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  • Proper NSArray initialization for ivar data in a method

    - by Joost Schuur
    I'm new to Objective-C and iPhone development and have been using Apress' Beginning iPhone 3 Programming book as my main guide for a few weeks now. In a few cases as part of a viewDidLoad: method, ivars like a breadTypes NSArray are initialized like below, with an intermediate array defined and then ultimately set to the actual array like this: NSArray *breadArray = [[NSArray alloc] initWithObjects:@"White", @"Whole Weat", @"Rye", @"Sourdough", @"Seven Grain", nil]; self.breadTypes = breadArray; [breadArray release]; Why is it done this way, instead of simply like this: self.breadTypes = [[NSArray alloc] initWithObjects:@"White", @"Whole Weat", @"Rye", @"Sourdough", @"Seven Grain", nil]; Both seem to work when I compile and run it. Is the 2nd method above not doing proper memory management? I assume initWithObjects: returns an array with a retain count of 1 and I eventually release breadTypes again in the dealloc: method, so that wraps things up nicely. I'm guessing 'self.breadTypes = ...' copies the data to the new array, which is why the original array can be safely released, correct?

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  • What is the ambiguity in this piece of code?

    - by cambr
    #include <iostream> using namespace std; class A { public: void eat(){ cout<<"A";} }; class B: public A { public: void eat(){ cout<<"B";} }; class C: public A { public: void eat(){ cout<<"C";} }; class D: public B,C { public: void eat(){ cout<<"D";} }; int main(){ A *a = new D(); a->eat(); } I am not sure this is called diamond problem or not, but why doesn't this work? When I said, a->eat() (remember eat() is not virtual), there is only one possible eat() to call, that of A. Why then, do I get this error: 'A' is an ambiguous base of 'D'

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  • Bidirectional one-to-many associations with indexed collections in NHibernate

    - by Jørn Schou-Rode
    Last summer, I asked a question regarding how to add new object to an IList mapped as a one-to-many with NHibernate. One of the answers let me to this paragraph in the documentation: Please note that NHibernate does not support bidirectional one-to-many associations with an indexed collection (list, map or array) as the "many" end, you have to use a set or bag mapping. While I am pretty sure I understand what this paragraph says, I have no idea why or how to work around this limitation. As I am now again working with a model that seems to require a "bidirectional one-to-many association with an index collection", I figured the time was right for follow-up questions: Why does NHibernate have this limitation on associations? It is my impression that the guys behind NHibernate are quite clever, so I assume there is a pretty good reason. What are the common workarounds for this shortcoming? Making the collection a non-indexed bag and adding an explicit Position property to the child class? Any better solutions?

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  • Concatenation Operator - PHP

    - by Chaitanya
    This might be a silly question but it struck me, and here i ask. <?php $x="Hi"; $y=" There"; $z = $x.$y; $a = "$x$y"; echo "$z"."<br />"."$a"; ?> $z uses the traditional concatenation operator provided by php and concatenates, conversely $a doesn't, My questions: a. by not using the concatenation operator, does it effect the performance? b. If it doesn't why at all have the concatenation operator. c. Why have 2 modes of implementation when one does the work?

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  • VS development on FDCC compliant Workstation

    - by paramesh kudlur
    Hi, I have a FDCC compliant workstation with FIPS 140-1 (Level 1) enabled. Now, i cannot run/debug any VS 2005/2008 applications on my machine I get the following error message on my browser Parser Error Message: This implementation is not part of the Windows Platform FIPS validated cryptographic algorithms. the Error points to line no 1 of default.aspx.cs file using system; The only way to successfully debug/run my application is to set the following registry key to 0 HKLM\System\CurrentControlSet\Control\Lsa\fipsalgorithmpolicy I understand that there are some Cryptographic algorithms that are not FIPS compliant on XP SP2 but i am not using cryptography at all. For that matter, the solution contains just default.aspx page with default code in .cs file, and even that fails to run. So my question is why the webpage fails to load, and why the error points to line #1 "using System;" statement? My next question is how can i develop on FIPS compliant locked down maching where i do not have edit rights on registry Thanks kudlur

