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• Looking to clean up a small ruby script.

  - by Badweather

  I'm looking for a much more idiomatic way to do the following little ruby script. File.open("channels.xml").each do |line| if line.match('(mms:\/\/{1}[a-zA-Z\.\d\/\w-]+)') puts line.match('(mms:\/\/{1}[a-zA-Z\.\d\/\w-]+)') end end Thanks in advance for any suggestions.

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• [[alloc] init] as a factory method

  - by iter

  I want to initialize an instance of one of the subclasses of a superclass depending on the arguments to init: [[Vehicle alloc] initWithItinerary: shortWay]; // returns a bicycle [[Vehicle alloc] initWithItinerary: longWay]; // returns a car I can't find examples of code like this. I wonder if this is not idiomatic in Objective C, or I simply am not looking in the right places.

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• Installing multiple versions of a shared library

  - by nsfyn55

  I am running ubuntu 10.04 and I want to use tmux 1.6. tmux has a dependency on libevent 2. My solution was to compile libevent2 and drop into /usr/local/lib then compile tmux against this lib and drop into /usr/local/bin. This works great until...I restart. This is just an assumption on my part but it seems that other binaries are now linking to the libevent2 library presumably because its on the library path. Because there are 60+ packages with libevent1 dependencies this causes my install to basically lose its mind. Is there an idiomatic way to approach running an application that has a core library dependency on a different version? Should I just statically link the lib?

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• How can I learn to effectively write Pythonic code?

  - by Matt Fenwick

  I'm tired of getting downvoted and/or semi-rude comments on my Python answers, saying things like "this isn't Pythonic" or "that's not the Python way of doing things". To clarify, I'm not tired of getting corrected and downvoted, and I'm not tired of being wrong: I'm tired of feeling like there's a whole field of Python that I know nothing about, and seems to be implicit knowledge of experienced Python programmers. Doing a google search for "Pythonic" reveals a wide range of interpretations. The wikipedia page says: A common neologism in the Python community is pythonic, which can have a wide range of meanings related to program style. To say that code is pythonic is to say that it uses Python idioms well, that it is natural or shows fluency in the language. Likewise, to say of an interface or language feature that it is pythonic is to say that it works well with Python idioms, that its use meshes well with the rest of the language. It also discusses the term "unpythonic": In contrast, a mark of unpythonic code is that it attempts to write C++ (or Lisp, Perl, or Java) code in Python—that is, provides a rough transcription rather than an idiomatic translation of forms from another language. The concept of pythonicity is tightly bound to Python's minimalist philosophy of readability and avoiding the "there's more than one way to do it" approach. Unreadable code or incomprehensible idioms are unpythonic. I suspect one way to learn the Pythonic way is just to program in Python a whole bunch. But I bet I could write a bunch of crap and not improve that much without some guidance, whereas a good resource might speed up the learning process significantly. PEP 8 might be exactly what I'm looking for, or maybe not. I'm not sure; on the one hand it covers a lot of ground, but on the other hand, I feel like it's more suited as a reference for knowledgeable programmers than a tutorial for fresh 'uns. How do I get my foot in the Pythonic/Python way of doing things door?

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• Should we enforce code style in our large codebase?

  - by eighttrackmind

  By "code style" I mean 2 things: Style, eg. // bad if(foo){ ... } // good if (foo) { ... } Conventions and idiomaticity, where two ways of writing the same thing are functionally equivalent, but one is more idiomatic. eg. // bad if (fooLib.equals(a, b)) { ... } // good if (a == b) { ... } I think it makes sense to use an auto-formatter to enforce #1 automatically. So my question is specifically about #2. I like to break things down into pros and cons, here's what I've come up with so far: Pros: Used by many large codebases (eg. Google, jQuery) Helps make it a bit easier to work on new areas of the codebase Helps make code more portable (this is not necessarily true) Code style is automatic once you get used to it Makes it easier to fast-decline pull requests Cons: Takes engineers’ and code reviewers’ time away from more important things (like developing features) Code should ideally be rewritten every 2-3 years anyway, so it’s more important to focus on getting the architecture right, and achieving high test coverage Adds strain to code reviews (eg. “don’t do it this way, I like this other way better”) Even if I’ve been using a code style for a while, I still sometime have to pause and think about how to write a line better Having an enforced, uniform code style makes it hard to experiment with potentially better styles Maintaining a style guide takes a lot of incremental effort Engineers rarely read through the style guide. More often, it's cited in code reviews And as a secondary question: we also have many smaller repositories - should the same code style be enforced there?

