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• How to design a scalable notification system?

  - by Trent

  I need to write a notification system manager. Here is my requirements: I need to be able to send a Notification on different platforms, which may be totally different (for exemple, I need to be able to send either an SMS or an E-mail). Sometimes the notification may be the same for all recipients for a given platform, but sometimes it may be a notification per recipients (or several) per platform. Each notification can contain platform specific payload (for exemple an MMS can contains a sound or an image). The system need to be scalable, I need to be able to send a very large amount of notification without crashing either the application or the server. It is a two step process, first a customer may type a message and choose a platform to send to, and the notification(s) should be created to be processed either real-time either later. Then the system needs to send the notification to the platform provider. For now, I end up with some though but I don't know how scalable it will be or if it is a good design. I've though of the following objects (in a pseudo language): a generic Notification object: class Notification { String $message; Payload $payload; Collection<Recipient> $recipients; } The problem with the following objects is what if I've 1.000.000 recipients ? Even if the Recipient object is very small, it'll take too much memory. I could also create one Notification per recipient, but some platform providers requires me to send it in batch, meaning I need to define one Notification with several Recipients. Each created notification could be stored in a persistent storage like a DB or Redis. Would it be a good it to aggregate this later to make sure it is scalable? On the second step, I need to process this notification. But how could I distinguish the notification to the right platform provider? Should I use an object like MMSNotification extending an abstract Notification? or something like Notification.setType('MMS')? To allow to process a lot of notification at the same time, I think a messaging queue system like RabbitMQ may be the right tool. Is it? It would allow me to queue a lot of notification and have several worker to pop notification and process them. But what if I need to batch the recipients as seen above? Then I imagine a NotificationProcessor object for which I could I add NotificationHandler each NotificationHandler would be in charge to connect the platform provider and perform notification. I can also use an EventManager to allow pluggable behavior. Any feedbacks or ideas? Thanks for giving your time. Note: I'm used to work in PHP and it is likely the language of my choice.

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• It's called College.

  - by jeffreyabecker

  Today I saw yet another 'GUID vs int as your primary key' article. Like most of the ones I've read this was filled with technical misrepresentations and out-right fallices. Chef's famous line that "There's a time and a place for everything children" applies here. GUIDs have distinct advantages and disadvantages which should be considered when choosing a data type for the primary key. Fallacy 1: "Its easier" An integer data type(tinyint, smallint, int, bigint) is a better artifical key than a GUID because its easier to remember. I'm a firm believer that your artifical primary keys should be opaque gibberish. PK's are an implementation detail which should never be exposed to the user or relied on for business logic. If you want things to come back in an order, add and ORDER BY clause and SortOrder fields. If you want a human-usable look-up add a business key with a unique constraint. If you want to know what order things were inserted into a table add a timestamp. Fallacy 2: "Size Matters" For many applications, the size of the artifical primary key is going to be irrelevant. The particular article which kicked this post off stated repeatedly that joining against an int has better performance than joining against a GUID. In computer science the performance of your algorithm is always a function of the number of data points. This still holds true for databases. Unless your table is very large, the performance difference between an int and a guid probably isnt going to be mesurable let alone noticeable. My personal experience is that the performance becomes an issue when you start having billions of rows in the table. At this point, you should probably start looking to move from int to bigint so the effective space/performance gain isnt as much as you'd think. GUID Advantages: Insert-ability / Mergeability: You can reliably insert guids into tables without key collisions. Database Independence: Saving entities to the database often requires knowing ids. With identity based ids the id must be selected back after every insert. GUIDs can be generated application-side allowing much faster inserts. GUID Disadvantages: Generatability: You can calculate the next id for an integer pk pretty easily in your head but will need a program to generate GUIDs. Solution: "Select top 100 newid() from sysobjects" Fragmentation: most GUID generation algorithms generate pseudo random GUIDs. This can cause inserts into the middle of your clustered index. Solutions: add a default of newsequentialid() or use GuidComb in NHibernate.

