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  • C++11 support for higher-order list functions

    - by Giorgio
    Most functional programming languages (e.g. Common Lisp, Scheme / Racket, Clojure, Haskell, Scala, Ocaml, SML) support some common higher-order functions on lists, such as map, filter, takeWhile, dropWhile, foldl, foldr (see e.g. Common Lisp, Scheme / Racket, Clojure side-by-side reference sheet, the Haskell, Scala, OCaml, and the SML documentation.) Does C++11 have equivalent standard methods or functions on lists? For example, consider the following Haskell snippet: let xs = [1, 2, 3, 4, 5] let ys = map (\x -> x * x) xs How can I express the second expression in modern standard C++? std::list<int> xs = ... // Initialize the list in some way. std::list<int> ys = ??? // How to translate the Haskell expression? What about the other higher-order functions mentioned above? Can they be directly expressed in C++?

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  • Inheritance vs containment while extending a large legacy project

    - by Flot2011
    I have got a legacy Java project with a lot of code. The code uses MVC pattern and is well structured and well written. It also has a lot of unit tests and it is still actively maintained (bug fixing, minor features adding). Therefore I want to preserve the original structure and code style as much as possible. The new feature I am going to add is a conceptual one, so I have to make my changes all over the code. In order to minimize changes I decided not to extend existing classes but to use containment: class ExistingClass { // .... existing code // my code adding new functionality private ExistingClassExtension extension = new ExistingClassExtension(); public ExistingClassExtension getExtension() {return extension;} } ... // somewhere in code ExistingClass instance = new ExistingClass(); ... // when I need a new functionality instance.getExtension().newMethod1(); All functionality that I am adding is inside a new ExistingClassExtension class. Actually I am adding only these 2 lines to each class that needs to be extended. By doing so I also do not need to instantiate new, extended classes all over the code and I may use existing tests to make sure there is no regression. However my colleagues argue that in this situation doing so isn't a proper OOP approach, and I need to inherit from ExistingClass in order to add a new functionality. What do you think? I am aware of numerous inheritance/containment questions here, but I think my question is different.

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  • Is this a ridiculous way to structure a DB schema, or am I completely missing something?

    - by Jim
    I have done a fair bit of work with relational databases, and think I understand the basic concepts of good schema design pretty well. I recently was tasked with taking over a project where the DB was designed by a highly-paid consultant. Please let me know if my gut intinct - "WTF??!?" - is warranted, or is this guy such a genius that he's operating out of my realm? DB in question is an in-house app used to enter requests from employees. Just looking at a small section of it, you have information on the users, and information on the request being made. I would design this like so: User table: UserID (primary Key, indexed, no dupes) FirstName LastName Department Request table RequestID (primary Key, indexed, no dupes) <...> various data fields containing request details UserID -- foreign key associated with User table Simple, right? Consultant designed it like this (with sample data): UsersTable UserID FirstName LastName 234 John Doe 516 Jane Doe 123 Foo Bar DepartmentsTable DepartmentID Name 1 Sales 2 HR 3 IT UserDepartmentTable UserDepartmentID UserID Department 1 234 2 2 516 2 3 123 1 RequestTable RequestID UserID <...> 1 516 blah 2 516 blah 3 234 blah The entire database is constructed like this, with every piece of data encapsulated in its own table, with numeric IDs linking everything together. Apparently the consultant had read about OLAP and wanted the 'speed of integer lookups' He also has a large number of stored procedures to cross reference all of these tables. Is this valid design for a small to mid-sized SQL DB? Thanks for comments/answers...

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  • Deciding between obj->func() and func(obj)

    - by GSto
    I was thinking about this when I was starting to set up some code for a new project: are there any rules of thumb for when a method should be part of an object, and when it should be a stand alone function that takes an object as a parameter? EDIT: as pointed out in a comment, this can depend on language. I was working in C++ when it came to mind, though I'm this is an issue across a number of languages (and would still love to see answers that pertain to them).

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  • How to recognize my performance plateau?

    - by Dat Chu
    Performance plateau happens right after one becomes "adequately" proficient at a certain task. e.g. You learn a new language/framework/technology. You become better progressively. Then all of the sudden you realize that you have spent quite some time on this technology and you are not getting better at it. As a programmer who is conscious about my performance/knowledge/skill, how do I detect when I am in a performance plateau? What can I do to jump out of it (and keep going upward)?