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• Circular dependency and object creation when attempting DDD

  - by Matthew

  I have a domain where an Organization has People. Organization Entity public class Organization { private readonly List<Person> _people = new List<Person>(); public Person CreatePerson(string name) { var person = new Person(organization, name); _people.Add(person); return person; } public IEnumerable<Person> People { get { return _people; } } } Person Entity public class Person { public Person(Organization organization, string name) { if (organization == null) { throw new ArgumentNullException("organization"); } Organization = organization; Name = name; } public Organization { get; private set; } public Name { get; private set; } } The rule for this relationship is that a Person must belong to exactly one Organization. The invariants I want to guarantee are: A person must have an organization this is enforced via the Person's constuctor An organization must know of its people this is why the Organization has a CreatePerson method A person must belong to only one organization this is why the organization's people list is not publicly mutable (ignoring the casting to List, maybe ToEnumerable can enforce that, not too concerned about it though) What I want out of this is that if a person is created, that the organization knows about its creation. However, the problem with the model currently is that you are able to create a person without ever adding it to the organizations collection. Here's a failing unit-test to describe my problem [Test] public void AnOrganizationMustKnowOfItsPeople() { var organization = new Organization(); var person = new Person(organization, "Steve McQueen"); CollectionAssert.Contains(organization.People, person); } What is the most idiomatic way to enforce the invariants and the circular relationship?

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• What is your unique programming problem-solving style? [closed]

  - by gcc

  Everyone has their own styles and technique for approaching and solving real world problems. These distinguish us from other people or other programmers. (Actually, I think it make us more desirable as programmers and improves computer science) To improve, we read a lot of books; for example, programming style, how to solve problems, how to approach problems, software and algorithms, et al. Can I learn your technique? In other words, if someone gives you a problem, at first step, what are you doing to solve it? I want learn the style in which you approach, analyze, and solve a problem. EDIT: every programmer is a unique instance; each of us approach problems and converge on solutions in our own... idiomatic manner. This manner is sometimes a quirk of training, a bias of tools, but often it is an insightful nugget, a little golden hammer that cracks nuts just slightly faster then others. When answering, give your general approaches but also take a moment to identify how you look at things in ways that your peers do not. Let's call this your Unique Solving Perspective, or USP.

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• Learning to code first game, few questions on basic game development and 3D

  - by ProgrammerByDay

  I've been programming for a while, and I'm concurrently learning how to make a basic game and slimdx, and wanted to talk to someone to hopefully get a few pointers. I've read that Tetris is the "Hello, world" of game programming, which made sense to me, so I decided to give it a shot. I've been able to code up a basic version in a few hours, which I'm quite happy with, but I had a few questions about 3D programming. Right now I'm using Direct3D to do display the blocks without any textures (just colored squares). I have a data structure (2d array of bytes, where each byte denotes the presence of a block and its color) which is the "game board," and on every render() call I create a new vertex buffer of the existing squares in the game board, and draw those primitives. This feels very inefficient, and I wondering what would be the idiomatic way of doing this in a 3D world, with matrix/rotations/translation operations. I know 3D is overkill for such a project, but I want to learn any 3d concepts that I can while I'm doing it. I understand that what you'd usually want to do is keep the same vertices/vertex buffers but manipulate them with matrices to achieve rotations/translations, etc. To do so, I assume what would happen is I'd have one vertex buffer for the "active" piece, since that'll be constantly rotated and moved, and have one vertex buffer for the frozen pieces on the bottom of the board, which is pretty much stationary, but will need to be changed/recreated when the active piece becomes frozen. Right now I'm just clearing and redrawing on every render call, which seems like the easiest way to do things, although I wonder if there's a more efficient way to deal with changes. Obviously there are a lot of questions I'm asking here, but if you can even just point me a step or two ahead in terms of how I should be thinking, it'd be great. Thanks