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• ArchBeat Link-o-Rama for 2012-07-11

  - by Bob Rhubart

  Is the future of retail showrooming? | GigaOm "The digital shopper isn’t just digital and she expects to be served seamlessly across all channels, physical and digital," reports GigaOm. Twenty years into the Internet era and the changes just keep coming. Solution architects take note... Agile Bureaucracy: When Practices become Principles | Jim Highsmith.com "Principles and values are a critical part of keeping individuals in organizations aligned and engaged," says Agile guru Jim Highsmith, "but the more pseudo-principles are piled on top of principles, the less and less organizations are able to adapt." Oracle Fusion Applications 11g Basics | Michel Schildmeijer "We are trying to build up a Oracle Fusion Apps environment on a Exalogic system, though still on bare metal, because officially there still is no Oracle VM available yet on Exalogic," says Michel Schildmeijer, an Oracle Fusion Middleware Architect at Qualogy. "It is a bit of a challenge, but getting to know the basics and which components the install, build and configure phase use, might bring you a step further on the way." Process Centric Banking: Loan Origination Solution | Manish Palaparthy This interesting, detailed post by Manish Palaparthy explains the process behind the execution of a proof-of-concept for a Fusion Middleware-based loan-origination solution for a bank. The solution incorporates Oracle BPM Suite, Webcenter, and ADF technolgies in a SOA infrastructure. How eBay and Facebook are Cleaning Up Data Centers | Amy Gallo - HBR The Cloud has needs! As reported by Amy Gallo in an article in the Harvard Business Review, "The electricity demand of data centers and the telecommunications network is rivaling that of most nations. If the cloud were itself a country, it would rank fifth in the world on energy demand behind the U.S., China, Russia, and Japan." Do WebLogic configuration from ANT | Edwin Biemond "With WebLogic WLST you can script the creation of all your Application DataSources or SOA Integration artifacts( like JMS etc)," says Oracle ACE Edwin Biemond. "This is necessary if your domain contains many WebLogic artifacts or you have more then one WebLogic environment. If so, you want to script this so you can configure a new WebLogic domain in minutes and you can repeat this task with always the same result." Oracle Special-Edition E-Book: Cloud Architecture for Dummies Learn how to architect and model your cloud implementation to drive efficiency and leverage economies of scale with Cloud Architecture for Dummies, a free Oracle e-book. (Registration required.) Thought for the Day "One of the best things to come out of the home computer revolution could be the general and widespread understanding of how severely limited logic really is." — Frank Herbert Source: SoftwareQuotes.com

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• GPU hung when switching graphic card

  - by Lie Ryan

  I have a laptop (Dell Inspiron N4110) with a switchable graphic. $ lspci | grep VGA 00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) 01:00.0 VGA compatible controller: ATI Technologies Inc NI Whistler [AMD Radeon HD 6600M Series] (rev ff) Normally, my laptop starts with both graphic cards enabled, which caused the laptop to turn very hot and the fan to become very noisy. I have been using a small script to disable the Radeon card. For some time, I'm quite happy with this arrangement. However, I have been having some issues with the Intel card (IGD), the Intel card often randomly hang when running OpenGL apps; and so I want to give the Radeon card (DIS) another chance. I have never been able to switch to the Radeon card, but recently, I found out that if I do a "delayed switching" (DDIS): # echo "DDIS" > /sys/kernel/debug/vgaswitcheroo/switch root@lieryan-dell-ubuntu:/sys/kernel/debug/vgaswitcheroo# cat switch 0:IGD:+:Pwr:0000:00:02.0 1:DIS: :Pwr:0000:01:00.0 then I logoff (i.e. to restart X), the screen switch to pseudo-tty and then it stuck there freezing. At this situation, mouse and keyboard stops working so I can't switch to another ptty. I tried ssh-ing from another computer to salvage logs (dmesg at that point) and whatnot; I found out that when freezing, the active graphic card is the AMD card: -- this is from ssh -- # cat switch 0:IGD: :Off:0000:00:02.0 1:DIS:+:Pwr:0000:01:00.0 but the GPU is apparently hung, looking at dmesg gives: ... [ 1411.649974] vga_switcheroo: client 0 refused switch [ 1411.649985] vga_switcheroo: setting delayed switch to client 1 [ 1423.911759] vga_switcheroo: processing delayed switch to 1 [ 1424.006564] fbcon: Remapping primary device, fb1, to tty 1-63 [ 1424.006799] i915: switched off [ 1424.840351] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id [ 1425.718088] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id [ 1426.622377] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id [ 1427.355683] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id [ 1428.193549] [drm:drm_mode_getfb] *ERROR* invalid framebuffer id ... the invalid framebuffer id error is repeated for many times over ... I were able to successfully recover by switching back to the Intel card and restarting X from ssh; indicating that only the Radeon card has problems switching. System info: $ uname -a Linux lieryan-dell-ubuntu 3.0.0-14-generic #23-Ubuntu SMP Mon Nov 21 20:28:43 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 11.10 Release: 11.10 Codename: oneiric The laptop also do not have the option to set graphic card at BIOS and the proprietary driver, fglrx, also have never worked; when I installed it through jockey ("Additional Drivers"), glxinfo showed that it still being rendered by Mesa, the /sys/kernel/debug/vgaswitcheroo directory has gone missing, and the driver crashes with a traceback if I use xorg.conf to tell X to use fglrx. Anyone had any idea if it is possible to use this AMD card either with the radeon or the fglrx driver? logs: dmesg

