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  • Scheme open source projects?

    - by Ben
    Hi I'm learning scheme and was wondering if there are any active open-source projects I might be able to get involved in? I'm nearing the end of SICP and although this has good complex examples no textbook code compares to real-world applications. eg testing code / benchmarking / revision control styles / sheer size and scope etc. Hence my curiousity at seeing a project in the wild. I tried searching google code but only found projects that are interpreters that implement RSR5/6. Perhaps there are not many projects out there and I should consider scala?! Advice or even pointers to specific projects appreciated.

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  • How to test if an array contains a pair of numbers whose product is odd?

    - by John
    How can I write a function that takes an array of integers and returns true if their exists a pair of numbers whose product is odd? What are the properties of odd integers? And of course, how do you write this function in Java? Also, maybe a short explanation of how you went about formulating an algorithm for the actual implementation. Yes, this is a function out of a textbook. No, this is not homework—I'm just trying to learn, so please no "do your own homework comments."

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  • Dynamically generate Triangle Lists for a Complex 3D Mesh

    - by Vulcan Eager
    In my application, I have the shape and dimensions of a complex 3D solid (say a Cylinder Block) taken from user input. I need to construct vertex and index buffers for it. Since the dimensions are taken from user input, I cannot user Blender or 3D Max to manually create my model. What is the textbook method to dynamically generate such a mesh? Edit: I am looking for something that will generate the triangles given the vertices, edges and holes. Something like TetGen. As for TetGen itself, I have no way of excluding the triangles which fall on the interior of the solid/mesh.

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  • Fitting place names into map shapes

    - by Old Man
    I'm drawing shapes using GDI+ using a list of lat/lon floats, and I need to place the name of the place within the borders of the polygon. Simply centering the text in the bounding rectangle doesn't work for irregular shapes. I have the text and the font so I can get the size of the rectangle that the text will need to fit in, but at that point I'm stuck. This seems like a common problem that all mapping software solves, as well as the kind of thing you would find in an algorithm or computer graphics textbook. So, given a list of floats for a polygon and a rectangle, is there a way to get the best possible point to place the text, using: 1) GDI+; 2) SQL Server Geospatial; or 3) c# code (or c, pseudocode, etc)

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  • Why do we need normalized coordinate system? Options

    - by jcyang
    Hi, I have problem understand following sentences in my textbook Computer Graphics with OpenGL. "To make viewing process independent of the requirements of any output device,graphic system convert object descriptions to normalized coordinates and apply the clipping routines." Why normalized coordinates could make viewing process independent of the requirements of any output devices? Isn't the projection coordinates already independent of output device?We only need to first scale and then translate the projection coordinate then we will get device coordinate. So why do we need first convert the projection coordinate to normalized coordinate first? "Clipping is usually performed in normlized coordinates.This allows us to reduce computations by first concatenating the various transformation matrices" Why clipping is usually performed in normlized coordinates? What kind of transformation concatenated? thanks. jcyang.

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  • Brendan Gregg's "Systems Performance: Enterprise and the Cloud"

    - by user12608550
    Long ago, the prerequisite UNIX performance book was Adrian Cockcroft's 1994 classic, Sun Performance and Tuning: Sparc & Solaris, later updated in 1998 as Java and the Internet. As Solaris evolved to include the invaluable DTrace observability features, new essential performance references have been published, such as Solaris Performance and Tools: DTrace and MDB Techniques for Solaris 10 and OpenSolaris (2006)  by McDougal, Mauro, and Gregg, and DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X and FreeBSD (2011), also by Mauro and Gregg. Much has occurred in Solaris Land since those books appeared, notably Oracle's acquisition of Sun Microsystems in 2010 and the demise of the OpenSolaris community. But operating system technologies have continued to improve markedly in recent years, driven by stunning advances in multicore processor architecture, virtualization, and the massive scalability requirements of cloud computing. A new performance reference was needed, and I eagerly waited for something that thoroughly covered modern, distributed computing performance issues from the ground up. Well, there's a new classic now, authored yet again by Brendan Gregg, former Solaris kernel engineer at Sun and now Lead Performance Engineer at Joyent. Systems Performance: Enterprise and the Cloud is a modern, very comprehensive guide to general system performance principles and practices, as well as a highly detailed reference for specific UNIX and Linux observability tools used to examine and diagnose operating system behaviour.  It provides thorough definitions of terms, explains performance diagnostic Best Practices and "Worst Practices" (called "anti-methods"), and covers key observability tools including DTrace, SystemTap, and all the traditional UNIX utilities like vmstat, ps, iostat, and many others. The book focuses on operating system performance principles and expands on these with respect to Linux (Ubuntu, Fedora, and CentOS are cited), and to Solaris and its derivatives [1]; it is not directed at any one OS so it is extremely useful as a broad performance reference. The author goes beyond the intricacies of performance analysis and shows how to interpret and visualize statistical information gathered from the observability tools.  It's often difficult to extract understanding from voluminous rows of text output, and techniques are provided to assist with summarizing, visualizing, and interpreting the performance data. Gregg includes myriad useful references from the system performance literature, including a "Who's Who" of contributors to this great body of diagnostic tools and methods. This outstanding book should be required reading for UNIX and Linux system administrators as well as anyone charged with diagnosing OS performance issues.  Moreover, the book can easily serve as a textbook for a graduate level course in operating systems [2]. [1] Solaris 11, of course, and Joyent's SmartOS (developed from OpenSolaris) [2] Gregg has taught system performance seminars for many years; I have also taught such courses...this book would be perfect for the OS component of an advanced CS curriculum.

