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  • What makes you come back to stackoverflow every day? [closed]

    - by rmarimon
    I know this is not a programming question. Let's try to label it a programming community question so that it doesn't get closed. I've been wondering what makes the programming community so prone to helping others in stackoverflow. Is this something particular to programmers? Do you think lawyers and accountants would help other lawyers and programmers as we do? What makes you come back to stackoverflow every day? It would be great to have an answer per reason so that we can get the list of reasons. In my case, I come to stackoverflow to ask questions that I can't solve quickly, and to test how good I am when answering questions. So far I’ve failed miserably at trying to answer questions but it has helped me understand how little I know.

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  • How do I prepare myself for a summer of working on Python using Linux environment?

    - by Shailesh Tainwala
    Hi, I have used just Windows for programming so far. Now, I have an internship starting in two weeks and I will be using just Linux environment with Python programming language. I've installed Ubuntu on my system but have no exposure to shell scripting. I need some advice on how I can quickly learn to use the Linux terminal quickly. Any books or web resources that you can suggest? Also, is there a particular IDE that is generally preferred for Python programming on Linux, or is Vim preferred? How can I best prepare myself for the internship ahead? Thanks for taking the time.

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  • Is this an F# quotations bug?

    - by ControlFlow
    [<ReflectedDefinition>] let rec x = (fun() -> x + "abc") () The sample code with the recursive value above produces the following F# compiler error: error FS0432: [<ReflectedDefinition>] terms cannot contain uses of the prefix splice operator '%' I can't see any slicing operator usage in the code above, looks like a bug... :) Looks like this is the problem with the quotation via ReflectedDefinitionAttribute only, normal quotation works well: let quotation = <@ let rec x = (fun() -> x + "abc") () in x @> produces expected result with the hidden Lazy.create and Lazy.force usages: val quotation : Quotations.Expr<string> = LetRecursive ([(x, Lambda (unitVar, Application (Lambda (unitVar0, Call (None, String op_Addition[String,String,String](String, String), [Call (None, String Force[String](Lazy`1[System.String]), [x]), Value ("abc")])), Value (<null>)))), (x, Call (None, Lazy`1[String] Create[String](FSharpFunc`2[Unit,String]), [x])), (x, Call (None, String Force[String](Lazy`1[String]), [x]))], x) So the question is: is this an F# compiler bug or not?

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  • org.hibernate.TransientObjectException during Criteria.list()

    - by rancidfishbreath
    I have seen posts all over the internet that talk about how to fix the TransientObjectExceptions during save/update/delete but I am having this problem when calling list on my Criteria. I have two objects A and B. A has a field named b which is of type B. In my mapping b is mapped as a many-to-one. This all runs in a larger persistence framework (the framework is kind of like Core Data) and so I don't use any cascades in my hibernate mappings since cascades are handled at a higher level. This is the interesting code surrounding my criteria: A a = new A(); B b = new B(); a.setB(b); session.save("B", b); // Actually handled by the higher level session.save("A", a); // framework, this is just for clarity // transaction committed and session closed ... // new session opened Criteria criteria = session.createCriteria(A.class); criteria.add(Restrictions.eq("b", b)); List<?> objects = criteria.list(); Basically I am looking for all objects of type A such that A.b equals a particular instance of b (I actually tried restructuring a query so that I was passing in the id of b just to make sure that b wasn't causing me problems). Here is the stack trace that occurs when I call criteria.list(): org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: B at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:244) at org.hibernate.type.EntityType.getIdentifier(EntityType.java:449) at org.hibernate.type.ManyToOneType.nullSafeSet(ManyToOneType.java:141) at org.hibernate.loader.Loader.bindPositionalParameters(Loader.java:1769) at org.hibernate.loader.Loader.bindParameterValues(Loader.java:1740) at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1612) at org.hibernate.loader.Loader.doQuery(Loader.java:717) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:270) at org.hibernate.loader.Loader.doList(Loader.java:2294) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2172) at org.hibernate.loader.Loader.list(Loader.java:2167) at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:119) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1706) at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:347) Here is my mapping: <class entity-name="A" lazy="false"> <tuplizer entity-mode="dynamic-map" class="MyTuplizer" /> <id type="long" column="id"> <generator class="native" /> </id> <many-to-one name="b" entity-name="B" column="b_id" lazy="false" /> </class> <class entity-name="B" lazy="false"> <tuplizer entity-mode="dynamic-map" class="MyTuplizer" /> <id type="long" column="id"> <generator class="native" /> </id> </class> Can anyone help me figure out why I would be getting a TransientObjectException during a fetch? Preferably I would like to find a solution that does not rely on cascades since they tend to mask problems that occur in the higher level framework.

