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• iPhone UITableView populating variable rows sections from flat array

  - by Biko

  I thought that would be very common and easy iPhone App. In the main app I connect to database, retrieve values from database (NSDate converted to NSString)n and put into single array. The in one of the views I populate UITableView with elements from the array. UITableView is grouped (sections). I step through array to discover number of sections (change section if new day). How do I retrieve correct element of array in cellForRowAtIndexPath? IndexPath.section and IndexPath.row seem useless as row starts count from zero for each section. If number of rows in each section was the same it would have been easy: [arryData objectAtIndex:(indexPath.row)+indexPath.section*[tblMatchesView numberOfRowsInSection:indexPath.section]]; But number of rows in each section varies... :-)

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• Working with EnumSet class in GWT

  - by zenmonkey

  I am having trouble using EnumSet on the client side. I get this runtime error message: java.util.EnumSet.EnumSetImpl is not default instantiable (it must have a zero-argument constructor or no constructors at all) and has no custom serializer. Is this is a known issue? Here is what I am doing (basically a hello world app) Service: String echo (EnumSet<Names> name) throws IllegalArgumentException; Client: echoServ.echo (EnumSet.of(Names.JOHN), new AsyncCallback<String>() { ....... }); Shared enum class enum Names { JOHN, NUMAN, OBAMA }

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• Pointers, links, object and reference count

  - by EugeneP

  String a = "a"; // allocate memory and write address of a memory block to a variable String b = "b"; // in a and b hold addresses b = a; // copy a address into b. // Now what? b value is completely lost and will be garbage collected //* next step a = null; // now a does not hold a valid address to any data, // still data of a object exist somewhere, yet we cannot get access to it. Correct me if there's a mistake somewhere in my reflexions. My question is: suppose anInstance object of type Instance has a property ' surname ' anInstance.getSurname() returns "MySurname". now String s = anInstance.getSurname(); anInstance = null; question is - is it true that getSurname value, namely MySurname will not be garbage collected because and only because it has active reference counter 0, and if other properties of anInstance have a zero reference counter, they'll be garbage collected?

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• Averaging corrupted images to eliminate the noise

  - by Mertie Pertie

  Hi all As you can get it from the title, I want to average some .jpg images which are corrupted by zero-mean Gaussian additive. After searching over internet, I figured out to add image matrices and divide the sum by the # of matrices. However the resultant image is totally black. Normally when the number of image increases then the resultant image gets better. But When I use more images it gets darker. I am using 800x600 black and white images with .jpg ext Here is the script I used; image1 = imread ('PIC1.jpg'); image2 = imread ('PIC2.jpg'); image3 = imread ('PIC3.jpg'); image4 = imread ('PIC4.jpg'); sum = image1 + image2 + image3 + image4; av = sum / 4; imshow(av); Thanks in advance

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• The shortest way to convert infix expressions to postfix (RPN) in C

  - by kuszi

  Original formulation is given here (you can try also your program for correctness) . Additional rules: 1. The program should read from standard input and write do standard output. 2. The program should return zero to the calling system/program. 3. The program should compile and run with gcc -O2 -lm -s -fomit-frame-pointer. The challenge has some history: the call for short implementations has been announced at the Polish programming contest blog in September 2009. After the contest, the shortest code was 81 chars long. Later on the second call has been made for even shorter code and after the year matix2267 published his solution in 78 bytes: main(c){read(0,&c,1)?c-41&&main(c-40&&(c%96<27||main(c),putchar(c))):exit(0);} Anyone to make it even shorter or prove this is impossible?

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• Any good way to set the exit status of a Cocoa application?

  - by buglesareking

  I have a Cocoa app which interacts with a server and displays a GUI. If there is a fatal error, I display an alert and exit. I'd like to set the exit status to a non-zero value to reflect that an error occurred, for ease of interaction with some other UNIX based tools. Unfortunately I've been unable to find a good way to do so - NSApplication doesn't seem to have any way to set an exit status. At the moment, I've subclassed NSApplication and added an exitStatus ivar (which I set in my app delegate when necessary), then overridden -terminate: so that it calls exit(exitStatus). This works fine, but it seems a bit grungy to me, not to mention that I may be missing something important that the stadnard `terminate: is doing behind the scenes. I can't call [super terminate:sender] in my subclassed method, because that exit()s without giving me a chance to set the status. Am I missing something obvious?