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• Drawing multiple objects from one Vertex Buffer Object in OpenGL/OpenTK

  - by stoney78us

  I am trying to experimenting drawing method using VBO in OpenGL. Many people normally use 1 vbo to store one object data array. I was trying to do something quite opposite which is storing multiple object data into 1 vbo then drawing it. There is story behind why i want to do this. I want to group many of objects as a single object sometime. However my code doesn't do the justice. Following is my pseudo code: //Data double[] vertices = {line strip 1, line strip 2, line strip 3}; //series of vertices int linestrip1offset = index of the first vertex in line strip 1; int linestrip2offset = index of the first vertex in line strip 2; int linestrip3offset = index of the first vertex in line strip 3; int linestrip1VertexNum = number of vertices in linestrip 1; int linestrip2VertexNum = number of vertices in linestrip 2; int linestrip3VertexNum = number of vertices in linestrip 3; //Setting Up void init() { int[] vBO = new int[1]; GL.GenBuffer(1, vBO); GL.BindBuffer(BufferTarget.ArrayBuffer, vBO[0]); GL.BufferData(BufferTarget.ArrayBuffer, new IntPtr(_vertices.Length * sizeof(double)), _vertices, BufferUsageHint.StaticDraw); GL.EnableClientState(Array.VertexArray); } //Drawing void draw() { GL.BindBuffer(BufferTarget.ArrayBuffer, vBO[0]); GL.EnableClientState(ArrayCap.VertexArray); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip1offset); //drawing first linestrip GL.DrawArrays(drawMode, linestrip1offset , linestrip1VertexNum ); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip2offset); //drawing second linestrip GL.DrawArrays(drawMode, linestrip2offset , linestrip2VertexNum ); GL.VertexPointer(3, VertexPointerType.Double, 0, linestrip3offset); //drawing third linestrip GL.DrawArrays(drawMode, linestrip3offset , linestrip3VertexNum ); GL.DisableClientState(ArrayCap.VertexArray); GL.BindBuffer(BufferTarget.ArrayBuffer, 0); } I don't know what i did wrong but i think technically it should work where we can tell OpenGL which part of the data in the vBO to be drawn.

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• Power Distribution amongst connected nodes

  - by Perky

  In my game the map is represented by connected nodes, each node has a number of connected nodes. The nodes represent a system in which players can build structures and move units about. If you're familiar with Sins of a Solar Empire the game map is very similar. I want each node to be able to produce power and share it with all connected nodes. For example if A, B, C & D are all connected and produce 100 power units, then each system should have 400 power units available. If node B builds a structure that consumes 100 power units then A, B, C & D should then have 300 power units available. I've been working on this system all day and haven't been able to get it working quite the way I want. My current implementation is to first recurse through each nodes's connected node adding up the power, I keep a list of closed nodes so it doesn't loop, it's quite similar to A* actually. Pseudo code: All nodes start with the properties node.power = 0 node.basePower = 100 // could be different for each node. node.initialPower = node.basePower - function propagatePower( node, initialPower, closedNodes ) node.power += initialPower add( closedNodes, node ) connectedNodes = connected_nodes_except_from( closedNodes ) foreach node in connectedNodes do propagatePower( node, initialPower, closedNodes ) end end After this I iterate through all power consumers. foreach consumer in consumers do node = consumer.parentNode if node.power >= consumer.powerConsumption then consumer.powerConsumed += consumer.powerConsumption node.producedPower -= consumer.powerConsumption end end Then I adjust the initial power for the next propagation cycle. foreach node in nodes do node.initialPower = node.basePower - node.producedPower node.displayPower = node.power // for rendering the power. node.power = 0 end This seemed to work at first but then I came into a problem. Say two nodes A & B produce 100Pu each, it's shared so both A & B have 200Pu. I then make two structures that consume 80Pu each on A (160Pu). Then the nodes power is adjusted to basePower - producedPower (100-160 = -60). Nodes are propagated, both nodes now have 40Pu (A: -60 + B: 100 = 40). Which is correct because they started with 200Pu - 160Pu = 40Pu. However now node.power >= consumer.powerConsumption is false. Whats worse is it's false for any structure that uses more that 40Pu, so the whole system goes down. I could deduct from consumer.powerConsumption but what do I do if power is reduced elsewhere? I don't have the correct data to perform the necessary checks. It's late so I'm probably not thinking straight but I thought to ask on here to see if anyone has any other implementations, better or worse I'd be interested to know.