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  • Is there an appropriate coding style for implementing an algorithm during an interview?

    - by GlenPeterson
    I failed an interview question in C years ago about converting hex to decimal by not exploiting the ASCII table if (inputDigitByte > 9) hex = inputDigitByte - 'a'. The rise of Unicode has made this question pretty silly, but the point was that the interviewer valued raw execution speed above readability and error handling. They tell you to review algorithms textbooks to prepare for these interviews, yet these same textbooks tend to favor the implementation with the fewest lines of code, even if it has to rely on magic numbers (like "infinity") and a slower, more memory-intensive implementation (like a linked list instead of an array) to do that. I don't know what is right. Coding an algorithm within the space of an interview has at least 3 constraints: time to code, elegance/readability, and efficiency of execution. What trade-offs are appropriate for interview code? How much do you follow the textbook definition of an algorithm? Is it better to eliminate recursion, unroll loops, and use arrays for efficiency? Or is it better to use recursion and special values like "infinity" or Integer.MAX_VALUE to reduce the number of lines of code needed to write the algorithm? Interface: Make a very self-contained, bullet-proof interface, or sloppy and fast? On the one extreme, the array to be sorted might be a public static variable. On the other extreme, it might need to be passed to each method, allowing methods to be called individually from different threads for different purposes. Is it appropriate to use a linked-list data structure for items that are traversed in one direction vs. using arrays and doubling the size when the array is full? Implementing a singly-linked list during the interview is often much faster to code and easier remember for recursive algorithms like MergeSort. Thread safety - just document that it's unsafe, or say so verbally? How much should the interviewee be looking for opportunities for parallel processing? Is bit shifting appropriate? x / 2 or x >> 1 Polymorphism, type safety, and generics? Comments? Variable and method names: qs(a, p, q, r) vs: quickSort(theArray, minIdx, partIdx, maxIdx) How much should you use existing APIs? Obviously you can't use a java.util.HashMap to implement a hash-table, but what about using a java.util.List to accumulate your sorted results? Are there any guiding principals that would answer these and other questions, or is the guiding principal to ask the interviewer? Or maybe this should be the basis of a discussion while writing the code? If an interviewer can't or won't answer one of these questions, are there any tips for coaxing the information out of them?

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  • Need help identifing what resources (eg. In MIT OpenCourseWare) can help me prepare for a test [closed]

