fields are all blank to prevent too much "noise" in the database? At the moment, I do the following: validate :must_have_some_data def must_have_some_data empty = true hash = self.attributes hash.delete("created_at") hash.delete("updated_at") hash.each_value do |value| empty = false if value.present? end if (empty) errors.add_to_base("Fields do not contain any data.") end end Maybe there is an more elegant, Rails-like way to do that. Thanks.

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• XML document being parsed as single element instead of sequence of nodes

  - by Rob Carr

  Given xml that looks like this: <Store> <foo> <book> <isbn>123456</isbn> </book> <title>XYZ</title> <checkout>no</checkout> </foo> <bar> <book> <isbn>7890</isbn> </book> <title>XYZ2</title> <checkout>yes</checkout> </bar> </Store> I am getting this as my parsed xmldoc: >>> from xml.dom import minidom >>> xmldoc = minidom.parse('bar.xml') >>> xmldoc.toxml() u'<?xml version="1.0" ?><Store>\n<foo>\n<book>\n<isbn>123456</isbn>\n</book>\n<t itle>XYZ</title>\n<checkout>no</checkout>\n</foo>\n<bar>\n<book>\n<isbn>7890</is bn>\n</book>\n<title>XYZ2</title>\n<checkout>yes</checkout>\n</bar>\n</Store>' Is there an easy way to pre-process this document so that when it is parsed, it isn't parsed as a single xml element?

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• Isolated storage misunderstand

  - by Costa

  Hi this is a discussion between me and me to understand isolated storage issue. can you help me to convince me about isolated storage!! This is a code written in windows form app (reader) that read the isolated storage of another win form app (writer) which is signed. where is the security if the reader can read the writer's file, I thought only signed code can access the file! If all .Net applications born equal and have all permissions to access Isolated storage, where is the security then? If I can install and run Exe from isolated storage, why I don't install a virus and run it, I am trusted to access this area. but the virus or what ever will not be trusted to access the rest of file system, it only can access the memory, and this is dangerous enough. I cannot see any difference between using app data folder to save the state and using isolated storage except a long nasty path!! I want to try give low trust to Reader code and retest, but they said "Isolated storage is actually created for giving low trusted application the right to save its state". Reader code: private void button1_Click(object sender, EventArgs e) { String path = @"C:\Documents and Settings\All Users\Application Data\IsolatedStorage\efv5cmbz.ewt\2ehuny0c.qvv\StrongName.5v3airc2lkv0onfrhsm2h3uiio35oarw\AssemFiles\toto12\ABC.txt"; StreamReader reader = new StreamReader(path); var test = reader.ReadLine(); reader.Close(); } Writer: private void button1_Click(object sender, EventArgs e) { IsolatedStorageFile isolatedFile = IsolatedStorageFile.GetMachineStoreForAssembly(); isolatedFile.CreateDirectory("toto12"); IsolatedStorageFileStream isolatedStorage = new IsolatedStorageFileStream(@"toto12\ABC.txt", System.IO.FileMode.Create, isolatedFile); StreamWriter writer = new StreamWriter(isolatedStorage); writer.WriteLine("Ana 2akol we ashrab kai a3eesh wa akbora"); writer.Close(); writer.Dispose(); }

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• scheme struct question

  - by qzar

  ;; definition of the structure "book" ;; author: string - the author of the book ;; title: string - the title of the book ;; genre: symbol - the genre (define-struct book (author title genre)) (define lotr1 (make-book "John R. R. Tolkien" "The Fellowship of the Ring" 'Fantasy)) (define glory (make-book "David Brin" "Glory Season" 'ScienceFiction)) (define firstFamily (make-book "David Baldacci" "First Family" 'Thriller)) (define some-books (list lotr1 glory firstFamily)) ;; count-books-for-genre: symbol (list of books) -> number ;; the procedure takes a symbol and a list of books and produces the number ;; of books from the given symbol and genre ;; example: (count-books-for-genre 'Fantasy some-books) should produce 1 (define (count-books-for-genre genre lob) (if (empty? lob) 0 (if (symbol=? (book-genre (first lob)) genre) (+ 1 (count-books-for-genre (rest lob) genre)) (count-books-for-genre (rest lob) genre) ) ) ) (count-books-for-genre 'Fantasy some-books) It produce following exception first: expected argument of type non-empty list; given 'Fantasy, I don't understand whats the problem. Can somebody give me some explanation ? Thank you very much !

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• Update a PDF to include an encrypted, hidden, unique identifier?

  - by Dave Jarvis

  Background The idea is this: Person provides contact information for online book purchase Book, as a PDF, is marked with a unique hash Person downloads book PDF passwords are annoying and extremely easy to circumvent. The ideal process would be something like: Generate hash based on contact information Store contact information and hash in database Acquire book lock Update an "include" file with hash text Generate book as PDF (using pdflatex) Apply hash to book Release book lock Send email with book download link Technologies The following technologies can be used (other programming languages are possible, but libraries will likely be limited to those supplied by the host): C, Java, PHP LaTeX files PDF files Linux Question What programming techniques (or open source software) should I investigate to: Embed a unique hash (or other mark) to a PDF Create a collusion-attack resistant mark Develop a non-fragile (e.g., PDF -> EPS -> PDF still contains the mark) solution Research I have looked at the following possibilities: Steganography Natural Language Processing (NLP) Convert blank pages in PDF to images; mark those images; reassemble PDF LaTeX watermark package ImageMagick Steganograhy requires keeping a master copy of the images, and I'm not sure if the watermark would survive PDF -> EPS -> PDF, or other types of conversion. LaTeX creates an image cache, so any steganographic process would have to intercept that process somehow. NLP introduces grammatical errors. Inserting blank pages as images is immediately suspect; it is easy to replace suspicious blank pages. The LaTeX watermark package draws visible marks. ImageMagick draws visible marks. What other solutions are possible? Related Links http://www.tcpdf.org/ invisible watermarks in images Thank you!

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• How to keep your unit test Arrange step simple and still guarantee DDD invariants ?

  - by ian31

  DDD recommends that the domain objects should be in a valid state at any time. Aggregate roots are responsible for guaranteeing the invariants and Factories for assembling objects with all the required parts so that they are initialized in a valid state. However this seems to complicate the task of creating simple, isolated unit tests a lot. Let's assume we have a BookRepository that contains Books. A Book has : an Author a Category a list of Bookstores you can find the book in These are required attributes : a book has to have an author, a category and at least a book store you can buy the book from. There's likely to be a BookFactory since it is quite a complex object, and the Factory will initialize the Book with at least all the mentioned attributes. Now we want to unit test a method of the BookRepository that returns all the Books. To test if the method returns the books, we have to set up a test context (the Arrange step in AAA terms) where some Books are already in the Repository. If the only tool at our disposal to create Book objects is the Factory, the unit test now also uses and is dependent on the Factory and inderectly on Category, Author and Store since we need those objects to build up a Book and then place it in the test context. Would you consider this is a dependency in the same way that in a Service unit test we would be dependent on, say, a Repository that the Service would call ? How would you solve the problem of having to re-create a whole cluster of objects in order to be able to test a simple thing ? How would you break that dependency and get rid of all these attributes we don't need in our test ? By using mocks or stubs ? If you mock up things a Repository contains, what kind of mock/stubs would you use as opposed to when you mock up something the object under test talks to or consumes ?

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