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• About the String#substring() method

  - by alain.janinm

  If we take a look at the String#substring method implementation : new String(offset + beginIndex, endIndex - beginIndex, value); We see that a new String is created with the same original content (parameter char [] value). So the workaround is to use new String(toto.substring(...)) to drop the reference to the original char[] value and make it eligible for GC (if no more references exist). I would like to know if there is a special reason that explain this implementation. Why the method doesn't create herself the new shorter String and why she keeps the full original value instead? The other related question is : should we always use new String(...) when dealing with substring?

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• Problem accessing base member in derived constructor

  - by LeopardSkinPillBoxHat

  Given the following classes: class Foo { struct BarBC { protected: BarBC(uint32_t aKey) : mKey(aKey) mOtherKey(0) public: const uint32_t mKey; const uint32_t mOtherKey; }; struct Bar : public BarBC { Bar(uint32_t aKey, uint32_t aOtherKey) : BarBC(aKey), mOtherKey(aOtherKey) // Compile error here }; }; I am getting a compilation error at the point indicated: error: class `Foo::Bar' does not have any field named `mOtherKey'. Can anyone explain this? I suspect it's a syntactical problem due to my Bar class being defined within the Foo class, but can't seem to find a way around it. This is simple public inheritance, so mOtherKey should be accessible from the Bar constructor. Right? Or is it something to do with the fact that mOtherKey is const and I have already initialised it to 0 in the BarBC constructor?

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• Do you have to create a View Controller to move between views?

  - by Frames84

  I want a single startup view with a button and a welcome screen. When the button is pressed I then want to navigate to a second view which contains a table view and toolbar. I've tried creating a ViewController but my button is shown on all views. I just want a single view, then when it's pressed i go to the next view and the 'real' app starts. Can someone please try and explain the best architecture to do this? (like in chapter 6 of beginning iPhone 3 Development by Dave Mark and Jeff LaMarche ) Thanks

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• Sprintf equivalent in Mathematica?

  - by jxy

  I don't know why Wikipedia lists Mathematica as a programming language with printf. I just couldn't find the equivalent in Mathematica. My specific task is to process a list of data files with padded numbers, which I used to do it in bash with fn=$(printf "filename_%05d" $n) The closest function I found in Mathematica is PaddedForm. And after some trial and error, I got it with "filename_" <> PaddedForm[ Round@#, 4, NumberPadding -> {"0", ""} ]& It is very odd that I have to use the number 4 to get the result similar to what I get from "%05d". I don't understand this behavior at all. Can someone explain it to me? And is it the best way to achieve what I used to in bash?

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• NetNamedPipe: varying response time when communication is idling

  - by Sven Künzler

  I have two WCF apps communicating one-way over named pipes. All is nice, except for one thing: Normally, the request/response cycle takes zero (marginal) time. However, if there was a time span of, say, half a minute without any communication, the request/response increases up to ~300-500ms. I looked around the net and I got the idea of using a heart beat/ping mechanism to keep the communication channel busy. Using trial and error I found that when doing a request each 10 seconds, the response times stay low. Starting at around 15s intervals, the "hiccup" response times begin to appear. Now I'm wondering where this phenomenon is originating from. I tried setting alle conceivable timeouts on both sides to 1 minute, but that did not help. Can anybody explain what's going on there?

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• segmentation fault

  - by gcc

  int num_arrays; char *p[20]; char tempc; int i=0; do { p[i]=malloc(sizeof(int)); scanf("%s",p[i]); tempc=p[i]; ++i; }while(tempc=='x'); num_arrays=atoi(p[0]); When i write num_arrays=atoi(..),gcc give me segmentation fault or memory stack is exceeded, I don't understand why it behaves like that can anyone explain, why?

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• After a period of time, nslookup still works, but pinging, and an auto-refeshed website, fails.

  - by Mark Hurd

  Contrary to this question this is for a dotted name (gw.localnet.au), and it doesn't happen straight away. Only after some period of time (quite a long time, possibly days). In fact this is for my ADSL router and its internal IP address which I have named within the router itself and in my Windows Server 2003 Domain Controller DNS Service. Specifically, localnet.au is a Active-Directory-backed primary domain. In fact, an ipconfig /flushdns may fix the problem, but only after a while (about the time it took me to type in this question :-) ). That doesn't explain the root cause though...

