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  • C++ Basic Class Layout

    - by Spencer
    Learning C++ and see the class laid out like this: class CRectangle { int x, y; public: void set_values (int,int); int area () {return (x*y);} }; void CRectangle::set_values (int a, int b) { x = a; y = b; } I know Java and methods(functions) in Java are written within the class. The class looks like a Java interface. I know I can write the class like this: class CRectangle { int x, y; public: void set_values (int a, int b) { x = a; y = b; }; int area () {return (x*y);} }; But is there a difference or standard?

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  • Is there a way to intersect/diff a std::map and a std::set?

    - by Jack
    I'm wondering if there a way to intersect or make the differences between two structures defined as std::set<MyData*> and std::map<MyData*, MyValue> with standard algorithms (like std::set_intersect) The problem is that I need to compute the difference between the set and the keyset of the map but I would like to avoid reallocating it (since it's something that is done many times per second with large data structures). Is there a way to obtain a "key view" of the std::map? After all what I'm looking is to consider just the keys when doing the set operation so from an implementation point it should be possible but I haven't been able to find anything.

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  • Specializing a template member function of a template class?

    - by uj2
    I have a template class that has a template member function that needs to be specialized, as in: template <typename T> class X { public: template <typename U> void Y() {} template <> void Y<int>() {} }; Altough VC handles this correctly, apperantly this isn't standard and GCC complains: explicit specialization in non-namespace scope 'class X<T>' I tried: template <typename T> class X { public: template <typename U> void Y() {} }; template <typename T> // Also tried `template<>` here void X<T>::Y<int>() {} But this causes both VC and GCC to complain. What's the right way to do this?

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  • Resolve circular typedef dependency?

    - by Nick
    What is the best way to resolve the following circular dependency in typedef-ing these structs? Note the C language tag - I'm looking for a solution in standard gcc C. typedef struct { char* name; int age; int lefthanded; People* friends; } Person; typedef struct { int count; int max; Person* data; } People;

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  • What is the reliable way to return error code from an MPI program?

    - by mezhaka
    The MPI standard (page 295) says: Advice to users. Whether the errorcode is returned from the executable or from the MPI process startup mechanism (e.g., mpiexec), is an aspect of quality of the MPI library but not mandatory. Indeed I had no success in running the following code: if(0 == my_rank) { FILE* parameters = fopen("parameters.txt", "r"); if(NULL == parameters) { fprintf(stderr, "Could not open parameters.txt file.\n"); printf("Could not open parameters.txt file.\n"); exit(EXIT_FAILURE); //Tried MPI_Abort() as well } fscanf(parameters, "%i %f %f %f", N, X_DIMENSION_Dp, Y_DIMENSION_Dp, HEIGHT_DIMENSION_Dp); fclose(generation_conf); } I am not able to get the error code back into the shell in order to make a decision on further actions. Neither of two error messages are printed. I think I might write the error codes and messages to a dedicated file. Has anyone ever had a similar problem and what were the options you've considered to do a reliable error reporting?

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  • Perl Matching ,Extracting , and printing emails

    - by user3448790
    How do I match an email using the The Official Standard: RFC 5322 in a html source code, after that i will extract the strings that are matched ONLY, and print out inly the emails, and not the whole source code? Is there any examples and output to illustrate this? Thnaks! elsif ($_ eq '-dDATA' or $_ eq '-ft') { opendir(DIR,'DATA'); my(@dir) = grep /\.htm/, readdir (DIR); closedir(DIR); my $value = join(@dir); print "$value\n"; foreach my $movies (@dir) { open (my $FHD, "<", "DATA/$movies") || die $!; print <$FHD>; } } }

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  • How do I tell gdb how long my zero-length array is?

    - by Joe
    Slightly oxymoronic title! Bonus points for Xcode answer but it's a gdb question. If I have a standard, statically sized array gdb will print all its elements [and Xcode will let me browse through it] but if I have a zero length array, it won't, because it doesn't know. Obviously I can print the array indexes one by one, but I'd like a dump of the whole thing. How do I tell gdb how much space I have allocated for the array to allow it to print the array (or to allow Xcode to view the array). Is it even possible?

