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  • What programming languages do you consider indispensable in your experience?

    - by Federico Ramponi
    Each programming language comes with its concepts, best practices, libraries, tools, community, in one word: culture. Learning more than one programming language will make you a better programmer, for the more concepts you learn, the faster you will feel comfortable when the next language or technology will come. Mine, so far, are C, some C++, and Python, and many times I read that it would be worth learning LISP, for "the profound enlightenment experience you will have when you finally get it" (quoting Eric Raymond). My questions are: Which is the next one you would consider a good investment to learn? Of the many programming languages you have learnt and worked with, which ones do you consider to be an essential part of one's CS culture, and why? EDIT. Further question: is there any language you would sincerely advise to avoid as a waste of time? (The famous, and questionable, slatings in this letter from Dijkstra come to my mind.)

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  • How to avoid Modal Storyboard infinite loop

    - by misthills
    I've written a number of iOS applications a year ago on an old version of Xcode. I've just started a new project and discovered the storyboard feature in the latest Xcode. It turns out this is perfect for the application I am writing as it consists of ~30 interlinked screens. My question is, how do I structure my storyboard and segues to allow my application to follow a circular path through my screens. I have seen a number of examples that simply segue screen 1 to screen 2 and then screen 2 to screen 1 using the modal option. This clearly works but when I debug an application built this way, it instantiates a new instance of each screen (view controller) for every segue performed. In the diagram below (apologies, I drew a nice picture but due to my newbie status, was not able to post it), how do I go from screen 1 to screen 2 to screen 3 and back to original screen 1 without creating a new instance? // Screen 1 --> Screen 2 --> Screen3 // ^ | // | | // +-------------------------+

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  • Avoid Circular Reference in Swing GUI

    - by drhorrible
    Maybe it's not worth worrying about in this scenario, but lets say you have two classes, a JFrame with all its components, and a server-like class that handles requests from remote clients. The user is able to start and stop server objects through the GUI, and is shown various events that happen to each server object. Whether or not I use an explicit pattern (like MVC), it seems like the JFrame needs a reference to the server class (to call start and stop) and the server needs a reference to the JFrame (to notify of it of certain events). Is this a problem, or am I looking at this situation in the wrong way?

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  • How to avoid nested functions when using AJAX?

    - by Fletcher Moore
    Sequential Asynchronous calls are gross. Is there a more readable solution? The problem is this is hard to follow: ajaxOne(function() { // do something ajaxTwo(function() { // do something ajaxThree() }); }); where the anonymous functions are callbacks that are called on server response. I'm using a third party API to make the AJAX calls, so I need a generic solution.

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  • how to avoid jQuery UI draggable from also triggering click event

    - by James Tauber
    A have a large div (a map) that is draggable via jQuery UI draggable. The div has child divs which are clickable. My problem is that if you drag the map, on mouse up, the click event is fired on whatever child div you started the drag from. How do I stop the mouse up from triggering the click event if its part of a drag (as opposed to someone just clicking without a drag, in which case the click event is desired).

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  • shell script segment to avoid overwriting files

    - by johndashen
    I have a perl script (or any executable) E which will take a file foo.xml and write a file foo.txt. I use a Beowulf cluster to run E for a large number of XML files, but I'd like to write a simple job server script in shell (bash) which doesn't overwrite existing txt files. I'm currently doing something like #!/bin/sh PATTERN="[A-Z]*0[1-2][a-j]"; # this matches foo in all cases todo=`ls *.xml | grep $PATTERN`; isdone=`ls *.foo | grep $PATTERN`; whatsleft=todo - isdone; # what's the unix magic? #and then call the job server; jobserve E "$whatsleft"; and then I don't know how to get the difference between $todo and $isdone. I'd prefer using sort/uniq to something like a for loop with grep inside, but I'm not sure how to do it (pipes? temporary files?) As a bonus question, is there a way to do lookahead search in bash grep?

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  • how to avoid temporaries when copying weakly typed object