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  • Is this method of writing Unit Tests correct?

    - by aspdotnetuser
    I have created a small C# project to help me learn how to write good unit tests. I know that one important rule of unit testing is to test the smallest 'unit' of code possible so that if it fails you know exactly what part of the code needs to fixed. I need help with the following before I continue to implement more unit tests for the project: If I have a Car class, for example, that creates a new Car object which has various attributes that are calculated when its' constructor method is called, would the two following tests be considered as overkill? Should there be one test that tests all calculated attributes of the Car object instead? [Test] public void CarEngineCalculatedValue() { BusinessObjects.Car car= new BusinessObjects.Car(); Assert.GreaterOrEqual(car.Engine, 1); } [Test] public void CarNameCalculatedValue() { BusinessObjects.Car car= new BusinessObjects.Car(); Assert.IsNotNull(car.Name); } Should I have the above two test methods to test these things or should I have one test method that asserts the Car object has first been created and then test these things in the same test method?

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  • Algorithmic problem - quickly finding all #'s where value %x is some given value

    - by Steve B.
    Problem I'm trying to solve, apologies in advance for the length: Given a large number of stored records, each with a unique (String) field S. I'd like to be able to find through an indexed query all records where Hash(S) % N == K for any arbitrary N, K (e.g. given a million strings, find all strings where HashCode(s) % 17 = 5. Is there some way of memoizing this so that we can quickly answer any question of this form without doing the % on every value? The motivation for this is a system of N distributed nodes, where each record has to be assigned to at least one node. The nodes are numbered 0 - (K-1) , and each node has to load up all of the records that match it's number: If we have 3 nodes Node 0 loads all records where Hash % 3 ==0 Node 1 loads all records where Hash % 3 ==1 Node 2 loads all records where Hash % 3 ==2 adding a 4th node, obviously all the assignments have to be recomputed - Node 0 loads all records where Hash % 4 ==0 ... etc I'd like to easily find these records through an indexed query without having to compute the mod individually. The best I've been able to come up with so far: If we take the prime factors of N (p1 * p2 * ... ) if N % M == I then p % M == I % p for all of N's prime factors e.g. 10 nodes : N % 10 == 6 then N % 2 = 0 == 6 %2 N % 5 = 1 == 6 %5 so storing an array of the "%" of N for the first "reasonable" number of primes for my data set should be helpful. For example in the above example we store the hash and the primes HASH PRIMES (array of %2, %3, %5, %7, ... ]) 16 [0 1 1 2 .. ] so looking for N%10 == 6 is equivalent to looking for all values where array[1]==1 and array[2] == 1. However, this breaks at the first prime larger than the highest number I'm storing in the factor table. Is there a better way?

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  • Why is database developer pay so high? [closed]

    - by user433500
    Just wondering why someone would get 10k+ in some area in US for just writing queries and creating tables. While the average salary for someone who does scripting, object oriented programming, J2EE and database all together is only ~12K in new york city. Is there similar opportunities in cities like new york where only doing database gets one 10K+? What is the rational of companies paying such a high salary to consultants for just writing simple queries? I am sure college grad can do that with ease and will be quite satisfied with a 60k+ pay for a couple of year. Does location really matter so much?

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  • Why do Core Data sqlite table columns start with 'Z'?

    - by Dia
    I was looking at the sqlite table that Core Data generates and noticed that all table columns start with 'Z'. I realize this is an implementation detail, but I was curious as to why that's the case and if there was a design decision involved in this. Anyone happen to know or guess why? Here's a sample schema output of Core Data sqlite database: sqlite .schema CREATE TABLE ZPOST ( Z_PK INTEGER PRIMARY KEY, Z_ENT INTEGER, Z_OPT INTEGER, ZPOSTID INTEGER, ZUSER INTEGER, ZCREATEDAT TIMESTAMP, ZTEXT VARCHAR ); CREATE TABLE ZUSER ( Z_PK INTEGER PRIMARY KEY, Z_ENT INTEGER, Z_OPT INTEGER, ZUSERID INTEGER, ZAVATARIMAGEURLSTRING VARCHAR, ZUSERNAME VARCHAR ); CREATE TABLE Z_METADATA (Z_VERSION INTEGER PRIMARY KEY, Z_UUID VARCHAR(255), Z_PLIST BLOB); CREATE TABLE Z_PRIMARYKEY (Z_ENT INTEGER PRIMARY KEY, Z_NAME VARCHAR, Z_SUPER INTEGER, Z_MAX INTEGER);