    - by jiewmeng
    I am entering uni soon. I can sit for a placement test to see if I elegible for exemptions. The details are http://www.comp.nus.edu.sg/undergraduates/TestScope11_12.html Or CS2100 Computer Organisation (please click title) The objective of this module is to familiarise students with the fundamentals of computing devices. Through this module students will understand the basics of data representation, and how the various parts of a computer work, separately and with each other. This allows students to understand the issues in computing devices, and how these issues affect the implementation of solutions. Topics covered include data representation systems, combinational and sequential circuit design techniques, assembly language, processor execution cycles, pipelining, memory hierarchy and input/output systems. Recommended Textbooks Digital Design: Principles and Practices [DDPP] by John F. Wakerly, Prentice-Hall. ISBN 0-13-324500-4. Computer Organizations and Design (The hardware/software interface) by David A. Patterson and John L. Hennessy. CS2105 Introduction to Computer Networks (please click title) This course aims to provide a broad introduction to computer networks and some appreciations of network application programming. It covers a range of topics including basic data communication and computer network concepts, protocols, networked computing concepts and principles, network applications development and network security. The emphasis of teaching is on the working principles and application of computer networks. As an integral part of the course, tutorials and practical assignments enforcing learning will also be given. These assignments provide an early exposure in network application programming and they should be able to complete by using personal computers and school's network facilities. Topics included: An overview of computer networks and the Internet Basic data communications Application layer Transport layer Network layer and routing Link layer and local area networks Recommended Textbook James F. Kurose & Keith W. Ross, Computer networking: A top-down approach featuring internet, Addison Wesley, 2001 I am wondering what resources eg. MIT OpenCourseWare or other universities resources are available to help he perpare for these particular modubles. I am thinking does the Networking one look like CCNA? The computer oragization. Its like electronics, assembly etc? I learnt some electronics in Poly but looking at the sample papers, uni looks very different... I have about 1 month to prepare if I want any chance of exempting from these modules :) any help?

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  • Organization &amp; Architecture UNISA Studies &ndash; Chap 13

    - by MarkPearl
    Learning Outcomes Explain the advantages of using a large number of registers Discuss the way in which compilers optimize register usage Discuss the evolution of CISC machines Describe the characteristics of RISC architecture Discuss the RISC vs. CISC controversy Describe the way in which RISC and CISC design principles can be combined Instruction Execution Characteristics To understand the the line of reasoning of RISC advocates, we need a brief overview of instruction execution characteristics. These include… Operations Operands Procedure Calls These three sections can be studied in depth in the textbook at pages 503 - 505 A number of groups have come up with the conclusion that the attempt to make the instruction set architecture closer to HLLs (High Level Languages) is not the most effective design strategy. Rather HLL’s can be best supported by optimizing performance of the most time-consuming features of typical HLL programs. Generally 3 main characteristics came up to improve performance… Use a large number of registers or use a compiler to optimize register usage Careful attention needs to be paid to the design of instruction pipelines A simplified (reduced) instruction set is indicated The use of a large register optimization One of the most important design principles of RISC machines is the use of a large number of registers. The concept of register windows and the use of a large register file versus the use of cache memory are discussed. On the face of it, the use of a large set of registers should decrease the need to access memory. The design task is to organize the registers in such a fashion that this goal is realized. Read page 507 – 510 for a detailed explanation. Compiler-based register optimization   Reduced Instructions Set Architecture There are two advantages to smaller programs… Because the program takes up less memory, there is a savings in that resource (this was more compelling when memory was more expensive) Smaller programs should improve performance, and this will happen in two ways – fewer instructions means fewer instruction bytes to be fetched and in a paging environment smaller programs occupy fewer pages, reducing page faults. Certain characteristics are common to RISC processors… One instruction per cycle Register-to-register operations Simple addressing modes Simple instruction formats RISC vs. CISC After initial enthusiasm for RISC machines, there has been a growing realization that RISC designs may benefit from the inclusion of some CISC features CISC designs may benefit from the inclusion of some RISC features

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  • Web server with static IP from cable provider

    - by Dmitri
    I have a subscription to 5 static IP addresses. I want to run a web server from behind a router. My network config is as follows: Server's local address is 10.1.10.2, has IIS running on it, port 80 and 443 (IIS is not my fault, had to be done) the server's ip address is static, the subnet mask is 255.255.255.0, gateway is 10.1.10.1, which is the local address of the cable modem / router / gateway thingy. All looks to be in textbook order as far as the LAN goes. I can get to anything on my LAN from any computer on my LAN, whether they have static IP or get it through DHCP from the cable modem/router thingy. however, I have no internet access form any of my LAN computers. I called Comcast tech support and they say they can connect to my modem/router just fine and can actually use it to ping any computer on the internet or any computer on my LAN from the router/modem (i checked, myself, this is in fact the case). However, nothing on my LAN has internet connectivity. I tried pinging the DNS servers, nothing. I tried directly typing in web sites' IP addresses, nothing, so doesn't seem to be a DNS issue. Any Ideas? What malfunction of a router could be causing such weird behavior? nay ideas or educated guesses are very much appreciated.