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• MySQL load data null values

  - by SP1

  Hello, I have a file that can contain from 3 to 4 columns of numerical values which are separated by comma. Empty fields are defined with the exception when they are at the end of the row: 1,2,3,4,5 1,2,3,,5 1,2,3 The following table was created in MySQL: +-------+--------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+--------+------+-----+---------+-------+ | one | int(1) | YES | | NULL | | | two | int(1) | YES | | NULL | | | three | int(1) | YES | | NULL | | | four | int(1) | YES | | NULL | | | five | int(1) | YES | | NULL | | +-------+--------+------+-----+---------+-------+ I am trying to load the data using MySQL LOAD command: load data infile '/tmp/testdata.txt' into table moo fields terminated by "," lines terminated by "\n"; The resulting table: +------+------+-------+------+------+ | one | two | three | four | five | +------+------+-------+------+------+ | 1 | 2 | 3 | 4 | 5 | | 1 | 2 | 3 | 0 | 0 | | 1 | 2 | 3 | NULL | NULL | +------+------+-------+------+------+ The problem lies with the fact that when a field is empty in the raw data and is not defined, MySQL for some reason does not use the columns default value (which is NULL) and uses zero. NULL is used correctly when the field is missing alltogether. Unfortunately, I have to be able to distinguish between NULL and 0 at this stage so any help would be appreciated. Thanks S.

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• Strange findFn malfunction

  - by gd047

  I noticed a strange malfunction in using findFn function (library sos) and I can't find out the source. While it works fine on my Windows XP pc, it does not on my Vista one. library (sos) findFn("randomization test") # in both finds 72 results findFn("{randomization test}") # In XP finds 19 or about so, but in Vista whenever I use {} and more than one word inside, # I keep getting the following: found 0 matches x has zero rows; nothing to display. Warning message: In findFn("{randomization test}") : HIT not found in HTML; processing one page only. R ver = 2.10.1 and packages updated. Any ideas where the problem might be? Bonus: As it's obvious, I was looking for functions about tests for randomized experiments

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• How to get min/max of two integers in Postgres/SQL?

  - by HRJ

  How do I find the maximum (or minimum) of two integers in Postgres/SQL? One of the integers is not a column value. I will give an example scenario: I would like to subtract an integer from a column (in all rows), but the result should not be less than zero. So, to begin with, I have: UPDATE my_table SET my_column = my_column - 10; But this can make some of the values negative. What I would like (in pseudo code) is: UPDATE my_table SET my_column = MAXIMUM(my_column - 10, 0);

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• Style question: Writing "this." before instance variable and methods: good or bad idea?

  - by Uri

  One of my nasty (?) programming habits in C++ and Java is to always precede calls or accesses to members with a this. For example: this.process(this.event). A few of my students commented on this, and I'm wondering if I am teaching bad habits. My rationale is: 1) Makes code more readable — Easier to distinguish fields from local variables. 2) Makes it easier to distinguish standard calls from static calls (especially in Java) 3) Makes me remember that this call (unless the target is final) could end up on a different target, for example in an overriding version in a subclass. Obviously, this has zero impact on the compiled program, it's just readability. So am I making it more or less readable? Related Question Note: I turned it into a CW since there really isn't a correct answer.

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• insane transformations of a view

  - by Mike

  I have this view and I do some rotation transformation to it using something like myView.transform = CGAffineTransformMakeRotation(degreesToRadian(90)); //The view was originally at angle 0. at some other point of my code, I would like to scale the view animating it, so I do [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:1.0]; myViews.transform = CGAffineTransformMakeScale(2.0f, 2.0f); [UIView commitAnimations]; but when I do that the animation is performed as the view is at 0 degrees, ignoring the previous transformation. It simply assumes as the view is yet at zero degrees, so, this animation scales the view and rotates it back to 0 degrees (!!!!?????) Is this some bug or am I missing something? thanks.

