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  • how is a macro expanded in clojure?

    - by john wang
    In the book Programming Clojure(Stuart), when read how macros are expanded I got confused. user=> (defmacro chain ([x form] (list '. x form)) ([x form & more] (concat (list 'chain (list '. x form)) more))) #'user/chain The above macro can be expanded as: user=> (macroexpand '(chain a b c)) (. (. a b) c) But the following is only expanded to the first level: user=> (macroexpand '(and a b c)) (let* [and__3822__auto__ a] (if and__3822__auto__ (clojure.core/and b c) and__3822__auto__)) The and macro source: user=> (source and) (defmacro and([] true) ([x] x) ([x & next] `(let [and# ~x] (if and# (and ~@next) and#)))) Why is the chain macro expanded all the way but the and not ? Why is it not expanded to something like the following: user=> (macroexpand '(chain a b c d)) (. (chain a b c) d)

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  • tutorials/books to create a plugin/module/library?

    - by fayer
    i wonder if there are tutorials/books explaining how you create a library/plugin/module for other to implement? libraries/frameworks like solr, doctrine, codeigniter etc. cause it seems that they follow the same pattern. having one "bootstrap" file to load configurations, other classes and so on. i aim to understand the basics, so i can create a such library. cause at the moment i want to code an address book that other can use. just include a bootstrap file and they are ready to use my classes (like Doctrine). recommendations of sources to learn these things of stuff? you experienced guys, how did you learn it? thanks.

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  • Win32: No Window Appears

    - by SoulBeaver
    I was programming the example code from Frank Luna's book "Introduction to 3D Game Programming with DirectX 10". The code is the first Win32 example in the Appendix A: Windows Programming section. Right now, the program compiles under both VC++ 2008/2010, but no window appears, although the debug session has started and I have to forcefully close it. I have no idea where it is, I'm not using Win32 Console mode, I have closed all other windows and no other IDE or session of VC++ is running. Any idea why this might be happening? PS: I have also checked my Processes. It is indeed running.

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  • Resources for dashboard app backend design

    - by Nix
    I am looking for examples of code/data/infrastructure design for a dashboard-style webapp. I am designing an interface for staff and faculty at a university to access departmental resources and be alerted of cyclical processes, events, deadlines, etc. Technologies I am working with: apache tomcat 6 and a mySQL database, JSP (including JSTL), bootstrap 3, and javascript/jquery. I have basic experience most of these technologies building smaller web apps but was hoping someone could direct me towards a book or other resource that discusses how to design the db architecture (and maybe how to template) for a dashboard, esp. for something like a notification systems. Any suggestions?

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  • What is the benefits and drawbacks of using header files?

    - by vodkhang
    I had some experience on programming languages like Java, C#, Scala as well as some lower level programming language like C, C++, Objective - C. My observation is that low level languages separate out header files and implementation files while other higher level programming language never separate it out. They use some identifiers like public, private, protected to do the jobs of header files. I saw one benefit of using header file (in some book like Code Complete), they talk about that using header files, people can never look at our implementation file and it helps with encapsulation. A drawback is that it creates too many files for me. Sometimes, it looks like verbose. It is just my thought and I don't know if there are any other benefits and drawbacks that people ever see and work with header file This question may not relate directly to programming but I think that if I can understand better about programming to interface, design software.

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  • Why use a do-end block in Lua?

    - by Mayron
    I keep trying to find answers for this but fail to do so. I wanted to know, what is the do-end block actually used for? It just says values are used when needed in my book so how could I use this? Do I use it to reduce the scope of local variables by placing a function in a do-end loop and place local variables outside of the function but inside this do-end block and the variables will be seen by the function? But then can the function still be called? Sorry for being very vague. I hope that makes sense. Maybe an illustrated example might be useful ^^

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  • Insert objects into a collection with LINQ based on a property of the existing objects in the collection

    - by DavidS
    Hi, I've got a collection of object which contains data as follows: FromTime Duration 2010-12-28 24.0000 2010-12-29 24.0000 2010-12-30 24.0000 2010-12-31 22.0000 2011-01-02 1.9167 2011-01-03 24.0000 2011-01-04 24.0000 2011-01-05 24.0000 2011-01-06 24.0000 2011-01-07 22.0000 2011-01-09 1.9167 2011-01-10 24.0000 In the "FromTime" column, there are data "gaps" i.e. 2011-01-01 and 2011-01-08 are "missing". So what I'd like to do is to loop through a range of dates (in this instance 2010-12-28 to 2011-01-10) and "fill in" the "missing" data with a duration of 0. As I've just started with LINQ, I feel that it should be "fairly" easy but I can't quite get it right. I'm reading the book "LINQ in Action" but feel that I'm still quite a way off before I can resolve this particular issue. So any help would be much appreciated. David

