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  • How to synchronize static method in java.

    - by Summer_More_More_Tea
    Hi there: I come up with this question when implementing singleton pattern in Java. Even though the example listed blow is not my real code, yet very similar to the original one. public class ConnectionFactory{ private static ConnectionFactory instance; public static synchronized ConnectionFactory getInstance(){ if( instance == null ){ instance = new ConnectionFactory(); } return instance; } private ConnectionFactory(){ // private constructor implementation } } Because I'm not quite sure about the behavior of a static synchronized method, I get some suggestion from google -- do not have (or as less as possible) multiple static synchronized methods in the same class. I guess when implementing static synchronized method, a lock belongs to Class object is used so that multiple static synchronized methods may degrade performance of the system. Am I right? or JVM use other mechanism to implement static synchronized method? What's the best practice if I have to implement multiple static synchronized methods in a class? Thank you all! Kind regards!

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  • representing graph using database

    - by prosseek
    I need to represent graph information with database. Let's say, a is connected to b, c, and d. a -- b |_ c |_ d I can have a node table for a, b, c, and d, and I can also have a link table (FROM, TO) - (a,b), (a,c), (a,d). For other implementation there might be a way to store the link info as (a,b,c,d), but the number of elements in the table is variable. Q1 : Is there a way to represent variable elements in a table? Q2 : Is there any general way to represent the graph structure using database?

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  • Making uppercase of std::string

    - by Daniel K.
    Which implementation do you think is better? std::string ToUpper( const std::string& source ) { std::string result; result.reserve( source.length() ); std::transform( source.begin(), source.end(), result.begin(), std::ptr_fun<int, int>( std::toupper ) ); return result; } and... std::string ToUpper( const std::string& source ) { std::string result( source.length(), '\0' ); std::transform( source.begin(), source.end(), result.begin(), std::ptr_fun<int, int>( std::toupper ) ); return result; } Difference is that the first one uses reserve method after the default constructor, but the second one uses the constructor accepting the number of characters.

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  • Determine coordinates of rotated rectangle

    - by MathieuK
    I'm creating an utility application that should detect and report the coordinates of the corners of a transparent rectangle (alpha=0) within an image. So far, I've set up a system with Javascript + Canvas that displays the image and starts a floodfill-like operation when I click inside the transparent rectangle in the image. It correctly determines the bounding box of the floodfill operation and as such can provide me the correct coordinates. Here's my implementation so-far: http://www.scriptorama.nl/image/ (works in recent Firefox / Safari ). However, the bounding box approach breaks down then the transparent rectangle is rotated (CW or CCW) as the resulting bounding box no longer properly represents the proper width and height. I've tried to come up with a few alternatives to detect to corners, but have not been able to think up a proper solution. So, does anyone have any suggestions on how I might approach this so I can properly detect the coordinates of 4 corners of the rotated rectangle?

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  • How should I go about learning Python?

    - by user345690
    I am currently learning PHP and want to learn about OOP. *1.*I know Python is a well-organized and is all OOP, so would learning Python be a wise choose to learn OOP? The thing is I am more towards web development then just general programming, and I know Python is just a general purpose language, but there is Django. *2*So how should I go about learning Python if I am lending towards web development? Is there any good books/websites that help me learn Python for web development? 3. Is there any free webhosting companies that allow Python? I never used Python before, only PHP, and not sure how it works? Can I run Python on a localhost?

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  • What is the most suitable for writing a high speed server C, C++ or C# ?

    - by wniroshan
    I'm goint to write a server which does lots of image processing. Server-end processsing is expected to be very tedious. Server will maily have mobile phones as its clients. I am really concerend about speed and effciency. Security is pretty important too. Server will be running on a windows platform. Can anyone tell me what should I use as the language C, C++ or C#? or at least what are the ares that I should be looking at when selecting one of them Thank you.