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• Function Returning Negative Value

  - by Geowil

  I still have not run it through enough tests however for some reason, using certain non-negative values, this function will sometimes pass back a negative value. I have done a lot of manual testing in calculator with different values but I have yet to have it display this same behavior. I was wondering if someone would take a look at see if I am missing something. float calcPop(int popRand1, int popRand2, int popRand3, float pERand, float pSRand) { return ((((((23000 * popRand1) * popRand2) * pERand) * pSRand) * popRand3) / 8); } The variables are all contain randomly generated values: popRand1: between 1 and 30 popRand2: between 10 and 30 popRand3: between 50 and 100 pSRand: between 1 and 1000 pERand: between 1.0f and 5500.0f which is then multiplied by 0.001f before being passed to the function above Edit: Alright so after following the execution a bit more closely it is not the fault of this function directly. It produces an infinitely positive float which then flips negative when I use this code later on: pPMax = (int)pPStore; pPStore is a float that holds popCalc's return. So the question now is, how do I stop the formula from doing this? Testing even with very high values in Calculator has never displayed this behavior. Is there something in how the compiler processes the order of operations that is causing this or are my values simply just going too high? If the later I could just increase the division to 16 I think.

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• Hebbian learning

  - by Bane

  I have asked another question on Hebbian learning before, and I guess I got a good answer which I accepted, but, the problem is that I now realize that I've mistaken about Hebbian learning completely, and that I'm a bit confused. So, could you please explain how it can be useful, and what for? Because the way Wikipedia and some other pages describe it - it doesn't make sense! Why would we want to keep increasing the weight between the input and the output neuron if the fire together? What kind of problems can it be used to solve, because when I simulate it in my head, it certainly can't do the basic AND, OR, and other operations (say you initialize the weights at zero, the output neurons never fire, and the weights are never increased!)

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• Need to read .symtab

  - by user361190

  I am frustrated. I have a simple doubt .. I compile a simple program with gcc and if I see the section header using objdump, it does not show the section ".symtab". for the same a.out file, readelf shows the section. see the below snip - [25] .symtab SYMTAB 00000000 000ca4 000480 10 26 2c 4 [26] .strtab STRTAB 00000000 001124 00025c 00 0 0 1 Why ? In the default linker script I don't find a definition for .symtab section. If I add a definition by myself like in the linker script : .... PROVIDE(__start_sym) .symtab : { *(.symtab)} PROVIDE(__end_sym) .... the difference b/w the addresses of __start_sym and __end_sym is zero, which means no such section is added in the output file. But the readelf is able to read the section and dump the contents of this section .. How ? why ?

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• Anyone Know a Great Sparse One Dimensional Array Library in Python?

  - by TheJacobTaylor

  I am working on an algorithm in Python that uses arrays heavily. The arrays are typically sparse and are read from and written to constantly. I am currently using relatively large native arrays and the performance is good but the memory usage is high (as expected). I would like to be able to have the array implementation not waste space for values that are not used and allow an index offset other than zero. As an example, if my numbers start at 1,000,000 I would like to be able to index my array starting at 1,000,000 and not be required to waste memory with a million unused values. Array reads and writes needs to be fast. Expanding into new territory can be a small delay but reads and writes should be O(1) if possible. Does anybody know of a library that can do it? Thanks!

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• Can we manipulate (subtract) the value of a property while template bidning?