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  • Function arguments VBA

    - by user1068249
    I have these three functions: When I run the first 2 functions, There's no problem, but when I run the last function (LMTD), It says 'Division by zero' yet when I debug some of the arguments have values, some don't. I know what I have to do, but I want to know why I have to do it, because it makes no sense to me. Tinn-function doesn't have Tut's arguments, so I have to add them to Tinn-function's arguments. Same goes for Tut, that doesn't know all of Tinn's arguments, and LMTD has to have both of Tinn and Tut's arguments. If I do that, it all runs smoothly. Why do I have to do this? Public Function Tinn(Tw, Qw, Qp, Q, deltaT) Tinn = (((Tw * Qw) + (Tut(Q, fd, mix) * Q)) / Qp) + deltaT End Function Public Function Tut(Q, fd, mix) Tut = Tinn(Tw, Qw, Qp, Q, deltaT) - (avgittEffektAiUiLMTD() / ((Q * fd * mix) / 3600)) End Function Public Function LMTD(Tsjo) LMTD = ((Tinn(Tw, Qw, Qp, Q, deltaT) - Tsjo) - (Tut(Q, fd, mix) - Tsjo)) / (WorksheetFunction.Ln ((Tinn(Tw, Qw, Qp, Q, deltaT) - Tsjo) / (Tut(Q, fd, mix) - Tsjo))) End Function

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  • Frameset frame cached by Firefox

    - by dragonfly
    Hi, I have a html page which contains nested frameset (don't ask why, I'm only servicing the app ;) ). What bothers me, is why FF caches Header.htm file constantly. I had to use clear cache to force browser to download it again. ctrl+f5 didn't help. <frameset rows="68,*" border="0" frameborder="no" framespacing="0"> <frame name="header" src="/Header.htm" scrolling="no" noresize> <frame name="footer" src="/Login.aspx?w=<% =company %>&amp;loc=<% =ccdom %>"> </frameset> Any ideas what is responsible for that behaviour? On the other hand, IE downloads the file without a hassle. Thanks, Pawel

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  • Multiple Tables or Multiple Schema

    - by Yan Cheng CHEOK
    http://stackoverflow.com/questions/1152405/postgresql-is-better-using-multiple-databases-with-1-schema-each-or-1-database I am new in schema concept for PostgreSQL. For the above mentioned scenario, I was wondering Why don't we use a single database (with default schema named public) Why don't we have a single table, to store multiple users row? Other tables which hold users related information, with foreign key point to the user table. Can anyone provide me a real case scenario, which single database, multiple schema will be extremely useful, and can't solve by conventional single database, single schema.

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  • Assigning a default value to a final variable in case of an exception in Java

    - by frenetisch applaudierend
    Why won't Java let me assign a value to a final variable in a catch block after setting the value in the try block, even if it is not possible for the final value to be written in case of an exception. Here is an example that demonstrates the problem: public class FooBar { private final int foo; private FooBar() { try { int x = bla(); foo = x; // In case of an exception this line is never reached } catch (Exception ex) { foo = 0; // But the compiler complains // that foo might have been initialized } } private int bla() { // You can use any of the lines below, neither works // throw new RuntimeException(); return 0; } } The problem is not hard to work around, but I would like to understand why the compiler does not accept this. Thanks in advance for any inputs!

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  • using array_sum() in a while loop

    - by m477
    Hi folks, I'm learning PHP. Having trouble understanding why this piece of code isn't working. In particular: why is the result of array_sum($x) (1596) greater than $cap? Perhaps I'm not understanding the nature of while loops, but it seems to me (looking at a print_r($x)), the loop should cut out a step before it actually does. <?php function fibonacci_sum($cap = 1000){ list( $cur, $nxt, $seq ) = array( 0, 1, array() ); while ( array_sum($seq) < $cap ) { $seq[] = $cur; $add = $cur + $nxt; $cur = $nxt; $nxt = $add; } return $seq; } $x = fibonacci_sum(); echo array_sum($x); ?> Any insight is appreciated. Best, matt

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  • Symfony/Doctrine: Unserialize in action vs template

    - by Tom
    Hi, Can anyone tell me why calling "unserialize" works fine in an action but gives an offset error in a template? It's basically possible to unserialize a database text result into a variable in an action and pass it to template, in which case it displays fine: $this->clean = unserialize($this->raw); <?php echo $clean ?> But not if called directly in a template: <?php echo unserialize($raw) ?> Would be interested in knowing why this is so and whether there's some workaround. Thanks.