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  • Archiving Database Tables using Java

    - by HonorGod
    My application demands archiving database tables between sybase and db2 and vice-a-versa and within(db2 to db2 and sybase to sybase) using java. I am trying to understand the best strategies around in terms performance, implementation, ease of use and scalability. Here is my current process - source and destination tables with the acceptable parameters (from java) are defined within xml. the application reads the source and destination configurations and execute them sequentially. destination is sometime optional when source is just deleting data from a specific table or when the source is just calling a stored procedure. dataset between source and destination is extremely large (in millions) From top of my head, it looks like I can define dependencies between multiple source and destination combination and have them execute in parallel in multiple treads. But will this improve any performance(i hope it will)? Are there any open-source frameworks for data archiving using java? Any other thoughts on the implements side will be really helpful. Thanks

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  • listbox isSelected databinding in DataTemplate

    - by Kinmarui
    I try to simply databind IsSelected property with IsSelected field in my class. But after I change the value in code its doesn't change the property, neither does clicking on ListBoxItem change the field value. XAML: <FlipView ItemsSource="{Binding Source={StaticResource itemsViewSource}}" ... > <FlipView.ItemTemplate> <DataTemplate> <UserControl Loaded="StartLayoutUpdates" Unloaded="StopLayoutUpdates"> <!-- other controls --> <ListBox Grid.Row="1" Grid.ColumnSpan="3" SelectionMode="Multiple" VerticalAlignment="Center" ItemsSource="{Binding Answers}"> <ListBox.Resources> <local:LogicToText x:Key="logToText" /> </ListBox.Resources> <!-- bind IsSelected only in one way from code to content --> <ItemsControl.ItemTemplate> <DataTemplate> <ListBoxItem IsSelected="{Binding IsSelected, Mode=TwoWay, Converter={StaticResource logToText}}" Content="{Binding IsSelected, Mode=TwoWay, Converter={StaticResource logToText}}"> </ListBoxItem> </DataTemplate> </ItemsControl.ItemTemplate> <!-- not working at all <ListBox.Resources> <Style TargetType="ListBoxItem"> <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/> <Setter Property="Content" Value="{Binding IsSelected, Mode=TwoWay}"/> </Style> </ListBox.Resources>--> </ListBox> </UserControl> </DataTemplate> </FlipView.ItemTemplate> </FlipView> Code: Answers private ObservableCollection<PrawoJazdyDataAnswer> _answers = new ObservableCollection<PrawoJazdyDataAnswer>(); public ObservableCollection<PrawoJazdyDataAnswer> Answers { get { return this._answers; } } Single item(Answer) public class PrawoJazdyDataAnswer : NPCHelper// PrawoJazdy.Common.BindableBase { public PrawoJazdyDataAnswer(String ans, bool ansb) { this._ans = ans; this._isSelected = ansb; } public override string ToString() { return _isSelected.ToString(); } //Only For debug purposes normally return _ans; private string _ans; public string Ans { get { return this._ans; } //set { this.SetProperty(ref this._ans, value); } } private bool _isSelected; public bool IsSelected { get { return this._isSelected; } set { _isSelected = value; FirePropertyChanged("IsSelected"); //this.SetProperty(ref this._isSelected, value); } } } FirePropertyChanged public class NPCHelper : INotifyPropertyChanged { public event PropertyChangedEventHandler PropertyChanged; public void FirePropertyChanged(string prop) { if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(prop)); } } Converter(which sometimes seems to be needed and others not..., I tried ~10 approaches from different tutorials/examples) public class LogicToText : IValueConverter { /// <summary> /// /// </summary> public object Convert(object value, Type targetType, object parameter, string language) { //if (value == null || (bool)value == false) // return "False"; return value.ToString(); } /// <summary> /// /// </summary> public object ConvertBack(object value, Type targetType, object parameter, string language) { return value.ToString().Contains("True") ? true : false; } Thanks in advance, and sorry for my English(still learning). @edit Thanks for quick reply. For test purposes i created a button and text block: It's in other controls part (above list box, but in FlipView) <Button Click="spr" >Sprawdz</Button> <TextBlock Text="{Binding Answers[0].IsSelected, Mode=TwoWay}" > </TextBlock> Click method private void spr(object sender, RoutedEventArgs e) { var ans = ((PrawoJazdyDataQuestion)this.flipView.SelectedItem).Answers; foreach (var item in ans) item.IsSelected = item.IsSelected ? false : true; } As I wrote when i'm changing data from code side its change text, but not appearance of ListBoxItem, and if i just select it on ListBox its doesn't change the date i textblock neither in ListBox itself.