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• Script language native extensions - avoiding name collisions and cluttering others' namespace

  - by H2CO3

  I have developed a small scripting language and I've just started writing the very first native library bindings. This is practically the first time I'm writing a native extension to a script language, so I've run into a conceptual issue. I'd like to write glue code for popular libraries so that they can be used from this language, and because of the design of the engine I've written, this is achieved using an array of C structs describing the function name visible by the virtual machine, along with a function pointer. Thus, a native binding is really just a global array variable, and now I must obviously give it a (preferably good) name. In C, it's idiomatic to put one's own functions in a "namespace" by prepending a custom prefix to function names, as in myscript_parse_source() or myscript_run_bytecode(). The custom name shall ideally describe the name of the library which it is part of. Here arises the confusion. Let's say I'm writing a binding for libcURL. In this case, it seems reasonable to call my extension library curl_myscript_binding, like this: MYSCRIPT_API const MyScriptExtFunc curl_myscript_lib[10]; But now this collides with the curl namespace. (I have even thought about calling it curlmyscript_lib but unfortunately, libcURL does not exclusively use the curl_ prefix -- the public APIs contain macros like CURLCODE_* and CURLOPT_*, so I assume this would clutter the namespace as well.) Another option would be to declare it as myscript_curl_lib, but that's good only as long as I'm the only one who writes bindings (since I know what I am doing with my namespace). As soon as other contributors start to add their own native bindings, they now clutter the myscript namespace. (I've done some research, and it seems that for example the Perl cURL binding follows this pattern. Not sure what I should think about that...) So how do you suggest I name my variables? Are there any general guidelines that should be followed?

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• Misconceptions about purely functional languages?

  - by Giorgio

  I often encounter the following statements / arguments: Pure functional programming languages do not allow side effects (and are therefore of little use in practice because any useful program does have side effects, e.g. when it interacts with the external world). Pure functional programming languages do not allow to write a program that maintains state (which makes programming very awkward because in many application you do need state). I am not an expert in functional languages but here is what I have understood about these topics until now. Regarding point 1, you can interact with the environment in purely functional languages but you have to explicitly mark the code (functions) that introduces them (e.g. in Haskell by means of monadic types). Also, AFAIK computing by side effects (destructively updating data) should also be possible (using monadic types?) but is not the preferred way of working. Regarding point 2, AFAIK you can represent state by threading values through several computation steps (in Haskell, again, using monadic types) but I have no practical experience doing this and my understanding is rather vague. So, are the two statements above correct in any sense or are they just misconceptions about purely functional languages? If they are misconceptions, how did they come about? Could you write a (possibly small) code snippet illustrating the Haskell idiomatic way to (1) implement side effects and (2) implement a computation with state?

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• Is the Entity Component System architecture object oriented by definition?

  - by tieTYT

  Is the Entity Component System architecture object oriented, by definition? It seems more procedural or functional to me. My opinion is that it doesn't prevent you from implementing it in an OO language, but it would not be idiomatic to do so in a staunchly OO way. It seems like ECS separates data (E & C) from behavior (S). As evidence: The idea is to have no game methods embedded in the entity. And: The component consists of a minimal set of data needed for a specific purpose Systems are single purpose functions that take a set of entities which have a specific component I think this is not object oriented because a big part of being object oriented is combining your data and behavior together. As evidence: In contrast, the object-oriented approach encourages the programmer to place data where it is not directly accessible by the rest of the program. Instead, the data is accessed by calling specially written functions, commonly called methods, which are bundled in with the data. ECS, on the other hand, seems to be all about separating your data from your behavior.