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• Imagecache, Views, file renaming, and output directories

  - by Bruno

  I have been trying to figure this one out for awhile and just seem to be getting myself deeper into a rabbit hole.. I think it would be best if I would just explain what I am trying to accomplish and go from there.. Essentially what I would like to happen is a user would upload a photograph from the filefield sources on a content type, and then using views, it would output that different image through different imagecache actions.. The problem seems to be that the actual directories it is making is really cluttered and I would like it to be a little bit more organized due to some file renaming. Here is how I would like the process to happen: Upload image.jpg Imagecache resize 100x100 square and save file to same directory and name the file image-100.jpg Imagecache desaturate 100x100 square and save file to same directory and name the file image-d-100.jpg Currently it seems that every imagecache action will save that file in its own directory.. How can I specify a more customized output? Thanks, Anthony

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• A simple group-by (no count) in Django

  - by Daniel Quinn

  If this were raw-SQL, it'd be a no-brainer, but in Django, this is proving to be quite difficult to find. What I want is this really: SELECT user_id FROM django_comments WHERE content_type_id = ? AND object_pk = ? GROUP BY user_id It's those last two lines that're the problem. I'd like to do this the "Django-way" but the only thing I've found is mention of aggregates and annotations, which I don't think solve this issue... do they? If someone could explain this to me, I'd really appreciate it.

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• Custom components vs default components in GUI Design. Which is more practical? (.NET)

  - by AlexRednic

  Ok, so is it better to create my own components (Either inherit them from existing ones or creating them from scratch) or to use the ones that come by default? I'm asking this under the umbrella of scalability, overhead and other factors that my contribute on each of the choices. UPDATE: Sorry if I'm to vague. I don't really know how to explain myself better. Isn't it a good idea to inherit each default component? For example what if I'm to design a rather large application and for example i need to change the display format on a DateTimePicker. Wouldn't it better to think ahead and inherit it and use the inherited component instead of the defaults? But, wouldn't it add a lot of overhead in small applications?

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• Purpose of Instance Methods vs. Class Methods in Objective-C

  - by qegal

  I have checked out all these questions... Difference Class and Instance Methods Difference between class methods and instance methods? Objective-C: Class vs Instance Methods? ...and all they explain is how instance methods are used on instances of a class and class methods are used with the class name, when a message is sent to a class object. This is helpful, but I'm curious to know why one would use a class method vs. an instance method. I'm fairly new to iOS application development, and usually use class methods, and I feel like I'm doing something wrong. Thanks in advanced!

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• Error: Get JSON Data from Web API Using Jquery

  - by Kenneth

  I'm really new at this. And I'm really stuck. I have the jquery code, it will load data from Web API, but it does not display on my page. $.getJSON("/api/Order", function(data) { if (data != null) { var str = ''; $.each(data, function (item) { str = '<li>' + item.ItemName + '</li>'; }); $("#contents").append(str); } }); Can anyone explain what is going on? Thanks.

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• Getting a CFG form the CFL

  - by Kristian

  Can Any One explain this Language how we converted to CFG Give a CFG for the CFL: {ai bj ck | i ? j or j ? k } //ai mean a^i I have the answer but I need an explaination (Step By Step) The answer : S --> S1|S2 S1 --> A Eab|Eab B|S1 c A --> a|aA B--> b|bB Eab --> Q|a Eab b S2 --> Eac C|A Eac C --> c|cC Eac --> Q|B|a Eac c

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• Setting a preferred item of a many-to-one in Django

