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• Concise description of the lua vm?

  - by anon

  I've skimmed Programing in Lua, I've looked at the Lua Reference. However, they both tells me this function does this, but not how. When reading SICP, I got this feeling of: "ah, here's the computational model underlying scheme"; I'm trying to get the same sense concerning lua -- i.e. a concise description of it's vm, a "how" rather than a "what". Does anyone know of a good document (besides the C source) describing this? Thanks!

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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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• Why does using cons to create a pair of two lists produce a list and two elements?

  - by fingerprint211b

  I've started learning Scheme, for fun mostly, and because I've never used a functional language before. I chose Scheme because I wanted to read SICP for a long time. Anyway, I'm currently learning about lists, and before that I learned about cons, car and cdr. And there's an example that creates a list of lists with cons, like this : (cons (list 1 2) (list 3 4)) The resulting list is ((1 2) 3 4), which doesn't make sense to me, I would expect ((1 2)(3 4)) to be the result (a list made out of two lists). Why does it behave like that? I realize that if I were to use car, I would get (1 2), and cdr I'd get (3 4) becaue cdr always returns "the rest", but I don't understand why the list isn't made of two lists?

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• What should I do or learn to better prepare myself for a co-op position?

  - by Chris Vinz

  I'm currently taking computer systems in a technical institute and I will start looking for a coop job by next September. Since summer vacation is only a few weeks away, I was wondering what I should learn or do to help me land a job and do well in it. I'm pretty sure I'm ahead of most of my classmates since I got around 1.5 years "head start." For now, I'm planning to learn how to use source control (git - for no reason really) and was actually thinking of learning Scheme through SICP and maybe build something nice with it at the end. On the other hand, I'm wondering if it's better to expand on what I know right now and I'm thinking of C++ since I enjoy it a lot more than others like Java. Can I get advice on this? thanks!

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• Fun with Python

  - by dotneteer

  I am taking a class on Coursera recently. My formal education is in physics. Although I have been working as a developer for over 18 years and have learnt a lot of programming on the job, I still would like to gain some systematic knowledge in computer science. Coursera courses taught by Standard professors provided me a wonderful chance. The three languages recommended for assignments are Java, C and Python. I am fluent in Java and have done some projects using C++/MFC/ATL in the past, but I would like to try something different this time. I first started with pure C. Soon I discover that I have to write a lot of code outside the question that I try to solve because the very limited C standard library. For example, to read a list of values from a file, I have to read characters by characters until I hit a delimiter. If I need a list that can grow, I have to create a data structure myself, something that I have taking for granted in .Net or Java. Out of frustration, I switched to Python. I was pleasantly surprised to find that Python is very easy to learn. The tutorial on the official Python site has the exactly the right pace for me, someone with experience in another programming. After a couple of hours on the tutorial and a few more minutes of toying with IDEL, I was in business. I like the “battery supplied” philosophy that gives everything that I need out of box. For someone from C# or Java background, curly braces are replaced by colon(:) and tab spaces. Although I tend to miss colon from time to time, I found that the idea of tab space is actually very nice once I get use to them. I also like to feature of multiple assignment and multiple return parameters. When I need to return a by-product, I just add it to the list of returns. When would use Python? I would use Python if I need to computer anything quick. The language is very easy to use. Python has a good collection of libraries (packages). The REPL of the interpreter allows me test ideas quickly before committing them into script. Lots of computer science work have been ported from Lisp to Python. Some universities are even teaching SICP in Python. When wouldn’t I use Python? I mostly would not use it in a managed environment, such as Ironpython or Jython. Both .Net and Java already have a rich library so one has to make a choice which library to use. If we use the managed runtime library, the code will tie to the particular runtime and thus not portable. If we use the Python library, then we will face the relatively long start-up time. For this reason, I would not recommend to use Ironpython for WP7 development. The only situation that I see merit with managed Python is in a server application where I can preload Python so that the start-up time is not a concern. Using Python as a managed glue language is an over-kill most of the time. A managed Scheme could be a better glue language as it is small enough to start-up very fast.

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• Looking for a real-world example illustrating that composition can be superior to inheritance

