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  • Does this code describe an Existential Type in C#?

    - by noblethrasher
    Currently watching Bart De Smet's explanation of IQueryable and he mentioned Existential Types (which I've been curious about for some time). After reading the answers to this question I'm just wondering if this is a way to construct it in C#: public abstract class ExistentialType { private ExistentialType() { } public abstract int Foo(); public ExistentialType Create() { return new ConcreateType1(); } private class ConcreateType1 : ExistentialType { public override int Foo() { throw new NotImplementedException(); } } private class ConcreateType2 : ExistentialType { public override int Foo() { throw new NotImplementedException(); } } private class ConcreateType3 : ExistentialType { public override int Foo() { throw new NotImplementedException(); } } }

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  • How can I test whether a csv file is currently open and being written to - the file, not a file hand

    - by Henry
    I've seen a few questions/answers here that deal with this, but none really give me an answer/solution. I've got a Clipper system writing csv files to a Windows directory. I have a perl script running on a Linux server that is reading a mount of that Windows directory and importing the files to a database. Right now we're using flag files to indicate when a csv is no longer being written to; the flag files gets written after the csv is done. I'd really rather just get what I need from the csv itself, but I can't seem to find a way to tell when the file is open and being written to. lsof doesn't seem to answer my need. I've tried using flock and open the file with an exclusive lock, thinking it might throw an error if the file is being modified, but it doesn't. Any thoughts?

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  • When should an array name be treated as a pointer and when does it just represent the array itself? [duplicate]

    - by user1087373
    This question already has an answer here: When is an array name or a function name 'converted' into a pointer ? (in C) 4 answers I just made a test program after reading the book and the result turned out confusing: #include <stdio.h> int main(void) { char text[] = "hello!"; printf("sizeof(text):%d sizeof(text+2):%d sizeof(text[0]):%d \n",(int)sizeof(text), sizeof(text+2), sizeof(text[0])); printf("text:%p sizeof(text):%d &text:%p sizeof(&text):%d \n",text, sizeof(text), &text, sizeof(&text)); printf("text+1:%p &text+1:%p \n", text+1, &text+1); return 0; } The result: sizeof(text):7 sizeof(text+2):4 sizeof(text[0]):1 text:0xbfc8769d sizeof(text):7 &text:0xbfc8769d sizeof(&text):4 text+1:0xbfc8769e &text+1:0xbfc876a4 What makes me feel confused are: why the value of 'sizeof(text)' is 7 whereas 'sizeof(text+2)' is 4 what's the difference between 'text' and '&text'?

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  • Exception is swallowed by finally

    - by fiction
    static int retIntExc() throws Exception{ int result = 1; try { result = 2; throw new IOException("Exception rised."); } catch (ArrayIndexOutOfBoundsException e) { System.out.println(e.getMessage()); result = 3; } finally { return result; } } A friend of mine is a .NET developer and currently migrating to Java and he ask me the following question about this source. In theory this must throw IOException("Exception rised.") and the whole method retIntExc() must throws Exception. But nothing happens, the method returns 2. I've not tested his example, but I think that this isn't the expected behavior. EDIT: Thanks for all answers. Some of you have ignored the fact that method is called retIntExc, which means that this is only some test/experimental example, showing problem in throwing/catching mechanics. I didn't need 'fix', I needed explanation why this happens.

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  • keyboard in UIWebView shows and then hides itself on input focus

    - by Jake
    I have a page that's loading into a UIWebView (which takes 100% of the screen) on an iPad. When I touch a text field, the page positions the text field to the right place and the keyboard starts to come up, but then it turns around and goes back down and blur is called on the input field. When I try this same page in mobile Safari, the keyboard is able to deploy successfully. I can't figure out what the rules are for the keyboard to show successfully and stay up = and why this is different for uiwebview than safari. All my research on the subject has yielded no answers.

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  • Doubt about constructor in JAVA

    - by Harry Joy
    I have few doubts regarding constructor in java Can a constructor be private? If yes then in which condition? Constructor is a method or not? If constructor does not return anything then why we are getting a new Object every time we call it. Whats the default access modifier of a constructor if we did not specify. Thanks & Regards Edit---------- Answer for 1 & 3 are very clear. But still doubt about 2&4 as i'm getting different answers for them.