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  • Potential impact of large broadcast domains

    - by john
    I recently switched jobs. By the time I left my last job our network was three years old and had been planned very well (in my opinion). Our address range was split down into a bunch of VLANs with the largest subnet a /22 range. It was textbook. The company I now work for has built up their network over about 20 years. It's quite large, reaches multiple sites, and has an eclectic mix of devices. This organisation only uses VLANs for very specific things. I only know of one usage of VLANs so far and that is the SAN which also crosses a site boundary. I'm not a network engineer, I'm a support technician. But occasionally I have to do some network traces for debugging problems and I'm astounded by the quantity of broadcast traffic I see. The largest network is a straight Class B network, so it uses a /16 mask. Of course if that were filled with devices the network would likely grind to a halt. I think there are probably 2000+ physical and virtual devices currently using that subnet, but it (mostly) seems to work. This practise seems to go against everything I've been taught. My question is: In your opinion and  From my perspective - What measurement of which metric would tell me that there is too much broadcast traffic bouncing about the network? And what are the tell-tale signs that you are perhaps treading on thin ice? The way I see it, there are more and more devices being added and that can only mean more broadcast traffic, so there must be a threshold. Would things just get slower and slower, or would the effects be more subtle than that?

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  • Why Apple’s New SDK Limitation is So Offensive

    - by TStewartDev
    I am not an Apple fanboy, nor have I ever been. However, I have owned a Mac, an iPod, and an iPhone in my lifetime, and for more than a decade, I have defended Apple against the untruths that the haters so enjoy spewing. I encouraged my wife to buy a MacBook when she needed a new laptop two years ago, and I often recommend them to my friends and relatives. I have proudly and happily used my first generation iPhone for nearly three years. Now, for the first time in well over ten years, I find myself ready to swear off Apple and encourage everyone I know to do the same. I was disappointed when Apple wouldn't allow native apps, but I still bought the iPhone. I've stomached their ambiguous app approval process even though it's apparent that Steve may just reject your app because he doesn't like you or feels threatened by you (I'm still lamenting the rejection of the Google Voice app). But, as a developer, I can no longer tolerate Apple's terms and the kind of totalitarian control they indicate Apple wants. In case you are not already familiar, Apple has dictated in their OS 4.0 SDK license agreement (the now infamous Section 3.3.1) that all apps developed for the iPhone must be coded in C, C++, or Objective C, and moreover, that using any cross-compiling platforms is a violation of the agreement. For those of you who aren't developers, let me try to illustrate why this angers those of us who are. Imagine you're a professional writer. You've had articles published in some journals and magazines, and you've got a couple popular books out there, too. You've got an idea for a new book, and so you take it to your publisher. Your publisher agrees that it's a good idea. "But," says the publisher, "we want to hold our books to a tighter standard so that our readers get the experience we want them to have. Therefore, from now on, all our writers may only use words from this list of the 10,000 most common English words. Furthermore, if you cite any other works or quote anyone, they must comply with that same list, or you'll have to rewrite the entire work as well in case our readers want to look up your citation." What do you do? If your work is a children's book, this probably isn't a big deal to you. If it's an autobiography, textbook, or even a novel, though, you're going to have a lot of trouble describing your content with only common words. It's going to take you longer to complete your book, too, since you'll be looking up less common words frequently to see if you can use them. You could always go to another publisher, but this one has the best ability to distribute your book. The next largest distributor can only do a quarter as much. You could abandon the project altogether, but then everyone loses. Isn't this a silly scenario? Who would put such a limitation on writers? Yet this is very much what Apple is doing. They are using their dominant position in the market to coerce developers to write their apps exclusively for the iPhone OS by making it too expensive to write for multiple platforms. It is at least a threefold attack, striking at Adobe who is set to release a compiler that lets Flash source be compiled to iPhone binaries; striking at Google whose Android platform stands the best chance at the moment of providing serious competition to the iPhone; and reinforcing their own strong position by keeping popular apps exclusively to iPhone. And while developers are already very upset about this, the sad fact is that most of us will cave and give in to Apple because consumers don't know any better. They will continue to buy Apple's toy forcing developers to play Apple's maniacal game in order to make any money, at least until Steve Jobs decides he doesn't like them or he intends to release a competing application (bye-bye OpenFeint). Apple has been kept in check on the desktop front by a very dominant Microsoft, but I'm afraid that their success with iPods, iTunes, and iPhones has created a monster that we may have to bear until it is slain by an anti-trust suit or dies with the retirement of Steve Jobs.