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  • Uses of Erlang in Telecom

    - by user94154
    I'm a web developer and a college student majoring in telecommunications. This means I'm decent at programming and I know a little about telecom networks (at a high, non-technical level). I keep reading that Erlang is used all over the telecom industry (supposedly for its performance). I'm wondering if there's anyway I can combine my programming skills with my telecommunications major with Erlang. Is most of the Erlang/telecom stuff closed source? Are there any open source telecom projects written Erlang? UPDATE: sipwiz's comment makes me think in terms of a question larger than "uses of Erlang". How can I leverage a high-level understanding of telecom networks and the telecom regulatory environment with programming. I hope this hasn't veered too off-topic for SO.

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  • Python re.sub MULTILINE caret match

    - by cdleary
    The Python docs say: re.MULTILINE: When specified, the pattern character '^' matches at the beginning of the string and at the beginning of each line (immediately following each newline)... By default, '^' matches only at the beginning of the string... So what's going on when I get the following unexpected result? >>> import re >>> s = """// The quick brown fox. ... // Jumped over the lazy dog.""" >>> re.sub('^//', '', s, re.MULTILINE) ' The quick brown fox.\n// Jumped over the lazy dog.'

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  • DAO, Spring and Hibernate

    - by EugeneP
    Correct me if anything is wrong. Now when we use Spring DAO for ORM templates, when we use @Transactional attribute, we do not have control over the transaction and/or session when the method is called externally, not within the method. Lazy loading saves resources - less queries to the db, less memory to keep all the collections fetched in the app memory. So, if lazy=false, then everything is fetched, all associated collections, that is not effectively, if there are 10,000 records in a linked set. Now, I have a method in a DAO class that is supposed to return me a User object. It has collections that represent linked tables of the database. I need to get a object by id and then query its collections. Hibernate "failed to lazily initialize a collection" exception occurs when I try to access the linked collection that this DAO method returns. Explain please, what is a workaround here?

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  • How does a virtual machine work?

    - by Martin
    I've been looking into how programming languages work, and some of them have a so-called virtual machines. I understand that this is some form of emulation of the programming language within another programming language, and that it works like how a compiled language would be executed, with a stack. Did I get that right? With the proviso that I did, what bamboozles me is that many non-compiled languages allow variables with "liberal" type systems. In Python for example, I can write this: x = "Hello world!" x = 2**1000 Strings and big integers are completely unrelated and occupy different amounts of space in memory, so how can this code even be represented in a stack-based environment? What exactly happens here? Is x pointed to a new place on the stack and the old string data left unreferenced? Do these languages not use a stack? If not, how do they represent variables internally?

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  • MEF part unable to import Autofac autogenerated factory

    - by Michael Wagner
    This is a (to me) pretty weird problem, because it was already running perfectly but went completely south after some unrelated changes. I've got a Repository which imports in its constructor a list of IExtensions via Autofacs MEF integration. One of these extensions contains a backreference to the Repository as Lazy(Of IRepository) (lazy because of the circular reference that would occur). But as soon as I try to use the repository, Autofac throws a ComponentNotRegisteredException with the message "The requested service 'ContractName=Assembly.IRepository()' has not been registered." That is, however, not really correct, because when I break right after the container-build and explore the list of services, it's there - Exported() and with the correct ContractName. I'd appreciate any help on this... Michael

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  • How do I pass a variable number of parameters along with a callback function?

    - by Bungle
    I'm using a function to lazy-load the Sizzle selector engine (used by jQuery): var sizzle_loaded; // load the Sizzle script function load_sizzle(module_name) { var script; // load Sizzle script and set up 'onload' and 'onreadystatechange' event // handlers to ensure that external script is loaded before dependent // code is executed script = document.createElement('script'); script.src = 'sizzle.min.js'; script.onload = function() { sizzle_loaded = true; gather_content(module_name); }; script.onreadystatechange = function() { if ((script.readyState === 'loaded' || script.readyState === 'complete') && !sizzle_loaded) { sizzle_loaded = true; gather_content(module_name); } }; // append script to the document document.getElementsByTagName('head')[0].appendChild(script); } I set the onload and onreadystatechange event handlers, as well as the sizzle_loaded flag to call another function (gather_content()) as soon as Sizzle has loaded. All of this is needed to do this in a cross-browser way. Until now, my project only had to lazy-load Sizzle at one point in the script, so I was able to just hard-code the gather_content() function call into the load_sizzle() function. However, I now need to lazy-load Sizzle at two different points in the script, and call a different function either time once it's loaded. My first instinct was to modify the function to accept a callback function: var sizzle_loaded; // load the Sizzle script function load_sizzle(module_name, callback) { var script; // load Sizzle script and set up 'onload' and 'onreadystatechange' event // handlers to ensure that external script is loaded before dependent // code is executed script = document.createElement('script'); script.src = 'sizzle.min.js'; script.onload = function() { sizzle_loaded = true; callback(module_name); }; script.onreadystatechange = function() { if ((script.readyState === 'loaded' || script.readyState === 'complete') && !sizzle_loaded) { sizzle_loaded = true; callback(module_name); } }; // append script to the document document.getElementsByTagName('head')[0].appendChild(script); } Then, I could just call it like this: load_sizzle(module_name, gather_content); However, the other callback function that I need to use takes more parameters than gather_content() does. How can I modify my function so that I can specify a variable number of parameters, to be passed with the callback function? Or, am I going about this the wrong way? Ultimately, I just want to load Sizzle, then call any function that I need to (with any arguments that it needs) once it's done loading. Thanks for any help!