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  • Too much to learn, so little time

    - by Phobia
    Okay, so I'm a java developer (or at least I think I am),and also a student at the same time I want to get a job when I graduate,I'll be graduating in a year or so (hopefully) (Note: my major has nothing to do with programming) Now, I'm between a rock and a hard place I also want to nail the foundations to become a good software developer. I want to be able to write programs that solve problems,not just glue code The software market in my country for java developers is just a few developers working with Java EE (struts,spring,hibernate....etc) I'm currently learning C++ with this book. I've also watched most of the 1st lecture of this course and I understood pretty much everything I watched To sum it up, I have three options Learn Java EE Learn C++ Learn Scheme Which is better for me at this point?

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  • Conflict resolution for two-way sync

    - by K.Steff
    How do you manage two-way synchronization between a 'main' database server and many 'secondary' servers, in particular conflict resolution, assuming a connection is not always available? For example, I have an mobile app that uses CoreData as the 'database' on the iOS and I'd like to allow users to edit the contents without Internet connection. In the same time, this information is available on a website the devices will connect to. What do I do if/when the data on the two DB servers is in conflict? (I refer to CoreData as a DB server, though I am aware it is something slightly different.) Are there any general strategies for dealing with this sort of issue? These are the options I can think of: 1. Always use the client-side data as higher-priority 2. Same for server-side 3. Try to resolve conflicts by marking each field's edit timestamp and taking the latest edit Though I'm certain the 3rd option will open room for some devastating data corruption. I'm aware that the CAP theorem concerns this, but I only want eventual consistency, so it doesn't rule it out completely, right? Related question: Best practice patterns for two-way data synchronization. The second answer to this question says it probably can't be done.

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  • What is Rainbow (not the CMS)

    - by Jeremy Thompson
    I was reading this excellent blog article regarding speeding up the badge page and in the last comment the author @waffles (a.k.a Sam Saffron) mentions these tools: dapper and a bunch of custom helpers like rainbow, sql builder etc Dapper and sql builder was easy to look up but rainbow keeps pointing me to a CMS, can someone please point me to the real source? Thanks. Obviously the architecture of these [SE] sites is uber cool and ultra fast so no comments on that thanks.

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  • Supporting and testing multiple versions of a software library in a Maven project

    - by Duncan Jones
    My company has several versions of its software in use by our customers at any one time. My job is to write bespoke Java software for the customers based on the version of software they happen to be running. I've created a Java library that performs many of the tasks I regularly require in a normal project. This is a Maven project that I deploy to our local Artifactory and pull down into other Maven projects when required. I can't decide the best way to support the range of software versions used by our customers. Typically, we have about three versions in use at any one time. They are normally backwards compatible with one another, but that cannot be guaranteed. I have considered the following options for managing this issue: Separate editions for each library version I make a separate release of my library for each version of my company software. Using some Maven cunningness I could automatically produce a tested version linked to each of the then-current company software versions. This is feasible, but not without its technical challenges. The advantage is that this would be fairly automatic and my unit tests have definitely executed against the correct software version. However, I would have to keep updating the versions supported and may end up maintaining a large collection of libraries. One supported version, but others tested I support the oldest software version and make a release against that. I then perform tests with the newer software versions to ensure it still works. I could try and make this testing automatic by having some non-deployed Maven projects that import the software library, the associated test JAR and override the company software version used. If those projects build, then the library is compatible. I could ensure these meta-projects are included in our CI server builds. I welcome comments on which approach is better or a suggestion for a different approach entirely. I'm leaning towards the second option.