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• Using foldr to append two lists together (Haskell)

  - by Luke Murphy

  I have been given the following question as part of a college assignment. Due to the module being very short, we are using only a subset of Haskell, without any of the syntactic sugar or idiomatic shortcuts....I must write: append xs ys : The list formed by joining the lists xs and ys, in that order append (5:8:3:[]) (4:7:[]) => 5:8:3:4:7:[] I understand the concept of how foldr works, but I am only starting off in Functional programming. I managed to write the following working solution (hidden for the benefit of others in my class...) : However, I just can't for the life of me, explain what the hell is going on!? I wrote it by just fiddling around in the interpreter, for example, the following line : foldr (\x -> \y -> x:y) [] (2:3:4:[]) which returned [2:3:4] , which led me to try, foldr (\x -> \y -> x:y) (2:3:4:[]) (5:6:7:[]) which returned [5,6,7,2,3,4] so I worked it out from there. I came to the correct solution through guess work and a bit of luck... I am working from the following definition of foldr: foldr = \f -> \s -> \xs -> if null xs then s else f (head xs) (foldr f s (tail xs) ) Can someone baby step me through my correct solution? I can't seem to get it....I already have scoured the web, and also read a bunch of SE threads, such as How foldr works

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• How to encourage domain experts familiar only with C into a C++ opensource project [closed]

  - by paperjam

  Possible Duplicate: How to persuade C fanatics to work on my C++ open source project? I am launching an open-source project into a space where a lot of development is done Linux-kernel-style, i.e. C-language with a low-level mindset. My project is broad and complex and uses aspects of the C++ language and libraries, including the Boost library to best effect for simple, slightly syntactically sweetened, elegant and well structured high level code. We are using C++ templates too to avoid duplication of code and for static polymorphism in code specialisation for performance. Many of the experts in this field are well used to pure C-language projects. How can I persuade them to contribute to my idiomatic C++ based project? I have no objection to C-language subcomponents or the use of a C-like subset for parts of the project so that might be part of the answer. This is a rewritten and retagged rehash of my previous question that was closed. Apologies to those who read and answered for it not being constructive. I hope this new question is viewed as constructive. Please note that this is not a language advocacy question and please keep answers in that spirit.

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• Do there exist programming languages where a variable can truly know its own name?

  - by Job

  In PHP and Python one can iterate over the local variables and, if there is only once choice where the value matches, you could say that you know what the variable's name is, but this does not always work. Machine code does not have variable names. C compiles to assembly and does not have any native reflection capabilities, so it would not know it's name. (Edit: per Anton's answer the pre-processor can know the variable's name). Do there exist programming languages where a variable would know it's name? It gets tricky if you do something like b = a and b does not become a copy of a but a reference to the same place. EDIT: Why in the world would you want this? I can think of one example: error checking that can survive automatic refactoring. Consider this C# snippet: private void CheckEnumStr(string paramName, string paramValue) { if (paramName != "pony" && paramName != "horse") { string exceptionMessage = String.Format( "Unexpected value '{0}' of the parameter named '{1}'.", paramValue, paramName); throw new ArgumentException(exceptionMessage); } } ... CheckEnumStr("a", a); // Var 'a' does not know its name - this will not survive naive auto-refactoring There are other libraries provided by Microsoft and others that allow to check for errors (sorry the names have escaped me). I have seen one library which with the help of closures/lambdas can accomplish error checking that can survive refactoring, but it does not feel idiomatic. This would be one reason why I might want a language where a variable knows its name.

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• Naming the implementation version of an interface function

  - by bolov

  When I need to write an implementation version of an interface function, I put the implementation function within a impl namespace, but with the same name as the interface function. Is this a bad practice? (the same name part, the namespace part I am confident it’s more than OK). For me, who I write the code, there is no confusion between the two, but I want to make sure this isn’t confusing for someone else. One other option would be to append impl suffix to the function name, but since it is already in a separate namespace named impl it seems redundant. Is there an idiomatic way to do this? E.g.: namespace n { namespace impl { // implementation function (hidden from users) // same name, is it ok? void foo() { // ... //sometimes it needs to call recursively or to call overloads of the interface version: foo(); // calls the implementation version. Is this confusing? n::foo(); // calls the interface version. Is this confusing? // ... } // namespace impl // interface function (exposed to users) void foo() { impl::foo(); } } // namespace n

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• C programming multiple storage backends

