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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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  • Standard (cross-platform) way for bit manipulation

    - by Kiril Kirov
    As are are different binary representation of the numbers (for example, take big/little endian), is this cross-platform: some_unsigned_type variable = some_number; // set n-th bit, starting from 1, // right-to-left (least significant-to most significant) variable |= ( 1 << ( n - 1 ) ); // clear the same bit: variable &= ~( 1 << ( n - 1 ) ); In other words, does the compiler always take care of the different binary representation of the unsigned numbers, or it's platform-specific? And what if variable is signed integral type (for example, int) and its value is zero positive negative? What does the Standard say about this? P.S. And, yes, I'm interesting in both - C and C++, please don't tell me they are different languages, because I know this :) I can paste real example, if needed, but the post will become too long

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  • Most common software development mistakes

    - by hgulyan
    Inspired by Dealing with personal failure, I remembered my own failed software development experience. Finally I agreed to rewrite existing application. It took me less than a week to rewrite existing app and more up to 2 months to write from zero my own. That 2 months were really hard and interesting. It was my first big software development process. I researched almost everything concerning to my application. Read Code Complete. Even some articles on how to create user interface. Some psychology stuff. Typography, Colors. DAL, DB Structure, SOA, Patterns, UML, Load testing etc. I hope, that after a month or 2 I would get opportunity to continue working on my failed project, but before that, I would like to ask: What are common mistakes in software development? What you shouldn't do in any case?

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  • Explicit initialization of struct/class members

    - by Zephon
    struct some_struct{ int a; }; some_struct n = {}; n.a will be 0 after this; I know this braces form of initialization is inherited from C and is supported for compatibility with C programs, but this only compiles with C++, not with the C compiler. I'm using Visual C++ 2005. In C this type of initialization struct some_struct n = {0}; is correct and will zero-initialize all members of a structure. Is the empty pair of braces form of initialization standard? I first saw this form of initialization in a WinAPI tutorial from msdn.

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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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  • What's a good way to detect wrap-around in a fixed-width message counter?

    - by Kristo
    I'm writing a client application to communicate with a server program via UDP. The client periodically makes requests for data and needs to use the most recent server response. The request message has a 16-bit unsigned counter field that is echoed by the server so I can pair requests with server responses. Since it's UDP, I have to handle the case where server responses arrive out of order (or don't arrive at all). Naively, that means holding on to the highest message counter seen so far and dropping any incoming message with a lower number. But that will fail as soon as we pass 65535 messages and the counter wraps back to zero. Is there a good way to detect (with reasonable probability) that, for example, message 5 actually comes after message 65,000? The implementation language is C++.

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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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  • 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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  • 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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  • Ambiguous Evaluation of Lambda Expression on Array

    - by Joe
    I would like to use a lambda that adds one to x if x is equal to zero. I have tried the following expressions: t = map(lambda x: x+1 if x==0 else x, numpy.array) t = map(lambda x: x==0 and x+1 or x, numpy.array) t = numpy.apply_along_axis(lambda x: x+1 if x==0 else x, 0, numpy.array) Each of these expressions returns the following error: ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all() My understanding of map() and numpy.apply_along_axis() was that it would take some function and apply it to each value of an array. From the error it seems that the the lambda is being evaluated as x=array, not some value in array. What am I doing wrong? I know that I could write a function to accomplish this but I want to become more familiar with the functional programming aspects of python.

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  • Zend Framework: The form filter I am using is not filtering!

    - by Andrew
    So I have a form that is using the Zend_Filter_Null filter. When I call it directly, it works: $makeZeroNull = new Zend_Filter_Null(); $null = $makeZeroNull->filter('0'); //$null === null However, when I try to add it to an element in my form, it doesn't filter the value when I call getValue(). class My_Form extends Zend_Form { public function init() { $makeZeroNull = new Zend_Filter_Null(); $this->addElement('text', 'State_ID', array('filters' => array($makeZeroNull))); } } //in controller if ($form->isValid($_POST)) { $zero = $form->State_ID->getValue(); //getValue() should return null, but it is returning 0 } What is going on? What am I doing wrong?

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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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  • Wireless Access Point stopped working

    - by Alex Pritchard
    I have a simple LAN set up at home using a Linksys WRT54GSV4 as my primary router and an Encore ENHWI-2AN3 as an access point. I connect the Encore to the Linksys by running a cable from one of the Linksys LAN ports into the Encore WAN input. I originally configured this using the Encore setup wizard, setting the device up in AP Router Mode. It detected the input network and worked about as expected, creating a second network that used my primary network to connect to the internet. It worked fine for about 2 weeks, then abruptly cut out today. I checked to make sure the network was still live through the cable going into the Encore (provides internet when connected to a laptop directly) and that devices are still able to connect to the network being broadcast by the Encore. When I try to rerun the connection wizard on the Encore, I receive the message "No Services found in WAN port." The WAN Settings is no longer retrieving a dynamic ip from the line. I tried providing a static IP, assigning an IP address within the subnet range of my primary router that wasn't being used and pointing the Default Gateway to the Linksys IP, but this did not work either. When I plug the cable into the WAN port, an internet light comes on that is not lit when a live network is not connected. I've tried doing a hard reset on the Encore (held down the rest button until the lights flashed, reconfigured from scratch), but the WAN settings are still not detected. Also tried powering off and on the modem, linksys, and encore. Any suggestions would be appreciated!

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  • How to do Linq aggregates when there might be an empty set?

