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  • What Precalculus knowledge is required before learning Discrete Math Computer Science topics?

    - by Ein Doofus
    Below I've listed the chapters from a Precalculus book as well as the author recommended Computer Science chapters from a Discrete Mathematics book. Although these chapters are from two specific books on these subjects I believe the topics are generally the same between any Precalc or Discrete Math book. What Precalculus topics should one know before starting these Discrete Math Computer Science topics?: Discrete Mathematics CS Chapters 1.1 Propositional Logic 1.2 Propositional Equivalences 1.3 Predicates and Quantifiers 1.4 Nested Quantifiers 1.5 Rules of Inference 1.6 Introduction to Proofs 1.7 Proof Methods and Strategy 2.1 Sets 2.2 Set Operations 2.3 Functions 2.4 Sequences and Summations 3.1 Algorithms 3.2 The Growths of Functions 3.3 Complexity of Algorithms 3.4 The Integers and Division 3.5 Primes and Greatest Common Divisors 3.6 Integers and Algorithms 3.8 Matrices 4.1 Mathematical Induction 4.2 Strong Induction and Well-Ordering 4.3 Recursive Definitions and Structural Induction 4.4 Recursive Algorithms 4.5 Program Correctness 5.1 The Basics of Counting 5.2 The Pigeonhole Principle 5.3 Permutations and Combinations 5.6 Generating Permutations and Combinations 6.1 An Introduction to Discrete Probability 6.4 Expected Value and Variance 7.1 Recurrence Relations 7.3 Divide-and-Conquer Algorithms and Recurrence Relations 7.5 Inclusion-Exclusion 8.1 Relations and Their Properties 8.2 n-ary Relations and Their Applications 8.3 Representing Relations 8.5 Equivalence Relations 9.1 Graphs and Graph Models 9.2 Graph Terminology and Special Types of Graphs 9.3 Representing Graphs and Graph Isomorphism 9.4 Connectivity 9.5 Euler and Hamilton Ptahs 10.1 Introduction to Trees 10.2 Application of Trees 10.3 Tree Traversal 11.1 Boolean Functions 11.2 Representing Boolean Functions 11.3 Logic Gates 11.4 Minimization of Circuits 12.1 Language and Grammars 12.2 Finite-State Machines with Output 12.3 Finite-State Machines with No Output 12.4 Language Recognition 12.5 Turing Machines Precalculus Chapters R.1 The Real-Number System R.2 Integer Exponents, Scientific Notation, and Order of Operations R.3 Addition, Subtraction, and Multiplication of Polynomials R.4 Factoring R.5 Rational Expressions R.6 Radical Notation and Rational Exponents R.7 The Basics of Equation Solving 1.1 Functions, Graphs, Graphers 1.2 Linear Functions, Slope, and Applications 1.3 Modeling: Data Analysis, Curve Fitting, and Linear Regression 1.4 More on Functions 1.5 Symmetry and Transformations 1.6 Variation and Applications 1.7 Distance, Midpoints, and Circles 2.1 Zeros of Linear Functions and Models 2.2 The Complex Numbers 2.3 Zeros of Quadratic Functions and Models 2.4 Analyzing Graphs of Quadratic Functions 2.5 Modeling: Data Analysis, Curve Fitting, and Quadratic Regression 2.6 Zeros and More Equation Solving 2.7 Solving Inequalities 3.1 Polynomial Functions and Modeling 3.2 Polynomial Division; The Remainder and Factor Theorems 3.3 Theorems about Zeros of Polynomial Functions 3.4 Rational Functions 3.5 Polynomial and Rational Inequalities 4.1 Composite and Inverse Functions 4.2 Exponential Functions and Graphs 4.3 Logarithmic Functions and Graphs 4.4 Properties of Logarithmic Functions 4.5 Solving Exponential and Logarithmic Equations 4.6 Applications and Models: Growth and Decay 5.1 Systems of Equations in Two Variables 5.2 System of Equations in Three Variables 5.3 Matrices and Systems of Equations 5.4 Matrix Operations 5.5 Inverses of Matrices 5.6 System of Inequalities and Linear Programming 5.7 Partial Fractions 6.1 The Parabola 6.2 The Circle and Ellipse 6.3 The Hyperbola 6.4 Nonlinear Systems of Equations

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  • Best way to remote restart Ubuntu from Windows machine

    - by robsoft
    Background: I'm looking to put a series of Ubuntu machines into retail locations, they're being used as dumb kiosks to show a series of slides onto large LCD panel TV screens. Once installed, they won't have a keyboard or mouse connected but will have a fixed IP on the local network. Everything is configured to auto-start, no automatic updates, no power saving etc - I think we're pretty-much good to go apart from one thing. I need the retail staff to be able to restart the boxes if a problem arises. We have VNC running (now that we've turned off desktop enhancements!) so that we can remotely get into the machines if we need to, but that's not something we would allow the retail staff to do. The machines are going to be physically 'out of the way' (probably in the ceiling space) so the power button is not easily accessible!. I'd like to have some means of allowing the retail staff to restart the Ubuntu machine, from the desktop of one of their Windows terminals. I don't really want to give them some kind of raw terminal access (the command line will frighten them!) and I don't want them to use VNC (as stated above). Ideally there would be an icon on the Windows desktop, they double-click it, reply to a simple 'are you sure?' prompt, and then the Ubuntu box is told to restart. The Windows side of that won't be a problem, we can write something using Delphi, Python & Qt4, whatever - it's the Ubuntu side of it I'm stuck with. Out of sight/view, could I have a Windows program open a terminal across the network and tell Ubuntu to restart? Is this what SSH could be used for (I have never set that kind of thing up). The Windows programming side isn't really an issue, it's just that I'm a total Ubuntu noob and don't know where to start from the platform point of view. The other thing we considered is also having the machine automatically restart itself at a set time each day (obviously out of store hours!). To me, that seems a bit unnecessary (though forcing a restart once a week/month might be worthwhile). Any thoughts or suggestions? Being able to restart the box on demand across the network is my prime requirement.

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  • ConsumeStructuredBuffer, what am I doing wrong?