  - by ahjmorton

  I am starting a side project in C which requires multiple storage backends to be driven by a particular piece of logic. These storage backends would each be linked with the decision of which one to use specified at runtime. So for example if I invoke my program with one set of parameters it will perform the operations in memory but if I change the program configuration it would write to disk. The underlying idea is that each storage backend should implement the same protocol. In other words the logic for performing operations should need to know which backend it is operating on. Currently the way I have thought to provide this indirection is to have a struct of function pointers with the logic calling these function pointers. Essentially the struct would contain all the operations needed to implement the higher level logic E.g. struct Context { void (* doPartOfDoOp)(void) int (* getResult)(void); } //logic.h void doOp(Context * context) { //bunch of stuff context->doPartOfDoOp(); } int getResult(Context * context) { //bunch of stuff return context->getResult(); } My questions is if this way of solving the problem is one a C programmer would understand? I am a Java developer by trade but enjoy using C/++. Essentially the Context struct provides an interface like level of indirection. However I would like to know if there is a more idiomatic way of achieving this.

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• Controlling FPU behavior in an OpenMP program?

  - by STingRaySC

  I have a large C++ program that modifies the FPU control word (using _controlfp()). It unmasks some FPU exceptions and installs a SEHTranslator to produce typed C++ exceptions. I am using VC++ 9.0. I would like to use OpenMP (v.2.0) to parallelize some of our computational loops. I've already successfully applied it to one, but the numerical results are slightly different (though I understand it could also be due to calculations being performed in a different order). I'm assuming this is because the FPU state is thread-specific. Is there some way to have the OpenMP threads inherit that state from the master thread? Or is there some way to specify using OpenMP that new threads execute a particular function that sets up the correct state? What is the idiomatic way to deal with this situation?

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• Rails 3: What is the proper way to respond to REST-ful actions with JSON in rails?

  - by Damien Wilson

  Hello SO. I'm trying to make an API for my rails application using JSON responses to RESTful resource controllers. This is a new experience for me, so I'm looking for some guidance and pointers. To start things off: In a rails application, what is the "proper" way to respond with JSON to REST-ful controller methods? (create, update, destroy) Is there an idiomatic way to indicate success/failure through a JSON response? Additional information: I'm currently working with rails 3.0.beta2 I would like to avoid using a plugin or gem to do the grunt work, my goal is to gain a better understanding of how to make a rails 3 API. Links to places I could find more information on the topic would also be appreciated, some quick searching on google didn't do me much good.

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• Defining a SPI in Clojure

  - by Joe Holloway

  I'm looking for an idiomatic way(s) to define an interface in Clojure that can be implemented by an external "service provider". My application would locate and instantiate the service provider module at runtime and delegate certain responsibilities to it. Let's say, for example, that I'm implementing a RPC mechanism and I want to allow a custom middleware to be injected at configuration time. This middleware could pre-process the message, discard messages, wrap the message handler with logging, etc. I know several ways to do this if I fall back to Java reflection, but feel that implementing it in Clojure would help my understanding. (Note, I'm using SPI in a general sense here, not specifically referring to the way it's defined in the JAR file specification) Thanks

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• Why the good append syntax is so ugly, asks python newbie

  - by Cawas

  Now following my series of "python newbie questions" and based on another question. Go to http://python.net/~goodger/projects/pycon/2007/idiomatic/handout.html#other-languages-have-variables and scroll down to "Default Parameter Values". There you can find the following: def bad_append(new_item, a_list=[]): a_list.append(new_item) return a_list def good_append(new_item, a_list=None): if a_list is None: a_list = [] a_list.append(new_item) return a_list So, question here is: why is the "good" syntax over a known issue ugly like that in a programming language that promotes "elegant syntax" and "easy-to-use"? Why not just something in the definition itself, that the "argument" name is attached to a "localized" mutable object like: def better_append(new_item, a_list=[].local): a_list.append(new_item) return a_list I'm sure there would be a better way to do this syntax, but I'm also almost positive there's a good reason to why it hasn't been done. So, anyone happens to know why?