  - by Job

  I watched a bunch of lectures on Clojure and functional programming by Rich Hickey as well as some of the SICP lectures, and I am sold on many concepts of functional programming. I incorporated some of them into my C# code at a previous job, and luckily it was easy to write C# code in a more functional style. At my new job we use Python and multiple inheritance is all the rage. My co-workers are very smart but they have to produce code fast given the nature of the company. I am learning both the tools and the codebase, but the architecture itself slows me down as well. I have not written the existing class hierarchy (neither would I be able to remember everything about it), and so, when I started adding a fairly small feature, I realized that I had to read a lot of code in the process. At the surface the code is neatly organized and split into small functions/methods and not copy-paste-repetitive, but the flip side of being not repetitive is that there is some magic functionality hidden somewhere in the hierarchy chain that magically glues things together and does work on my behalf, but it is very hard to find and follow. I had to fire up a profiler and run it through several examples and plot the execution graph as well as step through a debugger a few times, search the code for some substring and just read pages at the time. I am pretty sure that once I am done, my resulting code will be short and neatly organized, and yet not very readable. What I write feels declarative, as if I was writing an XML file that drives some other magic engine, except that there is no clear documentation on what the XML should look like and what the engine does except for the existing examples that I can read as well as the source code for the 'engine'. There has got to be a better way. IMO using composition over inheritance can help quite a bit. That way the computation will be linear rather than jumping all over the hierarchy tree. Whenever the functionality does not quite fit into an inheritance model, it will need to be mangled to fit in, or the entire inheritance hierarchy will need to be refactored/rebalanced, sort of like an unbalanced binary tree needs reshuffling from time to time in order to improve the average seek time. As I mentioned before, my co-workers are very smart; they just have been doing things a certain way and probably have an ability to hold a lot of unrelated crap in their head at once. I want to convince them to give composition and functional as opposed to OOP approach a try. To do that, I need to find some very good material. I do not think that a SCIP lecture or one by Rich Hickey will do - I am afraid it will be flagged down as too academic. Then, simple examples of Dog and Frog and AddressBook classes do not really connivence one way or the other - they show how inheritance can be converted to composition but not why it is truly and objectively better. What I am looking for is some real-world example of code that has been written with a lot of inheritance, then hit a wall and re-written in a different style that uses composition. Perhaps there is a blog or a chapter. I am looking for something that can summarize and illustrate the sort of pain that I am going through. I already have been throwing the phrase "composition over inheritance" around, but it was not received as enthusiastically as I had hoped. I do not want to be perceived as a new guy who likes to complain and bash existing code while looking for a perfect approach while not contributing fast enough. At the same time, my gut is convinced that inheritance is often the instrument of evil and I want to show a better way in a near future. Have you stumbled upon any great resources that can help me?

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• University teaches DOS-style C++, how to deal with it

  - by gaidal

  Half a year ago I had a look at available programming educations. I chose this one because unlike most of the choices: The majority of the courses seemed to be about something concrete and useful; the languages used are C++ and Java which are platform-independent; later courses include developing for mobile devices and a course on Android development, which seemed modern and relevant. Now after two introductory courses we're just starting with C++, and my programming professor seems a bit weird. He's tested us on things like "why should you use constants" and "why are globals bad" in a kind of mechanical way, without much context, before teaching actual programming. His handouts use system("pause"), system("cls"), and getch() from some conio.h that seems ancient according to what I've read. I just did a task that was about printing the "ASCII letters from 32 to 255" (huh?), with an example picture showing a table with Windows' Extended ASCII - of course I got other results for 128-255 on my Arch Linux that uses Unicode, and this isn't mentioned at all. I don't know, it just doesn't seem right... As if he is teaching programming because he has to, perhaps? Should I bring such things up? Hmm. I was looking forward to learning from someone who really knows stuff, and in an academic, rigorous way, like SICP or something. Aren't professors in programming supposed to be like that? I studied math for a while and every teacher and assistant there were really precise about what they said, but this is my second programming teacher that is sort of disappointing. Oh well. Now, question: Is this what to expect from universities or Not OK, and how do I deal with it? I have never touched the language C++ (or C) until now, and am not the right person to jump up and say "This is So Wrong!", so if I google something and find 10 people who say "xxx is blasphemy", how do I skillfully communicate this? I do think it would be better for those classmates who are total beginners not to learn bad habits (such as these vibes of total ignorance of other platforms!) during the upcoming courses, but don't want to disrespect the teacher. I don't know if it's reasonable or just cocky to bring up things like "what about other platforms?" or "but what about this article or stackoverflow answer that I read that said..." for every assignment? Or, if he keeps ignoring non-Windows-programming, should I give up and focus on my own projects or somehow argue that this really isn't OK nowadays? Are there any programming teachers out there, what do you think? By the way these are web-based courses, all interaction between teachers and students takes place in a forum. EDIT: A few answers seem to be making some incorrect assumptions, so maybe I should add a few things. I have been doing programming for fun on and off for 10 years, am pretty comfortable in 3 languages and read programming blogs et c regularly. Also, I feel kind of done being a student, having a degree in another field. I just need another, relevant diploma to work as a programmer, so I'm going back for that. Studying computer science for 5 years is not for me anymore, even though I enjoy learning and solving problems in my free time. Second, let me highlight that I don't expect it to be like the industry at all, quite the contrary. I expect it to be academic, dry and unnecessarily correct. No, it's not just math. Every professor I have had in math, or Japanese (major) or Chinese (minor) have been very very academic, discussing subtle points for hours with passion. But the courses I'm taking now and a previous one in programming don't seem serious. They neither resemble industry NOR academia. That is the problem. And it's not because I can't learn programming anyway. Third, I don't necessarily want to learn C++ or Android development, and I know I could teach myself those and anything else if I wanted to. But I am going back to school anyway, and those platform-independent languages and mobile stuff made me think that maybe they're serious about teaching something relevant here. Seems like I got this wrong, but we'll see.