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  • Good File Organization Suggestions for Developer

    - by Paul
    I am struggling a little with folder organization to organize the many projects that I work on. I work on OS X - right now I am using ~/Development/ as the root folder, and I have many types of projects. For example, I have my iPhone apps under ~/Development/Xcode I develop in many languages, from PHP, to Ruby, to Python, to Objective-C. So, for example, I might have a couple of open-source apps based on PHP where I am using the Zend framework. Some of these projects are for clients, others are tests/experiments when learning a new language or general experimenting. I am really interested in how other developers have organized code/projects and could pass along some advice to make it very easy to navigate through code/projects related to many languages and types of projects.

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  • Sprintf equivalent in Mathematica?

    - by jxy
    I don't know why Wikipedia lists Mathematica as a programming language with printf. I just couldn't find the equivalent in Mathematica. My specific task is to process a list of data files with padded numbers, which I used to do it in bash with fn=$(printf "filename_%05d" $n) The closest function I found in Mathematica is PaddedForm. And after some trial and error, I got it with "filename_" <> PaddedForm[ Round@#, 4, NumberPadding -> {"0", ""} ]& It is very odd that I have to use the number 4 to get the result similar to what I get from "%05d". I don't understand this behavior at all. Can someone explain it to me? And is it the best way to achieve what I used to in bash?

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  • Setting up separate ctags db's for C/C++ standard libs, boost, and third party libs

    - by Robert S. Barnes
    I want to set up separate ctags databases for various libraries in /usr/include/ for use with OmniCppComplete. The idea is to be able to pull in only the libraries needed for a particular project in the target language - C or C++. For example, I'd like to have one database for the standard C libraries, one for system libraries that might be used by either C or C++ programs ( sockets / networking comes to mind ) one for the standard C++ libs / STL / Boost, and then other databases for various third party libraries such as QT or glib. Then I could pull something in simply by typing set tags+= ~/.vim/somelib.tags in vim. I assume that everything related to the C++ stdlib and STL are in the /usr/include/c++ and that Boost is all in /usr/include/boost. Unfortunately it seems that the standard C libs and system libs are just kind of dumped directly into /usr/include/ with a variety of other stuff. How can I get a list of which files and directories belong to which libs? I'm on Ubuntu 8.04.

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  • Abstracting the adding of click events to elements selected by class using jQuery

