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  • Implementing `let` without using a macro

    - by Matt Fenwick
    I'm learning Lisp, and I've just gotten to let, which I don't quite understand (the implementation of). A common definition for it is given in terms of lambda as a macro. However, nowhere have I seen that let must be implemented as a macro or in terms of lambda. Is it possible to define let without using a macro or lambda? I know it can be implemented as a primitive, but I want to know whether it can be implemented in Lisp without creating a macro -- by creating a special form or a function.

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  • How is it possible to write the compiler of a programming language with that language itself [closed]

    - by tugberk
    Possible Duplicate: How could the first C++ compiler be written in C++? You probably heard that Microsoft released a new language called TypeScript which is a the typed superset of JavaScript. The most interesting thing that makes me wonder is the fact that its compiler writen in TypeScript itself. Call me ignorant but I really couldn't figure out in my head how that is possible. This is just like chicken and egg problem in my head because there is no compiler to compile TypeScript's compiler in the first place. How is it possible to write a compiler of the compiler of a programming language with that language?

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  • I know of three ways in which SRP helps reduce coupling. Are there even more? [closed]

    - by user1483278
    I'd like to figure all the possible ways SRP helps us reduce coupling. Thus far I can think of three: 1) If class A has more than one responsibility, these responsibilities become coupled and as such changes to one of these responsibilities may require changes to other of A's responsibilities. 2) Related functionality usually needs to be changed for the same reason and by grouping it togerther in a single class, the changes can be made in as few places as possible ( at best changes only need be made to the class which groups together these functionalities) 3) Assuming class A performs two tasks ( thus may change for two reasons ), then number of classes utilising A will be greater than if A performed just a single task ( reason being that some classes will need A to perform first task, other will need A for second task, and still others will utilise it for both tasks ).This also means that when A breaks, the number of classes ( utilising A ) being impaired will be greater than if A performed just a single task. Can SRP also help reduce coupling in any other way, not described above? Thank you

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  • What is the current frequency of my processor (CPU-Z equivalent)?

    - by Anake
    Is there a ubuntu program like CPU-Z which will show me the actual frequency of my processor? I do a fair amount of scientific computing which leads to me running my programs for up to 10 hrs. To alleviate this problem a little I overclock my CPU. However I can't see what the actual clock of my processor from within ubuntu which means I either have to restart and look at the bios or load into windows. If there was an applet or command line command to find out this information it would be very helpful. Thanks for your help

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  • how to install gerix on ubuntu 12.04 using backtrack repositories?

    - by werever
    I got instructions from here, and I found several sites with similar instructions but somethig is wrong with the repositories on 12.04. This should work for 11.10 and previous versions. Any ideas how to install backtrack repos and some back track apps on 12.04? I read about downloading the .deb package for gerix and manually making the same folder structure that gerix uses on backtrack, then manually run the python script, but this way didn't work for me either. How can I get gerix installed and working on my Ubuntu 12.04 system?

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  • Internet TV streaming applications

    - by mark kirby
    Are there any programs for Ubuntu that can pull TV streams from the Internet ? For example like on a blu-ray player you get BBC iplayer and hulu and youtube as apps, so is there an application that can do this ? I know XMBC can but its to fiddly and resource hungry, I just want the net TV apps and not the full media center. Boxee was great for this, it was a media center but had an interface for the apps not just sticking them in some strange menu like XBMC. Please let me know of anything you know of

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  • Architecting persistence (and other internal systems). Interfaces, composition, pure inheritance or centralization?

    - by Vandell
    Suppose that you need to implement persistence, I think that you're generally limited to four options (correct me if I'm wrong, please) Each persistant class: Should implement an interface (IPersistent) Contains a 'persist-me' object that is a specialized object (or class) that's made only to be used the class that contains it. Inherit from Persistent (a base class) Or you can create a gigantic class (or package) called Database and make your persistence logic there. What are the advantages and problems that can come from each of one? In a small (5kloc) and algorithmically (or organisationally) simple app what is probably the best option?

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  • How to show dashboard for Micrmax 353G in ubuntu 12.04?

    - by newuser
    I am using ubuntu 12.04 and Micromax 353G dongle for internet. Everything is working fine. But here I want to see my data used in that session and the balance data. It is showing all the features in windows but as I am using ubuntu and I love this so I want all this in ubuntu. So is this possible to get a dashboard for Micromax dongle dashboard on ubuntu 12.04? Any help and suggestions will be highly appreciable.

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  • Storing images in file system and returning URLs or virtually resizing and returning byte arrays?