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  • twitter share url forgeting the tweet content after login

    - by tpk
    I'm trying to add a "share via twitter" link to our website. I'm aware of the standard http://twitter.com/home?status=TWEET method, and it works good enough for my purposes when the user is logged in to twitter already. If, however, the user is not logged in, twitter displays the login form first (which is only reasonable). After the login, the home screen is displayed without the tweet content. Am I missing something obvious, or is this a know flaw in this method? If so, what is the easiest way (apart from using services like TweetMeme, which I noticed asks for login in advance) to make the share button work as expected?

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  • Boost Shared Pointers and Memory Management

    - by Izza
    I began using boost rather recently and am impressed by the functionality and APIs provided. In using boost::shared_ptr, when I check the program with Valgrind, I found a considerable number of "Still reachable" memory leaks. As per the documentation of Valgrind, these are not a problem. However, since I used to use the standard C++ library only, I always made sure that any program written is completely free from memory leaks. My question is, are these memory leaks something to worry about? I tried using reset(), however it only decrements the reference count, doesn't deallocate memory. Can I safely ignore these, or any way to forcibly deallocate the memory allocated by boost::shared_ptr? Thank you.

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  • AJAX in ASP.NET - How do I check a checkbox and have the action reflected in the database?

    - by hamlin11
    This is about as beginner as it gets regarding AJAX, but here it goes. I want to have one checkbox somewhere on an ASP.NET web form (ASPX). When the user clicks the checkbox, I want one of those spinning indicators to show. While that spinning indicator is showing, I want an update operation to occur in the database to reflect that the user has intended for that checkbox to be checked. update MyTable set CheckboxChecked = 1 Then, as soon as the update operation has occurred, I want that to be reflected in the checkbox by removing the spinning indicator and replacing it with the standard checked checkbox. I'm guessing this is done with an UpdatePanel and possibly an update statement followed by a looped call to a select statement... but I have never used AJAX before and have no idea how to go about it. Thanks!

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  • Including Libraries C++

    - by m00st
    How do I properly include libraries in C++? I'm used to doing the standard libraries in C++ and my own .h files. I'm trying to include wxWidgets or GTK+ in code::blocks and/or netbeans C/C++ plugin. I've included ALL libraries but I constantly get errors such as file not found when it is explicitly in the include! One error: test1.cpp:1:24: wx/msw/wx.rc: No such file or directory : Yes the .h file library is included; what am I missing? Do I need to be importing other things as well? Is there a tutorial for this? Obviously my shoddy textbook hasn't prepared me for this.

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  • Simple integer encryption

    - by tloflin
    Is there a simple algorithm to encrypt integers? That is, a function E(i,k) that accepts an n-bit integer and a key (of any type) and produces another, unrelated n-bit integer that, when fed into a second function D(i,k) (along with the key) produces the original integer? Obviously there are some simple reversible operations you can perform, but they all seem to produce clearly related outputs (e.g. consecutive inputs lead to consecutive outputs). Also, of course, there are cryptographically strong standard algorithms, but they don't produce small enough outputs (e.g. 32-bit). I know any 32-bit cryptography can be brute-forced, but I'm not looking for something cryptographically strong, just something that looks random. Theoretically speaking it should be possible; after all, I could just create a dictionary by randomly pairing every integer. But I was hoping for something a little less memory-intensive.

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  • In SQL how do I get the maximum value for an integer?

    - by CoffeeMonster
    Hi, I am trying to find out the maximum value for an integer (signed or unsigned) from a MySQL database. Is there a way to pull back this information from the database itself? Are there any built-in constants or functions I can use (either standard SQL or MySQL specific). At http://dev.mysql.com/doc/refman/5.0/en/numeric-types.html it lists the values - but is there a way for the database to tell me. The following gives me the MAX_BIGINT - what I'd like is the MAX_INT. SELECT CAST( 99999999999999999999999 AS SIGNED ) as max_int; # max_int | 9223372036854775807 Thanks in advance,

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  • Python - How can I make this code asynchronous?

