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  • why is java.lang.Throwable a class?

    - by mdma
    In java adjectives ending in -able are interfaces Serializable, Comparable etc... So why is Throwable a class? Wouldn't exception handling be easier if Throwable were an interface? Obviously, changing it now is out the question. But could it be made abstract? Wouldn't that avoid the bad practice of throw new Throwable();

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  • Writing fortran robust and "modern" code

    - by Blklight
    In some scientific environments, you often cannot go without FORTRAN as most of the developers only know that idiom, and there is lot of legacy code and related experience. And frankly, there are not many other cross-platform options for high performance programming ( C++ would do the task, but the syntax, zero-starting arrays, and pointers are too much for most engineers ;-) ). I'm a C++ guy but I'm stuck with some F90 projects. So, let's assume a new project must use FORTRAN (F90), but I want to build the most modern software architecture out of it. while being compatible with most "recent" compilers (intel ifort, but also including sun/HP/IBM own compilers) So I'm thinking of imposing: global variable forbidden, no gotos, no jump labels, "implicit none", etc. "object-oriented programming" (modules with datatypes + related subroutines) modular/reusable functions, well documented, reusable libraries assertions/preconditions/invariants (implemented using preprocessor statements) unit tests for all (most) subroutines and "objects" an intense "debug mode" (#ifdef DEBUG) with more checks and all possible Intel compiler checks possible (array bounds, subroutine interfaces, etc.) uniform and enforced legible coding style, using code processing tools C stubs/wrappers for libpthread, libDL (and eventually GPU kernels, etc.) C/C++ implementation of utility functions (strings, file operations, sockets, memory alloc/dealloc reference counting for debug mode, etc.) ( This may all seem "evident" modern programming assumptions, but in a legacy fortran world, most of these are big changes in the typical programmer workflow ) The goal with all that is to have trustworthy, maintainable and modular code. Whereas, in typical fortran, modularity is often not a primary goal, and code is trustworthy only if the original developer was very clever, and the code was not changed since then ! (i'm a bit joking here, but not much) I searched around for references about object-oriented fortran, programming-by-contract (assertions/preconditions/etc.), and found only ugly and outdated documents, syntaxes and papers done by people with no large-scale project involvement, and dead projects. Any good URL, advice, reference paper/books on the subject?

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  • Is ASP.NET MVC is really MVC? Or how to separate model from controller?

    - by Andrey
    Hi all, This question is a bit rhetorical. At some point i got a feeling that ASP.NET MVC is not that authentic implementation of MVC pattern. Or i didn't understood it. Consider following domain: electric bulb, switch and motion detector. They are connected together and when you enter the room motion detector switches on the bulb. If i want to represent them as MVC: switch is model, because it holds the state and contains logic bulb is view, because it presents the state of model to human motion detector is controller, because it converts user actions to generic model commands Switch has one private field (On/Off) as a State and two methods (PressOn, PressOff). If you call PressOn when it is Off it goes to On, if you call it again state doesn't change. Bulb can be replaced with buzzer, motion detector with timer or button, but the model still represent the same logic. Eventually system will have same behavior. This is how i understand classical MVC decomposition, please correct me if i am wrong. Now let's decompose it in ASP.Net MVC way. Bulb is still a view Controller will be switch + motion detector Model is some object that will just pass state to bulb. So the logic that defines behavior moves to controller. Question 1: Is my understanding of MVC and ASP.NET MVC correct? Question 2: If yes, do you agree that ASP.NET MVC is not 100% accurate implementation? And back to life. The final question is how to separate model from controller in case of ASP.NET MVC. There can be two extremes. Controller does basic stuff and call model to do all the logic. Another is controller does all the logic and model is just something like class with properties that is mapped to DB. Question 3: Where should i draw the line between this extremes? How to balance? Thanks, Andrey

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  • Advantage of using a static member function instead of an equivalent non-static member function?

    - by jonathanasdf
    I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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  • Data access pattern, combining push and pull?