    - by ismaelf
    I need to create a REST web service to manage user submitted images and displaying them all in a website. There are multiple websites that are going to use this service to manage and display images. The requirements are to have 5 pre-defined image sizes available. The 2 options I see are the following: The web service will create the 5 images, store them in the file system and and store the URL's in the database when the user submits the image. When the image is requested, the web service will return an array of URLs. I see this option to be a little hard on the hard drive. The estimates are 10,000 users per site, and lets say, 100 sites. The heavy processing will be done when the user submits the image and each image is going to be pulled from the File System. The web service will store just the image that the user submits in the file system and it's URL in the database. When the user request images, the web service will get the info from the DB, load the image on memory, create its 5 instances and return an object with 5 image arrays (I will probably cache the arrays). This option is harder on the processor and memory. The heavy processing will be done when the images get requested. A plus I see for option 2 is that it will give me the option to rewrite the URL of the image and make them site dependent (prettier) than having a image repository for all websites. But this is not a big deal. What do you think of these options? Do you have any other suggestions?

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  • system requirement

    - by Sol
    My laptop developed a bad sectors and not working well. It was with ubutuntu 12.04 LTS operating system. Now, I want to install ubuntu in an relatively old desktop with the following specifications Hp compaq dx 2390 Intel ® Pentium Dual Core CPU, E2180 @ 2.00 GHZ, 1.20 GHz, 1 GB Ram, 160 GB Hard Drive Which k/x/ubuntu version is suitable to this desktop? PS. I am working in my final thesis and I need a stable k/x/ubuntu to this specification. Thank u

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  • Best way to manage a changelog

    - by Gnial0id
    I'm currently developing a WinForm application. In order to inform the client about the improvements and corrections made during the last version, I would like to manage and display a changelog. I mostly found existing changelog on website (the term changelog is pretty used) or explanation on how to manage the release numbers, which I don't care. So, these are my questions: Is there a good practice in changelog management (using XML, pure text in the app, etc.) in a desktop application ? What is the best way to display it (external website, inside the winform application) ? Thanks.

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  • Clarify the Single Responsibility Principle.

    - by dsimcha
    The Single Responsibility Principle states that a class should do one and only one thing. Some cases are pretty clear cut. Others, though, are difficult because what looks like "one thing" when viewed at a given level of abstraction may be multiple things when viewed at a lower level. I also fear that if the Single Responsibility Principle is honored at the lower levels, excessively decoupled, verbose ravioli code, where more lines are spent creating tiny classes for everything and plumbing information around than actually solving the problem at hand, can result. How would you describe what "one thing" means? What are some concrete signs that a class really does more than "one thing"?

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  • Search multiple tables

    - by gilden
    I have developed a web application that is used mainly for archiving all sorts of textual material (documents, references to articles, books, magazines etc.). There can be any given number of archive tables in my system, each with its own schema. The schema can be changed by a moderator through the application (imagine something similar to a really dumbed down version of phpMyAdmin). Users can search for anything from all of the tables. By using FULLTEXT indexes together with substring searching (fields which do not support FULLTEXT indexing) the script inserts the results of a search to a single table and by ordering these results by the similarity measure I can fairly easily return the paginated results. However, this approach has a few problems: substring searching can only count exact results the 50% rule applies to all tables separately and thus, mysql may not return important matches or too naively discards common words. is quite expensive in terms of query numbers and execution time (not an issue right now as there's not a lot of data yet in the tables). normalized data is not even searched for (I have different tables for categories, languages and file attatchments). My planned solution Create a single table having columns similar to id, table_id, row_id, data Every time a new row is created/modified/deleted in any of the data tables this central table also gets updated with the data column containing a concatenation of all the fields in a row. I could then create a single index for Sphinx and use it for doing searches instead. Are there any more efficient solutions or best practises how to approach this? Thanks.

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  • IXRepository and test problems

