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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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• Settings object with singleton pattern

  - by axis

  I need to build an object that will have only one instance because this Object is dedicated to the storage of vital settings for my application and I would like to avoid a misuse of this type or a conflict at run-time. The most popular solution for this, according to the internet, is the Singleton pattern. But I would like to know about other ideas or solutions for this; also I would like to know if other solutions can be much more easy to grasp for an user of this hypothetical library. Thanks.

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• Efficient Algorithm for Recording gameplay's objects positions

  - by Scorch

  So, I have a game idea in mind, and for that I need to record the game around the player. I'me not talking about recording it as video, but rather recording the scene objects, and their positions within the game, and then render them, giving the player the ability to go back and forth, to stop time and move around. I've made a prototype with some data structures in C#, since this is going to be the programming language we'll be using in our game, but if we want the player to be able to go back just five minutes back with the data of just 100 NPC's, it takes almost 1GB of RAM. Right now, I'm just storing a Doubly linked list, each item with the object position. In the game, I'll need to store even more data in each node, so I need something even more ligher. Of course, this algorithm is zero optimized, but still, that is a lot. The alternatives would be create the NPC's that aren't really important to the game when the user is viewing the past, but I don't really like it very much for the sake of realism. I wonder if there is a better way to store this? Thanks in advance, Scorch

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• What is the most concise, unambiguous syntax for operator associated methods (for overloading etc.) that doesn't pollute the namespace?

  - by Doug Treadwell

  Python tends to add double underscores before its built-in or overloadable operator methods, like __add(), whereas C++ requires declaring overloaded operators as operator + (Thing& thing) { /* code */ } for example. Personally I like the operator syntax because it seems to be more explicit and keeps these operator overloading methods separated from other methods without introducing weird prefix notation. What are your thoughts? Also, what about the case of built-in methods that are needed for the programming language to work properly? Is name mangling (like adding __ prefix or sys or something) the best solution here? What do you think about having another type of method declaration, like ... "system method" for lack of creativity at the moment. So there would be two kinds of declarations: int method_name() { ... } system int method_name() { ... } ... and the call would need to be different to distinguish between them. obj.method_name(); vs obj:method_name(); perhaps, assuming a language where : can be unambiguously used in this situation. obj.method_name() vs obj.(system method_name)() Sure, the latter is ugly, but the idea is to make the common case simple and system stuff should be kept out of the way. Maybe the Objective-C notation of method calls? [obj method_name]? Are there more alternatives? Please make suggestions.

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• Is it a good idea to dynamically position and size controls on a form or statically set them?

  - by CrystalBlue

  I've worked mostly with interface building tools such as xCode's Interface Builder and Visual Studio's environment to place forms and position them on screens. But I'm finding that with my latest project, placing controls on the form through a graphical interface is not going to work. This more has to do with the number of custom controls I have to create that I can't visually see before hand. When I first tackled this, I began to position all of my controls relative to the last ones that I created. Doing this had its own pros and cons. On the one hand, this gave me the opportunity to set one number (a margin for example) and when I changed the margin, the controls all sized correctly to one another (such as shortening controls in the center while keeping controls next to the margin the same). But this started to become a spiders-web of code that I knew wouldn't go very far before getting dangerous. Change one number and everything re sizes, but remove one control and you've created many more errors and size problems for all the other controls. It became more surgery then small changes to controls and layout. Is there a good way or maybe a preferred way to determine when I should be using relative or absolute positioning in forms?

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• Use constructor or setter method?

  - by user633600

  I am working on a UI code where I have an Action class, something like this - public class MyAction extends Action { public MyAction() { setText("My Action Text"); setToolTip("My Action Tool tip"); setImage("Some Image"); } } When this Action class was created it was pretty much assumed that the Action class wont be customizable (in a sense- its text, tooltip or image will be not be changed anywhere in the code). Of late, now we are in need of changing the action text at some location in code. So I suggested my co-worker to remove the hardcoded action text from the constructor and accept it as an argument, so that everybody is forced to pass the action text. Something like this code below - public class MyAction extends Action { public MyAction(String actionText) { setText(actionText); setTooltip("My Action tool tip); setImage("My Image"); } } He however thinks that since setText() method belongs to base class. It can be flexibly used to pass the action text wherever action instance is created. That way, there is no need to change the existing MyAction class. So his code would look something like this. MyAction action = new MyAction(); //this creates action instance with the hardcoded text action.setText("User required new action text"); //overwrite the exisitng text. I am not sure if that is a correct way to deal with problem. I think in above mentioned case user is anyway going to change the text, so why not force him while constructing the action. The only benefit I see with the original code is that user can create Action class without much thinking about setting text.