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  • SlideDown then call custom function

    - by user275074
    Hi, Having difficulty understanding why my function is being called twice. I'm trying to detect when a radio button is called (intRev_yes), check if a div is empty, slide down another div and then call a custome function which dynamically creates a date field. if(this.id=="intRev_yes"){ if($('div#mainField').is(':empty')){ $('.intRevSections').slideDown('slow',function(){ current=-1; addIrField(); }); } } When I alert out at each stage, after getting to the end (i.e. addIrField()), the script seems to go back to the slideDown() section and recalls addIrField(). I can't understand why, there are no loops. current is used as an index for the date field.

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  • MSP430 CMP operator

    - by Ludicrous
    Let's say I have the MSP430 assembly segment below: r15: 439c Memory map: 4390: 6045 0200 9c43 6400 8844 5044 363a 0000 Code: 448a: cmp #0x363a, 0x0(r15) 4490: jnz $+0x1c 4492: Code continues . . . 44ac: Jump to location The goal is to have the Z flag high. To do this with a cmp, both src and dst must be equal. If I have 363a in the memory location of r15, why is it that the resulting cmp does not trigger the Z flag? Through experimentation, I found that putting 3a36 in the memory location of r15 did in fact trigger the Z flag, but I don't understand why. If anyone could bring this to light, I would greatly appreciate it. If more information is needed, I will gladly provide it.

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  • java vs python. In what way is Java Better?

    - by oxinabox.ucc.asn.au
    What are the advantages of Java over Python? What are the disadvantagesof Python, over Java? Why isn't Java more like Python? Like why don't java have an command line iterpretor? I beleive Java must have some advantages, but...I'm yet to see them. Logically all languages have an advantage afaict: I learnt java before python, - a 6 month unicourse. I spend a couple of weeks using python (writting a script to make a C source file). I hated it at first (as it was so differnt from C). I realised I had fallen in love it it, when I noticed that when I went to do a follow on Java Course at uni, I'ld stopped giving my variables types, and was tryign to multiply strings.

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  • Concatenation Operator

    - by Chaitanya
    This might be a silly question but it struck me, and here i ask. <?php $x="Hi"; $y=" There"; $z = $x.$y; $a = "$x$y"; echo "$z"."<br />"."$a"; ?> $z uses the traditional concatenation operator provided by php and concatenates, conversely $a doesn't, My questions: by not using the concatenation operator, does it effect the performance? If it doesn't why at all have the concatenation operator. Why have 2 modes of implementation when one does the work?

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  • Scala actors: receive vs react