    - by John
    I'm trying to implement the 3rd exercise in chapter 12 of Introduction to 3D Game Programming with DirectX 11, that is: Implement a Compute Shader to calculate the length of 64 vectors. Previous exercises ask you to do the same with typed buffers and regular structured buffers and I had no problems with them. For what I've read, [Consume|Append]StructuredBuffers are bound to the pipeline using UnorderedAccessViews (as long as they use the D3D11_BUFFER_UAV_FLAG_APPEND, and the buffers have both D3D11_BIND_SHADER_RESOURCE and D3D11_BIND_UNORDERED_ACCESS bind flags). Problem is: my AppendStructuredBuffer works, since I can append data to it and retrieve it from the application to write to a results file, but the ConsumeStructuredBuffer always returns zeroed data. Data is in the buffer, since if I change the UAV to a ShaderResourceView and to a StructuredBuffer in the HLSL side it works. I don't know what I am missing: Should I initialize the ConsumeStructuredBuffer on the GPU, or can I do it when I create the buffer (as I amb currently doing). Is it OK to bind the buffer with a UAV as described above? Do I need to bind it as a ShaderResourceView somehow? Maybe I am missing some step? This is the declaration of buffers in the Compute Shader: struct Data { float3 v; }; struct Result { float l; }; ConsumeStructuredBuffer<Data> gInput; AppendStructuredBuffer<Result> gOutput; And here the creation of the buffer and UAV for input data: D3D11_BUFFER_DESC inputDesc; inputDesc.Usage = D3D11_USAGE_DEFAULT; inputDesc.ByteWidth = sizeof(Data) * mNumElements; inputDesc.BindFlags = D3D11_BIND_SHADER_RESOURCE | D3D11_BIND_UNORDERED_ACCESS; inputDesc.CPUAccessFlags = 0; inputDesc.StructureByteStride = sizeof(Data); inputDesc.MiscFlags = D3D11_RESOURCE_MISC_BUFFER_STRUCTURED; D3D11_SUBRESOURCE_DATA vinitData; vinitData.pSysMem = &data[0]; HR(md3dDevice->CreateBuffer(&inputDesc, &vinitData, &mInputBuffer)); D3D11_UNORDERED_ACCESS_VIEW_DESC uavDesc; uavDesc.Format = DXGI_FORMAT_UNKNOWN; uavDesc.ViewDimension = D3D11_UAV_DIMENSION_BUFFER; uavDesc.Buffer.FirstElement = 0; uavDesc.Buffer.Flags = D3D11_BUFFER_UAV_FLAG_APPEND; uavDesc.Buffer.NumElements = mNumElements; md3dDevice->CreateUnorderedAccessView(mInputBuffer, &uavDesc, &mInputUAV); Initial data is an array of Data structs, which contain a XMFLOAT3 with random data. I bind the UAV to the shader using the Effects framework: ID3DX11EffectUnorderedAccessViewVariable* Input = mFX->GetVariableByName("gInput")->AsUnorderedAccessView(); Input->SetUnorderedAccessView(uav); // uav is mInputUAV Any ideas? Thank you.

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  • Why does my int, booleans, doubles does not work?

    - by SystemNetworks
    As you see, my code does not work. When armor1 is true, it would add my life. goldA is another class. public void goldenArmor(GameContainer gc, StateBasedGame sbg, Graphics g) { if(armor1==true) { goldA.life = life; goldA.intelligence = intelligence; goldA.power = power; goldA.lifeLeft = lifeLeft; goldA.head(); goldA.body(); goldA.legs(); } } My other class: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.Image; import org.newdawn.slick.Input; import org.newdawn.slick.SlickException; /* Note: Copyright(C)2012 System Networks | Square NET | Julius Bryan Gambe. You cannot copy the style, story of the game and gameplay! To programmers: The int,doubles,strings,booleans are properly sorted out. Please don't mess it up. */ /* NOTE: We have loops but not for programming. The loop is: 1.show the world to user 2.Obtain input from the user 3.Shows the update, repeat step 1 */ import org.newdawn.slick.*; import org.newdawn.slick.state.*; import org.lwjgl.input.Mouse; //contents: // public class GoldenArmor{ //get it from play public int life; public double intelligence; public int lifeLeft; public double power; public GoldenArmor() { // TODO Auto-generated constructor stub } //start here public void head() { life += 10; intelligence +=0.5; } public void body() { lifeLeft += 100; } public void legs() { power += 100; } } /* SYSTEM NETWORKS(C) 2012 NET FRONT */ The life, intelligence, power, lifeLeft are nothing but to use it as just reference to prevent stack overflow. And at my main class, it becomes my real booleans, int, doubles. How do I fix this? It does not add it to my normal int.

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  • Parsing T-SQL – The easy way

    - by Dave Ballantyne
    Every once in a while, I hit an issue that would require me to interrogate/parse some T-SQL code.  Normally, I would shy away from this and attempt to solve the problem in some other way.  I have written parsers before in the the past using LEX and YACC, and as much fun and awesomeness that path is,  I couldnt justify the time it would take. However, this week I have been faced with just such an issue and at the back of my mind I can remember reading through the SQLServer 2012 feature pack and seeing something called “Microsoft SQL Server 2012 Transact-SQL Language Service “.  This is described there as : “The SQL Server Transact-SQL Language Service is a component based on the .NET Framework which provides parsing validation and IntelliSense services for Transact-SQL for SQL Server 2012, SQL Server 2008 R2, and SQL Server 2008. “ Sounds just what I was after.  Documentation is very scant on this so dont take what follows as best practice or best use, just a practice and a use. Knowing what I was sort of looking for something, I found the relevant assembly in the gac which is the simply named ,’Microsoft.SqlServer.Management.SqlParser’. Even knowing that you wont find much in terms of documentation if you do a web-search, but you will find the MSDN documentation that list the members and methods etc… The “scanner”  class sounded the most appropriate for my needs as that is described as “Scans Transact-SQL searching for individual units of code or tokens.”. After a bit of poking, around the code i ended up with was something like [System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SqlServer.Management.SqlParser") | Out-Null $ParseOptions = New-Object Microsoft.SqlServer.Management.SqlParser.Parser.ParseOptions $ParseOptions.BatchSeparator = 'GO' $Parser = new-object Microsoft.SqlServer.Management.SqlParser.Parser.Scanner($ParseOptions) $Sql = "Create Procedure MyProc as Select top(10) * from dbo.Table" $Parser.SetSource($Sql,0) $Token=[Microsoft.SqlServer.Management.SqlParser.Parser.Tokens]::TOKEN_SET $Start =0 $End = 0 $State =0 $IsEndOfBatch = $false $IsMatched = $false $IsExecAutoParamHelp = $false while(($Token = $Parser.GetNext([ref]$State ,[ref]$Start, [ref]$End, [ref]$IsMatched, [ref]$IsExecAutoParamHelp ))-ne [Microsoft.SqlServer.Management.SqlParser.Parser.Tokens]::EOF) { try{ ($TokenPrs =[Microsoft.SqlServer.Management.SqlParser.Parser.Tokens]$Token) | Out-Null $TokenPrs $Sql.Substring($Start,($end-$Start)+1) }catch{ $TokenPrs = $null } } As you can see , the $Sql variable holds the sql to be parsed , that is pushed into the $Parser object using SetSource,  and then we will use GetNext until the EOF token is returned.  GetNext will also return the Start and End character positions within the source string of the parsed text. This script’s output is : TOKEN_CREATE Create TOKEN_PROCEDURE Procedure TOKEN_ID MyProc TOKEN_AS as TOKEN_SELECT Select TOKEN_TOP top TOKEN_INTEGER 10 TOKEN_FROM from TOKEN_ID dbo TOKEN_TABLE Table note that the ‘(‘, ‘)’  and ‘*’ characters have returned a token type that is not present in the Microsoft.SqlServer.Management.SqlParser.Parser.Tokens Enum that has caused an error which has been caught in the catch block.  Fun, Fun ,Fun , Simple T-SQL Parsing.  Hope this helps someone in the same position,  let me know how you get on.