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  • Mocking concrete class - Not recommended

    - by Mik378
    I've just read an excerpt of "Growing Object-Oriented Software" book which explains some reasons why mocking concrete class is not recommended. Here some sample code of a unit-test for the MusicCentre class: public class MusicCentreTest { @Test public void startsCdPlayerAtTimeRequested() { final MutableTime scheduledTime = new MutableTime(); CdPlayer player = new CdPlayer() { @Override public void scheduleToStartAt(Time startTime) { scheduledTime.set(startTime); } } MusicCentre centre = new MusicCentre(player); centre.startMediaAt(LATER); assertEquals(LATER, scheduledTime.get()); } } And his first explanation: The problem with this approach is that it leaves the relationship between the objects implicit. I hope we've made clear by now that the intention of Test-Driven Development with Mock Objects is to discover relationships between objects. If I subclass, there's nothing in the domain code to make such a relationship visible, just methods on an object. This makes it harder to see if the service that supports this relationship might be relevant elsewhere and I'll have to do the analysis again next time I work with the class. I can't figure out exactly what he means when he says: This makes it harder to see if the service that supports this relationship might be relevant elsewhere and I'll have to do the analysis again next time I work with the class. I understand that the service corresponds to MusicCentre's method called startMediaAt. What does he mean by "elsewhere"? The complete excerpt is here: http://www.mockobjects.com/2007/04/test-smell-mocking-concrete-classes.html

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  • Can we put percentage on amount of work of a certain role in project's lifecycle?

    - by deviDave
    The title may be confusing, but I will elaborate it here. I am trying to figure our how much time and effort each person spend during some project. I divided roles into: - junior developer (works mainly on UI and some light things) - senior developer (develops complex logic, database structures, etc.) - lead developer (leads the team, usually most experienced person) - negotiator/resolver (a person who directly talk to a client trying to either negotiate terms and timeframe or to clarify vagueness presented by a team leader) My AIM is to calculate percentage of role's involvement based on quality, not time (obviously a junior will spend most time in project, but with the least quality). In the end I would get a table which may look like this: Total: 100% ---------------- Junior: 10% Senior: 50% Lead: 30% Negotiator: 10% Can this be achieved? Has anyone found any source which may help me?

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  • Looking for terminology for the relation of a subject and a predicate

    - by kostja
    While writing some predicates for collection filtering I have stumbled over the choice of the right words for the relation of the subject and the predicate (English is a foreign language for me). What I ended up writing was "Subjects matching this predicate..." This seems to be incorrect, since predicates are functions and not regular expressions. But saying "Subjects for which this predicate returns true..." sounds awkward to me as well.. So what would be the correct term?

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  • Is it time to deprecate synchronized, wait and notify?

    - by OldCurmudgeon
    Is there a single scenario (other than compatibility with ancient JVMs) where using synchronized is preferable to using a Lock? Can anyone justify using wait or notify over the newer systems? Is there any algorithm that must use one of them in its implementation? I see a previous questions that touched on this matter but I would like to take this a little further and actually deprecate them. There are far too many traps and pitfalls and caveats with them that have been ironed out with the new facilities. I just feel it may soon be time to mark them obsolete.

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  • Designing a plug-in system

    - by madflame991
    I'm working on a Java project and I would like to add a plug-in system. More precisely, I would like to let the user design his own module, pack it into a jar, leave it in a "plugins/" subfolder of my application and be done with it. I've managed to get a child classloader to instantiate objects of classes located in external jars, but now I'm facing a design dilemma: Say Joe makes a plug-in and he packs it in joeplugin.jar. I would really like Joe to have a class named "instantiation.Factory" and I would also like everyone to have this class with this exact location and name. (This factory class obviously implements a interface that I provide and through it I get what I want from the plug-in.) If Joe wouldn't be restricted in this way I would have to look into his entire jar for some class that implements my factory interface and I don't want to imagine how complicated things get. So my question is: should I enforce a strict naming convention for this single class? I have no idea how plug-in systems work.

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  • How would you design an application with many target platforms and devices?

    - by Pierre 303
    I'm in a very beginning of the design phase of an application that will have to run in the following platforms/devices: Desktop: Windows, Linux & Mac Mobile: Android, iPhone/iPad & Windows Phone 7 Web: Silverlight I will use C# on Mono and I want to maximize code re-usability. Except for the desktop (I'll use WinForms/GTK#), my concern is related to many different GUI that I will face. What would be your approach? Obviously, the views will be different, but what about the controllers, data access, utility classes, etc. Is it really acceptable to share everything but the views?