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  • IOS SDK : first advices for beginners

    - by VdesmedT
    I too often answer the same kind of questions regarding basic topics like memory management, UITableView, Interface Orientation, MVC, etc... I understand very well that everyone starting with that SDK is too exited about getting its hand on it but a few reading would save them hours of debugging and the frustration that come along with the feeling that "We miss something here". I'd like experience users to share the few small articles, white papers, docs, book chapters that helps other save their time and avoid frustration. My first vote would be for : IOS Memory Management Guide View Controller Programming Guide Table View Guide And as a General recommendation, read the Overview section that come along with every class documention in the reference library, they contains most of what you need to know to avoid big traps !

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  • Why There is a difference between assembly languages like Windows, Linux ?

    - by mcaaltuntas
    I am relatively new to all this low level stuff,assembly language.. and want to learn more detail. Why there is a difference between Linux, Windows Assembly languages? As I understand when I compile a C code Operating system does not really produce pure machine or assembly code, it produces OS dependent binary code.But why ? For example when I use a x86 system, CPU only understands x86 ASM am I right?.So Why we dont write pure x86 assembly code and why there are different assembly variations based on Operating system? If we would write pure ASM or OS produce pure ASM there wouldn't be binary compatilibty issues between Operating systems or Not ? I am really wondering all reasons behind them. Any detailed answer, article, book would be great. Thanks.

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  • CakePHP Routing Alias, no prefix

    - by Jason McCreary
    I have a dashboard with a series of widgets. Per specification, the widgets need to be buried under a /widgets/ directory. So I have added the following to my routes.php Router::connect('/widget/:controller/:action/*', array()); But I seem to be running into trouble on widgets/links/ and widgets/links/view/1 I am new to CakePHP, but this doesn't seem all that impressive. I have yet to find anything in the Book or by search. So any help is appreciated. Thanks.

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  • What are these values representative of in C bitwise operations?

    - by ajax81
    Hi All, I'm trying to reverse the order of bits in C (homework question, subject: bitwise operators). I found this solution, but I'm a little confused by the hex values (?) used -- 0x01 and 0x80. unsigned char reverse(unsigned char c) { int shift; unsigned char result = 0; for (shift = 0; shift < CHAR_BITS; shift++) { if (c & (0x01 << shift)) result |= (0x80 >> shift); } return result; } The book I'm working out of hasn't discussed these kinds of values, so I'm not really sure what to make of them. Can somebody shed some light on this solution? Thank you!

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  • Where can I learn advanced Haskell?

    - by FredOverflow
    In a comment to one of my answers, SO user sdcwc essentially pointed out that the following code: comb 0 = [[]] comb n = let rest = comb (n-1) in map ('0':) rest ++ map ('1':) rest could be replaced by: comb n = replicateM n "01" which had me completely stunned. Now I am looking for a tutorial, book or PDF that teaches these advanced concepts. I am not looking for a "what's a monad" tutorial aimed at beginners or online references explaining the type of replicateM. I want to learn how to think in monads and use them effectively, monadic "patterns" if you will.

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  • Please Recommend CS Project books

    - by kunjaan
    Programming Collective Intelligence is an awesome way to get your feet wet in Machine learning. I am looking for similar books which has small but interesting programming projects. Do you have any recommendations? Edit: It need not be related to machine learning. It could be any programming project-based books. Thanks. Edit2: Collective Intelligence in Action is one more book that looks at some interesting CS stuffs. Do you guys have any similar recommendations?

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  • An interesting project to implement to learn Antlr

    - by ajay
    Hi, I am learning Antlr from the book 'The Definitive Antlr reference'. I am still in the beginning stages. I like to do hands on stuff, so I was thinking it would be a great learning experience to do a good sample project. I am looking for a decently sized project, not too big. But just big and complicated enough to help me learn Antlr well. Your inputs will be greatly appreciated! Thanks!

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  • byte-sized bit pattern in C and its relevance?