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  • SFX Played Once per Collision or Hit

    - by David Dimalanta
    I have a question about using Box2D (engine for LibGDX used to make realistic physics). I observed on the code that I've made for the physics here below: @Override public boolean touchUp(int screenX, int screenY, int pointer, int button) { // TODO Touch Up Event if(is_Next_Fruit_Touched) { BodyEditorLoader Fruit_Loader = new BodyEditorLoader(Gdx.files.internal("Shape_Physics/Fruity Physics.json")); Fruit_BD.type = BodyType.DynamicBody; Fruit_BD.position.set(x, y); FixtureDef Fruit_FD = new FixtureDef(); // --> Allows you to make the object's physics. Fruit_FD.density = 1.0f; Fruit_FD.friction = 0.7f; Fruit_FD.restitution = 0.2f; MassData mass = new MassData(); mass.mass = 5f; Fruit_Body[n] = world.createBody(Fruit_BD); Fruit_Body[n].setActive(true); // --> Let your dragon fall. Fruit_Body[n].setMassData(mass); Fruit_Body[n].setGravityScale(1.0f); System.out.println("Eggs... " + n); Fruit_Loader.attachFixture(Fruit_Body[n], Body, Fruit_FD, Fruit_IMG.getWidth()); Fruit_Origin = Fruit_Loader.getOrigin(Body, Fruit_IMG.getWidth()).cpy(); is_Next_Fruit_Touched = false; up = y; Gdx.app.log("Initial Y-coordinate", "Y at " + up); //Once it's touched, the next fruit will set to drag. if(n < 50) { n++; }else{ System.exit(0); } } return true; } Now, I'm thinking which part o line should I implement for the sound effects. My objectives to make SFX played once for every collision (Or should I say "SFX played once per collision"?) on the following: SFX played once if they hit on the objects of its kind. (e.g. apple vs. apple) SFX played once on a different sound when it hit on the ground. (e.g. apple land on the mud) Take note that I'm using Box2D for the Java programming version thanks to LibGDX via Box2D engine and I edited the physics body using Physics Body Editor before I implement it to code. I tried to check every available methods for body, fixture definition, or body definition to code for the SFX when hit but it seems only for the gravity and weight. Is there possibly available on the document for SFX played when collision happens if possible?

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  • How to convert pitch and yaw to x, y, z rotations?

    - by Aaron Anodide
    I'm a beginner using XNA to try and make a 3D Asteroids game. I'm really close to having my space ship drive around as if it had thrusters for pitch and yaw. The problem is I can't quite figure out how to translate the rotations, for instance, when I pitch forward 45 degrees and then start to turn - in this case there should be rotation being applied to all three directions to get the "diagonal yaw" - right? I thought I had it right with the calculations below, but they cause a partly pitched forward ship to wobble instead of turn.... :( So my quesiton is: how do you calculate the X, Y, and Z rotations for an object in terms of pitch and yaw? Here's current (almost working) calculations for the Rotation acceleration: float accel = .75f; // Thrust +Y / Forward if (currentKeyboardState.IsKeyDown(Keys.I)) { this.ship.AccelerationY += (float)Math.Cos(this.ship.RotationZ) * accel; this.ship.AccelerationX += (float)Math.Sin(this.ship.RotationZ) * -accel; this.ship.AccelerationZ += (float)Math.Sin(this.ship.RotationX) * accel; } // Rotation +Z / Yaw if (currentKeyboardState.IsKeyDown(Keys.J)) { this.ship.RotationAccelerationZ += (float)Math.Cos(this.ship.RotationX) * accel; this.ship.RotationAccelerationY += (float)Math.Sin(this.ship.RotationX) * accel; this.ship.RotationAccelerationX += (float)Math.Sin(this.ship.RotationY) * accel; } // Rotation -Z / Yaw if (currentKeyboardState.IsKeyDown(Keys.K)) { this.ship.RotationAccelerationZ += (float)Math.Cos(this.ship.RotationX) * -accel; this.ship.RotationAccelerationY += (float)Math.Sin(this.ship.RotationX) * -accel; this.ship.RotationAccelerationX += (float)Math.Sin(this.ship.RotationY) * -accel; } // Rotation +X / Pitch if (currentKeyboardState.IsKeyDown(Keys.F)) { this.ship.RotationAccelerationX += accel; } // Rotation -X / Pitch if (currentKeyboardState.IsKeyDown(Keys.D)) { this.ship.RotationAccelerationX -= accel; } I'm combining that with drawing code that does a rotation to the model: public void Draw(Matrix world, Matrix view, Matrix projection, TimeSpan elsapsedTime) { float seconds = (float)elsapsedTime.TotalSeconds; // update velocity based on acceleration this.VelocityX += this.AccelerationX * seconds; this.VelocityY += this.AccelerationY * seconds; this.VelocityZ += this.AccelerationZ * seconds; // update position based on velocity this.PositionX += this.VelocityX * seconds; this.PositionY += this.VelocityY * seconds; this.PositionZ += this.VelocityZ * seconds; // update rotational velocity based on rotational acceleration this.RotationVelocityX += this.RotationAccelerationX * seconds; this.RotationVelocityY += this.RotationAccelerationY * seconds; this.RotationVelocityZ += this.RotationAccelerationZ * seconds; // update rotation based on rotational velocity this.RotationX += this.RotationVelocityX * seconds; this.RotationY += this.RotationVelocityY * seconds; this.RotationZ += this.RotationVelocityZ * seconds; Matrix translation = Matrix.CreateTranslation(PositionX, PositionY, PositionZ); Matrix rotation = Matrix.CreateRotationX(RotationX) * Matrix.CreateRotationY(RotationY) * Matrix.CreateRotationZ(RotationZ); model.Root.Transform = rotation * translation * world; model.CopyAbsoluteBoneTransformsTo(boneTransforms); foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.World = boneTransforms[mesh.ParentBone.Index]; effect.View = view; effect.Projection = projection; effect.EnableDefaultLighting(); } mesh.Draw(); } }

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  • How to handle this unfortunately non hypothetical situation with end-users?

    - by User Smith
    I work in a medium sized company but with a very small IT force. Last year (2011), I wrote an application that is very popular with a large group of end-users. We hit a deadline at the end of last year and some functionality (I will call funcA from now on) was not added into the application that was wanted at the very end. So, this application has been running in live/production since the end of 2011, I might add without issue. Yesterday, a whole group of end-users started complaining that funcA that was never in the application is no longer working. Our priority at this company is that if an application is broken it must be fixed first prior to prioritized projects. I have compared code and queries and there is no difference since 2011, which is proofA. I then was able to get one of the end-users to admit that it never worked proofB, but since then that end-user has went back and said that it was working previously......I believe the horde of end-users has assimilated her. I have also reviewed my notes for this project which has requirements and daily updates regarding the project which specifically states, "funcA not achieved due to time constraints", proofC. I have spoken with many of them and I can see where they could be confused as they are very far from a programming background, but I also know they are intelligent enough to act in a group in order to bypass project prioritization orders in order to get functionality that they want to make their job easier. The worst part is is that now group think is setting in and my boss and the head of IT is actually starting to believe them, even though there is no code or query changes. As far as reviewing the state of the logic it is very cut and dry to the point of if 1 = 1, funcA will not work. So, this is the end of the description of my scenario, but I am trying not to get severally dinged on my performance metrics due to this which would essentially have me moved to fixing a production problem that doesn't exist that will probably take over 1 month. I am looking for direct answers to this question. This question is not for rants, polling, or discussions as this is not the format for StackExchange. Please don't downvote me too terribly it is pretty common on this specific site of stack, I am looking for honest answers to this situation and I couldn't find a forum more appropriate.