  - by Subhen

  Hi, I am currently defining few grids as following: <Grid.RowDefinitions> <RowDefinition Height="{TemplateBinding Height-Height/5}"/> <RowDefinition Height="{TemplateBinding Height/15}"/> <RowDefinition Height="{TemplateBinding Height/20}"/> <RowDefinition Height="{TemplateBinding Height/6}"/> </Grid.RowDefinitions> While the division works fine , the subtraction isn't yielding the output. Ialso tried like following: <RowDefinition Height="{TemplateBinding Height-(Height/5)}"/> Still no result. Any suggestions plz. Thanks, Subhen ** Update ** Now In My XAML I tried implementing the IvalueConverter like : <RowDefinition Height="{TemplateBinding Height, Converter={StaticResource heightConverter}}"/> Added the reference as <local:medieElementHeight x:Key="heightConverter"/> In side generic.cs I have coded as following: public class medieElementHeight : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { //customVideoControl objVdeoCntrl=new customVideoControl(); double custoMediaElementHeight = (double)value;//objVdeoCntrl.customMediaPlayer.Height; double mediaElementHeight = custoMediaElementHeight - (custoMediaElementHeight / 5); return mediaElementHeight; } #region IValueConverter Members object IValueConverter.ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { throw new NotImplementedException(); } #endregion } But getting the exception Unknown Element Height in the element RowDefination.

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• Python 3: Recursivley find if number is even

  - by pythonhack

  I am writing a program that must find if a number is even or not. It needs to follow this template. I can get it to find if a number is even or not recursively (call function and subtract 2, base case zero), but I am having a hard time following this template, based on how the isEven function is called in the main function. Any help would be greatly appreciated. Write a recursive function called isEven that finds whether a number is even or not: def isEven() #recursivley determine whether number is even or not def main(): number=int(input(“Enter a number : “)) if (isEven(number)): print(“Number is even”) else: print(“Number is not even”) main() Thank you! Appreciate it.

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• Why does GetTextFace always return "system"?

  - by user545142

  I am trying to get the font of controls in other applications. When I try WM_GETFONT, it returns 0. This my code: [DllImport("User32.DLL")] public static extern IntPtr SendMessage(IntPtr hWnd, int Msg, int wParam, int lParam); IntPtr fx = SendMessage(button1.Handle, 0x31, 0, 0); When I use GetTextFace with a button, it always returns "system". This is my code: StringBuilder Buff = new StringBuilder(256); IntPtr dc = GetDCEx(button1.Handle, IntPtr.Zero, DeviceContextValues.Window |DeviceContextValues.Cache | DeviceContextValues.ClipSiblings | DeviceContextValues.IntersectRgn); IntPtr hfont = GetTextFace(dc, 256, Buff); Of course I'm sure I changed the font type. How can I solve this problem? I am using C# under Windows 7.

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• SQL Azure server as unit of billing

  - by vtortola

  Hi, One of the azure training kit presentation says: Each account has zero or more logical servers Provisioned via a common portal Establishes a billing instrument Each logical server has one or more databases Contains metadata about database & usage Unit of authentication, geo-location, billing, reporting Generated DNS-based name Each database has standard SQL objects Users, Tables, Views, Indices, etc Unit of consistency So now I'm lost :D. Were not the databases themselves the units of billing? I mean, I thought that servers were just like logical containers and you were charged per number and size of databases. How servers are billed? Thanks.

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• COUNT issue across multiple tables

  - by Kim

  I am trying to count across 2 tables and I dont see whats wrong with my query yet I get a wrong result. User 2 does not exist in table_two, so the zero is correct. SELECT t1.creator_user_id, COUNT(t1.creator_user_id), COUNT(t2.user_id) FROM table_one AS t1 LEFT JOIN table_two AS t2 ON t2.user_id = t1.creator_user_id GROUP BY t1.creator_user_id, t2.user_id Actual result 1 192 192 2 9 0 Expected result 1 16 12 2 9 0 The result indicate a missing group by condition, but I already got both fields used. Where am I wrong ? Also, can I sum up all users that doesnt exist in table_two for t1 ? Like user 3 exists 21 times in t1, then the results would be: 1 16 12 (users with > 0 in t2 will need their own row) 2 30 0 (user 2=9 + user 3=21 => 30) Its okay for the user Id to be wrong for sum of t1 for all users with 0 in t2. If not possible, then I'll just do two queries.