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  • c++11 atomic ordering: extended total order memory_order_seq_cst for locks

    - by itaj
    There's this note in c++11 29.3-p3: [ Note: Although it is not explicitly required that S include locks, it can always be extended to an order that does include lock and unlock operations, since the ordering between those is already included in the "happens before" ordering. - end note ] What does it mean by "always"? I can understand that any certain implementation can be designed to support such an extended S. But in some general implementation that wasn't designed for it, I don't see that S can be extended so. I had sent this question to comp.std.c++ but got no answers there. http://groups.google.com/group/comp.std.c++/browse_frm/thread/5242fa70d0594d1b#

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  • What grid distributed computing frameworks are currently favoured for trading systems

    - by Rich
    There seems to a quite a few grid computing frameworks out there, but which ones are actually being used to any great extent by the investment banks for purposes of low latency distributing calculation? I'd be interested to hear answers covering both windows,Linux and cross platform. Also, what RPC mechanisms seem to be favoured most? I've heard that for reason of low latency and speed, the calculations themselves are quite often written in C++/C as calculations running on VMs are several orders of magnitude slower than native code. Does this seem to be a common scenario in practice? e.g distributed .NET grid framework running calculations written in native c++/c?

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  • Efficient most common suffix algorithm?

    - by taw
    I have a few GBs worth of strings, and for every prefix I want to find 10 most common suffixes. Is there an efficient algorithm for that? An obvious solution would be: Store sorted list of <string, count> pairs. Identify by binary search extent for prefix we're searching. Find 10 highest counts in this extent. Possibly precompute it for all short prefixes, so it doesn't ever need to look at large portion of data. I'm not sure if that would actually be efficient at all. Is there a better way I overlooked? Answers must be real time, but it can take as much preprocessing as necessary.

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  • What is the worst real-world macros/pre-processor abuse you've ever come across?

    - by Trevor Boyd Smith
    What is the worst real-world macros/pre-processor abuse you've ever come across (please no contrived IOCCC answers *haha*)? Please add a short snippet or story if it is really entertaining. The goal is to teach something instead of always telling people "never use macros". p.s.: I've used macros before... but usually I get rid of them eventually when I have a "real" solution (even if the real solution is inlined so it becomes similar to a macro). Bonus: Give an example where the macro was really was better than a not-macro solution. Related question: When are C++ macros beneficial?

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  • jQuery UI: How to change the color of a ProgressBar?

    - by IronGoofy
    I've set up a simple jQueryUI progressbar: <script type="text/javascript"> $(function() { $("#progressbar").progressbar({ value: 35 }); }); </script> <div id="progressbar"> </div> Now, I'd like to color the of the bar based on it's value (e.g. <10 red, <50 yellow, 50 green). How do I do this? Note: There are similar questions, but the answers were not clear enough to help me get things done. Hopefully, someone can point out an easier way or provide more detailed instructions. Thanks.

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  • Downloading large files with AFNetworking

    - by goodfella
    I'm trying to implement downloading of a large file and show to user current progress, but block in: -[AFURLConnectionOperation setDownloadProgressBlock:] returns incorrect bytesRead and totalBytesRead values (they are smaller than they should be). For example: If I have a 90MB file and when it downloads completely, latest block invocation in setDownloadProgressBlock: gives me totalBytesRead value about 30MB. On other side, if file is 2MB large, latest block invocation gives correct totalBytesRead 2MB value. AFNetworking is updated to the latest version from github. If AFNetworking can't do it correctly, what solution can I use? Edit: I've determined that even if file is not downloaded completely (and this happens every time with relatively big file) AFNetworking calls success block in: -[AFHTTPRequestOperation setCompletionBlockWithSuccess:failure] I asked a similar question here about this situation, but didn't get any answers. I can check in code downloaded and real file sizes, but AFNetworking has no API for continuation of partial download.

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  • iphone web app: open directions in external maps application

    - by munchybunch
    I've seen the answers for opening the Maps app in a native iPhone app, but is there any way to do this in a web app? I've tried changing window.location to http://maps.google.com/maps?q=cupertino for example, to no avail. I've tried using a simple anchor tag linked to http://maps.google.com/maps?q=cupertino, also to no avail. Has anyone gotten this to work before? I'm working on a map-heavy application, and I'd like to provide users with directions at the end. I figured it would be easiest to simply open it up in the Map application. Note: I'm currently testing with just the simulator, could that lead to problems? My iPhone is down for the count at the moment.