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  • linebreak in url with Bibtex and hyperref package

    - by Tim
    Why is this item not shown properly in my bibliography? @misc{ann, abstract = {ANN is an implbmentation of nearest neighbor search.}, author = {David M. Mount and Sunil Arya}, howpublished = {\url{http://www.cs.umd.edu/~mount/ANN/}}, keywords = {knn}, posted-at = {2010-04-08 00:05:04}, priority = {2}, title = {ANN.}, url = "http://www.cs.umd.edu/~mount/ANN/", year = {2008} } @misc{Nilsson96introductionto, author = {Nilsson, Nils J.}, citeulike-article-id = {6995464}, howpublished = {\url{http://robotics.stanford.edu/people/nilsson/mlbook.html}}, keywords = {*file-import-10-04-11}, posted-at = {2010-04-11 06:52:28}, priority = {2}, title = {Introduction to Machine Learning: An Early Draft of a Proposed Textbook.}, year = {1996} } EDIT: I am using \usepackage{hyperref}, not \usepackage{url}. I don't know what changes I just made made the first item appear properly now @misc{ann, abstract = {ANN is an implbmentation of nearest neighbor search.}, author = {David M. Mount and Sunil Arya}, howpublished = {\url{http://www.cs.umd.edu/~mount/ANN/}}, keywords = {ann}, posted-at = {2010-04-08 00:05:04}, priority = {2}, title = {The \textsc{A}pproximate \textsc{N}earest \textsc{N}eighbor \textsc{S}earching \textsc{L}ibrary.}, url = "http://www.cs.umd.edu/~mount/ANN/", year = {2008} } EDIT: Since I am using hyperref package, it produces error when using url package together with it. So the two cannot work together? I would like to use hyper links inside pdf file, so I would like to use hyperref package instead of url package. I googled a bit, and try \usepackage[hyperindex,breaklinks]{hyperref}, but there is still no line break just as before. How can I do it? Is there conflict in the packages that I am now using?: \usepackage{amsmath} \usepackage{amsfonts} \usepackage[dvips]{graphicx} \usepackage{wrapfig} \graphicspath{{./figs/}} \DeclareGraphicsExtensions{.eps} \usepackage{fixltx2e} \usepackage{array} \usepackage{times} \usepackage{fancyhdr} \usepackage{multirow} \usepackage{algorithmic} \usepackage{algorithm} \usepackage{slashbox} \usepackage{multirow} \usepackage{rotating} \usepackage{longtable} \usepackage[hyperindex,breaklinks]{hyperref} \usepackage{forloop} \usepackage{lscape} \usepackage{supertabular} \usepackage{amssymb} \usepackage{amsthm}

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  • Accurate least-squares fit algorithm needed

    - by ggkmath
    I've experimented with the two ways of implementing a least-squares fit (LSF) algorithm shown here. The first code is simply the textbook approach, as described by Wolfram's page on LSF. The second code re-arranges the equation to minimize machine errors. Both codes produce similar results for my data. I compared these results with Matlab's p=polyfit(x,y,1) function, using correlation coefficients to measure the "goodness" of fit and compare each of the 3 routines. I observed that while all 3 methods produced good results, at least for my data, Matlab's routine had the best fit (the other 2 routines had similar results to each other). Matlab's p=polyfit(x,y,1) function uses a Vandermonde matrix, V (n x 2 matrix) and QR factorization to solve the least-squares problem. In Matlab code, it looks like: V = [x1,1; x2,1; x3,1; ... xn,1] % this line is pseudo-code [Q,R] = qr(V,0); p = R\(Q'*y); % performs same as p = V\y I'm not a mathematician, so I don't understand why it would be more accurate. Although the difference is slight, in my case I need to obtain the slope from the LSF and multiply it by a large number, so any improvement in accuracy shows up in my results. For reasons I can't get into, I cannot use Matlab's routine in my work. So, I'm wondering if anyone has a more accurate equation-based approach recommendation I could use that is an improvement over the above two approaches, in terms of rounding errors/machine accuracy/etc. Any comments appreciated! thanks in advance.

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  • Computer science textbooks

    - by Barrett Conrad
    I would like to try the book question a little bit differently. My goal is to know what the community thinks are the quintessential computer science textbooks. <beginsadstory>I lost all of my computer science and math books from college in Hurricane Katrina in 2005. I greatly miss having my familiar tomes to refer to when topics and problems come up, so I am looking to rebuild my library.<endsadstory> What are your recommendations for the best examples of academic caliber books for the field of computer science and its associated mathematics? I am looking for books on subjects like computational theory, programming languages, compilers, operating systems, algorithms and so on. Don't limit your suggestions to your textbooks only. If there is a book you have read that covers computer science or a related math in a formal way, but is not strictly a textbook, I would be love to hear about them as well. Finally, for the sake of creating a good reference for all of us, may I suggest posting one book per answer so they can be rated individually.