    - by Nikunj Banka
    I a reading Kerninghan and Ritchie's C programming language book and on page 37 it mentions byte sized bit patterns like : '\013' for vertical tab . '\007' for bell character . My doubts : What is byte sized in it and and what's a bit pattern ? What relevance does this hold and where can I apply it ? Is it in any sense related to escape sequences ? I can't seem to find any information what so ever about these byte sized bit patterns on the web . please help . thanks .

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  • Bug in Programming Interviews Exposed?

    - by Sam
    Hi, I could not find an errata for the 2nd edition of this book. My question concerns the if-statement in the following piece of code. void removeHead (Node ** head) { Node * temp; if (!(*head)) { temp = (*head)->next; delete *head; *head = temp; } } So I understand that the point of the if-statement is to check if the Node is null. However by adding an additional "!" to the evaluation, wouldn't this negate the false value of null? Would it be correct to change it to something like: if (*head) { ... } Also if anyone knows where I can find an official errata for the 2nd edition that would be great. Thanks, Sam

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  • Question on preprocessor directives

    - by dotnetdev
    If I use proprocessor directives to define which code an OS will run, like so: #if winXP // Compiling for Windows XP platformName = "Microsoft Windows XP"; #elif win2000 // Compiling for Windows 2000 platformName = "Microsoft Windows 2000"; #elif win7 // Compiling for Windows 7 platformName = "Microsoft Windows 7"; #else // Unknown platform specified platformName = "Unknown"; How does the system pick up which OS is being used? This is an example from the book Visual C# 2010 Recipes, where the author says that the platformName variable (declaration ommitted), wil equal the OS above. Thanks

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  • Why does this C++ code result in a segmentation fault?

    - by user69514
    I keep getting a segmentation fault when the readAuthor() method is called. Does anybody know why this happens? I am supposed to use dynamic arrays, I know this would be so easy if I was using static array. #include <iostream> #include <string> #include <cstring> #include <cstdlib> using namespace std; /** declare arrays **/ int* isbnArr = new int[25]; char* authorArr = new char[25]; char* publisherArr = new char[25]; char* titleArr = new char[25]; int* editionArr = new int[25]; int* yearArr = new int[25]; int* pagesArr = new int[25]; float* retailPriceArr = new float[25]; float* discountedPriceArr = new float[25]; int* stockArr = new int[25]; /** function prototypes **/ int readIsbn(); char* readAuthor(); char* readPublisher(); char* readTitle(); int readEdition(); int readYear(); int readPages(); float readMsrp(); float readDiscountedPrice(); int readStockAmount(); void readonebook(int* isbn, char* author, char* title, char* publisher, int* edition, int* year, int* pages, float* msrp, float* discounted, int* inventory); int main() { bool stop = false; //flag when to stop loop int ind = 0; //index for current book while( !stop ){ cout << "Add book: press A: "; cout << "another thing here "; char choice; cin >> choice; if( choice == 'a' || choice == 'A' ){ readonebook(&isbnArr[ind], &authorArr[ind], &titleArr[ind], &publisherArr[ind], &editionArr[ind], &yearArr[ind], &pagesArr[ind], &retailPriceArr[ind], &discountedPriceArr[ind], &stockArr[ind]); test(&authorArr[ind]); ind++; } } return 0; } /** define functions **/ int readIsbn(){ int isbn; cout << "ISBN: "; cin >> isbn; return isbn; } char* readAuthor(){ char* author; cout << "Author: "; cin >> author; return author; } char* readPublisher(){ char* publisher = NULL; cout << "Publisher: "; cin >> publisher; return publisher; } char* readTitle(){ char* title = NULL; cout << "Title: "; cin >> title; return title; } int readEdition(){ int edition; cout << "Edition: "; cin >> edition; return edition; } int readYear(){ int year; cout << "Year: "; cin >> year; return year; } int readPages(){ int pages; cout << "Pages: "; cin >> pages; return pages; } float readMsrp(){ float price; cout << "Retail Price: "; cin >> price; return price; } float readDiscountedPrice(){ float price; cout << "Discounted Price: "; cin >> price; return price; } int readStockAmount(){ int amount; cout << "Stock Amount: "; cin >> amount; return amount; } void readonebook(int* isbn, char* author, char* title, char* publisher, int* edition, int* year, int* pages, float* msrp, float* discounted, int* inventory){ *isbn = readIsbn(); author = readAuthor(); title = readTitle(); publisher = readPublisher(); *edition = readEdition(); *year = readYear(); *pages = readPages(); *msrp = readMsrp(); *discounted = readDiscountedPrice(); *inventory = readStockAmount(); }

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  • Fitting maximum amount of shapes on a surface

    - by Fuu
    In industry, there is often a problem where you need to calculate the most efficient use of material, be it fabric, wood, metal etc. So the starting point is X amount of shapes of given dimensions, made out of polygons and/or curved lines, and target is another polygon of given dimensions. I assume many of the current CAM suites implement this, but having no experience using them or of their internals, what kind of computational algorithm is used to find the most efficient use of space? Can someone point me to a book or other reference that discusses this subject?