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  • What is a programmer's life like?

    - by Zee JollyRoger
    Imagine like an 8-hour long video of any "typical/average" programming job. What is it like? Before I get myself involved in that path, what can I expect? I am interested in gathering first-hand information and accounts of the typical life of a programmer. My goal is to grasp the fundamental concepts of working in the professional field of programming. I just want to "see" into what it is/means to come to an entry-level programming job and program. See what kind of skills, mentality, expectations, and such are required.

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  • Best way to plan a task ?

    - by Indigo Praveen
    Hi All, As I am very new to programming, I am very curious about learning the best ways/practices of programming. Whenever I want to write any program , I strat directly with coding while some guys say that you should plan your program first before starting the code. But I don't understand the real value of creating the class diagrams and all that kind of stuff coz I think that ultimately I have to write the code. Can you guys please share your experiences about how you are doing your programming means what is your first step when you start an application.

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  • Advanced control of recursive parser in scala

    - by Jeriho
    val uninterestingthings = ".".r val parser = "(?ui)(regexvalue)".r | (uninterestingthings~>parser) This recursive parser will try to parse "(?ui)(regexvalue)".r until the end of input. Is in scala a way to prohibit parsing when some defined number of characters were consumed by "uninterestingthings" ? UPD: I have one poor solution: object NonRecursiveParser extends RegexParsers with PackratParsers{ var max = -1 val maxInput2Consume = 25 def uninteresting:Regex ={ if(max<maxInput2Consume){ max+=1 ("."+"{0,"+max.toString+"}").r }else{ throw new Exception("I am tired") } } lazy val value = "itt".r def parser:Parser[Any] = (uninteresting~>value)|parser def parseQuery(input:String) = { try{ parse(parser, input) }catch{ case e:Exception => } } } Disadvantages: - not all members are lazy vals so PackratParser will have some time penalty - constructing regexps on every "uninteresting" method call - time penalty - using exception to control program - code style and time penalty

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  • Project Idea with Hadoop MapReduce

    - by Aditya Andhalikar
    Hello, I learnt Hadoop a few months back and managed to do a very introductory programming project on it. I want to do a small - medium sized project or series of small programming assignments with Hadoop. I have seen lot of ideas around but I dont see anything that can be finished in about 60-70 hours of work so a pretty small scale project as I want to do that in my spare time along with other studies. Most project ideas I have seen sort of large to go on for 2-3 months. My main objective out of this exercise to develop good expertise in programming with Hadoop environment not to do any research or solve specific problems. I see Hadoop being used lot of with webservices maybe that would be an interesting track for small projects. Thank you in advance. Regards, Aditya

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  • Is being a programmer a younger person's job?

    - by Saobi
    After you get old, say past 30 or 40. Can you still keep up with the young coders from your company, those fresh out of school, who can code for 15+ hours on 10 cans of redbulls (most people in Google, Facebook, etc) ? And given the lightning speed with which today's programming frameworks and architectures evolve, can you keep up with the most up to date stuff and be as proficient at them as the next college grad? I know for jobs like unix/c/embedded programming, it might be that the older the better. But for programming jobs in say web development, social media, search engine technology, etc. Do you become less and less competitive career-wise versus youngsters? For example, most coders in Google and Facebook, I believe are under 25 years old. In other words, once you reach a certain age, would it be unwise to continue to be a coder, and is it better to try becoming a project manager or architect?

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  • What first game did you program, and did it make you a better developer?