    - by Truncheon
    Hi. I'm writing a series classes that inherit from a base class using virtual. They are INT, FLOAT and STRING objects that I want to use in a scripting language. I'm trying to implement weak typing, but I don't want STRING objects to return copies of themselves when used in the following way (instead I would prefer to have a reference returned which can be used in copying): a = "hello "; b = "world"; c = a + b; I have written the following code as a mock example: #include <iostream> #include <string> #include <cstdio> #include <cstdlib> std::string dummy("<int object cannot return string reference>"); struct BaseImpl { virtual bool is_string() = 0; virtual int get_int() = 0; virtual std::string get_string_copy() = 0; virtual std::string const& get_string_ref() = 0; }; struct INT : BaseImpl { int value; INT(int i = 0) : value(i) { std::cout << "constructor called\n"; } INT(BaseImpl& that) : value(that.get_int()) { std::cout << "copy constructor called\n"; } bool is_string() { return false; } int get_int() { return value; } std::string get_string_copy() { char buf[33]; sprintf(buf, "%i", value); return buf; } std::string const& get_string_ref() { return dummy; } }; struct STRING : BaseImpl { std::string value; STRING(std::string s = "") : value(s) { std::cout << "constructor called\n"; } STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } bool is_string() { return true; } int get_int() { return atoi(value.c_str()); } std::string get_string_copy() { return value; } std::string const& get_string_ref() { return value; } }; struct Base { BaseImpl* impl; Base(BaseImpl* p = 0) : impl(p) {} ~Base() { delete impl; } }; int main() { Base b1(new INT(1)); Base b2(new STRING("Hello world")); Base b3(new INT(*b1.impl)); Base b4(new STRING(*b2.impl)); std::cout << "\n"; std::cout << b1.impl->get_int() << "\n"; std::cout << b2.impl->get_int() << "\n"; std::cout << b3.impl->get_int() << "\n"; std::cout << b4.impl->get_int() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_ref() << "\n"; std::cout << b2.impl->get_string_ref() << "\n"; std::cout << b3.impl->get_string_ref() << "\n"; std::cout << b4.impl->get_string_ref() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_copy() << "\n"; std::cout << b2.impl->get_string_copy() << "\n"; std::cout << b3.impl->get_string_copy() << "\n"; std::cout << b4.impl->get_string_copy() << "\n"; return 0; } It was necessary to add an if check in the STRING class to determine whether its safe to request a reference instead of a copy: Script code: a = "test"; b = a; c = 1; d = "" + c; /* not safe to request reference by standard */ C++ code: STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } If was hoping there's a way of moving that if check into compile time, rather than run time.

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  • Question about C Pointers (just learning)

    - by Mike
    I am curious as to why this is an error and what the error message means. Here is some code. int *x[] = {"foo", "bar", "baz"}; int *y[] = {"foo", "bar", "baz"}; x = y; I try to compile and I get this: error: incompatible types when assigning to type ‘char [3]’ from type ‘char *’ Question #1 why is this an error? and Question #2 why are the types different? Thanks for you help.

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  • How to avoid that the Parameter Pane Area in Drill-Through Report is hidden

    - by nojetlag
    I have a report that via a text box property action triggers a drill-through report (and gives it two parameters (start date, end date)). That all works fine in the report designer, however after deploying the report on the server the pane in the drill-through reports is hidden. Is there a way I can change this behavior. Our users want the pane to be visible in the drill-through report.

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  • Learning to work with audio in C++

    - by Skilldrick
    My degree was in audio engineering, but I'm fairly new to programming. I'd like to learn how to work with audio in a programming environment, partly so I can learn C++ better through interesting projects. First off, is C++ the right language for this? Is there any reason I shouldn't be using it? I've heard of Soundfile and some other libraries - what would you recommend? Finally, does anyone know of any good tutorials in this subject? I've learnt the basics of DSP - I just want to program it! EDIT: I use Windows. I'd like to play about with real-time stuff, a bit like Max/MSP but with more control.

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  • CSS fixed div. Avoid unwanted overlapping

    - by Justa Randomone
    I've got a CSS layout made of 2 columns. the navigation column to the left is a fix div. It stays there while scrolling down the main content in the column to the right. The problem comes when I reduce the browser window, or zoom in: when scrolling the browser windom horizontally, the main content on the right starts overlapping the navigation column on the left. How can I fix it so that whatever the size of my browser window or my zoom level is, when i scroll horizontally the fixed div isn't overlapped but pushes the main column to the right? You can see it for real at: http://justarandomone.tumblr.com/ All the code is in the source (It is pretty messy, sorry for that). Hope some one can help. Thanks!

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  • Best practice to avoid InvalidOperationException: Collection was modified?

    - by Roflcoptr
    Very often I need something like that: foreach (Line line in lines) { if (line.FullfilsCertainConditions()) { lines.Remove(line) } } This does not work, because I always get a InvalidOperationException because the Enumerator was changed during the loop. So I changed all my loops of this kind to the following: List<Line> remove = new List<Line>(); foreach (Line line in lines) { if (line.FullfilsCertainConditions()) { remove.Add(line) } } foreach (Line line in remove) { { lines.Remove(line); } I'm not sure if this is really the best way since in the worst case I have to iterate 2 times over the original list and so it needs time 2n instead of n. Is there a better way to do this?

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  • How to avoid recursion in Java SecurityManager checkConnect?