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  • CakePHP hasOne ineffeciency?

    - by Andre
    I was looking at examples on the CakePHP website, in particular hasOne used in linking models. http://book.cakephp.org/view/78/Associations-Linking-Models-Together My question is this, is CakePHP using two queries to build the array structure of data returned in a model that uses hasOne linkage? Taken from CakePHP: //Sample results from a $this-User-find() call. Array ( [User] => Array ( [id] => 121 [name] => Gwoo the Kungwoo [created] => 2007-05-01 10:31:01 ) [Profile] => Array ( [id] => 12 [user_id] => 121 [skill] => Baking Cakes [created] => 2007-05-01 10:31:01 ) ) Hope this all makes sense.

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  • Determining the number of objects in an NSArray

    - by Viral
    Hi friends, I am making a book application. To move to the next topic I am using a button. The Button works as it moves to the next topic, but at the end of the file my application gets the message obj_fatal and it crashes. If I knew how many objects there are in my NSArray then the problem will be solved. I am getting the details from a .plist file and storing it in to a array. So if any one knows how, please let me know. Thanks in advance. Viral.

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  • should variable be retained or not? iphone-sdk

    - by psebos
    Hi, in the following piece of code I got from a book. The NSString *pPath which is defined in the class as an instance variable. @interface MainViewController : UIViewController { NSString *pPath; } In the implementation after being set it is being retained. I assume that with the assignment the object is automatically retained (because it is an NSString) and there is no need to additionally retain it. - (void) initPrefsFilePath { NSString *documentsDirectory = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"]; pPath = [documentsDirectory stringByAppendingPathComponent: @"flippingprefs.plist"]; [pPath retain]; }

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  • MySQL: Limit output according to associated ID

    - by Jess
    So here's my situation. I have a books table and authors table. An author can have many books... In my authors page view, the user (logged in) can click an author in a tabled row and be directed to a page displaying the author's books (collected like this URI format: viewauthorbooks.php?author_id=23), very straight forward... However, in my query, I need to display the books for the author only, and not all books stored in the books table (as i currently have!) As I am a complete novice, I used the most simple query of: SELECT * FROM tasks_tb This returns the books for me, but returns every single value (book) in the database, and not ones associated with the selected author. And when I click a different author the same books are displayed for them...I think everyone gets what I'm trying to achieve, I just don't know how to perform the query. I'm guessing that I need to start using more advanced query clauses like INNER JOIN etc. Anyone care to help me out :)

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  • JavaScript inheritance extend function

    - by Zach
    I'm having some trouble understanding the IF clause at the end of this function from Pro JavaScript Design Patterns: function extend(subClass, superClass) { var F = function() {}; F.prototype = superClass.prototype; subClass.prototype = new F(); subClass.prototype.constructor = subClass; subClass.superclass = superClass.prototype; if(superClass.prototype.constructor == Object.prototype.constructor) { superClass.prototype.constructor = superClass; } } The book explains that these lines ensure that the superclass's constructor attribute is correctly set, even if the superclass is the Object class itself. Yet, if I omit those three lines and do the following: function SubClass() {}; extend(SubClass, Object); alert(Object.prototype.constructor == Object); The alert says 'true', which means the superclass's constructor is set correctly even without those last three lines. Under what conditions, then, does this IF statement do something useful? Thanks.

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  • iphone singleton object synchronization

    - by user127091
    I'm working on an iphone app but this is probably a general question. I have a singleton Model class and there would be scenarios where multiple NSOperations (threads) would exist and work with the singleton object. If they all call the same method in this object, do i need to have some locking mechanism? Or can this method be executed only one at a time? I do not have a computer science background but my guess is that all threads would have their CALL to the same address (this method). Also can you please suggest a good beginner programming book that discusses general programming concepts. I don't have the brains for Knuth kinda books.

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