    - by thenonhacker
    What first game did you program? Name your game, the OS and language, and even a Website URL to get your game. Old DOS Games and Flash Games with ActionScript are allowed. Game kits are allowed, too. ...and did it make you a better developer? Programming games can be addicting, and it will bring out the best in us as we create our first game. What lessons did you learn form most? Algorithm and/or AI's? Graphics? User Interface? File Formats and Data Storage? Project and Time Management? Can you say that because you practiced programming by creating this game, you became more immersed with the programming language you used and helped you become a better developer?

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  • Nhibernate multilevel hierarchy save error?

    - by nisbus
    Hi, I have a database with a 6 level hierarchy and a domain model on top of that. something like this: Category -SubCategory -Container -DataDescription | Meta data -Data The mapping I'm using follows the following pattern: <class name="Category, Sample" table="Categories"> <id name="Id" column="Id" type="System.Int32" unsaved-value="0"> <generator class="native"/> </id> <property name="Name" access="property" type="String" column="Name"/> <property name="Metadata" access="property" type="String" column="Metadata"/> <bag name="SubCategories" cascade="save-update" lazy="true" inverse="true"> <key column="Id" foreign-key="category_subCategory_fk"/> <one-to-many class="SubCategory, Sample" /> </bag> </class> <class name="SubCategory, Sample" table="SubCategories"> <id name="Id" column="Id" type="System.Int32" unsaved-value="0"> <generator class="native"/> </id> <many-to-one name="Category" class="Category, Sample" foreign-key="subCat_category_fk"/> <property name="Name" access="property" type="String"/> <property name="Metadata" access="property" type="String"/> <bag name="Containers" inverse="true" cascade="save-update" lazy="true"> <key column="Id" foreign-key="subCat_container_fk" /> <one-to-many class="Container, Sample" /> </bag> </class> <class name="Container, Sample" table="Containers"> <id name="Id" column="Id" type="System.Int32" unsaved-value="0"> <generator class="assigned"/> </id> <many-to-one name="SubCategory" class="SubCategory,Sample" foreign-key="container_subCat_fk"/> <property name="Name" access="property" type="String" column="Name"/> <bag name="DataDescription" cascade="all" lazy="true" inverse="true"> <key column="Id" foreign-key="container_ DataDescription_fk"/> <one-to-many class="DataDescription, Sample" /> </bag> <bag name="MetaData" cascade="all" lazy="true" inverse="true"> <key column="Id" foreign-key="container_metadata_cat_fk"/> <one-to-many class="MetaData, Sample" /> </bag> </class> For some reason when I try to save the category (with the subcategory, container etc. attached) I get a foreign key violation from the database. The code is something like this (Pseudo). var category = new Category(); var subCategory = new SubCategory(); var container = new Container(); var dataDescription = new DataDescription(); var metaData = new MetaData(); category.AddSubCategory(subCategory); subCategory.AddContainer(container); container.AddDataDescription(dataDescription); container.AddMetaData(metaData); Session.Save(category); Here is the log from this test : DEBUG NHibernate.SQL - INSERT INTO Categories (Name, Metadata) VALUES (@p0, @p1); select SCOPE_IDENTITY(); @p0 = 'Unit test', @p1 = 'unit test' DEBUG NHibernate.SQL - INSERT INTO SubCategories (Category, Name, Metadata) VALUES (@p0, @p1, @p2); select SCOPE_IDENTITY(); @p0 = '1', @p1 = 'Unit test', @p2 = 'unit test' DEBUG NHibernate.SQL - INSERT INTO Containers (SubCategory, Name, Frequency, Scale, Measurement, Currency, Metadata, Id) VALUES (@p0, @p1, @p2, @p3, @p4, @p5, @p6, @p7); @p0 = '1', @p1 = 'Unit test', @p2 = '15', @p3 = '1', @p4 = '1', @p5 = '1', @p6 = 'unit test', @p7 = '0' ERROR NHibernate.Util.ADOExceptionReporter - The INSERT statement conflicted with the FOREIGN KEY constraint "subCat_container_fk". The conflict occurred in database "Sample", table "dbo.SubCategories", column 'Id'. The methods for adding items to objects is always as follows: public void AddSubCategory(ISubCategory subCategory) { subCategory.Category = this; SubCategories.Add(subCategory); } What am I missing?? Thanks, nisbus

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  • what is a performance way to 'tree-walking' through my Entity Framework data

    - by Greg
    Hi, I have a Entity Framework design with a few tables that define a "graph". So there can be a large chain of relationships between objects in the few tables via concept of parent/child relationships. What is a performance way to 'tree-walking' through my Entity Framework data? That is I assume I wouldn't want to load the full set of all NODES and RELATIONSHIPS from the database for the purpose of walking the tree, where the end result may only be identifying leaf nodes? Or would this be OK with the way lazy loading may work at the column/parameter level? Else how could I load just the skeleton of the objects and then when needing to refer to any attributes have them lazy load then?