  - by Mike DeSimone

  I'm trying to create a Django model that handles the following: An Item can have several Names. One of the Names for an Item is its primary Name, i.e. the Name displayed given an Item. (The model names were changed to protect the innocent.) The models.py I've got looks like: class Item(models.Model): primaryName = models.OneToOneField("Name", verbose_name="Primary Name", related_name="_unused") def __unicode__(self): return self.primaryName.name class Name(models.Model): item = models.ForeignKey(Item) name = models.CharField(max_length=32, unique=True) def __unicode__(self): return self.name class Meta: ordering = [ 'name' ] The admin.py looks like: class NameInline(admin.TabularInline): model = Name class ItemAdmin(admin.ModelAdmin): inlines = [ NameInline ] admin.site.register(Item, ItemAdmin) It looks like the database schema is working fine, but I'm having trouble with the admin, so I'm not sure of anything at this point. My main questions are: How do I explain to the admin that primaryName needs to be one of the Names of the item being edited? Is there a way to automatically set primaryName to the first Name found, if primaryName is not set, since I'm using inline admin for the names?

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• php multidimensional array problem

  - by ntan

  Hi to all, i am trying to setup a multidimensional array but my problem is that i can not get the right order from incoming data. Explain $x[1][11]=11; $x[1]=1; var_dump($x); In the above code i get only x[1]. To right would be $x[1]=1; $x[1][11]=11; var_dump($x); But in my case i can dot ensure that x[1] will come first, and x[1][11] will come after. Is there any way that i can use the first example and get right the array. Keep in mind that the array depth is large. Thats

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• Help with output generated by this C code using fork()

  - by Seephor

  I am trying to figure out the output for a block of C code using fork() and I am having some problems understanding why it comes out the way it does. I understand that when using fork() it starts another instance of the program in parallel and that the child instance will return 0. Could someone explain step by step the output to the block of code below? Thank you. main() { int status, i; for (i=0; i<2; ++i){ printf("At the top of pass %d\n", i); if (fork() == 0){ printf("this is a child, i=%d\n", i); } else { wait(&status); printf("This is a parent, i=%d\n", i); } } }

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• Regex Question..

  - by Josh

  Hello everyone- In my C# Console App I'm trying to use Regex to search a string to determine if there is a match or not. Below is my code but it is not quite working right so I will explain further. sSearchString is set to "_One-Call_Pipeline_Locations" and pDS.Name is a filename it is searching against. Using the code below it is set to true for Nevada_One-Call_Pipeline_Locations and Nevada_One-Call_Pipeline_LocationsMAXIMUM. There should be a match for Nevada_One-Call_Pipeline_Locations But Not for Nevada_One-Call_Pipeline_LocationsMAXIMUM. How can I change my code to do this properly? Thanks in advance if (Regex.IsMatch(pDS.Name, sSearchString))

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• Autorelease and properties

  - by ganuke

  I have few questions to ask about the following class #import <Cocoa/Cocoa.h> @interface SomeObject { NSString *title; } @property (retain) NSString *title; @end implementation SomeObject @synthesize title; -(id)init { if (self=[super init]) { self.title=[NSString stringWithFormat:@"allyouneed"]; } return self; } -(void)testMethod{ self.title=[[NSString alloc] init] ; } -(void)dealloc { self.title=nil; [super dealloc]; } In the .h file do we need to declare the title and sub when we add the property. is it not enough to add the @property (retain) NSString *title; line. 2.Do i need to autorelease both assignment to title in the init and testMethod. if So why? Can some one explain these things to me.

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• Space requirements of a merge-sort

  - by Arkaitz Jimenez

  I'm trying to understand the space requirements for a Mergesort, O(n). I see that time requirements are basically, amount of levels(logn) * merge(n) so that makes (n log n). Now, we are still allocating n per level, in 2 different arrays, left and right. I do understand that the key here is that when the recursive functions return the space gets deallocated, but I'm not seeing it too obvious. Besides, all the info I find, just states space required is O(n) but don't explain it. Any hint? function merge_sort(m) if length(m) = 1 return m var list left, right, result var integer middle = length(m) / 2 for each x in m up to middle add x to left for each x in m after middle add x to right left = merge_sort(left) right = merge_sort(right) result = merge(left, right) return result