    - by baroquedub
    I'm slowly getting up to speed with jQuery and am starting to want to abstract my code. I'm running into problems trying to define click events at page load. In the code below, I'm trying to run through each div with the 'block' class and add events to some of its child elements by selecting them by class: <script language="javascript" type="text/javascript"> $(document).ready(function (){ $('HTML').addClass('JS'); // if JS enabled, hide answers $(".block").each(function() { problem = $(this).children('.problem'); button = $(this).children('.showButton'); problem.data('currentState', 'off'); button.click(function() { if ((problem.data('currentState')) == 'off'){ button.children('.btn').html('Hide'); problem.data('currentState', 'on'); problem.fadeIn('slow'); } else if ((problem.data('currentState')) == 'on'){ button.children('.btn').html('Solve'); problem.data('currentState', 'off'); problem.fadeOut('fast'); } return false; }); }); }); </script> <style media="all" type="text/css"> .JS div.problem{display:none;} </style> <div class="block"> <div class="showButton"> <a href="#" title="Show solution" class="btn">Solve</a> </div> <div class="problem"> <p>Answer 1</p> </div> </div> <div class="block"> <div class="showButton"> <a href="#" title="Show solution" class="btn">Solve</a> </div> <div class="problem"> <p>Answer 2</p> </div> </div> Unfortunately using this, only the last of the divs' button actually works. The event is not 'localised' (if that's the right word for it?) i.e. the event is only applied to the last $(".block") in the each method. So I have to laboriously add ids for each element and define my click events one by one. Surely there's a better way! Can anyone tell me what I'm doing wrong? And how I can get rid of the need for those IDs (I want this to work on dynamically generated pages where I might not know how many 'blocks' there are...) <script language="javascript" type="text/javascript"> $(document).ready(function (){ $('HTML').addClass('JS'); // if JS enabled, hide answers // Preferred version DOESN'T' WORK // So have to add ids to each element and laboriously set-up each one in turn... $('#problem1').data('currentState', 'off'); $('#showButton1').click(function() { if (($('#problem1').data('currentState')) == 'off'){ $('#showButton1 > a').html('Hide'); $('#problem1').data('currentState', 'on'); $('#problem1').fadeIn('slow'); } else if (($('#problem1').data('currentState')) == 'on'){ $('#showButton1 > a').html('Solve'); $('#problem1').data('currentState', 'off'); $('#problem1').fadeOut('fast'); } return false; }); $('#problem2').data('currentState', 'off'); $('#showButton2').click(function() { if (($('#problem2').data('currentState')) == 'off'){ $('#showButton2 > a').html('Hide'); $('#problem2').data('currentState', 'on'); $('#problem2').fadeIn('slow'); } else if (($('#problem2').data('currentState')) == 'on'){ $('#showButton2 > a').html('Solve'); $('#problem2').data('currentState', 'off'); $('#problem2').fadeOut('fast'); } return false; }); }); </script> <style media="all" type="text/css"> .JS div.problem{display:none;} </style> <div class="block"> <div class="showButton" id="showButton1"> <a href="#" title="Show solution" class="btn">Solve</a> </div> <div class="problem" id="problem1"> <p>Answer 1</p> </div> </div> <div class="block"> <div class="showButton" id="showButton2"> <a href="#" title="Show solution" class="btn">Solve</a> </div> <div class="problem" id="problem2"> <p>Answer 2</p> </div> </div>

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  • How to hash and check for equality of objects with circular references

    - by mfya
    I have a cyclic graph-like structure that is represented by Node objects. A Node is either a scalar value (leaf) or a list of n=1 Nodes (inner node). Because of the possible circular references, I cannot simply use a recursive HashCode() function, that combines the HashCode() of all child nodes: It would end up in an infinite recursion. While the HashCode() part seems at least to be doable by flagging and ignoring already visited nodes, I'm having some troubles to think of a working and efficient algorithm for Equals(). To my surprise I did not find any useful information about this, but I'm sure many smart people have thought about good ways to solve these problems...right? Example (python): A = [ 1, 2, None ]; A[2] = A B = [ 1, 2, None ]; B[2] = B A is equal to B, because it represents exactly the same graph. BTW. This question is not targeted to any specific language, but implementing hashCode() and equals() for the described Node object in Java would be a good practical example.

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  • MEMORY(HEAP) vs. InnoDB in a Read and Write Envirnment

    - by Johannes
    I want to programm a real-time application using MySQL. It needs a small table (less than 10000 rows) that will be under heavy read (scan) and write (update and some insert/delete) load. I am really speaking of 10000 updates or selects per second. These statements will be executed on only a few (less than 10) open mysql connections. The table is small and does not contain any data that needs to be stored on disk. So I ask which is faster: InnoDB or MEMORY (HEAP)? My thoughts are: Both enginges will probably serve SELECTs directly from memory, as even InnoDB will cache the whole table. What about the UPDATAEs? (innodb_flush_log_at_trx_commit?) My main concern is the locking behavior: InnoDB row lock vs. MEMORY table lock. Will this present the bottleneck in the MEMORY implementation? Thanks for your thoughts!