    - by Ridermansb
    Recently had a doubt about how and where to test repository methods. Let the following situation: I have an interface IRepository like this: public interface IRepository<T> where T: class, IEntity { IQueryable<T> Query(Expression<Func<T, bool>> expression); // ... Omitted } And a generic implementation of IRepository public class Repository<T> : IRepository<T> where T : class, IEntity { public IQueryable<T> Query(Expression<Func<T, bool>> expression) { return All().Where(expression).AsQueryable(); } } This is an implementation base that can be used by any repository. It contains the basic implementation of my ORM. Some repositories have specific filters, in which case we will IEmployeeRepository with a specific filter: public interface IEmployeeRepository : IRepository<Employee> { IQueryable<Employee> GetInactiveEmployees(); } And the implementation of IEmployeeRepository: public class EmployeeRepository : Repository<Employee>, IEmployeeRepository // TODO: I have a dependency with ORM at this point in Repository<Employee>. How to solve? How to test the GetInactiveEmployees method { public IQueryable<Employee> GetInactiveEmployees() { return Query(p => p.Status != StatusEmployeeEnum.Active || p.StartDate < DateTime.Now); } } Questions Is right to inherit Repository<Employee>? The goal is to reuse code once all implementing IRepository already been made. If EmployeeRepository inherit only IEmployeeRepository, I have to literally copy and paste the code of Repository<T>. In our example, in EmployeeRepository : Repository<Employee> our Repository lies in our ORM layer. We have a dependency here with our ORM impossible to perform some unit test. How to create a unit test to ensure that the filter GetInactiveEmployees return all Employees in which the Status != Active and StartDate < DateTime.Now. I can not create a Fake/Mock of IEmployeeRepository because I would be testing? Need to test the actual implementation of GetInactiveEmployees. The complete code can be found on Github

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  • How should I implement the repository pattern for complex object models?

    - by Eric Falsken
    Our data model has almost 200 classes that can be separated out into about a dozen functional areas. It would have been nice to use domains, but the separation isn't that clean and we can't change it. We're redesigning our DAL to use Entity Framework and most of the recommendations that I've seen suggest using a Repository pattern. However, none of the samples really deal with complex object models. Some implementations that I've found suggest the use of a repository-per-entity. This seems ridiculous and un-maintainable for large, complex models. Is it really necessary to create a UnitOfWork for each operation, and a Repository for each entity? I could end up with thousands of classes. I know this is unreasonable, but I've found very little guidance implementing Repository, Unit Of Work, and Entity Framework over complex models and realistic business applications.

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  • Storing translation data as JSON column

    - by j0ntech
    We're deciding on how to store translations of some descriptions of database items. We could go the traditional way and keep a translations table (and a language table and an object_translation linking table) OR we thought it might be better to just have a Description column that contains JSON like the following: { "EN": "This is the translation in English", "EE" : "See on kirjeldus eesti keeles" } Are there any serious downsides as to why we shouldn't use this? (I haven't seen it being used anywhere else)

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  • What simple offline GUI database should I use for this application?

    - by gcc
    I am looking an open source application. Application should have : * database support ( create two or three table ) * GUI ( what I have created should be seen ) Example : Assume that I have created a table ; X_table : | A | B | C | D | After creating table, I am loading data | A | B | C | D | | 1 | 11 | b | f | - | 3 | 12 | a | o | - data | 4 | 13 | r | o | - When I am opening application not for loading data, I want see data in graphical interface. Are there any open source application which have above feature ? Application can be so simple, * no internet connection * support only one database * static table creation ( once created never changed ) Application can be run Ubuntu 12.04 and/or Windows. In other words, I am wanting database viewer and editor. EDIT: I should load pdf file, image etc. or give path of the file to the application. This link can be reference to my question . ( Interface should be like this, just a list )

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  • Pattern for loading and handling resources

    - by Enoon
    Many times there is the need to load external resources into the program, may they be graphics, audio samples or text strings. Is there a patten for handling the loading and the handling of such resources? For example: should I have a class that loads all the data and then call it everytime I need the data? As in: GraphicsHandler.instance().loadAllData() ...//and then later: draw(x,y, GraphicsHandler.instance().getData(WATER_IMAGE)) //or maybe draw(x,y, GraphicsHandler.instance().WATER_IMAGE) Or should I assign each resource to the class where it belongs? As in (for example, in a game): Graphics g = GraphicsLoader.load(CHAR01); Character c = new Character(..., g); ... c.draw(); Generally speaking which of these two is the more robust solution? GraphicsHandler.instance().getData(WATER_IMAGE) //or GraphicsHandler.instance().WATER_IMAGE //a constant reference

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  • Is it dangerous for me to give some of my Model classes Control-like methods?