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• In a state machine, is it a good idea to separate states and transitions?

  - by codablank1

  I have implemented a small state machine in this way (in pseudo code): class Input {} class KeyInput inherits Input { public : enum { Key_A, Key_B, ..., } } class GUIInput inherits Input { public : enum { Button_A, Button_B, ..., } } enum Event { NewGame, Quit, OpenOptions, OpenMenu } class BaseState { String name; Event get_event (Input input); void handle (Event e); //event handling function } class Menu inherits BaseState{...} class InGame inherits BaseState{...} class Options inherits BaseState{...} class StateMachine { public : BaseState get_current_state () { return current_state; } void add_state (String name, BaseState state) { statesMap.insert(name, state);} //raise an exception if state not found BaseState get_state (String name) { return statesMap.find(name); } //raise an exception if state or next_state not found void add_transition (Event event, String state_name, String next_state_name) { BaseState state = get_state(state_name); BaseState next_state = get_state(next_state_name); transitionsMap.insert(pair<event, state>, next_state); } //raise exception if couple not found BaseState get_next_state(Event event, BaseState state) { return transitionsMap.find(pair<event, state>); } void handle(Input input) { Event event = current_state.get_event(input) current_state.handle(event); current_state = get_next_state(event, current_state); } private : BaseState current_state; map<String, BaseState> statesMap; //map of all states in the machine //for each couple event/state, this map stores the next state map<pair<Event, BaseState>, BaseState> transitionsMap; } So, before getting the transition, I need to convert the key input or GUI input to the proper event, given the current state; thus the same key 'W' can launch a new game in the 'Menu' state or moving forward a character in the 'InGame' state; Then I get the next state from the transitionsMap and I update the current state Does this configuration seem valid to you ? Is it a good idea to separate states and transitions ? And I have some kind of trouble to represent a 'null state' or a 'null event'; What initial value can I give to the current state and which one should be returned by get_state if it fails ?

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• Understanding how OpenGL blending works

  - by yuumei

  I am attempting to understand how OpenGL (ES) blending works. I am finding it difficult to understand the documentation and how the results of glBlendFunc and glBlendEquation effect the final pixel that is written. Do the source and destination out of glBlendFunc get added together with GL_FUNC_ADD by default? This seems wrong because "basic" blending of GL_ONE, GL_ONE would output 2,2,2,2 then (Source giving 1,1,1,1 and dest giving 1,1,1,1). I have written the following pseudo-code, what have I got wrong? struct colour { float r, g, b, a; }; colour blend_factor( GLenum factor, colour source, colour destination, colour blend_colour ) { colour colour_factor; float i = min( source.a, 1 - destination.a ); // From http://www.khronos.org/opengles/sdk/docs/man/xhtml/glBlendFunc.xml switch( factor ) { case GL_ZERO: colour_factor = { 0, 0, 0, 0 }; break; case GL_ONE: colour_factor = { 1, 1, 1, 1 }; break; case GL_SRC_COLOR: colour_factor = source; break; case GL_ONE_MINUS_SRC_COLOR: colour_factor = { 1 - source.r, 1 - source.g, 1 - source.b, 1 - source.a }; break; // ... } return colour_factor; } colour blend( colour & source, colour destination, GLenum source_factor, // from glBlendFunc GLenum destination_factor, // from glBlendFunc colour blend_colour, // from glBlendColor GLenum blend_equation // from glBlendEquation ) { colour source_colour = blend_factor( source_factor, source, destination, blend_colour ); colour destination_colour = blend_factor( destination_factor, source, destination, blend_colour ); colour output; // From http://www.khronos.org/opengles/sdk/docs/man/xhtml/glBlendEquation.xml switch( blend_equation ) { case GL_FUNC_ADD: output = add( source_colour, destination_colour ); case GL_FUNC_SUBTRACT: output = sub( source_colour, destination_colour ); case GL_FUNC_REVERSE_SUBTRACT: output = sub( destination_colour, source_colour ); } return output; } void do_pixel() { colour final_colour; // Blending if( enable_blending ) { final_colour = blend( current_colour_output, framebuffer[ pixel ], ... ); } else { final_colour = current_colour_output; } } Thanks!