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• PHP I am pulling my hair out trying to find the best! [closed]

  - by darga33

  PULLING MY HAIR OUT I have heard of Martin Fowler's book PoEAA and the other book Head First OOA OOD but those are not in PHP. I DESPERATELY WANT TO READ THEM, but ONLY in PHP utilizing SOLID principles! Does anyone know of the absolute best, most recent PHP book that utilizes the SOLID principles and GRASP, and all the other best practices? I want to learn from the best possible source! Not beginner books! I already understand OOP. This seems like an almost impossible question to find the answer to and so I thought, hey, might as well post on stackexchange!! Surely someone out there must know!!!!!!!!!! Or if noone knows Maybe they know of an open source application that utilizes these principles that is relatively small that is not a framework. Something that I can go through every single class, and spend time understanding the insides and outs of how the program was developed. Thanks so much in advance! I really really really really appreciate it!

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• Dynamic Strategy Pattern [migrated]

  - by Karl Barker

  So I'm writing a web service architecture which includes FunctionProvider classes which do the actual processing of requests, and a main Endpoint class which receives and delegates requests to the proper FunctionProvider. I don't know exactly the FunctionProviders available at runtime, so I need to be able to 'register' (if that's the right word) them with my main Endpoint class, and query them to see if they match an incoming request. public class MyFunc implements FunctionProvider{ static { MyEndpoint.register(MyFunc); } public Boolean matchesRequest(Request req){...} public void processRequest(Request req){...} } public class MyEndpoint{ private static ArrayList<FunctionProvider> functions = new ArrayList<FunctionProvider>(); public void register(Class clz){ functions.add(clz); } public void doPost(Request request){ //find the FunctionProvider in functions //matching the request } } I've really not done much reflective Java like this (and the above is likely wrong, but hopefully demonstrates my intentions). What's the nicest way to implement this without getting hacky?

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• How can I better manage far-reaching changes in my code?

  - by neuviemeporte

  In my work (writing scientific software in C++), I often get asked by the people who use the software to get their work done to add some functionality or change the way things are done and organized right now. Most of the time this is just a matter of adding a new class or a function and applying some glue to do the job, but from time to time, a seemingly simple change turns out to have far-reaching consequences that require me to redesign a substantial amount of existing code, which takes a lot of time and effort, and is difficult to evaluate in terms of time required. I don't think it has as much to do with inter-dependence of modules, as with changing requirements (admittedly, on a smaller scale). To provide an example, I was thinking about the recently-added multi-user functionality in Android. I don't know whether they planned to introduce it from the very beginning, but assuming they didn't, it seems hard to predict all the areas that will be affected by the change (apps preferences, themes, need to store account info somehow, etc...?), even though the concept seems simple enough, and the code is well-organized. How do you deal with such situations? Do you just jump in to code and then sort out the cruft later like I do? Or do you do a detailed analysis beforehand of what will be affected, what needs to be updated and how, and what has to be rewritten? If so, what tools (if any) and approaches do you use?

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• What kind of programs/solutions can only be written with OOP or are too hard to achieve without it?

  - by user1598390

  Paraphrasing a recent question: What is Object Oriented Programming ill-suited for? I would like to ask the opposite question: What kind of programs cannot be written unless you use OOP? What kind of programs are not recommended to be written using non-OOP techniques? What kind of programs need OOP in order to even be written? What kind of programs would be too hard to write without OOP ? The answer to this question can help sell the idea of OOP to project leaders that have no special interest in code quality. At least they could buy the idea if one shows them the kind of things that are not even possible unless you use OOP.

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• When creating a GUI wizard, should all pages/tabs be of the same size? [closed]

  - by Job

  I understand that some libraries would force me to, but my question is general. If I have a set of buttons at the bottom: Back, Next, Cancel?, (other?), then should their location ever change? If the answer is no, then what do I do about pages with little content? Do I stretch things? Place them in the lone upper left corner? According to Steve Krug, it does not make sense to add anything to GUI that does not need to be there. I understand that there are different approaches to wizards - some have tabs, others do not. Some tabs are lined horizontally at the top; others - vertically on the left. Some do not show pages/tabs, and are simply sequences of dialogs. This is probably a must when the wizard is "non-linear", e.g. some earlier choices can result in branching. Either way the problem is the same - sacrifice on the consistency of the "big picture" (outline of the page/tab + location of buttons), or the consistency of details (some tabs might be somewhat packed; others having very little content). A third choice, I suppose is putting extra effort in the content in order to make sure that organizing the content such that it is more or less evenly distributed from page to page. However, this can be difficult to do (say, when the very first tab contains only a choice of three things, and then branches off from there; there are probably other examples), and hard to maintain this balance if any of the content changes later. Can you recommend a good approach? A link to a relevant good blog post or a chapter of a book is also welcome. Let me know if you have questions.

