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• sqrt(int_value + 0.0) ? The point?

  - by Earlz

  Hello, while doing some homework in my very strange C++ book, which I've been told before to throw away, had a very peculiar code segment. I know homework stuff always throws in extra "mystery" to try to confuse you like indenting 2 lines after a single-statement for-loop. But this one I'm confused on because it seems to serve some real-purpose. basically it is like this: int counter=10; ... if(pow(floor(sqrt(counter+0.0)),2) == counter) ... I'm interested in this part especially: sqrt(counter+0.0) Is there some purpose to the +0.0? Is this the poormans way of doing a static cast to a double? Does this avoid some compiler warning on some compiler I do not use? The entire program printed the exact same thing and compiled without warnings on g++ whenever I left out the +0.0 part. Maybe I'm not using a weird enough compiler?

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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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• 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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• Please help me regarding Time Zones of different Countries

  - by Rajesh Rolen- DotNet Developer

  I am creating a web site which in which the service providers can create their schedule (date and time) at which they can provide service and client can book them. but the problem is that service providers are from different countries. so their is Time zone problem. please give me a best solution for it, that i should convert the time of service providers (while inserting schedule) to GMT in javascript (client side) or in my CS file (server side) how to manage all this.. plez give me a link of any such demo in which time zone are handled properly.... if i converts it at client side then problem is that may be client have set wrong time zone on his pc... and if i convert it at server side.. than how to manage .. how to show it to service providers their schedule and to clients accordingly.. please help me out.. i am using asp.net (VS 2005) and sql server.

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• What books help one to learn to read code?

  - by Daniel

  Lion's Commentary on Unix Sixth Edition with Source Code is a wonderful book to learn how to read code. Reading code is important -- how does one learn how to write excellent code without having read excellent code? But, sadly, while great writers, of fiction and non-fiction, all spend a great deal of time reading stuff, we, programmers, seem to avoid it like the plague. Worse still, programming books usually go the same way. They might show a pattern or a style, but they often avoid showing good, complex code, and helping one go through it. There are exceptions, of course. I hope. So, with that in mind, what books are to be found which help one learn how to read code?

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• Why in Objective-C, we use self = [super init] instead of just [super init]?

  - by ????

  In a book, I saw that if a subclass is overriding a superclass's method, we may have self = [super init]; First, is this supposed to be done in the subclass's init method? Second, I wonder why the call is not just [super init]; ? I mean, at the time of calling init, the memory is allocated by alloc already (I think by [Foobar alloc] where Foobar is the subclass's name. So can't we just call [super init] to initialize the member variables? Why do we have to get the return value of init and assign to self? I mean, before calling [super init], self should be pointing to a valid memory allocation chuck... so why assigning something to self again? (if assigning, won't [super init] just return self's existing value?)

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• sample/good rails projects to learn from

  - by learningrails

  I am just starting with Rails. I've read through the AWDR book and am currently working on a side project in rails. I want to get an idea of what a good rails project should look like in order to learn what the best practices are. Can you guys point me to some good rails projects on github that not only work well but are well written? Or am I better off reading Rails best practices? if so, any good ones?

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• Drupal Navigation Conundrum

  - by Vecta

  I'm attempting to set up navigation withing a Drupal site and am having a bit of trouble. I'm trying to have a series of pages that each have a set number of sub-pages. These pages will need to link to one another. All pages will contain similar content. For instance: Page 1 will have sub-pages a, b, c, d, e, and f all with content related to the topic of page 1 Page 2 will have sub-pages a, b, c, d, e, and f with content related to the topic of page 2 I'd like these links to appear in a horizontal nav bar on each page. Is it possible to accomplish this using the book module? I've also read some information about the taxonomy menu module that sounds promising, but I'm not really sure how that would work. What route should I look into? Thanks for any input!

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• iPhone development books

  - by hhafez

  I've looked on SO and it seems that most people have been recomending books as the best iphone development resource due to the lack of resources on the web. I've seen the book the The Pragmatic Programmer: iPhone SDK development been recomended a few times. I'm planning to go buy a couple of books. Which should I go for? Please give reason :) A bit of background : I have a strong background in C and I've played around with Cocoa so something iphone specific would be best ( but I'm open for suggestions ;)) Update I'm not looking for simple listings of iphone SDK related books, I can google that ;) I want books that people are reading/have read and would recomend :) Final Update I just ordered my copy of Beginning iPhone Development: Exploring the iPhone SDK. My main reasons on chosing it are that it's already in print (unlike the pragmatic one) and I looked at the preview on their website and I liked it.