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  • Place the business logic in Java Beans?

    - by Lirik
    I was reading this page and I found the following statement: MVC in Java Server Pages Now that we have a convenient architucture to separate the view, how can we leverage that? Java Server Pages (JSP) becomes more interesting because the HTML content can be separated from the Java business objects. JSP can also make use of Java Beans. The business logic could be placed inside Java Beans. If the design is architected correctly, a Web Designer could work with HTML on the JSP site without interfering with the Java developer. Interestingly in my textbook I pulled the following quote: In the MVC architecture... the original request is always handled by a servlet. The servlet invokes the business logic and data access code and creates beans to represent the results (that’s the model). Then, the servlet decides which Java Server Page is appropriate to present those particular results and forwards the request there (the JSP is the view). The servlet decides what business logic code applies and which JSP should present the results (the servlet is the controller). The two statements seem slightly contradicting. What is the best way to use beans: should we place business logic in them or should we only place results in them? Are there ways in which beans are inadequate for representing a model?

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  • What is a good standard exercise to learn the OO features of a language?

    - by FarmBoy
    When I'm learning a new language, I often program some mathematical functions to get used to the control flow syntax. After that, I like to implement some sorting algorithms to get used to the array/list constructs. But I don't have a standard exercise for exploring the languages OO features. Does anyone have a stock exercise for this? A good answer would naturally lend to inheritance, polymorphism, etc., for a programmer already comfortable with these concepts. An ideal answer would be one that could be communicated in a few words, without ambiguity, in the way that "implement mergesort" is completely unambiguous. (As an example, answering "design a game" is so vague as to be useless.) Any ideas? EDIT: I have to remark that the results here are somewhat ironic. 10 upvotes and (originally) 5 favorites suggest that this is a question others are interested in. Yet the most upvoted answer is one that says there is no good answer. Oh well. I think I'll look at the textbook below, I've found games useful in the past for OO.

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  • Manually listing objects in Django (problem with field ordering)

    - by Chris
    I'm having some trouble figuring out the best/Djangoic way to do this. I'm creating something like an interactive textbook. It has modules, which are more or less like chapters. Each module page needs to list the topics in that module, grouped into sections. My question is how I can ensure that they list in the correct order in the template? Specifically: 1) How to ensure the sections appear in the correct order? 2) How to ensure the topics appear in the correct order in the section? I imagine I could add a field to each model purely for the sake of ordering, but the problem with that is that a topic might appear in different modules, and in whatever section they are in there they would again have to be ordered somehow. I would probably give up and do it all manually were it not for the fact that I need to have the Topic as object in the template (or view) so I can mark it up according to how the user has labeled it. So I suppose my question is really to do with whether I should create the contents pages manually, or whether there is a way of ordering the query results in a way I haven't thought of. Thanks for your help!

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  • What is the fastest, most efficient way to get up to speed on a new technology?

    - by SLC
    My current job involves working with a huge number of technologies, most of which are very niche and unheard of. In some cases I have to write something about the technology, or with the technology, such as some lessons, examples, or tutorials, on behalf of the developer of that technology or someone that is backing it. When I get told to learn about a new technology, my first port of call is to check our internal library, and then look on amazon for a book on the subject. Failing that, or if the project is too small to warrant a purchase, I hit up google and youtube. However the results of randomly googling what I want to learn are hit and miss. Some days, I can find everything I want to know in a series of lessons or videos, and it's no problem. Other times, I can find almost nothing, and I really have to piece together things from sites. The result is that there are various resources out there, videos, interactive lessons, tutorials, books etc. but when I need to learn something fast, I often don't know the best way to go about it. It's not about fun, because I don't always have the luxury of working my way through a 600 page textbook named "A Complete Guide To Technology X", I have to deliver results quickly. One of the examples I'd like to use is ASP.NET MVC 2 which is something I have been told to learn. I grabbed a book on MVC 1 to refresh my knowledge, but googling it does't produce much useful information. I've seen a ton of ScottGu's tutorials on it, but they are mostly feature presentations, and some date back almost a year. The same applies to channel 9 and there are no books out yet on amazon. My question therefore has two parts, the first asks, "Where are the best places to look to get the information needed to learn a new technology?" and the second asks "What is the most efficient way to use such resources to learn a new technology?"