    - by dave
    Here's some code that illustrates my problem: def blocking1(): while True: yield 'first blocking function example' def blocking2(): while True: yield 'second blocking function example' for i in blocking1(): print 'this will be shown' for i in blocking2(): print 'this will not be shown' I have two functions which contain while True loops. These will yield data which I will then log somewhere (most likely, to an sqlite database). I've been playing around with threading and have gotten it working. However, I don't really like it... What I would like to do is make my blocking functions asynchronous. Something like: def blocking1(callback): while True: callback('first blocking function example') def blocking2(callback): while True: callback('second blocking function example') def log(data): print data blocking1(log) blocking2(log) How can I achieve this in Python? I've seen the standard library comes with asyncore and the big name in this game is Twisted but both of these seem to be used for socket IO. How can I async my non-socket related, blocking functions?

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  • JavaScript pack("d") - binary strings

    - by Tim Whitlock
    I'm trying to replicate the Perl and PHP style pack and unpack functions in JavaScript. Unsigned integers were easy enough, so my pack('n') and pack('N') are ok. But my lack of a computer science background is a hurdle now and I don't know where to start with pack('d') for packing JavaScript's standard floating point. Is there a JavaScript library for this out there? If not, is there a good resource where I can learn how to do this? I am fine with bitwise and binary level operations in JS, I just don't know where to start with the logic. Thanks.

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  • Adding Timestamp to Java's GC messages in Tomcat 6

    - by ripper234
    I turned on Java's GC log options -XX:+PrintGC -XX:+PrintGCTimeStamps -XX:+PrintGCDetails Which print out these messages to standard output (catalina.out): 314.884: [CMS-concurrent-mark-start] 315.014: [CMS-concurrent-mark: 0.129/0.129 secs] [Times: user=0.14 sys=0.00, real=0.13 secs] 315.014: [CMS-concurrent-preclean-start] 315.016: [CMS-concurrent-preclean: 0.003/0.003 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 315.016: [CMS-concurrent-abortable-preclean-start] 332.055: [GC 332.055: [ParNew: 17128K->84K(19136K), 0.0017700 secs] 88000K->70956K(522176K) icms_dc=4 , 0.0018660 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] CMS: abort preclean due to time 352.253: [CMS-concurrent-abortable-preclean: 0.023/37.237 secs] [Times: user=0.78 sys=0.02, real=37.23 secs] How can I make these log lines appear with an actual timestamp (including date) instead of these numbers, which presumably mean "time since JVM started" ?

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  • Get file size of BufferedImage before writing the data

    - by David
    I'm working on a Java program that needs to send an image (preferably in PNG format, though I could perhaps use another format if necessary) over the network. The logical way to do this is, of course, to first send the length of the PNG image data, then the data itself. Problem: I don't see any method in ImageIO or anywhere else that will give me the length of the image data. Does this exist somewhere in the Java 1.6 standard library? I know I could just write it to a ByteArrayOutputStream and get the length of the resulting array, but before resorting that I wanted to make sure I'm not missing something built in. And besides, that makes an extra copy of the image data, which I'd rather not do if it's not necessary.

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  • What is the accepted way to replace java.util.Date(year,month,day)

    - by dagw
    I'm trying to do something really simple, but starting to realize that dates in Java are a bit of minefield. All I want is to get passed groups of three ints ( a year, a month and a date) create some Date objects, do some simple test on them (along the lines of as date A before date B and after January 1 1990), convert them to java.sql.Date objects and pass them off to the database via JDBC. All very simple and works fine using the java.util.Date(int year,int month,int day) constructor. Of course that constructor is depreciated, and I'd like to avoid using depreciated calls in new code I'm writing. However all the other options to solve this simple problem seem stupidly complicated. Is there really no simple way to do what I want without using depreciated constructors? I know the standard answer to all Java date related questions is "use joda time", but I really don't want to start pulling in third party libraries for such a seemingly trivial problem.

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  • Multiple svn projects into one git repository?