    - by andlju
    I need some advice on what kind of pattern(s) I should use for pushing/pulling data into my application. I'm writing a rule-engine that needs to hold quite a large amount of data in-memory in order to be efficient enough. I have some rather conflicting requirements; It is not acceptable for the engine to always have to wait for a full pre-load of all data before it is functional. Only fetching and caching data on-demand will lead to the engine taking too long before it is running quickly enough. An external event can trigger the need for specific parts of the data to be reloaded. Basically, I think I need a combination of pushing and pulling data into the application. A simplified version of my current "pattern" looks like this (in psuedo-C# written in notepad): // This interface is implemented by all classes that needs the data interface IDataSubscriber { void RegisterData(Entity data); } // This interface is implemented by the data access class interface IDataProvider { void EnsureLoaded(Key dataKey); void RegisterSubscriber(IDataSubscriber subscriber); } class MyClassThatNeedsData : IDataSubscriber { IDataProvider _provider; MyClassThatNeedsData(IDataProvider provider) { _provider = provider; _provider.RegisterSubscriber(this); } public void RegisterData(Entity data) { // Save data for later StoreDataInCache(data); } void UseData(Key key) { // Make sure that the data has been stored in cache _provider.EnsureLoaded(key); Entity data = GetDataFromCache(key); } } class MyDataProvider : IDataProvider { List<IDataSubscriber> _subscribers; // Make sure that the data for key has been loaded to all subscribers public void EnsureLoaded(Key key) { if (HasKeyBeenMarkedAsLoaded(key)) return; PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } // Force all subscribers to get a new version of the data for key public void ForceReload(Key key) { PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } void PublishDataToSubscribers(Key key) { Entity data = FetchDataFromStore(key); foreach(var subscriber in _subscribers) { subscriber.RegisterData(data); } } } // This class will be spun off on startup and should make sure that all data is // preloaded as quickly as possible class MyPreloadingThread { IDataProvider _provider; MyPreloadingThread(IDataProvider provider) { _provider = provider; } void RunInBackground() { IEnumerable<Key> allKeys = GetAllKeys(); foreach(var key in allKeys) { _provider.EnsureLoaded(key); } } } I have a feeling though that this is not necessarily the best way of doing this.. Just the fact that explaining it seems to take two pages feels like an indication.. Any ideas? Any patterns out there I should have a look at?

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  • add schema to path in postgresql

    - by veilig
    I'm the process of moving applications over from all in the public schema to each having their own schema. for each application, I have a small script that will create the schema and then create the tables,functions,etc... to that schema. Is there anyway to automatically add a newly created schema to the search_path? Currently, the only way I see is to find the users current path SHOW search_path; and then add the new schema to it SET search_path to xxx,yyy,zzz; I would like some way to just say, append schema zzz to the users_search path. is this possible?

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  • MYSQL Event to update another database table

    - by Lee
    Hey All, I have just taken over a project for a client and the database schema is in a total mess. I would like to rename a load of fields make it a relationship database. But doing this will be a painstaking process as they have an API running of it also. So the idea would be to create a new database and start re-writing the code to use this instead. But I need a way to keep these tables in sync during this process. Would you agree that I should use MYSQL EVENT's to keep updating the new table on Inserts / updates & deletes?? Or can you suggest a better way?? Hope you can advise !! thanks for any input I get

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  • Usability: call for action

    - by Shyam
    I am designing a page, with tiny portlets. Now, I personally like my actions on the right side, yet I wonder if there are methodologies that are targeted about usability. After all, most applications are aimed at the user. What about yourself? Do you prefer information to be on top, on the left or on the right? I've you need to take some sort of action, do you prefer buttons on the left? References to good books and webpages are very welcome!

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  • How does this code break the Law of Demeter?

    - by Dave Jarvis
    The following code breaks the Law of Demeter: public class Student extends Person { private Grades grades; public Student() { } /** Must never return null; throw an appropriately named exception, instead. */ private synchronized Grades getGrades() throws GradesException { if( this.grades == null ) { this.grades = createGrades(); } return this.grades; } /** Create a new instance of grades for this student. */ protected Grades createGrades() throws GradesException { // Reads the grades from the database, if needed. // return new Grades(); } /** Answers if this student was graded by a teacher with the given name. */ public boolean isTeacher( int year, String name ) throws GradesException, TeacherException { // The method only knows about Teacher instances. // return getTeacher( year ).nameEquals( name ); } private Grades getGradesForYear( int year ) throws GradesException { // The method only knows about Grades instances. // return getGrades().getForYear( year ); } private Teacher getTeacher( int year ) throws GradesException, TeacherException { // This method knows about Grades and Teacher instances. A mistake? // return getGradesForYear( year ).getTeacher(); } } public class Teacher extends Person { public Teacher() { } /** * This method will take into consideration first name, * last name, middle initial, case sensitivity, and * eventually it could answer true to wild cards and * regular expressions. */ public boolean nameEquals( String name ) { return getName().equalsIgnoreCase( name ); } /** Never returns null. */ private synchronized String getName() { if( this.name == null ) { this.name == ""; } return this.name; } } Questions How is the LoD broken? Where is the code breaking the LoD? How should the code be written to uphold the LoD?