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• practicing C over the summer

  - by Jefferson Shawn

  Hi, I'm a student with a bit of experience in Java and C++ (one semester each) Currently, I'm going through K&R and working on the exercises in the book. However, I was thinking of what I could work on over the summer since I'm almost done with K&R and I will have a lot of free time soon. I really like building command line applications so I was thinking of getting involved with the coreutils project somehow. My question is, is it too early for me to be messing with coreutils? Should I be working on something a bit simpler perhaps? I'm a bit new with the Linux/Open source world if that matters but I'm really enjoying it. I've done some project euler problems and I don't really like it that much.

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• question about missing element in array

  - by davit-datuashvili

  i have following problem from book introduction algorithm second edition by MIT university problem is following An array A[1 . . n] contains all the integers from 0 to n except one. It would be easy to determine the missing integer in O(n) time by using an auxiliary array B[0 . . n] to record which numbers appear in A. In this problem, however, we cannot access an entire integer in A with a single operation. The elements of A are represented in binary, and the only operation we can use to access them is “fetch the j th bit of A[i],” which takes constant time. Show that if we use only this operation, we can still determine the missing inte- ger in O(n) time please help

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• Why does the right-shift operator produce a zero instead of a one?

  - by mrt181

  Hi, i am teaching myself java and i work through the exercises in Thinking in Java. On page 116, exercise 11, you should right-shift an integer through all its binary positions and display each position with Integer.toBinaryString. public static void main(String[] args) { int i = 8; System.out.println(Integer.toBinaryString(i)); int maxIterations = Integer.toBinaryString(i).length(); int j; for (j = 1; j < maxIterations; j++) { i >>= 1; System.out.println(Integer.toBinaryString(i)); } In the solution guide the output looks like this: 1000 1100 1110 1111 When i run this code i get this: 1000 100 10 1 What is going on here. Are the digits cut off? I am using jdk1.6.0_20 64bit. The book uses jdk1.5 32bit.

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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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• Is there a font that can't be recognised by an OCR?

  - by user1820564

  I am trying to write a document that can only be read by humans. The document content can't be copied. For that purpose, I am converting its pages to pictures and adding them back to a PDF file. The main issue is that any OCR program can get back the whole written text, especially that the page is going to be clear (as opposed to a scanned book) which will increase the OCR accuracy. So, is there a font that can't be recognized by an OCR. Otherwise, is there a technique that will make my document only readable by humans, yet unrecognised by an OCR? (for instance, adding a specific background, etc...) Thank you in advance.

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• Best and shortest books on C++/STL/C#/J2SE to prepare for job inteview/tests

  - by Nerd

  I am a software developer with 10+ years commercial experience, I am comfortable with nearly all of imperative languages. But I realized that most of employers prefer not candidates who is able to deliver good software but those who is trained to answer questions like "what are ten differences between pointers and references in C++" or "what this messy code fragment will print". Last time I have read a book on C++ 15 years ago in secondary school and yes, that was Bjarne Stroustrup. But today I need something quick, without long philosophical explanations about polymorphism etc but with focus to silly interview tests. So, can you recommend any short and effective books to refresh my theoretical knowledge? Thank you.

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• How to convince a colleague that code duplication is bad?

  - by vitaut

  A colleague of mine was implementing a new feature in a project we work on together and he did it by taking a file containing the implementation of a similar feature from the same project, creating a copy of it renaming all the global declarations and slightly modifying the implementation. So we ended up with two large files that are almost identical apart from renaming. I tried to explain that it makes our project more difficult to maintain but he doesn't want to change anything saying that it is easier for him to program in such way and that there is no reason to fix the code if it "ain't broke". How can I convince him that such code duplication is a bad thing? It is related to this questions, but I am more interested in the answers targeted to a technical person (another programmer), for example a reference to an authoritative source like a book would be great. I have already tried simple arguments and haven't succeeded.

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• Simple Obj-C Memory Management Question

  - by yar

  This is from some sample code from a book // On launch, create a basic window - (void)applicationDidFinishLaunching:(UIApplication *)application { UIWindow *window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]; UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:[[HelloController alloc] init]]; [window addSubview:nav.view]; [window makeKeyAndVisible]; } But a release is never called for window nor for nav. Release should be called since alloc was called, right? If #1 is right, then I would need to store a reference to each of these in an instance variable in order to release them in the dealloc? Perhaps I'm wrong all around...

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• Animation on single UIWebView

  - by Shri

  I have searched quite a bit(sample one, Sample two) but cant seem to get the correct answer. I have a webview on my XYZ view controller class. When i press on a button, it takes an URL from an array and re-loads the same webview. Now I need to do the flip book animation on it. Same webview should be reloaded. That is the webview should rotate around its own axis 180/360 degree while the loading of next url is going on. Is this possible?