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• Dynamic/runtime method creation (code generation) in Python

  - by Eli Bendersky

  Hello, I need to generate code for a method at runtime. It's important to be able to run arbitrary code and have a docstring. I came up with a solution combining exec and setattr, here's a dummy example: class Viking(object): def __init__(self): code = ''' def dynamo(self, arg): """ dynamo's a dynamic method! """ self.weight += 1 return arg * self.weight ''' self.weight = 50 d = {} exec code.strip() in d setattr(self.__class__, 'dynamo', d['dynamo']) if __name__ == "__main__": v = Viking() print v.dynamo(10) print v.dynamo(10) print v.dynamo.__doc__ Is there a better / safer / more idiomatic way of achieving the same result?

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• In Clojure - How do I access keys in a vector of structs

  - by Nick

  I have the following vector of structs: (defstruct #^{:doc "Basic structure for book information."} book :title :authors :price) (def #^{:doc "The top ten Amazon best sellers on 16 Mar 2010."} best-sellers [(struct book "The Big Short" ["Michael Lewis"] 15.09) (struct book "The Help" ["Kathryn Stockett"] 9.50) (struct book "Change Your Prain, Change Your Body" ["Daniel G. Amen M.D."] 14.29) (struct book "Food Rules" ["Michael Pollan"] 5.00) (struct book "Courage and Consequence" ["Karl Rove"] 16.50) (struct book "A Patriot's History of the United States" ["Larry Schweikart","Michael Allen"] 12.00) (struct book "The 48 Laws of Power" ["Robert Greene"] 11.00) (struct book "The Five Thousand Year Leap" ["W. Cleon Skousen","James Michael Pratt","Carlos L Packard","Evan Frederickson"] 10.97) (struct book "Chelsea Chelsea Bang Bang" ["Chelsea Handler"] 14.03) (struct book "The Kind Diet" ["Alicia Silverstone","Neal D. Barnard M.D."] 16.00)]) I would like to sum the prices of all the books in the vector. What I have is the following: (defn get-price "Same as print-book but handling multiple authors on a single book" [ {:keys [title authors price]} ] price) Then I: (reduce + (map get-price best-sellers)) Is there a way of doing this without mapping the "get-price" function over the vector? Or is there an idiomatic way of approaching this problem?

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• Standard Place for an Empty String Array in the JDK

  - by Simon B

  Hi is there a standard place for accessing empty array constants in the JDK 1.5. When I want to do a conversion from a String Collection (e.g. ArrayList)to a String Array I find myself using my own which is defined in my own Constants class: public static final String[] EMPTY_STRING_ARRAY = new String[0]; And then in my client code something like: String[] retVal = myStringList.toArray(Constants.EMPTY_STRING_ARRAY); return retVal; I was wondering if this is the "idiomatic" of doing it or if I'm missing something I get the impression from the brief search I did that this kind of thing is prevalent in many people's code. Any ideas, answers, comment (aside from that I shouldn't really use String Arrays) greatly appreciated, Cheers Simon

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• Should I stop redirecting after successful POST or PUT requests?

  - by Andres Jaan Tack

  It seems common in the Rails community, at least, to respond to successful POST, PUT or DELETE requests by redirecting instead of returning success. For instance, if I PUT a legal change to my user profile, the idiomatic response would be a 302 Redirect to the profile page. Isn't this wrong? Shouldn't we be returning 200 OK from the request? Or a 201 Created, in the case of a POST request? Either of those, in the HTTP/1.1 Status Definitions are allowed to (or required to) include a response, anyway. I guess I'm wondering, before I go and "fix" my application, whether there is there a darn good reason why the community has gone the way of redirects instead of successful responses.

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• What frameworks to use to bootstrap my first production scala project ?

  - by Jacques René Mesrine

  I am making my first foray into scala for a production app. The app is currently packaged as a war file. My plan is to create a jar file of the scala compiled artifacts and add that into the lib folder for the war file. My enhancement is a mysql-backed app exposed via Jersey & will be integrated with a 3rd party site via HttpClient invocations. I know how to do this via plain java. But when doing it in scala, there are several decision points that I am pussyfooting on. scala 2.7.7 or 2.8 RC ? JDBC via querulous Is this API ready for production ? sbt vs maven. I am comfortable with maven. Is there a scala idiomatic wrapper for HttpClient (or should I use it just like in java) ? I'd love to hear your comments and experiences on starting out with scala. Thanks

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