    - by jqno
    Let me first say that I have quite a lot of Java experience, but have only recently become interested in functional languages. Recently I've started looking at Scala, which seems like a very nice language. However, I've been reading about Scala's Actor framework in Programming in Scala, and there's one thing I don't understand. In chapter 30.4 it says that using react instead of receive makes it possible to re-use threads, which is good for performance, since threads are expensive in the JVM. Does this mean that, as long as I remember to call react instead of receive, I can start as many Actors as I like? Before discovering Scala, I've been playing with Erlang, and the author of Programming Erlang boasts about spawning over 200,000 processes without breaking a sweat. I'd hate to do that with Java threads. What kind of limits am I looking at in Scala as compared to Erlang (and Java)? Also, how does this thread re-use work in Scala? Let's assume, for simplicity, that I have only one thread. Will all the actors that I start run sequentially in this thread, or will some sort of task-switching take place? For example, if I start two actors that ping-pong messages to each other, will I risk deadlock if they're started in the same thread? According to Programming in Scala, writing actors to use react is more difficult than with receive. This sounds plausible, since react doesn't return. However, the book goes on to show how you can put a react inside a loop using Actor.loop. As a result, you get loop { react { ... } } which, to me, seems pretty similar to while (true) { receive { ... } } which is used earlier in the book. Still, the book says that "in practice, programs will need at least a few receive's". So what am I missing here? What can receive do that react cannot, besides return? And why do I care? Finally, coming to the core of what I don't understand: the book keeps mentioning how using react makes it possible to discard the call stack to re-use the thread. How does that work? Why is it necessary to discard the call stack? And why can the call stack be discarded when a function terminates by throwing an exception (react), but not when it terminates by returning (receive)? I have the impression that Programming in Scala has been glossing over some of the key issues here, which is a shame, because otherwise it's a truly excellent book.

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  • Scraped HTML is not written at the beginning of text file.

    - by karikari
    Currently, I'm scraping the HTML code of a page, and writing it to a text file. My problem is, why must there be empty spaces or empty lines at the beginning? The HTML codes written to the txt file do not seem to start at the beginning of the text file. This means that the '<' is not located at the position 0 of the txt file. After a few runs, my HTML is always written a few lines down inside the text file. Can anyone tell me why?

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  • Creating Instance of a DataContract Class on the client side

    - by hgulyan
    I'm not sure, if it's right to do this, but I'd like to ask this question again ( http://stackoverflow.com/questions/2498644/creating-instance-of-a-service-side-datacontract-class-on-client-side-in-wcf ). The main question is - why there's difference between creating instance on the client side and creating it on the server side? Why there're some properties, that lose their values when you create them on the client side and pass it to service's functions? What could be the issue? Any version will be appreciated. I've written about my problem in the update part of the question in that link. Thank You. p.s. If this is against the rules, I'll delete it.

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  • Help needed to resolve RMI RemoteException

    - by Gabriel Parenza
    Hello friends, Any idea why do I get RemoteException while trying to invoke methods on Unix machine from Windows. I am inside the network and dont think this is because of firewall problem as I can do "telnet" from Windows to Unix box after starting the RMI server at the unix box. I also could not understand why is it going to local loopback IP? Stack Trace:: RemoteException occured, details java.rmi.ConnectException: Connection refused to host: 127.0.0.1; nested exception is: java.net.ConnectException: Connection refused: connect java.rmi.ConnectException: Connection refused to host: 127.0.0.1; nested exception is: java.net.ConnectException: Connection refused: connect Many thanks in advance.

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  • Java: Local Enums

    - by bruno conde
    Today, I found myself coding something like this ... public class LocalEnums { public LocalEnums() { } public void foo() { enum LocalEnum { A,B,C }; // .... // class LocalClass { } } } and I was kind of surprised when the compiler reported an error on the local enum: The member enum LocalEnum cannot be local Why can't enums be declared local like classes? I found this very useful in certain situations. In the case I was working, the rest of the code didn't need to know anything about the enum. Is there any structural/design conflict that explains why this is not possible or could this be a future feature of Java?

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  • what's ur idea about this two way for creat a folder in oracle

    - by rima
    According to my last question about how to create folder here I find some codes that s.b before write it! looking : (sorry for limitation i cant put codes here) they try to Create a bat file,by oracle outfile text_IO,file_type then they write these statement! body_of_file = 'Net use x: \\address' body_of_file += 'md' || filename body_of_file += 'start '|| file name then open bat file and write inside it! then they call it by HOST!!!! like: Host('cmd /c \\address\.x.bat host_folder'|| sysdate); but they can easily and directly by calling HOST! and also I dont know why they code just can in oracle 6i!!!! we use 2 oracle 6i and 10g. please would you help me : 1- why this code dont work in 10g? 2- which way is better?create a batch file and create folder or use HOST for run each command?(in my Idea both is same,How about u?)

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