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  • Mastering snow and Java development at jDays in Gothenburg

    - by JavaCecilia
    Last weekend, I took the train from Stockholm to Gothenburg to attend and present at the new Java developer conference jDays. It was professionally arranged in the Swedish exhibition hall close to the amusement park Liseberg and we got a great deal out of the top-level presenters and hallway discussions. Understanding and Improving Your Java Process Our main purpose was to spread information on JVM and our monitoring tools for Java processes, so I held a crash course in the most important terms and concepts if you want to affect the performance of your Java process. From the beginning - the JVM specification to interpretation of heap usage graphs. For correct analysis, you also need to understand something about process memory - you need space for the Java heap (-Xms for initial size and -Xmx for max heap size), but the process memory also contain the thread stacks (to a size of -Xss), JVM internal data structures used for keeping track of Java objects on the heap, method compilation/optimization, native libraries, etc. If you get long pause times, make sure to monitor your application, see the allocation rate and frequency of pause times.My colleague Klara Ward then held a presentation on the Java Mission Control product, the profiling and diagnostics tools suite for HotSpot, coming soon. The room was packed and very appreciated, Klara demonstrated four different scenarios, e.g. how to diagnose and fix latencies due to lock contention for logging.My German colleague, OpenJDK ambassador Dalibor Topic travelled to Sweden to do the second keynote on "Make the Future Java". He let us in on the coming features and roadmaps of Java, now delivering major versions on a two-year schedule (Java 7 2011, Java 8 2013, etc). Also letting us in on where to download early versions of 8, to report problems early on. Software Development in teams Being a scout leader, I'm drilled in different team building and workshop techniques, creating strong groups - of course, I had to attend Henrik Berglund's session on building successful teams. He spoke about the importance of clear goals, autonomy and agreed processes. Thomas Sundberg ended the conference by doing live remote pair programming with Alex in Rumania and a concrete tips for people wanting to try it out (for local collaboration, remember to wash and change clothes). Memory Master Keynote The conference keynote was delivered by the Swedish memory master Mattias Ribbing, showing off by remembering the order of a deck of cards he'd seen once. He made it interactive by forcing the audience to learn a memory mastering technique of remembering ten ordered things by heart, asking us to shout out the order backwards and we made it! I desperately need this - bought the book, will get back on the subject. Continuous Delivery The most impressive presenter was Axel Fontaine on Continuous Delivery. Very well prepared slides with key images of his message and moved about the stage like a rock star. The topic is of course highly interesting, how to create an infrastructure enabling immediate feedback to developers and ability to release your product several times per day. Tomek Kaczanowski delivered a funny and useful presentation on good and bad tests, providing comic relief with poorly written tests and the useful rules of thumb how to rewrite them. To conclude, we had a great time and hope to see you at jDays next year :)

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  • Confusion about inheritance

    - by Samuel Adam
    I know I might get downvoted for this, but I'm really curious. I was taught that inheritance is a very powerful polymorphism tool, but I can't seem to use it well in real cases. So far, I can only use inheritance when the base class is an abstract class. Examples : If we're talking about Product and Inventory, I quickly assumed that a Product is an Inventory because a Product must be inventorized as well. But a problem occured when user wanted to sell their Inventory item. It just doesn't seem to be right to change an Inventory object to it's subtype (Product), it's almost like trying to convert a parent to it's child. Another case is Customer and Member. It is logical (at least for me) to think that a Member is a Customer with some more privileges. Same problem occurred when user wanted to upgrade an existing Customer to become a Member. A very trivial case is the Employee case. Where Manager, Clerk, etc can be derived from Employee. Still, the same upgrading issue. I tried to use composition instead for some cases, but I really wanted to know if I'm missing something for inheritance solution here. My composition solution for those cases : Create a reference of Inventory inside a Product. Here I'm making an assumption about that Product and Inventory is talking in a different context. While Product is in the context of sales (price, volume, discount, etc), Inventory is in the context of physical management (stock, movement, etc). Make a reference of Membership instead inside Customer class instead of previous inheritance solution. Therefor upgrading a Customer is only about instantiating the Customer's Membership property. This example is keep being taught in basic programming classes, but I think it's more proper to have those Manager, Clerk, etc derived from an abstract Role class and make it a property in Employee. I found it difficult to find an example of a concrete class deriving from another concrete class. Is there any inheritance solution in which I can solve those cases? Being new in this OOP thing, I really really need a guidance. Thanks!

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  • Software Tuned to Humanity

    - by Phil Factor
    I learned a great deal from a cynical old programmer who once told me that the ideal length of time for a compiler to do its work was the same time it took to roll a cigarette. For development work, this is oh so true. After intently looking at the editing window for an hour or so, it was a relief to look up, stretch, focus the eyes on something else, and roll the possibly-metaphorical cigarette. This was software tuned to humanity. Likewise, a user’s perception of the “ideal” time that an application will take to move from frame to frame, to retrieve information, or to process their input has remained remarkably static for about thirty years, at around 200 ms. Anything else appears, and always has, to be either fast or slow. This could explain why commercial applications, unlike games, simulations and communications, aren’t noticeably faster now than they were when I started programming in the Seventies. Sure, they do a great deal more, but the SLAs that I negotiated in the 1980s for application performance are very similar to what they are nowadays. To prove to myself that this wasn’t just some rose-tinted misperception on my part, I cranked up a Z80-based Jonos CP/M machine (1985) in the roof-space. Within 20 seconds from cold, it had loaded Wordstar and I was ready to write. OK, I got it wrong: some things were faster 30 years ago. Sure, I’d now have had all sorts of animations, wizzy graphics, and other comforting features, but it seems a pity that we have used all that extra CPU and memory to increase the scope of what we develop, and the graphical prettiness, but not to speed the processes needed to complete a business procedure. Never mind the weight, the response time’s great! To achieve 200 ms response times on a Z80, or similar, performance considerations influenced everything one did as a developer. If it meant writing an entire application in assembly code, applying every smart algorithm, and shortcut imaginable to get the application to perform to spec, then so be it. As a result, I’m a dyed-in-the-wool performance freak and find it difficult to change my habits. Conversely, many developers now seem to feel quite differently. While all will acknowledge that performance is important, it’s no longer the virtue is once was, and other factors such as user-experience now take precedence. Am I wrong? If not, then perhaps we need a new school of development technique to rival Agile, dedicated once again to producing applications that smoke the rear wheels rather than pootle elegantly to the shops; that forgo skeuomorphism, cute animation, or architectural elegance in favor of the smell of hot rubber. I struggle to name an application I use that is truly notable for its blistering performance, and would dearly love one to do my everyday work – just as long as it doesn’t go faster than my brain.