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  • What is XcvPort (used in OpenPrinter function)

    - by RiskX
    I'm usin the OpenPrinter function and the first parameter the function gets called "pPrinterName" and that's it's MSDN description: [in] Pointer to a null-terminated string that specifies the name of the printer or print server, the printer object, the XcvMonitor, or the XcvPort. For a printer object use: PrinterName,Job xxxx. For an XcvMonitor, use: ServerName,XcvMonitor MonitorName. For an XcvPort, use: ServerName,XcvPort PortName. Obviously I'm interested in the bold part. What exactly is XcvPort? I know it seems like a question of lazy person but I really couldn't find info abou this concept. If I would like to open a printer on port ABC I should write: "\\MySrever,XcvPort ABC"? Thank you for your answers!

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  • API For Flex Apps To Interact

    - by dimo414
    I have a large flex application (the app) running on one server, and many small flex applications (widgets) running on another server, which are to be included in the app so that visually the user see's one continuous application. Due to proprietary third party software, this structure cannot be changed. I am looking for some way to allow the app and the widgets to communicate, allowing the app to make changes to the widgets and the the widgets to notify the app when events are triggered, so that user interaction is fluid and continuous. There are a few related questions which indicate it's possible to do this by setting up event triggers and listeners. I am wondering if there is any standardized way to do this (the answers aren't very clear) or if anyone has developed a library or API to make this easier.

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  • How to generate Makefiles with Cmake to create tarballs of project?

    - by Rizo
    I like to keep my Makefiles flexible and multifunctional. One of the tasks I usually add to make command is tar, for example the following instruction does the job: tar: tar -cvf $(PROGNAME).tar $(SRCS) Makefile My question is: How can CMake be used to generate personalized commands like tar? I would like to see some code samples. For the full functionality it would be useful to create project's components and be able to use them as parameters. (Exempli gratia: archive only header files or some specific library). Thanks in advance for your answers!

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  • apache tomcat 8 websocket origin and client address

    - by user2926082
    i hope someone can help me ... i am using apache tomcat 8.0.0-RC5 and JSR-356 web socket API ... I have 2 questions: 1) Is it possible to get the client ip on @OnOpen method ?? 2) Is it possible to get the origin of the connection ??? I followed the websocket example which comes with the distribution of tomcat and i was not able to find the answers .... My java class is basically as follow @ServerEndpoint(value = "/data.socket") public class MyWebSocket { @OnOpen public void onOpen(Session session) { // Here is where i need the origin and remote client address } @OnClose public void onClose() { // disconnection handling } @OnMessage public void onMessage(String message) { // message handling } @OnError public void onError(Session session, Throwable throwable) { // Error handling } }

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  • Flushing stdin after every input - which approach is not buggy?

    - by Aseem Bansal
    While using scanf() in C there is always the problem of extra input lying in the input buffer. So I was looking for a function that I call after every scanf call to remedy this problem. I used this, this, this and this to get these answers //First approach scanf("%*[^\n]\n"); //2ndapproach scanf("%*[^\n]%*c"); //3rd approach int c; while((c = getchar()) != '\n' && c != EOF) /* discard */ ; All three are working as far as I could find by hit-and-trial and going by the references. But before using any of these in all of my codes I wanted to know whether any of these have any bugs?

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  • Abstract Classes and ReadOnly Properties

    - by serhio
    Let's have three classes; Line PoliLine SuperPoliLine for all that three classes a Distance is defined. But only for the Line a Distance can be Set. Is there a possibility to build a common abstract (MustInherit) class Segment, having a Distance as (abstract +? ReadOnly) member? Question for VB.NET, but C# answers welcomed too. Business Background Imagine a Bus. It has a lot of Stations, MainStations, and 2 TerminalStations. So Line is between 2 Stations, PoliLine is between 2 MainStations, and SuperPoliLine is between 2 TerminalStations. All "lines" are "Segments", but only the distance A-B between 2 stations - Line can be defined.

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  • Why do date manipulation in Java with milliseconds?