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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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• Chapters Two, Three, and Four

  - by drsql

  I am trying to blog all of the chapters of the book, but due to deadlines and a lot of shuffling about, I never got around it for these three chapters, two of which I have added since I wrote the original table of contents. All of these contain mostly material from previous editions of the book, updated a good amount, but nothing tremendously different if you had memorized the material from the previous edition. As such, the pre-writing blog ritual wasn’t as necessary (for me at least) as it is going...(read more)

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• Does an inventory limit in an MMORPG make sense?

  - by Philipp

  I am currently developing a simple 2d MMORPG. My current focus is the inventory system. I am currently wondering if I should implement a limit on what a player character can carry. Either in form of a maximum weight, a limited number of inventory slots, or a combination of both. Almost every MMORPG I ever played limits inventory space. But plausibility aside, is this really necessary from a gameplay point of view? Maybe it would in fact improve the game experience when I just let the players carry as much stuff as they want. tl;dr: What is the game development rationale behind limiting carrying capacity of player characters?

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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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• Full Text Search Strategy For My Website

  - by Hosea146

  I have a website that allows users to search for items in various categories. Each category is a separate area (page) of my website. For example, some categories might be cars, bikes, books etc. At the moment a user has to search for an item by going to the page (for example, cars) and searching for the car they want. I would like to allow the user to search for anything on my site, from my main home page. At the moment, each page (category) has its own set of tables, and I don't really want to turn Full Text Search on for each table (20+ of them) and search each table individually when a search is done. This is going to be slow and tedious. What I'm thinking of doing is creating a single table that will hold all searchable information for each category of item (when an item is saved in its respective table, I would copy all searchable information over to my 'Search' table). I would then turn Full Text Search on for that table, and search that table. Does this sound reasonable? Is there a better way? I've never used Full Text Search before, so this is new to me.

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• Is there a better way to organize my module tests that avoids an explosion of new source files?

  - by luser droog

  I've got a neat (so I thought) way of having each of my modules produce a unit-test executable if compiled with the -DTESTMODULE flag. This flag guards a main() function that can access all static data and functions in the module, without #including a C file. From the README: -- Modules -- The various modules were written and tested separately before being coupled together to achieve the necessary basic functionality. Each module retains its unit-test, its main() function, guarded by #ifdef TESTMODULE. `make test` will compile and execute all the unit tests, producing copious output, but importantly exitting with an appropriate success or failure code, so the `make test` command will fail if any of the tests fail. Module TOC __________ test obj src header structures CONSTANTS ---- --- --- --- -------------------- m m.o m.c m.h mfile mtab TABSZ s s.o s.c s.h stack STACKSEGSZ v v.o v.c v.h saverec_ f.o f.c f.h file ob ob.o ob.c ob.h object ar ar.o ar.c ar.h array st st.o st.c st.h string di di.o di.c di.h dichead dictionary nm nm.o nm.c nm.h name gc gc.o gc.c gc.h garbage collector itp itp.c itp.h context osunix.o osunix.c osunix.h unix-dependent functions It's compile by a tricky bit of makefile, m:m.c ob.h ob.o err.o $(CORE) itp.o $(OP) cc $(CFLAGS) -DTESTMODULE $(LDLIBS) -o $@ $< err.o ob.o s.o ar.o st.o v.o di.o gc.o nm.o itp.o $(OP) f.o where the module is compiled with its own C file plus every other object file except itself. But it's creating difficulties for the kindly programmer who offered to write the Autotools files for me. So the obvious way to make it "less weird" would be to bust-out all the main functions into separate source files. But, but ... Do I gotta?

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• Is it correct to add booleans in order to count the number of true values in a vector?

  - by gerrit

  Is it conceptually correct to sum a vector of booleans? From a mathematical point of view, I would argue it's not: True + True != 2. But it's quite practical to do so still! Example using the vectorised Python library numpy: In [1]: X = rand(10) In [2]: large = X>0.6 In [3]: large.dtype Out[3]: dtype('bool') In [4]: large.sum() Out[4]: 7 I don't like it, but it's very practical. Is this a good practice? Update: the aim is to count the number of true values in a vector.

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• Best setup/workflow for distributed team to integrated DSVC with fragmented huge .NET site?

  - by lazfish

  So we have a team with 2 developers one manager. The dev server sits in a home office and the live server sits in a rack somewhere handled by the larger part of my company. We have freedom to do as we please but I want to incorporate Kiln DSVC and FogBugz for us with some standard procedures to make sense of our decisions/designs/goals. Our main product is web-based training through our .NET site with many videos etc, and we also do mobile apps for multiple platforms. Our code-base is a 15 yr old fragmented mess. The approach has been rogue .asp/.aspx pages with some class management implemented in the last 6 years. We still mix our html/vb/js all on the same file when we add a feature/page to our site. We do not separate the business logic from the rest of the code. Wiring anything up in VS for Intelli-sense or testing or any other benefit is more frustrating than it is worth, because of having to manually rejigger everything back to one file. How do other teams approach this? I noticed when I did wire everything up for VS it wants to make a class for all functions. Do people normally compile DLLs for page-specific functions that won't be reusable? What approaches make sense for getting our practices under control while still being able to fix old anti-patterns and outdated code and still moving towards a logical structure for future devs to build on?