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• x86 Assembly - printf doesn't print without "\n"

  - by Bitani

  So I'm confused. I'm going through the book "Programming from the Ground Up" and am working with using libraries. printf is working just fine so long as I include a "\n" in the string, but without it it will print absolutely nothing. Any idea why this happens? Code: .section .data my_str: .ascii "Jimmy Joe is %d years old!\n\0" my_num: .long 76 .section .text .globl _start _start: pushl my_num pushl $my_str call printf movl $1, %eax movl $0, %ebx int $0x80 Also, when I use -m elf_i386 for 32-bit mode and -dynamic-linker /lib/ld-linux.so.2 -lc to link, I get the warning ld: skipping incompatible /usr/lib64/libc.so when searching for -lc If that makes any difference, or if anybody has any suggestions as to how to have it load the 32-bit library directly. Thanks!

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• Get Data from Windows Form into C# program

  - by Jimmy

  I want my C# program to collect data. Then, when the OK button is clicked, I want this data to be loaded into my program -- such as into variables in Main(), or into data members of a class I have constructed, and I want the form to then go away -- not be hidden, but actually closed. Alas, read as I might in the book I have, the data collected by the form stays in the form, execution proceeds within the form, and the same form is used to display the result of the program's computations. Sheesh. All I want is to capture the form's information, close the form and proceed with my program. I would appreciate some tips on geting data from a form into Main() or into a class's data members. Thanks, Lucky

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• Iterator in Java.

  - by theband

  What is Iterator and collections? Does these two have any relations? // the interface definition Interface Iterator { boolean hasNext(); Object next(); // note "one-way" traffic void remove(); } // an example public static void main (String[] args){ ArrayList cars = new ArrayList(); for (int i = 0; i < 12; i++) cars.add (new Car()); Iterator it = cats.iterator(); while (it.hasNext()) System.out.println ((Car)it.next()); } Does the Interface Iterator has these method names alone predefined or its user defined?. What does these four lines below actually tell? cars.add (new Car()); Iterator it = cats.iterator(); while (it.hasNext()) System.out.println ((Car)it.next()); Thanks i am going through a book in collections.

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• Should I use block identifiers ("end;") in my code?

  - by JosephStyons

  Code Complete says it is good practice to always use block identifiers, both for clarity and as a defensive measure. Since reading that book, I've been doing that religiously. Sometimes it seems excessive though, as in the case below. Is Steve McConnell right to insist on always using block identifiers? Which of these would you use? //naughty and brief with myGrid do for currRow := FixedRows to RowCount - 1 do if RowChanged(currRow) then if not(RecordExists(currRow)) then InsertNewRecord(currRow) else UpdateExistingRecord(currRow); //well behaved and verbose with myGrid do begin for currRow := FixedRows to RowCount - 1 do begin if RowChanged(currRow) then begin if not(RecordExists(currRow)) then begin InsertNewRecord(currRow); end //if it didn't exist, so insert it else begin UpdateExistingRecord(currRow); end; //else it existed, so update it end; //if any change end; //for each row in the grid end; //with myGrid

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• Why use constants in programming?

  - by Adam N

  I've just been going back over a bit of C studying using Ivor Horton's Beginning C book. I got to the bit about declaring constants which seems to get mixed up with variables in the same sentence. Just to clarify, what is the difference in specifying constants and variables in C, and really, when do you need to use a constant instead of a variable? I know folks say to use a constant when the information doesn't change during program execution but I can't really think of a time when a variable couldn't be used instead. Thanks

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• Basic iPhone app help

  - by LaSha

  I'm new to iphone development and have about 5 days of experience with xcode, so I need some help developing the following app. I'm not sure where to start. The app is very simple, it's like a simplified version of the address book that came with the iphone a screen shows a list of all items in a list view list can be filtered through search list can also be favorites or unfavorites selecting an item will take the user to another screen with more detailed information (a pic, location,) the data should be stored in an xml file. Can you guys point me to the right path? or know any code samples that does this? Been stuck on this for days now. Thanks!!!

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• Does anybody have practice in programming PCMEF - architectures?

  - by Erkki

  PCMEF is an architecture style presented in the book Practical Software Engineering by Maciaszek and Liong. The layers are: P: Presentation C: Controller M: Mediator E: Entity F: Foundation. It is some kind of enchancement compared with MVC - architecture. I recommend it to interactice, data and communicating - oriented purposes. I have programmed it using Visual Prolog. Foundation in my applications is the data model (domains) for the application. PCMEF is like a simulated computer: Presentation is the display, Controller the user interface and event handling, Mediator the internal logic and data highway. Entity is the database or external interfaces and F defines the knowledge. This is a really nice small architecture. Does any other have experiance of it?

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