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  • Having an issue with org.hibernate.SessionException: Session is closed! in Hibernate

    - by hal10001
    I've done quite a bit a research on this with no luck, but all the answers have a tendency to point toward the session context settings in the config file. What is odd is that I get a session connection the very first time I hit the page (and therefore, a successful result set), but then when I reload I get the following exception: org.hibernate.SessionException: Session is closed! Here are my config settings that are not DB connection string related: <property name="hibernate.show_sql">false</property> <property name="hibernate.dialect">org.hibernate.dialect.SQLServerDialect</property> <property name="hibernate.current_session_context_class">thread</property> <property name="hibernate.cache.provider_class">org.hibernate.cache.NoCacheProvider</property> <property name="hibernate.cache.use_query_cache">false</property> <property name="hibernate.cache.use_minimal_puts">false</property> Here is an example of a call I make that produces the situation I described above. public T get(int id) { session.beginTransaction(); T type; try { type = getTypeClass().cast(session.get(getTypeClass(), id)); } catch (ClassCastException classCastException) { throw new ClassCastException(classCastException.getMessage()); } session.getTransaction().commit(); return type; } The session variable reference is to a static field that contains the current session. All of the session connection details are textbook reference manual. For example, here is my Hibernate session utility: import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; public class HibernateSessionFactoryUtil { private static final SessionFactory sessionFactory = buildSessionFactory(); private static SessionFactory buildSessionFactory() { try { return new Configuration().configure().buildSessionFactory(); } catch (Throwable ex) { System.err.println("Initial SessionFactory creation failed." + ex); throw new ExceptionInInitializerError(ex); } } public static SessionFactory getSessionFactory() { return sessionFactory; } }

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  • Basic compile issue with QT4

    - by Cobus Kruger
    I've been trying to get a dead simple listing from a university textbook to compile with the newest QT SDK for Windows I downloaded last night. After struggling through the regular nonsense (no make.bat, need to manually add environment variables and so on) I am finally at the point where I can build. But only one of the two libraries seem to work. The .pro file I use is dead simple: SUBDIRS += utils \ dataobjects TEMPLATE = subdirs In each of these two subfolders I have the source for a library. Running QMAKE generates a makefile and running Make runs through all the preliminaries and then fails on the g++ call: g++ -enable-stdcall-fixup -Wl,-enable-auto-import -Wl,-enable-runtime-pseudo-reloc --out-implib,libdataobjects.a -shared -mthreads -Wl -Wl,--out-implib,c:\Users\Cobus\workspace\lib\libdataobjects.a -o ..\..\lib\dataobjects.dll object_script.dataobjects.Debug -L"c:\Users\Cobus\Portab~1\Qt\2010.02.1\qt\lib" -LC:\Users\Cobus\workspace\lib -lutils -lQtXmld4 -lQtGuid4 -lQtCored4 c:/users/cobus/portab~1/qt/2010.02.1/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../../mingw32/bin/ld.exe: cannot find -lutils The problem seems to be right near the end of the command line, where -lutils is added, indicating that there is a library by the name of utils. While I would have expected to see that, you'll notice the library names after --out include lib in the name, so they become libutils and libdataobjects. I have tried to figure out why this is happening, to no avail. Anyone have an idea what's going on?

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  • Multiple Unpacking Assignment in Python when you don't know the sequence length

    - by doug
    The textbook examples of multiple unpacking assignment are something like: import numpy as NP M = NP.arange(5) a, b, c, d, e = M # so of course, a = 0, b = 1, etc. M = NP.arange(20).reshape(5, 4) # numpy 5x4 array a, b, c, d, e = M # here, a = M[0,:], b = M[1,:], etc. (ie, a single row of M is assigned each to a through e) (My Q is not numpy specfic; indeed, i would prefer a pure python solution.) W/r/t the piece of code i'm looking at now, i see two complications on that straightforward scenario: i usually won't know the shape of M; and i want to unpack a certain number of items (definitely less than all items) and i want to put the remainder into a single container so back to the 5x4 array above, what i would very much like to be able to do is, for instance, assign the first three rows of M to a, b, and c respectively (exactly as above) and the rest of the rows (i have no idea how many there will be, just some positive integer) to a single container, all_the_rest = []. I'm not sure if i have explained this clearly; in any event, if i get feedback i'll promptly edit my Question.