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• Is there such a thing these days as programming in the small?

  - by WeNeedAnswers

  With all the programming languages that are out there, what exactly does it mean to program in the small and is it still possible, without the possibility of re-purposing to the large. The original article which mentions in the small was dated to 1975 and referred to scripting languages (as glue languages). Maybe I am missing the point, but any language that you can built components of code out of, I would regard to being able to handle "in the large". Is there a confusion on what Objects are and do they really figure as being mandatory to being able to handle "the large". Many have argued that this is the true meaning of "In the large" and that the concepts of objects are best fit for the job.

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• Can a domain specific language be used to representing the Open SRD

  - by NeoModulus

  I am in the early stages of creating an open source C# library that would allow developers to drop in the open SRD (http://www.d20srd.org/) into an existing project. Abstracted it is a complex set of tightly coupled business rules. Having previously worked on an adaptive object model project for health care risk management I began with that pattern in mind. Due to the high coupling of rules it is becoming apparent that the project may require some kind of scripting. Have started researching DSL implementation I am now considering scraping the adaptive object model for a domain specific language. I have not work with domain specific languages so my question is it reasonable to assume a domain specific language can be used to representing the open SRD?

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• How can I get better at explaining complex software processes to developers?

  - by Lostsoul

  I'm really struggling with my software specs. I am not a professional programmer but enjoy doing it for fun and made some software that I want to sell later but I'm not happy with the code quality. So I wanted to hire a real developer to rewrite my software in a more professional way so it will be maintainable by other developers in the future. I read and found some sample specs and made my own by applying their structure to my document and wanted to get my developer friend to read it and give me advice. After an hour and a half he understood exactly what I was trying to do and how I did it(my algorithms,stack,etc.). How can I get better at explaining things to developers? I add many details and explanations for everything(including working code) but I'm unsure the best way I can learn to pass detailed domain knowledge(my software applies big data, machine learning, graph theory to finance). My end goal is to get them to understand as much as possible from the document and then ask anything they do not understand, but right now it seems they need to extract alot of information from me. How can I get better at communicating domain knowledge to developers?

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• How to implement string matching based on a pattern

  - by Vincent Rischmann

  I was asked to build a tool that can identify if a string match a pattern. Example: {1:20} stuff t(x) {a,b,c} would match: 1 stuff tx a 20 stuff t c It is a sort of regex but with a different syntax Parentheses indicate an optional value {1:20} is a interval; I will have to check if the token is a number and if it is between 1 and 20 {a,b,c} is just an enumeration; it can be either a or b or c Right now I implemented this with a regex, and the interval stuff was a pain to do. On my own time I tried implementing some kind of matcher by hand, but it turns out it's not that easy to do. By experimenting I ended up with a function that generates a state table from the pattern and a state machine. It worked well until I tried to implement the optional value, and I got stuck and how to generate the state table. After that I searched how I could do this, and that led me to stuff like LL parser, LALR parser, recursive-descent parser, context-free grammars, etc. I never studied any of this so it's hard to know what is relevant here, but I think this is what I need: A grammar A parser which generates states from the grammar and a pattern A state machine to see if a string match the states So my first question is: Is this right ? And second question, what do you recommend I read/study to be able to implement this ?

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• Where can I find a Script for a crowdfunding website? [closed]

  - by Lincedit

  Possible Duplicate: crowd funding platform? I am looking for a project for a script (PHP/MySql) that provides me the functionality of a crowdfunding website. There are many scripts which should be usable, but I need maybe some scripts for Joomla CMS or any other kind of opensource CMS Websites. I checked all the Resources on Google and could not find some kind of this scripts, because there are no German language installed or prepared for multilingual websites. It is non profit project and I am just looking for any kind of advices, which can be helpfull to me. I hope you can help me here. Please send me some information about some scripts which are running? Many Thanks

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• Should single purpose utility app use a class

  - by jmoreno

  When writing a small utility app, that does just one thing, should that one thing be encapsulated in a seperate class, or just let it be part of whatever class/module is used to start the application? I.e. Main would consist of 2 or three lines calling the constructor and then the DoIt methods, nothing else. Or should Main be the DoIt method, with whatever functions it needs added to the main class? Asking because I want to get some alternative perspective, but couldn't find a similar question. If my google-fu is bad and there's a dup, please close.

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