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• OpenCv not initializing usb camera

  - by brainbarshan

  I am trying to capture video from usb camera using OpenCv. #include <highgui.h> #include <iostream> using namespace std; using namespace cv ; int main() { VideoCapture cap (-1); if(!cap.isOpened()) cout << "Cam initialize failed" ; else cout << "Cam initialized" ; return 0; } It is failing to initialize the camera. cap.isOpened() is returning zero. The same program, with same version of OpenCv and same usb camera, is correctly running in my friend's machine. I am running fedora 16. I did some searching in Google and Stack Overflow. But no useful help. Any idea ?

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• Incrmenting a Cookies with PHP (Beginner Question)

  - by BandonRandon

  Hello, I have used sessions before but never cookies. I would like to use cookies for two reasons: 1) it's something new to learn 2) I would like to have the cookie expire in an hour or so (i know in the code example it expires in 40 sec) I am trying to write a basic if statement that if($counter=="1") { //do this second } elseif ($counter >="2") { //do this every time after the first and second } else {// this is the first action as counter is zero } Here is the code I'm using to set the cookie: // if cookie doesnt exsist, set the default if(!isset($_COOKIE["counter_cookie"])) { $counter = setcookie("counter_cookie", 0 ,time()+40); } // increment it $counter++; // save it setcookie("counter_cookie", $counter,time()+40); $counter = $_COOKIE["counter_cookie"]; The problem is that the counter will be set from 0 to 1 but won't be set from 1 to 2 and so on. Any help would be great I know this is a really simple stupid question :| Thanks!

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• Visit neighbor of a position in a 2d-array

  - by Martin

  I have the following two dimensional array: static int[,] arr = new int[5, 5] { { 00, 00, 00, 01, 00 }, { 00, 00, 01, 01, 00 }, { 00, 00, 01, 01, 00 }, { 00, 00, 01, 01, 00 }, { 00, 00, 00, 01, 00 }, }; I have to a implement a method called Hit(int x, int y). When we hit a 0 in the array (i.e. Hit(0, 0), Hit(1, 1), but not Hit(3, 0)) I would like all the adjacent zeros to the zero we hit to be incremented by 10. So if I call Hit(1, 1), the array should become the following. static int[,] arr = new int[5, 5] { { 10, 10, 10, 01, 00 }, { 10, 10, 01, 01, 00 }, { 10, 10, 01, 01, 00 }, { 10, 10, 01, 01, 00 }, { 10, 10, 10, 01, 00 }, }; Any idea how I could implement that? It sounds to me like a Depth First Search/Recursive sort-of algorithm should do the job, but I haven't been able to implement it for an 2d array. Thanks for the help!

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• Initializing structs in C++

  - by Neil Butterworth

  As an addendum to this question, what is going on here: #include <string> using namespace std; struct A { string s; }; int main() { A a = {0}; } Obviously, you can't set a std::string to zero. Can someone provide an explanation (backed with references to the C++ Standard, please) about what is actually supposed to happen here? And then explain for example): int main() { A a = {42}; } Are either of these well-defined? Once again an embarrassing question for me - I always give my structs constructors, so the issue has never arisen before.

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• PHP strtotime without leap-years

  - by Christian Sciberras

  With regards to this thread, I've developed a partial solution: function strtosecs($time,$now=null){ static $LEAPDIFF=86400; $time=strtotime($time,$now); return $time-((date('Y',$time)-1968)/4*$LEAPDIFF); } The function is supposed to get the number of seconds given a string without checking leap-years. It does this calculating the number of leap-years 1970 [(year-1986)/4], multiplying it by the difference in seconds between a leap-year and a normal year (which in the end, it's just the number of seconds in a day). Finally, I simply remove all those excess leap-year seconds from the calculated time. Here's some examples of the inputs/outputs: // test code echo strtosecs('+20 years',0).'=>'.(strtosecs('+20 years',0)/31536000); echo strtosecs('+1 years',0).'=>'.(strtosecs('+1 years',0)/31536000); // test output 630676800 => 19.998630136986 31471200 => 0.99794520547945 You will probably ask why am I doing a division on the output? It's to test it out; 31536000 is the number of seconds in a year, so that 19.99... should be 20 and 0.99... should be a 1. Sure, I could round it all and get "correct" answer, but I'm worried about the inaccuracies.

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