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  • Windows7 Console with session memory [closed]

    - by Mateusz
    I am searching console for windows 7 which have memory of typed commands which is stored when I close the cmd prompt. I got frustrated when I have to type again paths with commands, I'm developing for android and I use adb so you can know it can be quite a lot of commands to issue. Other workarounds would be appreciated. Open source or freeware prefed. I have, Console2 (don't store commands), git bash (can't work with that, have some paths issues).

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  • When and why are certain data structures used in the context of web development?

    - by Ein Doofus
    While browsing around the MSDN I came across: http://msdn.microsoft.com/en-us/library/aa287104%28v=vs.71%29 which lists various data structures such as: Queues Stacks Hashtables Binary Trees Binary Search Trees Graphs (I believe there are also Lists) and I was hoping to get a high-level overview of when these various data structures can be used in the broad context of web development, and when used, why one data structure is generally used instead of any other one.

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  • How to get projects and payments formally in the name of company.

    - by piemesons
    I am having a serviced based registered firm. I am having some basic questions. I want to know how to take projects formally in the name of the company.(I have clients, Just need to know the procedure.) I need to make some general agreement for clients? Also, how to take payment. I was working as part time free lancer from 1.5 years and was taking payments directly in my account. Now as I have registered the firm so i want to know the exact procedure to follow. Please let me know about this. EDIT I am having a registered firm in India and most of the clients are from US(80%) or UK(20%)

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  • Which online/hosted bug tracking tool do you use for your own work and projects?

    - by blueberryfields
    I've accumulated a lot of side projects over the years, which I slowly improve on over time. Whenever I return to one, I take some time reading over text files that include design, recent bugs, next features, etc... that I should be working on - it's not pretty. I'm looking to switch to something more formal. Ideally, this would be a full featured, online, bug tracking system, which allows for free or nearly free bug tracking for my own projects. Also, ideally this would be doable in a private manner - I don't really want everyone to see my side projects and what a mess I've made of some of them.

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  • It's hard to judge your own product. Is there a name for this issue?

    - by Epicmaster
    I was just talking to my partner about how hard it is to personally judge how good your product is after a while because you use it so often. You literally spend hours on your computer doing nothing but work on this Consumer Facing application, and you start to feel a little fatigue of using it over and over and over, at least a hundred times a day. You get scared this fatigue may mean the product you are building may have the same effect on the users and might mean you are doing something wrong. Is there a name for this in product development? For the fact that as a designer+ programmer+everything else, your product might not suck as much as you think simply because you spend way too much time with it, or a variation of this?

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  • good literature for teaching object oriented thinking in C [closed]

    - by Dipan Mehta
    Quite often C is the primary platform for the development. And when things are large scale, I have seen partitioning of the system as different objects is quite a natural thing. Some or many of the object orientated analysis and design principles are used here very well. This is not a debate question about whether or not C is a good candidate for object oriented programming or not. This is also NOT a question how to do OO in C. You can refer to this question and there are probably many such citations. As far as I am concerned, I have learned some of this things while working with many open source and commercial projects. (libjpeg, ffmpeg, Gstreamer which is based on GObject). I can probably extend a few references that explains some of these concepts such as - 1. Event Helix article, 2. Linux Mag article 3. one of my answers which links Schreiner's reference. Unfortunately, when we induct younger folks, it seems too hard to make them learn all of it the hard way. Usually, when we say it's C, a general reaction is to throw away all of the "Object thinking". Looking for help extending above references from those who have been in the similar areas of work. Are there any good formal literature that explains how Object thinking can be made to use while you are working in C? I have seen tons of book on general "object oriented paradigms" but they all focus on advanced languages mostly not in C. You see most C books - but most focus only on the syntax and the obfuscated corners of C and that's it. There are hardly ANY good reference, specially books or any systematic (I mean formal) literature on how to apply OO in C. This is very surprising given that so many large scale open source projects use C which are truly using this very well; but we hardly see any good formal literature on this subject.

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