    - by Zilupe
    I'm trying to take control of a Java code base that does lots of un-documented things. I'm using a custom SecurityManager to check permission requests. Specifically, my code is checking SocketPermission checks -- checkConnect. checkConnect is called when the application tries to resolve a host name to IP address and to connect to a specific IP address. The problem is that I don't know how to properly call host name resolution (InetAddress.getAddressByName) without falling into infinite recursion, because normally checkConnect is called even when I resolve the name from inside the SecurityManager.checkConnect. I have read on the web that I have to call the address resolution from a doPrivileged block, but no idea how. P.S. Is this possible without writing any policy files?

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  • Mysql - GROUP BY Avoid using tempoary

    - by jwzk
    The goal of this query is to get a total of unique records (by IP) per ref ID. SELECT COUNT(DISTINCT ip), GROUP_CONCAT(ref.id) FROM `sess` sess JOIN `ref` USING(row_id) WHERE sess.time BETWEEN '2010-04-21 00:00:00' AND '2010-04-21 23:59:59' GROUP BY ref.id ORDER BY sess.time DESC The query works fine, but its using a temporary table. Any ideas?

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  • Looking for resources for learning SharePoint Foundation on the Internet

    - by Kabeer
    Hello. While I am quite comfortable with the .Net world, I am a baby as far as SharePoint technologies are concerned. With the advent of SharePoint 2010 (Foundation especially), I'd like to directly learn the new version. However, I am not getting enough resources on the Internet that can be helpful. Besides knowing to maneuver a SharePoint site, I'd like to understand stuff under the hood from the architecture standpoint and subsequently the APIs. Can the community please guide me to the most suitable resource(s) available on the Internet?

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  • Making linq avoid using in memory filtering where possible

    - by linqmonkey
    Consider the these two LINQ2SQL data retrieval methods. The first creates a 'proper' SQL statement that filters the data, but requires passing the data context into the method. The second has a nicer syntax but loads the entire list of that accounts projects, then does in memory filtering. Is there any way to preserve the syntax of the second method but with the performance advantage of the first? public partial class Account { public IQueryable<Project> GetProjectsByYear(LinqDataContext context, int year) { return context.Projects.Where(p => p.AccountID==this.AccountID && p.Year==year).OrderBy(p => p.ProjectNo) } public IQueryable<Project> GetProjectsByYear(int year) { return this.Projects.Where(p => p.Year==year).OrderBy(p => p.ProjectNo).AsQueryable() } }

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  • How to avoid resending data on refresh in php

    - by Priyanka
    Hello.I have a page "index.php" where i have a link called "add_users.php".In "add_users.php",i accept user information and come back to the same page "index.php" where information comes through post action and gets inserted into the database.When i refresh the page orhit back button,resend box appears.I went through many solution where they asked me to create third page.I tried doing that as follows:After inserting values in database,I redirected ht page as header('Location:http://mysite.com/thankyou.php, and in thankyou.php I again redirected the page to index.php.But getting warning as Cannot modify header information - headers already sent by.... provide me a better solution. Thank You in advance.

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  • mvc - how to avoid log out when refresh a page

    - by user235973457
    I have built the MVC application with WCF service. The major problem I have experienced with refreshing page. I have created a login page with session (username and password). But when you refresh the home page by pressing F5, it would automatically log out. That is my problem. I need to stay the home page after refresh. I have been googling around to find a solution but it seems not helpful. Any idea? Your advise or code example much appreciated.

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  • best way to avoid sql injection

    - by aauser
    I got similar domain model 1) User. Every user got many cities. @OneToMany(targetEntity=adv.domain.City.class...) 2) City. Every city got many districts @OneToMany(targetEntity=adv.domain.Distinct.class) 3) Distintc My goal is to delete distinct when user press delete button in browser. After that controller get id of distinct and pass it to bussiness layer. Where method DistinctService.deleteDistinct(Long distinctId) should delegate deliting to DAO layer. So my question is where to put security restrictions and what is the best way to accomplish it. I want to be sure that i delete distinct of the real user, that is the real owner of city, and city is the real owner of distinct. So nobody exept the owner can't delete ditinct using simple url like localhost/deleteDistinct/5. I can get user from httpSession in my controller and pass it to bussiness layer. After that i can get all cities of this user and itrate over them to be sure, that of the citie.id == distinct.city_id and then delete distinct. But it's rather ridiculous in my opinion. Also i can write sql query like this ... delete from t_distinct where t_distinct.city_id in (select t_city.id from t_city left join t_user on t_user.id = t_city.owner_id where t_user.id = ?) and t_distinct.id = ? So what is the best practice to add restrictions like this. I'm using Hibernate, Spring, Spring MVC by the way.. Thank you

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