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  • Python: How To copy function parameters into object's fields effortlessly ?

    - by bandana
    Many times I have member functions that copy parameters into object's fields. For Example: class NouveauRiches(object): def __init__(self, car, mansion, jet, bling): self.car = car self.mansion = mansion self.jet = jet self.bling = bling Is there a python language construct that would make the above code less tedious? One could use *args: def __init__(self, *args): self.car, self.mansion, self.jet, self.bling = args +: less tedious -: function signature not revealing enough. need to dive into function code to know how to use function -: does not raise a TypeError on call with wrong # of parameters (but does raise a ValueError) Any other ideas? (Whatever your suggestion, make sure the code calling the function does stays simple)

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  • What are the exact versions of stuff you have to install in order to be able to step-debug a Scala p

    - by Alex R
    How do YOU debug a Scala program? I mean YOU as in the person posting the Answer :) Please answer only from personal experience, not from stuff you've heard or read on the Internet. You should not believe everything you read on the Internet, especially tales of complex open-source software configurations that actually work :-) The are many Java tools which claim to support Scala in some way or another, but I have so far struck out in trying to get any one of them to actually let me set a breakpoint in Scala code and step through it. These are big, major open-source IDEs I'm talking about here. The main problem in getting a debugger to work seems to be the "version hell" with fast-changing IDEs, Plug-Ins, JDKs, and the Scala language itself. Hence, the more detailed re-statement of the question is appropriate: What is the exact version number of the IDE, Plug-In, JDK, Scala, and even Operating System, that you are successfully using? My question is related to this one, but wider in scope: http://stackoverflow.com/questions/2272705/how-to-debug-scala-code-when-outside-of-an-ide Thanks

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  • Django i18n: makemessages only on site level possible?

    - by AndiDog
    I have several strings in my site that don't belong to any app, for example {% block title %}{% trans "Login" %}{% endblock %} or a modified authentication form used to set the locale cookie class AuthenticationFormWithLocaleOption(AuthenticationForm): locale = forms.ChoiceField(choices = settings.LANGUAGES, required = False, initial = preselectedLocale, label = _("Locale/language")) Now when I execute django-admin.py makemessages --all -e .html,.template in the site directory, it extracts the strings from all Python, .html and .template files, including those in my apps. That is because I develop my apps inside that directory: Directory structure: sitename myapp1 myapp2 Is there any way to extract all strings that are not in my apps? The only solution I found is to move the app directories outside the site directory structure, but I'm using bzr-externals (similar to git submodules or svn externals) so that doesn't make sense in my case. Moving stuff that needs translation into a new app is also possible but I don't know if that is the only reasonable solution.

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  • JS Variable inside another variable

    - by Tusk
    I have a function that would use other variables, depending on what has been passed. Like this = ActionBar(slot) slot contains "one". and I would like to create a call inside that like object.slot.name but it should convert it before hand to make the command look like object.one.name. Is there a way to do this in javascript/jquery? I remember vaguely that some other language does this as {slot} or something like that. Sorry if this question was already asked, I've checked google and stackoverflow too, but didn't find an answer. Also I'd like to know what's the proper programming term for this kind of variable passing? Edited it cause of misunderstandings. I'm looking into OOP js, so object is an object, one is an object, and name is an attribute, but when passing I'm passing "one" as a string to the function. Tried eval, it doesn't work while dotted with an object.

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  • STL deque accessing by index is O(1)?