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  • What are some best practises and "rules of thumb" for creating database indexes?

    - by Ash
    I have an app, which cycles through a huge number of records in a database table and performs a number of SQL and .Net operations on records within that database (currently I am using Castle.ActiveRecord on PostgreSQL). I added some basic btree indexes on a couple of the feilds, and as you would expect, the peformance of the SQL operations increased substantially. Wanting to make the most of dbms performance I want to make some better educated choices about what I should index on all my projects. I understand that there is a detrement to performance when doing inserts (as the database needs to update the index, as well as the data), but what suggestions and best practices should I consider with creating database indexes? How do I best select the feilds/combination of fields for a set of database indexes (rules of thumb)? Also, how do I best select which index to use as a clustered index? And when it comes to the access method, under what conditions should I use a btree over a hash or a gist or a gin (what are they anyway?).

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  • Sequence numbers best practice

    - by Abdullah Jibaly
    What's the best practice or well known methods to implement sequence numbers for business entities such as invoices, purchase orders, job numbers, etc? I want to be able to save the latest value in the database and be able to set it programatically. Is it OK to use a table for this purpose that has a SEQUENCE_NAME, SEQUENCE_NUMBER tuple? I know some databases have a first class sequence type but others (eg, MySQL) do not so it's not something I want to rely on. If a table is used to hold these sequences what is the right way to get and increment them in a synchronized fashion to ensure no data inconsistencies arise?

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  • Why Use PHP OOP over Basic Functions and When?

    - by Codex73
    There are some posts about this matter, but I didn't clearly get when to use Object Oriented coding and when to use programmatic functions in an include. Somebody also mentioned to me that OOP is very heavy to run, and makes more workload. Is this right? Lets say I have a big file with 50 functions, why will I want to call these in a class? and not by function_name(). Should I switch and create object which holds all of my functions? What will be the advantage or specific difference? What benefits does it bring to code OOP in php ? Modularity?

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  • Database Table of Boolean Values

    - by guazz
    What's the best method of storing a large number of booleans in a database table? Should I create a column for each boolean value or is there a more optimal method? Employee Table IsHardWorking IsEfficient IsCrazy IsOverworked IsUnderpaid ...etc.

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  • Branchless memory manager?

    - by Richard Fabian
    Anyone thought about how to write a memory manager (in C++) that is completely branch free? I've written a pool, a stack, a queue, and a linked list (allocating from the pool), but I am wondering how plausible it is to write a branch free general memory manager. This is all to help make a really reusable framework for doing solid concurrent, in-order CPU, and cache friendly development. Edit: by branchless I mean without doing direct or indirect function calls, and without using ifs. I've been thinking that I can probably implement something that first changes the requested size to zero for false calls, but haven't really got much more than that. I feel that it's not impossible, but the other aspect of this exercise is then profiling it on said "unfriendly" processors to see if it's worth trying as hard as this to avoid branching.

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  • IoC, Containers, and NServiceBus confusion

    - by andy
    Hey guys, here's my setup Castle Windsor is my container NServiceBus is itself using it's own container internally, Spring by default I'm implementing the PubSub config. Ok, if I have my Bus.Publish happening within my IWantToRunAtStartup class, then everything is fine. As a test for example on Run() we can start a timer and it'll go into a Service style loop. However, what if I want to abstract NServiceBus from my app, and have my app go: new CustomPulisherClass().Notify(ISomeMessage msg); In this situation, how do I implement CustomPublisherClass. My confusion is coming from the fact that NServiceBus is already running as a Service, it's already been "Started". How to I get at the correct instance of the Bus object? cheers andy

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  • Best practice for DAO pattern ?

    - by Tony
    I've seen a lot of codes use a service-dao pattern , I don't know the origin of this pattern . It force the front layer call service , then delegates some of the service task to dao. I want to ask : Does DAO layer do purely data access related task ? What about exception encapsulation ? Is there other pattern can be used to replace this ?

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  • When should I use Dependency Injection and when utility methods?

    - by Roman
    I have a Java EE project with Spring IoC container. I've just found in Utils class static method sendMail(long list of params). I don't know why but I feel that it would look better if we had separate class (Spring bean with singleton scope) which will be responsible for sending email. But I can't find any arguments which can prove my position. So, are there any pros (or cons) in using DI in this (rather general) situation?