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• SQL Stored Procedure

  - by Nathan

  I am trying to run a stored procedure with a while loop in it using Aqua Data Studio 6.5 and as soon as the SP starts Aqua Data starts consuming an increasing amount of my CPU's memory which makes absolutely no sense to me because everything should be off on the Sybase server I am working with. I have commented out and tested every piece of the SP and narrowed the issue down to the while loop. Can anyone explain to me what is going on? create procedure sp_check_stuff as begin declare @counter numeric (9), @max_id numeric (9), @exists numeric (1), @rows numeric (1) select @max_id = max(id) from my_table set @counter = 0 set @exists = 0 set @rows = 0 while @count <= @max_id begin //More logic which doesn't affect memory usage based //on commenting it out and running the SP set @counter = @counter + 1 set @exists = 0 set @rows = 0 end end return

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• Employer wants direct, no-hack, ie6 support for CSS. Should I talk him out of it?

  - by DavidR

  I'm currently employed by a website Designer, he gets the clients and sends me a mockup in a fireworks file, and I send him the html/css/js. The problem is that he wants direct ie6 compatibility for every site I build. That is, no conditional ie6 hack, no separate style sheets. A lot of my html has suffered because of it. I just started writing html with him last summer, he took me in as an intern and taught me everything about it. Since then I built 4 web pages, but I haven't yet made anything I'm really proud of. Should I be trying harder to create stellar code beside my limitations or should I set him down and explain that his demands are killing the code for modern browsers?

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• ASP.NET web services leak memory when (de)serializing disposable objects?

  - by Serilla

  In the following two cases, if Customer is disposable (implementing IDisposable), I believe it will not be disposed by ASP.NET, potentially being the cause of a memory leak: [WebMethod] public Customer FetchCustomer(int id) { return new Customer(id); } [WebMethod] public void SaveCustomer(Customer value) { // save it } This flaw applies to any IDisposable object. So returning a DataSet from a ASP.NET web service, for example, will also result in a memory leak - the DataSet will not be disposed. In my case, Customer opened a database connection which was cleaned up in Dispose - except Dispose was never called resulting in loads of unclosed database connections. I realise there a whole bunch of bad practices being followed here (its only an example anyway), but the point is that ASP.NET - the (de)serializer - is responsible for disposing these objects, so why doesn't it? This is an issue I was aware of for a while, but never got to the bottom of. I'm hoping somebody can confirm what I have found, and perhaps explain if there is a way of dealing with it.

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• C# Bug or Brain Teaser? Cast working only with Coalesce (??) Operator

  - by Alex

  This is very strange, maybe someone can explain what's happening, or this is a bug (though I tend to think that this is probably just something intricate about C#). The following code throws the error "Cannot implicitly convert type 'uint?' to 'uint'.": public void Test(UInt32? p) { UInt32 x = p; } However, this code works without error: public void Test(UInt32? p) { UInt32 x = p ?? 1; } Huh? Why does this work? Why would the coalesce operator cause implicit conversion of UInt32? (nullable) to UInt32 (non-nullable), while the first error message says that there is no implicit conversion between those types?

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• jQuery text attribute selector

  - by Shagglez

  I am trying to use the text attribute as a selector, but I can't quite grasp the behaviour, would really appreciate if someone could explain. For example given <span class="span_class"><a class="a_class">text</a></span>, $('a.a_class').text() gives "text" as expected. However $('a.a_class[text]') wouldn't match any elements, and neither would $('span.span_class > a.a_class[text]'), but $('span.span_class* > a.a_class[text]') would (although not in IE). The only workaround I can think of for IE, is loop through all anchors contained in a span, use .text() on each and match it against a certain criteria, but it seems slower than using in-built selectors. Anyone have better ideas?

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• When to use <strong> and when to use <b>?

  - by metal-gear-solid

  When to use <strong> and when to use <b> or other ways to give look of bold? strong has semantic value ( and useful for screen reader while b is presentation (and even valid in HTML 5). my question is not what is the difference between strong and b. The question is when to use semantic tag and when to use just to make text bold Should I always use <strong> if client's content files (MS word files) has some words bold in content paragraphs? How can we know when client want to give emphasis to text and when he just want to make text bold for presentation/aesthetic purpose? If it's client job to tell us, then how to explain this scenario to client to give us clear info on "when he just want to make text bold for presentation/aesthetic purpose" ?

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