    - by trondgzi
    Hi, I have started to use git-svn for some of my work to be able to do local commits. This works great for projects that use standard svn layout. Recently I started working on a Java project that is split into multiple connected modules (20-25), and each module have its own root folder in the same svn repo with its own trunk/branches/tags. svnrepo/ module-1 trunk branches tags module-N trunk branches tags I have cloned each and every module with git svn clone -s /path/to/svnrepo/module[1-N]. The "problem" is that when I want to do git svn rebase on all modules i have to do it N times. I have tried to do git svn clone /path/to/svnrepo/ do avoid doing the rebase operation N times, but that leaves me with a directory layout that is the same as in the svn repo. Is there a way that I can track all the trunks of all modules in one git repo? So that I get a directory layout like this within my git repository: module-1 module-2 module-N

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  • C# asp.net MVC: When to update LastActivityDate?

    - by Oskar Kjellin
    I'm using asp.net mvc and creating a public website. I need to keep track of users that are online. I see that the standard way in asp.net of doing this is to keep track of LastActivityDate. My question is when should I update this? If I update it every time the users clicks somewhere, I will feel a performance draw back. However if I do not do that, people that only surf arround will be listed as offline. What is the best way to do this in asp.net MVC?

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  • What is the most "database independent" way of creating a variable length text field in a database

    - by Thibaut Colar
    I want to create a text field in the database, with no specific size (it will store text of length unknown in some case) - the particular text are serialized simple object (~ JSON) What is the most database independent way to do this : - a varchar with no size specified (don't think all db support this) - a 'text' field, this seems to be common, but I don't believe it's a standard - a blob or other object of that kind ? - a varchar of a a very large size (that's inefficient and wastes disk space probably) - Other ? I'm using JDBC, but I'd like to use something that is supported in most DB (oracle, mysql, postgresql, derby, HSQL, H2 etc...) Thanks.

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  • Is the XML processing instructions node mandatory ?

    - by ereOn
    I had a discussion with a colleague of mine about the XML processing instructions node (I'm talking about this = <?xml version="1.0" encoding="UTF-8"?>). I believe that for something to be called "valid XML", it requires a processing instructions node. My colleague states that the processing instruction node is optionnal, since the default encoding is UTF-8 and the version is always 1.0. This make sense, but what does the standard says ? In short, given the following file: <books> <book id="1"><title>Title</title></book> </book> Can we say that: It is valid XML ? It is a valid XML node ? It is a valid XML document ? Thank you very much.

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  • How can I implement a tail-recursive list append?

    - by martingw
    A simple append function like this (in F#): let rec app s t = match s with | [] -> t | (x::ss) -> x :: (app ss t) will crash when s becomes big, since the function is not tail recursive. I noticed that F#'s standard append function does not crash with big lists, so it must be implemented differently. So I wondered: How does a tail recursive definition of append look like? I came up with something like this: let rec comb s t = match s with | [] -> t | (x::ss) -> comb ss (x::t) let app2 s t = comb (List.rev s) t which works, but looks rather odd. Is there a more elegant definition?

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  • Apache file caching

    - by danp
    How does apache handle caching of certain files, and is it possible to explicitly say that certain files should be aggressively cached more than others, through the standard config files for a given host or virtualhost? To put it in context, I keep a lot of site content in various XML files, and I'd like to be able to say that this file will be used a lot, and therefore cache it as much as possible..? Does apache do this kind of thing intelligently and on the fly..? Will it observe which files are more popular than others and try to match cache hits appropriately..? Lots of questions in one, but the basic idea should be clear enough. edit: to be clear, these are resource files which are loaded and interpreted by PHP - but php as a process is spawned inside apache.. right? Please help!

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  • Data storage advice needed: Best way to store location + time data?

    - by sobedai
    I have a project in mind that will require the majority of queries to be keyed off of lat/long as well as date + time. Initially, I was thinking of a standard RDBMS where lat, long, and the datetime field are properly indexed. Then, I began thinking of a document based system where the document was essentially a timestamp and each document has lat/long with in it. Each document could have n objects associated with it. I'm looking for advice on what would be the best type of storage engine for this sort of thing is - which of the above idea would be better or if there is something else completely that is the ideal solution. Thanks

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