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  • how to run this qt script? (newbie question)

    - by GB_J
    I have a qt script(barchart.qs) that creates a graph for me. I don't know how i can incorporate(ie show the graph) in my qt mainwindow. Can some one please help me look at the code and what its outputs are? I tried engine.evaluate, but i do not know what is the QScriptValue i'm getting in return. Thanks sooo much. This is the script: BarChart.prototype = new QWidget; BarChart.prototype.suffix = ""; function BarChart(parent) { QWidget.call(this, parent); } // find the maximum value and widest (pixel-wise) label and suffix BarChart.prototype.showEvent = function(event) { var fm = new QFontMetrics(this); this.margin = 20; this.titleHeight = fm.height(); this.barHeight = 1.5 * fm.height(); this.barSpacing = 0.6 * fm.height(); this.maxValue = this.suffixWidth = this.labelWidth = 0; var count = 0; for (d in this.data) { this.labelWidth = Math.max(this.labelWidth, fm.width(d)); this.maxValue = Math.max(this.maxValue, this.data[d]); this.suffixWidth = Math.max(this.suffixWidth, fm.width(String(this.data[d]) + " " + this.suffix)); count++; } this.startHue = 15; this.hueDelta = 360 / count; this.size = new QSize(640, this.titleHeight + 2 * this.margin + (this.barHeight + this.barSpacing) * count); } BarChart.prototype.paintEvent = function(event) { var p = new QPainter; p.begin(this); // background and title p.fillRect(this.rect, new QBrush(new QColor(255, 255, 255))); p.drawText(0, 0, this.width, this.margin + this.titleHeight, Qt.AlignCenter, this.windowTitle, 0); var ofs = this.labelWidth + this.margin; var ww = this.width - this.suffixWidth - ofs - 2 * this.margin; var hue = this.startHue; var y = 0; p.translate(this.margin, this.titleHeight + 1.5 * this.margin); for (d in this.data) { // label on the left side p.setPen(new QColor(Qt.black)); p.drawText(0, y, this.labelWidth, this.barHeight, Qt.AlignVCenter + Qt.AlignRight, d, 0); // the colored bar var gradient = new QLinearGradient(new QPoint(ofs, y), new QPoint(ofs, y + this.barHeight)); gradient.setColorAt(0, QColor.fromHsv(hue, 255, 240)); gradient.setColorAt(1, QColor.fromHsv(hue, 255, 92)); p.setBrush(new QBrush(gradient)); p.setPen(new QColor(96, 96, 96)); var bw = this.data[d] * ww / this.maxValue; p.drawRect(ofs, y, bw, this.barHeight); // extra text at the end of the bar var text = new String(this.data[d] + " " + this.suffix); p.setPen(new QColor(Qt.black)); p.drawText(ofs + bw + this.margin/2, y, this.suffixWidth, this.barHeight, Qt.AlignVCenter + Qt.AlignLeft, text, 0); // for the next bar y += (this.barHeight + this.barSpacing); hue += this.hueDelta; if (hue >= 360) hue -= 360; } p.end(); } BarChart.prototype.wheelEvent = function(event) { this.startHue += event.delta() / 8 / 5; if (this.startHue = 360) this.startHue -= 360; if (this.startHue < 0) this.startHue += 360; this.update(); event.ignore(); } BarChart.prototype.mousePressEvent = function(event) { var fname = QFileDialog.getSaveFileName(this, "Save", ".", "*.png", 0, 0); if (fname.length > 0) { var img = new QImage(this.size, QImage.Format_ARGB32_Premultiplied); this.render(img); img.save(new QFile(fname)); } } var chart = new BarChart; chart.windowTitle = "Monthly"; chart.suffix = "reports"; chart.data = { "September" : 45, "October" : 60, "November" : 56, "December" : 0 }; chart.show(); QCoreApplication.exec();

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  • How do I correctly model data in SQL-based databases that have some columns in common, but also have

    - by Brandon Weiss
    For instance, let's say I have a User model. Users have things like logins, passwords, e-mail addresses, avatars, etc. But there are two types of Users that will be using this site, let's say Parents and Businesses. I need to store some different information for the Parents (e.g. childrens' names, domestic partner, salaries, etc.) than for the Businesses (e.g. industry, number of employees, etc.), but also some of it is the same, like logins and passwords. How do I correctly structure this in a SQL-based database? Thanks!

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  • Designer tool integration with TFS?

    - by reallyJim
    Are there good tools for professional designers to use that support source control integration with Team Foundation Server? I'm aware of the Expression tools, but curious to see if there is something else, as proper designer tools really aren't my area of expertise.

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