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  • Building Tag Cloud Declarative ADF Component

    - by Arunkumar Ramamoorthy
    When building a website, there could a requirement to add a tag cloud to let the users know the popular tags (or terms) used in the site. In this blog, we would build a simple declarative component to be used as tag cloud in the page. To start with, we would first create the declarative component, which could display the tag cloud. We will do that by creating a new custom application from the new gallery. Give a name for the app and the project and from the new gallery, let us create a new ADF Declarative Component We need to specify the name for the declarative component, attributes in it etc. as follows For displaying the tags as cloud, we need to pass the content to this component. So, we will create an attribute to hold the values for the tag. Let us name it as "value" and make it as java.lang.String  type. Once after this, to hold the component, we need to create a tag library. This can be done by clicking on the Add Tag Library button. Clicking on OK buttons in all the open dialogs would create a declarative component for us. Now, we need to display the tag cloud based on the value passed to the component. To do that, we assume that the value is a Tree Binding and has two attributes in it, say "Name" and "Weight". To make a tag cloud, we would put together the "Name" in a loop and set it's font size based on the "Weight". After putting our logic to work, here is how the source look Attributes added to the declarative components can be retrieved by using #{attrs.<attribute_name>}. Now, we need to deploy this project as ADF Library Jar file, so that this can be distributed to the consuming applications. We'll select ADF Library Jar as type and create the profile. We would be getting the jar file after deployment. To test the functionality, we could create a simple Fusion Web Application. To add our custom component to the consuming application, we can create a file system connection pointing to the location where the jar file is and add it or, add through the project properties of the ViewController project. Now, our custom component has been added to the consuming application. We could test that by creating a VO in the model project with a query like, select 'Faces' as Name,25 as Weight from dual union all select 'ADF', 15 from dual  union all select 'ADFdi', 30 from dual union all select 'BC4J', 20 from dual union all select 'EJB', 40 from dual union all select 'WS', 35 from dual Add this VO to the AppModule, so that it would be exposed to the data control. Then, we could create a jspx page, and add a tree binding to the VO created. We can now see our Tag Cloud declarative component is available in the component palette.  It can be inserted from the component palette to our page and set it's value property to CollectionModel of the tree binding created. Now that we've created the Declarative component and added that to our page successfully, we can run the page to see how it looks. As per the query, the Tags are displayed in different fonts, based on their weight.

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  • Construction Paper, Legos, and Architectural Modeling

    I can remember as a kid playing with construction paper and Legos to explore my imagination. Through my exploration I was able to build airplanes, footballs, guns, and more, out of paper. Additionally I could create entire cities, robots, or anything else I could image out of Legos.  These toys, I now realize were in fact tools that gave me an opportunity to explore my ideas in the physical world through the use of modeling.  My imagination was allowed to run wild as I, unknowingly at the time, made design decisions that directly affected the models I was building from the raw materials.  To prove my point further, I can remember building a paper airplane that seemed to go nowhere when I tried to throw it. So I decided to attach a paper clip to the plane before I decided to throw it the next time to test my concept that by adding more weight to the plane that it would fly better and for longer distances. The paper airplane allowed me to model my design decision through the use of creating an artifact in that I created a paper airplane that was carrying extra weight through the incorporation of the paper clip in to the design. Also, I remember using Legos to build all sorts of creations, and these creations became artifacts of my imagination. As I further and further defined my Lego creations through the process of playing I was able to create elaborate artifacts of my imagination. These artifacts represented design decision I had made in the evolution of my creation through my child like design process. In some form or fashion the artifacts I created as a kid are very similar to the artifacts that I create when I model a software architectural concept or a software design in that the process of making decisions is directly translated in to a tangible model in the form of an architectural model. Architectural models have been defined as artifacts that depict design decisions of a system’s architecture.  The act of creating architectural models is the act of architectural modeling. Furthermore, architectural modeling is the process of creating a physical model based architectural concepts and documenting these design decisions. In the process of creating models, the standard notation used is Architectural modeling notation. This notation is the primary method of capturing the essence of design decisions regarding architecture.  Modeling notations can vary based on the need and intent of a project; typically they range from natural language to a diagram based notation. Currently, Unified Markup Language (UML) is the industry standard in terms of architectural modeling notation  because allows for architectures to be defined through a series of boxes, lines, arrows and other basic symbols that encapsulate design designs in to virtual components, connectors, configurations and interfaces.  Furthermore UML allows for additional break down of models through the use of natural language as to explain each section of the model in plain English. One of the major factors in architectural modeling is to define what is to be modeled. As a basic rule of thumb, I tend to model architecture based on the complexity of systems or sub sub-systems of architecture. Another key factor is the level of detail that is actually needed for a model. For example if I am modeling a system for a CEO to view then the low level details will be omitted. In comparison, if I was modeling a system for another engineer to actually implement I would include as much detailed information as I could to help the engineer implement my design.

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  • Was I wrong about JavaScript?

    - by jboyer
    Yes, I was. Recently, I’ve taken a good hard look at JavaScript. I’ve used it before but mostly in the capacity of web design. Using JQuery to make your web page do cool stuff is different than really creating a JavaScript application using all of the language constructs. What I’m finding as I use it more is that I may have been wrong about my assumptions about it. Let me explain.   I enjoyed doing cool stuff with JQuery but the limited experience with JavaScript as a language coupled with the bad things that I heard about it led me to not have any real interest in it. However, JavaScript is ubiquitous on the web and if I want to do any web development, which I do, I need to learn it. So here I am, diving deep into the language with the help of the JavaScript Fundamentals training course at Pluralsight (great training for a low price) and the JavaScript: The Good Parts book by Douglas Crockford.   Now, there are certainly parts of JavaScript that are bad. I think these are well known by any developer that uses it. The parts that I feel are especially egregious are the following: The global object null vs. undefined truthy and falsy limited (nearly nonexistent) scoping ‘==’ and ‘===’ (I just don’t get the reason for coercion)   However, what I am finding hiding under the covers of the bad things is a good language. I am finding that I am legitimately enjoying JavaScript. This I was not expecting. I’m not going to go into a huge dissertation on what I like about it, but some things include: Object literal notation dynamic typing functional style (JavaScript: The Good Parts describes it as LISP in C clothing) JSON (better than XML) There are parts of JavaScript that seem strange to OOP developers like myself. However, just because it is different or seems strange does not mean it is bad. Some differences are quite interesting and useful.   I feel that it is important for developers to challenge their assumptions and also to be able to admit when they are wrong on a topic. Many different situations can arise that lead to this, such as choosing the wrong technology for a problem’s solution, misunderstanding the requirements, etc. I decided to challenge my assumptions about JavaScript instead of moving straight into CoffeeScript or Dart. After exploring it, I find that I am beginning to enjoy it the more I use it. As long as there are those like Crockford to help guide me in the right way to code in JavaScript, I can create elegant and efficient solutions to problems and add another ‘arrow’ to the ‘quiver’, so to speak. I do still intend to learn CoffeeScript to see what the hub-bub is about, but now I no longer have to be afraid of JavaScript as a legitimate programming language.   Has something similar ever happened to you? Tell me about it in the comments below.

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  • WiX, MSDeploy and an appealing configuration/deployment paradigm