    - by Pureferret
    In my personal project I have tried to stick to MVC, but I've also been made aware that sticking to MVC too tightly can be a bad thing as it makes writing awkward and forces the flow of the program in odd ways (i.e. some simple functions can be performed by something that normally wouldn't, and avoid MVC related overheads). So I'm beginning to feel justified in this compromise: I have some 'manager programs' that 'own' data and have some way to manipulate it, as such I think they'd count as both part of the model, and part of the control, and to me this feels more natural than keepingthem separate. For instance: One of my Managers is the PlayerCharacterManager that has these methods: void buySkill(PlayerCharacter playerCharacter, Skill skill); void changeName(); void changeRole(); void restatCharacter(); void addCharacterToGame(); void createNewCharacter(); PlayerCharacter getPlayerCharacter(); List<PlayerCharacter> getPlayersCharacter(Player player); List<PlayerCharacter> getAllCharacters(); I hope the mothod names are transparent enough that they don't all need explaining. I've called it a manager because it will help manage all of the PlayerCharacter 'model' objects the code creates, and create and keep a map of these. I may also get it to store other information in the future. I plan to have another two similar classes for this sort of control, but I will orchestrate when and how this happens, and what to do with the returned data via a pure controller class. This splitting up control between informed managers and the controller, as opposed to operating just through a controller seems like it will simplify my code and make it flow more. My question is, is this a dangerous choice, in terms of making the code harder to follow/test/fix? Is this somethign established as good or bad or neutral? I oculdn't find anything similar except the idea of Actors but that's not quite why I'm trying to do. Edit: Perhaps an example is needed; I'm using the Controller to update the view and access the data, so when I click the 'Add new character to a player button' it'll call methods in the controller that then go and tell the PlayerCharacterManager class to create a new character instance, it'll call the PlayerManager class to add that new character to the player-character map, and then it'll add this information to the database, and tell the view to update any GUIs effected. That is the sort of 'control sequence' I'm hoping to create with these manager classes.

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  • How to calculate production when player is offline

    - by Kaizer
    What is the best way to do for example food growth based on how many food buildings you have? Lets say I have a webbased game where you can build a farm wich generates 60 food units per hour. A player has 1 farm in his possession. What is the best way to keep on producing these units even when the player is offline? Should I do the math when the player get's back online again? If so..how can I do this without having to save his last online time every 5 seconds so I can do some maths with it when he logs back in (datetime.now - lastonlinetime)? Next thing is when the player is online, should I refresh his resource count every 5 seconds or so by going to the database and back? This would seem weird to do for every logged on player. I hope you understand my question. kind regards

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  • Copy and Pasting Web page Content into an Office Application.

    - by gcc
    I want take information from any website and paste it into Libre Office (text and images). Firstly, I want record the name/URL, description and some basic information from each website. Afterwards, my intention is to copy/paste the web-page content into LibreOffice in order to analyze it. Can Libre Office do this and is it my best option? if not can you recommend a tool which is available for 12.04?

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  • Android Bitmap: Collision Detecting

    - by Aekasitt Guruvanich
    I am writing an Android game right now and I would need some help in the collision of the Pawns on screen. I figured I could run a for loop on the Player class with all Pawn objects on the screen checking whether or not Width*Height intersects with each other, but is there a more efficient way to do this? And if you do it this way, many of the transparent pixel inside the rectangular area will also be considered as collision as well. Is there a way to check for collision between Bitmap on a Canvas that disregard transparent pixels? The class for player is below and the Pawn class uses the same method of display. Class Player { private Resources res; // Used for referencing Bitmap from predefined location private Bounds bounds; // Class that holds the boundary of the screen private Bitmap image; private float x, y; private Matrix position; private int width, height; private float velocity_x, velocity_y; public Player (Resources resources, Bounds boundary) { res = resources; bounds = boundary; image = BitmapFactory.decodeResource(res, R.drawable.player); width = image.getWidth(); height = image.getHeight(); position = new Matrix(); x = bounds.xMax / 2; // Initially puts the Player in the middle of screen y = bounds.yMax / 2; position.preTranslate(x,y); } public void draw(Canvas canvas) { canvas.drawBitmap(image, position, null); } }

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  • Is it okay to introduce LESS to not so savvy UI Designers?

    - by Jason Nathan
    I just got a job as lead developer and I thought it would be best to seek the expertise of my peers (that's you) before proceeding! I had the opportunity to review my designers and they are mostly photoshop pros with dreamweaver as their main HTML/CSS editor. A more visual experience. I, on the other hand, have had much experience hand-writing all my code. From HTML markup to CSS. From my understanding, my designers have basic CSS knowledge and I am considering a simple 101 style set of tutorials for them to get a better grasp of markup before I moved into more advanced topics like accessibility and microformat markup. We need to get started up quickly. Do you think it's okay to dive into LESS from the get-go?

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  • Accepting a numerical range in a function call

    - by dekpos
    I have encountered two ways of doing it: void foo(int from, int to); /* 'from' inclusive, 'to' exclusive */ void foo(int startIndex, int rangelength); Has one style historically been preferred over the other? If so, was it just a matter of convention or was it due to some deeper underlying reason? I'm currently programming in Java and noticed that the Arrays class uses the former style. The exclusivity of the to argument felt somewhat unintuitive to me, which led me to ask this question.

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