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  • Great computer-science speeches

    - by sub
    I've looked into some questions here where the "best" programming books are listed and then thought why there isn't a question concerning speeches yet. I think that speeches or presentations from developers or even creators of programming languages which were or are heavily used at some point are particulary interesting. One of my favorite speeches was recommended to me by someone here on SO: The future of C# I also like Guido van Rossum's speeches but he sometimes seems pretty nervous. Another in my opinion good presentation would be the Google tech talk about Go. Which (recorded) programming presentations/speeches are worth watching? edit: Made this a community wiki as the answer would probably be a pretty long list.

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  • How to do "See Also" to a book using doxygen

    - by Paul J. Lucas
    The Javadoc @see allows a simple string as an argument to refer to something like a book, e.g.: @see "The Java Programming Language." As far as I can tell, the Doxygen \see offers no equivalent. Is there any way to have a book reference generated in the documentation, e.g.: See Also The C++ Programming Language, Bjarne Stroustrup, Addison-Wesley, 2000, section 19.4.1: The Standard Allocator ? Clarification This question is about how to do a "See Also" as part of a comment, e.g.: /** * Allocates memory in an amazing way. * \param size The number of bytes to allocate. * \return Returns a pointer to the start of the allocated memory. * \see MyOtherClass::alloc() * \see "The C++ Programming Language," Bjarne Stroustrup, Addison-Wesley, 2000, * section 19.4.1: The Standard Allocator. */ void* my_alloc( size_t size ); Of course the above does not work in Doxygen. Note that if there are multiple \see tags, they should be merged into a single "See Also" section (like the way \see normally works.

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  • Vim Editor is very smart?

    - by Narek
    I am programming in C++ or Java. So I want to use Vim editor, because it is very flexible. I have heard that I can configure the Vim editor to be able to go from object to the definition from function to the definition from class name to the definition Do we have any professional Vim-er that could tell me how exactly to configure Vim for that? Thanks in advance. P.S. In case readers will consider this question is not connected with programming, I would say that this is improving speed of programming. So it is a help to the programmer. So please don't close this question. EDIT: Also I would like to know how vim works with code completion and can vim hint the list of methods that are available for the certain object? If yes, then I would like to know how to configure these options too?

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  • Pomodoro technique & other ways to increase personal productivity

    - by Jayson
    I recently came across the Pomodoro Technique as a way to increase productivity, get in the zone, and in general feel a sense of accomplishment at setting some short programming goals and achieving them. So far I have enjoyed it and the sense of accomplishment I get after seeing a bunch of short goals add up at the end of the day to a lot of work done on a programming project. What other ideas, similar or not, add a little variety to achieving goals, personal productivity, get in the programming zone, and so forth? What ideas or techniques are expressed formally, such as those in the Pomodoro paper, rather than trite maxims?

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  • How do I get started on a bigger project?

    - by Axilus
    Hey guys, Most of the time I have been programming little apps either for myself or for the benifit of learning. Now that my programming skills are considered somewhat intermediate, I was wondering how I would tackle a large programming project. Lets suppose I wanted to make an application that has a lot of features and is intended for the use of others and not just myself; how do I go about planning for such projects? Do I just jump in and start coding the thing or is there some sort of recommended process? Thanks in advance :D

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  • Exception "Illegal attempt to associate a collection with two open sessions" when saving object

    - by Alex
    I am using CastleProject ActiveRecord and I use lazy load feature of this ORM. In order to make lazy load work, it is required to create SessionScope. I do this in Program.cs: public static SessionScope sessionScope; private static void InitializeActiveRecord() { ActiveRecordStarter.Initialize(); sessionScope = new SessionScope(); } This works fine for loading, however, when I try to save my objects, I get an exception saying "Illegal attempt to associate a collection with two open sessions". I guess this is due to the fact that I created one session myself. How to avoid this exception?

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  • is it better to use a "natural" language to write code?

    - by M.H
    I recently saw a programming language called supernova and they said in the web page : The Supernova Programming language is a modern scripting language and the First one presents the concept of programming with direct Fiction Description using Clear subset of pure Human Language. and you can write code like: i want window and the window title is Hello World. i want button and button caption is Close. and button name is btn1. btn1 mouse click. instructions are you close window end of instructions my question is not about the language itself but it is that are we need such languages and did they make writing code easier or not?

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