    - by alexhildyard
    I do a lot of application and server configuration; I've done this for many years and have tended to view the complexity of this strictly in terms of the complexity of the ultimate configuration to be deployed. For example, specific APIs aside, I would tend to regard installing a server certificate as a more complex activity than, say, copying a file or adding a Registry entry.My prejudice revolved around the idea of a sequential deployment script that not only had the explicit prescription to apply a specific server configuration, but also made the implicit presumption that the server in question was in a good known state. Scripts like this fail for hundreds of reasons -- the Default Website didn't exist; the application had already been deployed; the application had already been partially deployed and failed to rollback fully, and so on. And so the problem is that the more complex the configuration activity, the more scope for error in any individual part of that activity, and therefore the greater the chance the server in question will not end up at exactly the desired configuration level.Recently I was introduced to a completely different mindset, which, for want of a better turn of phrase, I will call the "make it so" mindset. It's extremely simple both to explain and to implement. In place of the head-down, imperative script you used to use, you substitute a set of checks -- much like exception handlers -- around each configuration activity, starting with a check of the current system state. Thus the configuration logic becomes: "IF these services aren't started then start them, and IF XYZ website doesn't exist then create it, and IF these shares don't exist then create them, and IF these shares aren't permissioned in some particular way, then permission them so." This works. Really well, in my experience. Scenario 1: You want to get a system into a good known state; it's already in a good known state; you quickly realise there is nothing to do.Scenario 2: You want to get the system into a good known state; your script is flawed or the system is bust; it cannot be put into that state. You know exactly where (at least part of) the problem is and why.Scenario 3: You want to get the system into a good known state; people are fiddling around with the system just now. That's fine. You do what you can, and later you come back and try it againScenario 4: No one wants to deploy anything; they want you to prove that the previous deployment was successful. So you re-run the deployment script with the "-WhatIf" flag. It reports that there was nothing to change. There's your proof.I mentioned two technologies in the title -- MSI and MSDeploy. I am thinking specifically of the conversation that took place here. Having worked with both technologies, I think Rob Mensching's response is appropriately nuanced, and in essence the difference is this: sometimes your target is either to achieve a specific new server state, or to rollback to a known good one. Then again, your target may be to configure what you can, and to understand what you can't. Implicitly MSDeploy's "rollback" is simply to redeploy the previous version, whereas a well-crafted MSI will actively put your system into that state without further intervention. Either way, if all goes well it will leave you with a system in one of two states, whereas MSDeploy could leave your system in one of many states. The key is that MSDeploy and MSI are complementary technologies; which suits you best depends as much on Operational guidance as your Configuration remit.What I wanted to say was that I have always been for atomic, transactional-based configuration, but having worked with the "make it so" paradigm, I have been favourably impressed by the actual results. I'm tempted to put a more technical post up on this in due course.

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  • Alternatives to multiple inheritance for my architecture (NPCs in a Realtime Strategy game)?

    - by Brettetete
    Coding isn't that hard actually. The hard part is to write code that makes sense, is readable and understandable. So I want to get a better developer and create some solid architecture. So I want to do create an architecture for NPCs in a video-game. It is a Realtime Strategy game like Starcraft, Age of Empires, Command & Conquers, etc etc.. So I'll have different kinds of NPCs. A NPC can have one to many abilities (methods) of these: Build(), Farm() and Attack(). Examples: Worker can Build() and Farm() Warrior can Attack() Citizen can Build(), Farm() and Attack() Fisherman can Farm() and Attack() I hope everything is clear so far. So now I do have my NPC Types and their abilities. But lets come to the technical / programmatical aspect. What would be a good programmatic architecture for my different kinds of NPCs? Okay I could have a base class. Actually I think this is a good way to stick with the DRY principle. So I can have methods like WalkTo(x,y) in my base class since every NPC will be able to move. But now lets come to the real problem. Where do I implement my abilities? (remember: Build(), Farm() and Attack()) Since the abilities will consists of the same logic it would be annoying / break DRY principle to implement them for each NPC (Worker,Warrior, ..). Okay I could implement the abilities within the base class. This would require some kind of logic that verifies if a NPC can use ability X. IsBuilder, CanBuild, .. I think it is clear what I want to express. But I don't feel very well with this idea. This sounds like a bloated base class with too much functionality. I do use C# as programming language. So multiple inheritance isn't an opinion here. Means: Having extra base classes like Fisherman : Farmer, Attacker won't work.

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  • Is it okay to have people with multiple roles in a Scrum team?

    - by Wayne M
    I'm evaluating some Agile-style methodologies for possible introduction to my team. With Scrum, is it allowable to have the same person perform multiple roles? We have a small team of four developers and a web designer; we don't really have a lead (I fulfill this role), QA testers or business analysts, and all of our development tasks come from the CIO. Automated testing is seen as a total waste of time, and everything focuses on speed and not quality. What will happen is the CIO will come up with a development task (whether a feature or a bug) and give it to a developer (not to the whole team, to an individual, often in private or out of the blue) who is then expected to get it completed. The CIO doesn't gather requirements beyond the initial idea (and this has bitten us before as we'll implement something only to find out that none of the end users can use the feature, because they weren't consulted or even informed about it before we developed it, and in a panic we'll be told to revert the change) but requires say in/approval of everything that we do. First things first, is a Scrum style something to consider to introduce some standards and practices? From reading, Scrum seems to rely on a bit more trust and communication and focuses more on project management than on development, which is something we are completely devoid of as we don't have any semblance of project management at present. Second, if it can work is it unreasonable for someone, let's say myself, to act as both ScrumMaster and a developer? Or for a developer to also be the Product Owner (although chances are this will be the CIO, who isn't a developer)? I realize the Scrum Master and the Product Owner should be different people but at the same time I don't think we have anyone who has the qualities of a Product Owner (chances are it would turn into a "I need all these stories, I don't care how but get it done" type of deal and/or any freeze would be unfrozen on a whim). It seems to me that I might need to pick and choose pieces of Scrum/XP/Lean to compensate for how things are done currently, as it's highly unlikely that the mentality can be changed; for instance Pair Programming would never fly (seen as a waste, you get half the tasks done if you need two people for everything), TDD would be a hard sell, but short cycles would be welcomed.

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  • Social Targeting: This One's Just for You

    - by Mike Stiles
    Think of social targeting in terms of the archery competition we just saw in the Olympics. If someone loaded up 5 arrows and shot them straight up into the air all at once, hoping some would land near the target, the world would have united in laughter. But sadly for hysterical YouTube video viewing, that’s not what happened. The archers sought to maximize every arrow by zeroing in on the spot that would bring them the most points. Marketers have always sought to do the same. But they can only work with the tools that are available. A firm grasp of the desired target does little good if the ad products aren’t there to deliver that target. On the social side, both Facebook and Twitter have taken steps to enhance targeting for marketers. And why not? As the demand to monetize only goes up, they’re quite motivated to leverage and deliver their incredible user bases in ways that make economic sense for advertisers. You could target keywords on Twitter with promoted accounts, and get promoted tweets into search. They would surface for your followers and some users that Twitter thought were like them. Now you can go beyond keywords and target Twitter users based on 350 interests in 25 categories. How does a user wind up in one of these categories? Twitter looks at that user’s tweets, they look at whom they follow, and they run data through some sort of Twitter secret sauce. The result is, you have a much clearer shot at Twitter users who are most likely to welcome and be responsive to your tweets. And beyond the 350 interests, you can also create custom segments that find users who resemble followers of whatever Twitter handle you give it. That means you can now use boring tweets to sell like a madman, right? Not quite. This ad product is still quality-based, meaning if you’re not putting out tweets that lead to interest and thus, engagement, that tweet will earn a low quality score and wind up costing you more under Twitter’s auction system to maintain. That means, as the old knight in “Indiana Jones and the Last Crusade” cautions, “choose wisely” when targeting based on these interests and categories to make sure your interests truly do line up with theirs. On the Facebook side, they’re rolling out ad targeting that uses email addresses, phone numbers, game and app developers’ user ID’s, and eventually addresses for you bigger brands. Why? Because you marketers asked for it. Here you were with this amazing customer list but no way to reach those same customers should they be on Facebook. Now you can find and communicate with customers you gathered outside of social, and use Facebook to do it. Fair to say such users are a sensible target and will be responsive to your message since they’ve already bought something from you. And no you’re not giving your customer info to Facebook. They’ll use something called “hashing” to make sure you don’t see Facebook user data (beyond email, phone number, address, or user ID), and Facebook can’t see your customer data. The end result, social becomes far more workable and more valuable to marketers when it delivers on the promise that made it so exciting in the first place. That promise is the ability to move past casting wide nets to the masses and toward concentrating marketing dollars efficiently on the targets most likely to yield results.