    - by staticsan
    I was recently faced with the problem of calculating the number of days from two dates in Java (without using joda, I'm afraid). Searching on the 'net shows most answers to this question say to get the milliseconds of the two days and convert that to days, which I found appalling. However, a scant few show a different approach: use a temporary variable to count how many times it takes adding 1 day to the first date to get to the second. This leaves the conversions to the code that does it best: the library. Why do so many people advocate the first? In another project, I had previously encountered numerous subtle date calculation problems involving time-zones, daylight-saving and once even leap years using seconds to do date comparisions and calculations. All these went away when all the comparison and calculation code was rewitten to use the language libraries. (This was in PHP, though, where the libraries are structured quite differently to Java.) So I'm understandably reluctant to use this "common wisdom" in the world of Java about comparing dates.

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  • Data Warehouse: One Database or many?

    - by drrollins
    At my new company, they keep all data associated with the data warehouse, including import, staging, audit, dimension and fact tables, together in the same physical database. I've been a database developer for a number of years now and this consolidation of function and form seems counter to everything I know. It seems to make security, backup/restore and performance management issues more manually intensive. Is this something that is done in the industry? Are there substantial reasons for doing or not doing it? The platform is Netezza. The size is in terabytes, hundreds of millions of rows. What I'm looking to get from answers to this question is a solid understanding of how right or wrong this path is. From your experience, what are the issues I should be focused on arguing if this is a path that will cause trouble for us down the road. If it is no big deal, then I'd like to know that as well.

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  • find a duplicate entry in an array in constant space and O(n) time [closed]

    - by Anubhav Agarwal
    Possible Duplicate: Algorithm to find a duplicate entry in constant space and O(n) time Given an array of N integer such that only one integer is repeated. Find the repeated integer in O(n) time and constant space. There is no range for the value of integers or the value of N For example given an array of 6 integers as 23 45 67 87 23 47. The answer is 23 (I hope this covers ambiguous and vague part) I searched on the net but was unable to find any such question in which range of integers was not fixed. Also here is an example that answers a similar question to mine but here he created a hash table with the highest integer value in C++.But the cpp does not allow such to create an array with 2^64 element(on a 64-bit computer).

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  • Copy a function in memory and execute it

    - by Elinghton
    Hi everybody, I would like to know how in C in can copy the content of a function into memroy and the execute it? I'm trying to do something like this: typedef void(*FUN)(int *); char * myNewFunc; char *allocExecutablePages (int pages) { template = (char *) valloc (getpagesize () * pages); if (mprotect (template, getpagesize (), PROT_READ|PROT_EXEC|PROT_WRITE) == -1) { perror ("mprotect"); } } void f1 (int *v) { *v = 10; } // allocate enough spcae but how much ?? myNewFunc = allocExecutablePages(...) /* Copy f1 somewere else * (how? assume that i know the size of f1 having done a (nm -S foo.o)) */ ((FUN)template)(&val); printf("%i",val); Thanks for your answers

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  • MSBuild syntax for deleting files/directories and reporting what was deleted

    - by Maslow
    Vs2010 .net 4.0 targeted project if that affects the answers at all. I want to delete the bin and obj directories and output a message for the path of what was deleted. <Target Name="CleanOutputs" Condition="'$(MvcBuildViews)'=='true'"> <Message Text="Cleaning Outputs" Importance="high"/> <RemoveDir Directories="$(OutputPath);obj" RemovedDirectories="@(removed)" /> <Message Text="Removed: %(removed.FullPath)" Importance="high"/> <Message Text=" "/> <!--<RemoveDir Directories="obj" />--> <MakeDir Condition="!Exists('$(OutputPath)')" Directories="$(OutputPath)" /> </Target> Is what I have, but the Removed: message never shows.

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  • start page with questions about interested tags?

    - by Stefan K.
    I'm new to stackoverflow and I'm looking for a question list, like the one on top, which just contains questions about interested tags. For example I'm interested in Java, but I have no clue about Python and questions about python clutters my questions page. I don't have answers concerning any python problem. I think it's too exhausting to enter my interested tags in the search combined with [xxx] OR. Is there a usable way to do this? By the way, what for are interested tags used right now? I added some in my profile but didn't see a benefit.

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