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• WCF: WSDL-first approach: Problems with generating fault types

  - by Juri

  Hi, I'm currently in the process of creating a WCF webservice which should be compatible with WS-I Basic Profile 1.1. I'm using a wsdl-first approach (actually for the first time), defining first the xsd for the complex types, the WSDL and then using svcutil.exe for generating the according server as well as client-side interfaces/proxies. So far everything works fine. Then I decided to add a fault to my WSDL. Regenerating with svcutil succeeded, but then I noticed that my generated fault doesn't have the properties I defined in my xsd file (which is imported by my WSDL). Fault XSD definition <?xml version="1.0" encoding="UTF-8"?> <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://product.mycompany.com/groupsfault_v1.xsd" xmlns:tns="http://product.mycompany.com/groupsfault_v1.xsd"> <complexType name="groupsFault"> <sequence> <element name="code" type="int"/> <element name="message" type="string"/> </sequence> </complexType> </schema> Generated .Net fault object [System.Diagnostics.DebuggerStepThroughAttribute()] [System.CodeDom.Compiler.GeneratedCodeAttribute("System.Runtime.Serialization", "3.0.0.0")] [System.Xml.Serialization.XmlSchemaProviderAttribute("ExportSchema")] [System.Xml.Serialization.XmlRootAttribute(IsNullable=false)] public partial class groupFault : object, System.Xml.Serialization.IXmlSerializable { private System.Xml.XmlNode[] nodesField; private static System.Xml.XmlQualifiedName typeName = new System.Xml.XmlQualifiedName("groupFault", "http://sicp.services.siag.it/groups_v1.wsdl"); public System.Xml.XmlNode[] Nodes { get { return this.nodesField; } set { this.nodesField = value; } } public void ReadXml(System.Xml.XmlReader reader) { this.nodesField = System.Runtime.Serialization.XmlSerializableServices.ReadNodes(reader); } public void WriteXml(System.Xml.XmlWriter writer) { System.Runtime.Serialization.XmlSerializableServices.WriteNodes(writer, this.Nodes); } public System.Xml.Schema.XmlSchema GetSchema() { return null; } public static System.Xml.XmlQualifiedName ExportSchema(System.Xml.Schema.XmlSchemaSet schemas) { System.Runtime.Serialization.XmlSerializableServices.AddDefaultSchema(schemas, typeName); return typeName; } } Is this ok?? I'd expect to have an object created that contains properties for "code" and "message" s.t. you can then throw it by using something like ... throw new FaultException<groupFault>(new groupFault { code=100, message="error" }); ... (sorry for the lower-case type definitions, but this is generated code from the WSDL) Why doesn't the svcutil.exe generate those properties?? Some sources on the web suggested to add the /useSerializerForFaults option. I tried it, it doesn't work giving me an exception that the fault type is missing on the wsdl:portType declaration. Validation with several other tools succeeded however. Any help is VERY appreciated :) thx

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• How to setup a webserver in common lisp?

  - by Serpico

  Several months ago, I was inspired by the magnificent book ANSI Common Lisp written by Paul Graham, and the statement that Lisp could be used as a secret weapon in your web development, published by the same author on his blog. Wow, that is amazing. That is something that I have been looking for long time. The author really developed a successful web applcation and sold it to Yahoo. With those encouraging images, I determined to spend some time (1 year or 2 year, who knows) on learning Common Lisp. Maybe someday I will development my web application and turn into a great Lisp expert. In fact, this is the second time for me to get to study Lisp. The first time was a couple of years ago when I was fascinated by the famous book SICP but found later Scheme was so unbelievably immature for real life application. After reading some chapters of ANSI Common Lisp, I was pretty sure that is a great book full of detailed exploration of Common Lisp. Then I began to set up a web server in Common Lisp. After all, this should be the best way if you want to learn something. Demonstrations are always better than definations. As suggested by the book Practical Common Lisp (by the way, this is also a great book), I chose to install AllegroServe on some Common Lisp implementation. Then, from somewhere else, I learned that Hunchentoot seems to be better than AllegroServe. (I don't remember where and whom this word is from. So don't argue with me.) Ironically, you know what, I never could installed the two packages on any Common Lisp implementation. More annoyingly, I even don't know why. The machine always spit up a lot of jargon and lead me into a chaos. I've tried searching the internet and have not found anything. Could anybody who has successfully installed these packages in Linux tell me how you did it? Have you run into any trouble? How did you figured out what is wrong and fixed it? The more detailed, the more helpful.

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