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  • Looking for an ultra portable laptop for Ubuntu

    - by prule
    Hi, I'm in the market for a new laptop, and portability is important since I really only use it when I'm travelling to and from work - primarily for programming. I've been searching high and low for something like this: less than 2kg hopefully Intel i5 (but negotiable) NO dvd drive - just don't need it 4G ram either 7200rpm disk or SSD (ssd preferable) 13 inch screen not too pricey (MacBook Air is about $1700 AUD) available in Australia The Dell Inspiron 13z and Lenovo Edge 13 look close, but I've not found anything that says I'm not going to have a fight with compatibility. The MacBook Air 13 looks like the PERFECT hardware, but I'm afraid it will just be easier to run MacOS than Ubuntu. I want to stay with Ubuntu, but the MacBook Air is only $1700 so I'm in danger of becoming another apple fanboi if I can't find anything competitive. Going through all the sites looking for stuff has been a huge waste of time System 76 doesn't deliver to Australia http://www.linux-laptop.net/ and http://www.linlap.com/ are hard work and not confidence inspiring http://www.vgcomputing.com.au/nsintro.html is hard work again, searching for every laptop they say has excellent compatibility on the web to find out what spec it is http://zareason.com/shop/Strata-Pro-13.html (at $1345 USD) looks interesting, but I've got no idea how much I'll get stung by customs importing Dell Inspiron 13z with i5, 4G, 320 7200rpm disk, ATI Mobility Radeon HD5430 - 1GB, Dell Wireless 1501 802.11b/g/n @ $1200 AUD seems like the only competitor but is it compatible? (Dell support offer no opinion - as far as they are concerned they only have 2 models that are certified for ubuntu) Am I worrying too much about the compatibility? Should I just go with Dell? Or switch to MacOS? (It would be good to have a searchable database that had the full machine specs, and compatibility - I'm thinking about building something... but I don't have much time right now...) Thanks. UPDATE I went with a MacBook Air. The price/weight/power was just right. Everything else was either too pricy (i5) or too heavy, or underpowered (SU7300 1.3GHz). Its a pity, because I didn't really want to leave Ubuntu. I'll still run it on my media center and spare (heavy) laptop.

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  • How do I maintain a really poorly written code base?

    - by onlineapplab.com
    Recently I got hired to work on existing web application because of NDA I'm not at liberty to disclose any details but this application is working online in sort of a beta testing stage before official launch. We have a few hundred users right now but this number is supposed to significantly increase after official launch. The application is written in PHP (but it is irrelevant to my question) and is running on a dual xeon processor standalone server with severe performance problems. I have seen a lot of bad PHP code but this really sets new standards, especially knowing how much time and money was invested in developing it. it is as badly coded as possible there is PHP, HTML, SQL mixed together and code is repeated whenever it is necessary (especially SQL queries). there are not any functions used, not mentioning any OOP there are four versions of the app (desktop, iPhone, Android + other mobile) each version has pretty much the same functionality but was created by copying the whole code base, so now there are some differences between each version and it is really hard to maintain the database is really badly designed, which is causing severe performance problems also for fixing some errors in PHP code there is a lot of database triggers used which are updating data on SELECT and on INSERT so any testing is a nightmare Basically, any sin of a bad programming you can imagine is there for example it is not only possible to use SQL injections in literally every place but you can log into app if you use a login which doesn't exist and an empty password. The team which created this app is not working on it any more and there is an outsourced team which suggested that there are some problems but was never willing to deal with the elephant in the room partially because they've got a very comfortable contract and partially due to lack of skills (just my opinion). My job was supposed to be fixing some performance problems and extending existing functionality but first thing I was asked to do was a review of the existing code base. I've made my review and it was quite a shock for the management but my conclusions were after some time finally confirmed by other programmers. Management made it clear that it is not possible to start rewriting this app from scratch (which in my opinion should be done). We have to maintain its operable state and at the same time fix performance errors and extend the functionality. My question is, as I don't want just to patch the existing code, how to transform this into properly written app while keeping the existing code working at the same time? My plan is: Unify four existing versions into common code base (fixing only most obvious errors). Redesign db and use triggers to populate it with data (so data will be maintained in two formats at the same time) All new functionality will be written as separate project. Step by step transfer existing functionality into the new project After some time everything will be in the new project Some explanation about #2, right now it is practically impossible to make any updates in existing db any change requires reviewing whole code and making changes in many places. Is such plan feasible at all? Another solution is to walk away and leave the headache to someone else.

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  • The cost of Programmer Team Clustering

    - by MarkPearl
    I recently was involved in a conversation about the productivity of programmers and the seemingly wide range in abilities that different programmers have in this industry. Some of the comments made were reiterated a few days later when I came across a chapter in Code Complete (v2) where it says "In programming specifically, many studies have shown order-of-magnitude differences in the quality of the programs written, the sizes of the programs written, and the productivity of programmers". In line with this is another comment presented by Code Complete when discussing teams - "Good programmers tend to cluster, as do bad programmers". This is something I can personally relate to. I have come across some really good and bad programmers and 99% of the time it turns out the team they work in is the same - really good or really bad. When I have found a mismatch, it hasn't stayed that way for long - the person has moved on, or the team has ejected the individual. Keeping this in mind I would like to comment on the risks an organization faces when forcing teams to remain together regardless of the mix. When you have the situation where someone is not willing to be part of the team but still wants to get a pay check at the end of each month, it presents some interesting challenges and hard decisions to make. First of all, when this occurs you need to give them an opportunity to change - for someone to change, they need to know what the problem is and what is expected. It is unreasonable to expect someone to change but have not indicated what they need to change and the consequences of not changing. If after a reasonable time of an individual being aware of the problem and not making an effort to improve you need to do two things... Follow through with the consequences of not changing. Consider the impact that this behaviour will have on the rest of the team. What is the cost of not following through with the consequences? If there is no follow through, it is often an indication to the individual that they can continue their behaviour. Why should they change if you don't care enough to keep your end of the agreement? In many ways I think it is very similar to the "Broken Windows" principles – if you allow the windows to break and don’t fix them, more will get broken. What is the cost of keeping them on? When keeping a disruptive influence in a team you risk loosing the good in the team. As Code Complete says, good and bad programmers tend to cluster - they have a tendency to keep this balance - if you are not going to help keep the balance they will. The cost of not removing a disruptive influence is that the good in the team will eventually help you maintain the clustering themselves by leaving.