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  • Which Stroustrup book should I use?

    - by Chris Simmons
    I'm a C# programmer that is looking to branch out. I'm bored of writing business software and want to start getting into graphics programming and games/simulators. So I figured, although writing that stuff isn't impossible in managed code, the "right" way to do that would be to look to C++, of course focussing on the language first, then getting into OpenGL or DirectX (or whatever). Way way back ('98? '99?) I had tried and failed to really grasp Stroustrup's The C++ Programming Language. I know that this book is often not recommended for the beginner. Anyway, I picked it back up (in a much more recent printing) and I'm actually getting it and enjoying it. I also have a copy of his textbook, Programming: Principles and Practice Using C++, which, as I understand it, is really geared toward teaching programming, not necessarily C++. I'm certainly not arrogant enough to claim I don't have anything more to learn about programming, data structures, algoriths, etc., however I'm not a novice there either. So my question is, with the goal of gaining the broader and more real-world-useful understanding of C++ and given my background, on which should I focus? The denser (as I perceive it) TCPPPL or the gentler Programming? EDIT: I thank everyone for the responses. However, I've got a personal choice here to make between these two books. Granted there are other very good books out there, but I'm already a good length into both of the books I mention and I'd like to finish one. So, can anyone respond on which would be the better and why? Time is not an issue; I'm not looking (at this point) at an "accelerated" read.

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  • JDBC call not executing

    - by dbyrne
    I am working on one of the DAOs for a medium sized web application. Unfortunately, it contains very convoluted logic, and makes hundreds of JDBC stored proc calls in loops. This is out of my control. I am working on a method inside the DAO which makes a single JDBC call. The simplified version of what this method looks like is this: DriverManager.registerDriver(new com.sybase.jdbc2.jdbc.SybDriver()); Connection con = DriverManager.getConnection((String)connectionDetails.get("DATABASE_URL") (String)connectionDetails.get("USERID"), (String)connectionDetails.get("PASSWORD")); String sqlToExecute = "{call " + STORED_PROC + "(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)}"; CallableStatement stmt = con.prepareCall(sqlToExecute); //Maybe I should try calling clearParameters here? stmt.setString(1,someData); //....Set of parameters.... if (!stmt.execute()) { //execute method never returns false } stmt.close(); Its pretty much a textbook JDBC call. All this stored proc does is insert a single row. Here is where things get crazy: This code works when you run it through a debugger line by line, but fails when you run it "full speed". Not only does it fail, but it doesn't throw any exception! The execute method always returns true. It just breezes right through the JDBC call without inserting a row to the database. If you go through the log files, copy the stored proc call and run it manually, it works (just like it does in debug mode). Whats strange is that the rest of the DAO, with all its hundreds of looped stored proc calls, works fine. My thinking is that Connection or CallableStatement is caching some value behind the scenes that is screwing things up. Has anyone ever seen anything like this before? A JDBC call failing with no exceptions? I know it will be impossible to provide a complete solution to this without seeing the whole application, I am just looking for suggestions on possible issues to investigate.

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  • C# Virtual method call in constructor - how to refactor?

    - by Cristi Diaconescu
    I have an abstract class for database-agnostic cursor actions. Derived from that, there are classes that implement the abstract methods for handling database-specific stuff. The problem is, the base class ctor needs to call an abstract method - when the ctor is called, it needs to initialize the database-specific cursor. I know why this shouldn't be done, I don't need that explanation! This is my first implementation, that obviously doesn't work - it's the textbook "wrong way" of doing it. The overridden method accesses a field from the derived class, which is not yet instantiated: public abstract class CursorReader { private readonly int m_rowCount; protected CursorReader() { m_rowCount = CreateCursor(sqlCmd); //virtual call ! } protected abstract int CreateCursor(string sqlCmd); } public class SqlCursorReader : CursorReader { private SqlConnection m_sqlConnection; public SqlCursorReader(string sqlCmd, SqlConnection sqlConnection) { m_sqlConnection = sqlConnection; //field initialized here } protected override int CreateCursor(string sqlCmd) { //uses not-yet-initialized member *m_sqlConnection* //so this throws a NullReferenceException var cursor = new CustomCursor(sqlCmd, m_sqlConnection); return cursor.Count(); } } I will follow up with an answer on my attempts to fix this...

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