    - by Shaul
    I have a Linq collection of Things, where Thing has an Amount (decimal) property. I'm trying to do an aggregate on this for a certain subset of Things: var total = myThings.Sum(t => t.Amount); and that works nicely. But then I added a condition that left me with no Things in the result: var total = myThings.Where(t => t.OtherProperty == 123).Sum(t => t.Amount); And instead of getting total = 0 or null, I get an error: System.InvalidOperationException: The null value cannot be assigned to a member with type System.Decimal which is a non-nullable value type. That is really nasty, because I didn't expect that behavior. I would have expected total to be zero, maybe null - but certainly not to throw an exception! What am I doing wrong? What's the workaround/fix?

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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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  • 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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  • 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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  • 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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  • Eliminating cyclic flows from a graph

    - by Jon Harrop
    I have a directed graph with flow volumes along edges and I would like to simplify it by removing all cyclic flows. This can be done by finding the minimum of the flow volumes along each edge in any given cycle and reducing the flows of every edge in the cycle by that minimum volume, deleting edges with zero flow. When all cyclic flows have been removed the graph will be acyclic. For example, if I have a graph with vertices A, B and C with flows of 1 from A?B, 2 from B?C and 3 from C?A then I can rewrite this with no flow from A?B, 1 from B?C and 2 from C?A. The number of edges in the graph has reduced from 3 to 2 and the resulting graph is acyclic. Which algorithm(s), if any, solve this problem?

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  • IIS 7 much slower than IIS 6

    - by JoeJoe
    I have a asp.net 3.5 web application running fine on Windows2003 IIS6. I published same exact application to IIS7.5 (Win2008R2) on a faster box (i5,8Gram) and it is significantly slower. 5-6 sec per page vs. 1-2 sec per page. During that time the Task Mgr CPU is always under 10%. Both attach to same database on other box. Benchmark is consistent from any other client browser or machine. I have connection pool on both, compression on both. Same network subnet. Forms authentication (no SSL yet). Can you give me steps on how to troubleshoot where the delays are being inserted or settings in IIS7 that I may have overlooked. Just using defaults. There is only 1 web site on each box. I understand the roles of an Application as defined in IIS has changed. There is no special Application defined in IIS.

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  • Why does C++ linking use virtually no CPU?

    - by John
    On a native C++ project, linking right now can take a minute or two, yet during this time CPU drops from 100% during compilation to virtually zero. Does this mean linking is primarily a disk activity? If so, is this the main area an SSD would make big changes? But, why aren't all my OBJ files (or as many as possible) kept in RAM after compilation to avoid this? With 4Gb of RAM I should be able to save a lot of disk access and make it CPU-bound again, no?

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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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  • 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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  • Can't ping localhost/or reach locally hosted domain

    - by Ian
    I can't reach a locally hosted domain, and in testing I have discovered I can't ping localhost or the actual IP either. OS is Windows7 64bit, Pro. DNS works, I can ping others on my network, they can ping me, and they can reach the hosted domain. The ONLY problem I have found is that I can't reach the locally hosted domains! C:\Users\ianipconfig /all Windows IP Configuration Host Name . . . . . . . . . . . . : leda Primary Dns Suffix . . . . . . . : Node Type . . . . . . . . . . . . : Hybrid IP Routing Enabled. . . . . . . . : No WINS Proxy Enabled. . . . . . . . : No DNS Suffix Search List. . . . . . : hcs Ethernet adapter Local Area Connection: Connection-specific DNS Suffix . : hcs Description . . . . . . . . . . . : Atheros AR8121/AR8113/AR8114 PCI-E Ethern et Controller Physical Address. . . . . . . . . : 00-23-54-7C-E2-2A DHCP Enabled. . . . . . . . . . . : No Autoconfiguration Enabled . . . . : Yes IPv4 Address. . . . . . . . . . . : 192.168.0.12(Preferred) Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 192.168.0.1 DNS Servers . . . . . . . . . . . : 192.168.0.1 NetBIOS over Tcpip. . . . . . . . : Enabled Ethernet adapter VirtualBox Host-Only Network #2: Connection-specific DNS Suffix . : Description . . . . . . . . . . . : VirtualBox Host-Only Ethernet Adapter #2 Physical Address. . . . . . . . . : 08-00-27-00-88-4A DHCP Enabled. . . . . . . . . . . : No Autoconfiguration Enabled . . . . : Yes Autoconfiguration IPv4 Address. . : 169.254.205.215(Preferred) Subnet Mask . . . . . . . . . . . : 255.255.0.0 Default Gateway . . . . . . . . . : NetBIOS over Tcpip. . . . . . . . : Enabled C:\Users\ianping localhost Pinging leda [127.0.0.1] with 32 bytes of data: Request timed out. Request timed out. Request timed out. Request timed out. Ping statistics for 127.0.0.1: Packets: Sent = 4, Received = 0, Lost = 4 (100% loss), C:\Users\ianping coachmaster.leda.hcs Pinging coachmaster.leda.hcs [192.168.0.12] with 32 bytes of data: Request timed out. Request timed out. Request timed out. Request timed out. Ping statistics for 192.168.0.12: Packets: Sent = 4, Received = 0, Lost = 4 (100% loss), C:\Users\ian I can reach a hosted VM in VirtualBox and the VM can browse the hosted sites. I've removed Zone Alarm and disabled Windows Firewall - same results. So how can I browse my locally hosted sited? What could be blocking it? Thanks Ian

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