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  • Fixing a NoClassDefFoundError

    - by Chris Okyen
    I have some code: package ftc; import java.util.Scanner; public class Fer_To_Cel { public static void main(String[] argv) { // Scanner object to get the temp in degrees Farenheit Scanner keyboard = new Scanner(System.in); boolean isInt = true; // temporarily put as true in case the user enters a valid int the first time int degreesF = 0; // initialy set to 0 do { try { // Input the temperature text. System.out.print("\nPlease enter a temperature (integer number, no fractional part) in degrees Farenheit: "); degreesF = Integer.parseInt(keyboard.next()); // Get user input and Assign the far. temperature variable, which is casted from String to int. } // Let the user know in a user friendly notice that the value entered wasnt an int ( give int value range ) , and then give error log catch(java.lang.Exception e) { System.out.println("Sorry but you entered a non-int value ( needs to be between ( including ) -2,147,483,648 and 2,147,483,647 ).. \n"); e.printStackTrace(); isInt = false; } } while(!isInt); System.out.println(""); // print a new line. final int degreesC = (5*(degreesF-32)/9); // convert the degrees from F to C and store the resulting expression in degreesC // Print out a newline, then print what X degrees F is in Celcius. System.out.println("\n" + degreesF + " degrees Farenheit is " + degreesC + " degrees Celcius"); } } And The following error: C:\Program Files\Java\jdk1.7.0_06\bin>java Fer_To_Cel Exception in thread "main" java.lang.NoClassDefFoundError: Fer_To_Cel (wrong name: ftc/Fer_To_Cel) at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:791) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:14 at java.net.URLClassLoader.defineClass(URLClassLoader.java:449) at java.net.URLClassLoader.access$100(URLClassLoader.java:71) at java.net.URLClassLoader$1.run(URLClassLoader.java:361) at java.net.URLClassLoader$1.run(URLClassLoader.java:355) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:354) at java.lang.ClassLoader.loadClass(ClassLoader.java:423) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308) at java.lang.ClassLoader.loadClass(ClassLoader.java:356) at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:480) The code compiled without compile errors, but presented errors during execution. Which leads me to two questions. I know Errors can be termed Compiler, Runtime and Logic Errors, but the NoClassDefFoundError inherits java.lang.LinkageError. Does that make it a Linker error, being niether of the three types of errors I listed, If I am right this is the answer. For someone else who obtains the singular .java file and compiles it, would this be the only way to solve this problem? Or can I (should I ) do/have done something to fix this problem? Basically, based on a basis of programming, is this a fault of me as the writer? Could this be done once on, my half and be distributed and not needed be done again?

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  • Portland Silverlight User Group: WP7 &amp; XNA &ndash; I survived.

    - by George Clingerman
    Last night I gave a talk to the Portland Silverlight User Group. http://www.portlandsilverlight.net/Meetings/Details/15 And I survived (which you should have probably already figured out since you’re reading this post AND that’s what I titled it…) Really though it was a fantastic time and I had a lot of fun! I was a little nervous getting ready for it, but I’m always a little nervous getting ready for things. I had the game all written,  I knew the general flow for what the talk was going to be. I read over Scott Hanselman’s 11 Top Tips for a Successful Technical presentation (which has become something I do EVERY time I’m preparing for a talk). I gave myself a brief list of points I wanted to make sure I covered or worked into the talk. But then I was ready and I waited. I hate the waiting. It makes me nervous. Once I was up in front of the room though with my laptop open and some XNA code in front of me, my nerves go away. Then I’m ready. I know XNA, I love talking about XNA and I love sharing what I know and hearing questions that make me think. And hopefully that came through while I was talking. I had a freaking blast. The swag went quickly (and I was even able to hand out some XNA 2.0 books that have been around forever!) and the pizza was been gobbled down. I started the talk at about 6:10 and managed to cover a very brief intro to programming against the game loop (it’s a different concept and one that seems to trip a lot of people up getting started with game development) and then rolled into making a basic 2D game for Windows Phone 7 using XNA. And I finished the whole thing before 8:30. Wahoo! I’m planning on posting the source code and assets on my site so those should be coming soon. And to make things even better, they recorded the whole thing on video so everyone will get to see me pretend I can speak! Just wait till you hear the new song I wrote for this talk…

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  • My co-worker has not been doing such a good job for the past decade. What do I do? [closed]

    - by stijn
    Possible Duplicate: How do I approach a coworker about his or her code quality? I started working with him almost a decade ago and back then I had never really programmed before, being a young hardware engineer. Right now however I have made quite some progress in all areas being part of software design and i am much, much more skilled than my co-worker who is 15 years older and has been programming more than twice as long. He is super nice and definitely smart enough, but lately his lack of skill and performance are starting to drag me down because we're more and more working on the same codebase. And soon we are going to do a quite ambitious start from scratch creating a whole new hard/software system. I feel it is time to address all issues now, but i do not know how to start. Here are some of the things that I would like to see him improve on: no consistent usage of style, spaces nor tabs (eg if(something ) a =b ) adds newlines around pieces of code to make it easier to read, then commits those with messages like 'no changes made' overall commit messages are useless and so are most of the comments, if there are any (eg 'remove solves for bug Rik' if Rik reported a bug). There is no function/class documentation. lots of spelling errors, in both English and native language, which sometimes are mixed 6/7/8 level deep deep nesting is no exception, a lot of functions start with one level already like if(ptr!=Null){ even when ptr is the result of allocation via new in the constructor numerous source files have over 10k lines of those lines, a major part is simply a result of copy-pasting functionality instead of using a function. This includes copying comments so we end up with 50 occurrences of var=NULL; //TODO TEST this!!!!!!! another part is hundreds of lines of dead code knows what versioning does, yet comments out old code and places new code underneath it when making changes coding skills are below par, especially for the type of rather high precision applications we do. Yet somehow, after a lot of trying and testing, stuff starts to work. But then breaks again some time later because every change casues a waterfall effect. violates every single item in the C++ FAQ lite, practices every bad practice I can think of still doesn't know how to properly use the debugger, but spends hours inspecting messy logfiles in notepad on a tiny laptop screen. Does not make any adjustments to the settings of the software he uses. Never uses keyboard shortcuts. does not seem to progress or learn new things at all. Work rather slow, mostly due to the lack of planning and incorrect usage of tools. How does one deal with this? For starters, how do I make him aware of all these problems? Should I tell the staff about it? And the next step, how to get him to learn new things and adopt another way of working?

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  • Designing a completly new database/gui solution for my compnay

    - by user1277304
    I'm no expert when it come to Everything Visual Studio 2010 and utilizing SQL server 2008. I'm sure some of my personal projects I've built for personal use would get laughed off the face of the planet, but SQLCe has been the solution I was looking for those home type of projects. And they work, flawlessly. Now I feel it's time to step up to the big league. I want to develop a complete, unified and module based solution for my compnay that I'm working for. We're still using stuff from the 80s for goodness sake! I use Excel and query the ancient database on my own because I can't stand the GUI. Nothing against people of age, but the IDE our programmers are using is from the stone age, and they use APL of all things with it. I've yet to see a radio buttton control anywhere in the GUI where it would make sense. Anyway, I want to do this right from the ground up. I'm by no means a newbie when it comes to programming in .NET 2010, however, I want the entire solution to be professionaly done. I want version control, test projects, project flow, SQL 2008 integration and all the bells and whistles that come with that. I know for a fact that if we had something like that runnning, not only would development costs and time be slashed four fold, but the possibilities for expansion and performance would sky rocket. (Between the GUI an our DB engine, it can only use ONE CORE! ONE! It's 2012 for goodness sake!) Our buisness is growing and our current ancient solution just can't keep up, and I'd hate to see our buisness go down in flames because our programmer is stuck in the 80's and refuses to use anything current. So I ask you guys, the experts and know-it-alls, where do I start? Are there any gems of good books out there in the haystack of all "This for dummies" type of deals? I already have several people backing me in this endevour, and while it may seem brash to just usurp the current programmers, I'm doing this for the company as a whole. Thank you guys for your time.

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