    - by jasonline
    I've read that accessing elements by position index can be done in constant time in a STL deque. As far as I know, elements in a deque may be stored in several non-contiguous locations, eliminating safe access through pointer arithmetic. For example: abc-defghi-jkl-mnop The elements of the deque above consists of a single character. The set of characters in one group indicate it is allocated in contiguous memory (e.g. abc is in a single block of memory, defhi is located in another block of memory, etc.). Can anyone explain how accessing by position index can be done in constant time, especially if the element to be accessed is in the second block? Or does a deque have a pointer to the group of blocks? Update: Or is there any other common implementation for a deque?

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  • Managed C++ prospects

    - by Srikanth
    Has anyone tried coding in managed C++? I have a few questions : How productive is the language compared to C#? Is there any restriction on type of projects that can be written? Can we write a web application in managed C++? Is it possible to mix managed and unmanaged C++ code in one application? Is MFC still valid in managed C++? Will it be the best option when considering migration of a VC++ application?

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  • jQuery is not defined

    - by dole
    Hi there, I have to use an external js file, in which I load the jquery. My js file look like this: document.write('<script language="javascript" type="text/javascript" src="http://code.jquery.com/jquery-1.4.4.min.js"></script>'); (function($) { $(document).ready(function() { alert('it works!!'); }); })(jQuery); On the firefox console I get the "jQuery is not defined" and I think it is because the jQuery library is loaded after the $ function from my js file. Do you have any idea about how can I fix this? If I run the script from the FF console all works fine.

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  • What strategies are efficient to handle concurrent reads on heterogeneous multi-core architectures?

    - by fabrizioM
    I am tackling the challenge of using both the capabilities of a 8 core machine and a high-end GPU (Tesla 10). I have one big input file, one thread for each core, and one for the the GPU handling. The Gpu thread, to be efficient, needs a big number of lines from the input, while the Cpu thread needs only one line to proceed (storing multiple lines in a temp buffer was slower). The file doesn't need to be read sequentially. I am using boost. My strategy is to have a mutex on the input stream and each thread locks - unlocks it. This is not optimal because the gpu thread should have a higher precedence when locking the mutex, being the fastest and the most demanding one. I can come up with different solutions but before rush into implementation I would like to have some guidelines. What approach do you use / recommend ?

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  • Zend + Wamp = Cant use curl/fput for a url locally

    - by bluedaniel
    Ive got a page in Zend all set up that will for now just echo "Hello", this address is at http://dev.local/hello and works when visiting in the browser. However when I try to use curl or file_get_contents from a script in my zend 'public' folder I get a 500 Internal error message. UPDATE Its failing because my application tries to set the langauge based on the browsers default language, when using headers like I have below, how do I add this locale? "User-Agent: XXXXXXX/2.0\r\n" . "Accept: */*\r\n" . "Accept-Charset: utf-8;\r\n" .

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  • byte-sized bit pattern in C and its relevance?

    - by Nikunj Banka
    I a reading Kerninghan and Ritchie's C programming language book and on page 37 it mentions byte sized bit patterns like : '\013' for vertical tab . '\007' for bell character . My doubts : What is byte sized in it and and what's a bit pattern ? What relevance does this hold and where can I apply it ? Is it in any sense related to escape sequences ? I can't seem to find any information what so ever about these byte sized bit patterns on the web . please help . thanks .

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  • What are the other new features of C# 4.0, after dynamic and optional parameters?

    - by Abel
    So, C# 4.0 came out yesterday. It introduced the much-debated dynamic keyword, named and optional parameters. Smaller improvements were the implicit ref and recognizing of indexed and default properties on COM methods, contra- and co-variance (really a .NET CLR feature, not C# only) and... Is that really it? Are dynamic and optional/named params the only real improvements to C#? Or did I miss something? Not that I'm complaining, but it seems a bit meager after C# 2.0 (generics) and C# 3.0 (lambda, LINQ). Maybe the language just reached actual maturity?

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