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• How do we provide valid time estimates during Sprint Planning without doing "too much" design?

  - by Michael Edenfield

  My team is getting up to speed with Scrum, but most of us are more familiar with non-agile or "pseudo-"agile methodologies. The part that is the biggest hurdle for us is running an efficient Sprint Planning meeting where we break our backlog items into tasks, and estimate hours. (I'm using the terminology from the VS2010 Scrum Template; apologies if I use the wrong word somewhere.) When we try to figure out how long a task is going to take, we often fall into the trap of designing the feature at the code level -- table layout, interfaces, etc -- in order to figure out how long that's going to take. I'm pretty sure this is not the appropriate place to be doing that kind of design. We should be scheduling tasks for these design meetings during the sprint. However, we are having trouble figuring out how else to come up with meaningful estimates for the tasks. Are there any practical habits/techniques/etc. for making a judgement call about how long a feature is going to take, without knowing how you plan to implement it? If our time estimates are going to change significantly once the design has been completed, how can we properly budget our Sprint backlog ahead of time? EDIT: Just to clarify, since some of the comments/answers are very valid but I think addressing the wrong question. We know that what we're doing is not right, and that we should be building time into the sprint for this design. Conceptually all of the developers understand that. We also also bringing in a team member with Scrum experience to keep us on track if we start going off into the weeds. The problem is that, without going through this design process, we are finding it difficult to provide concrete time estimates for anything. We are constantly saying things like "well if we design it this way it might take 8 hours but if we end up having to do this other way instead that will take about 32 but it might not be as bad once we start trying to write it...". I also assume that this process will get better once we have some historical velocity to work from, but many of the technologies and architectural patterns we are using are new to us. But if potentially-wildly-wrong estimates are just a natural part of adapting this process then we will just need to recondition ourselves to accept that :)

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• Why do old programming languages continue to be revised?

  - by SunAvatar

  This question is not, "Why do people still use old programming languages?" I understand that quite well. In fact the two programming languages I know best are C and Scheme, both of which date back to the 70s. Recently I was reading about the changes in C99 and C11 versus C89 (which seems to still be the most-used version of C in practice and the version I learned from K&R). Looking around, it seems like every programming language in heavy use gets a new specification at least once per decade or so. Even Fortran is still getting new revisions, despite the fact that most people using it are still using FORTRAN 77. Contrast this with the approach of, say, the typesetting system TeX. In 1989, with the release of TeX 3.0, Donald Knuth declared that TeX was feature-complete and future releases would contain only bug fixes. Even beyond this, he has stated that upon his death, "all remaining bugs will become features" and absolutely no further updates will be made. Others are free to fork TeX and have done so, but the resulting systems are renamed to indicate that they are different from the official TeX. This is not because Knuth thinks TeX is perfect, but because he understands the value of a stable, predictable system that will do the same thing in fifty years that it does now. Why do most programming language designers not follow the same principle? Of course, when a language is relatively new, it makes sense that it will go through a period of rapid change before settling down. And no one can really object to minor changes that don't do much more than codify existing pseudo-standards or correct unintended readings. But when a language still seems to need improvement after ten or twenty years, why not just fork it or start over, rather than try to change what is already in use? If some people really want to do object-oriented programming in Fortran, why not create "Objective Fortran" for that purpose, and leave Fortran itself alone? I suppose one could say that, regardless of future revisions, C89 is already a standard and nothing stops people from continuing to use it. This is sort of true, but connotations do have consequences. GCC will, in pedantic mode, warn about syntax that is either deprecated or has a subtly different meaning in C99, which means C89 programmers can't just totally ignore the new standard. So there must be some benefit in C99 that is sufficient to impose this overhead on everyone who uses the language. This is a real question, not an invitation to argue. Obviously I do have an opinion on this, but at the moment I'm just trying to understand why this isn't just how things are done already. I suppose the question is: What are the (real or perceived) advantages of updating a language standard, as opposed to creating a new language based on the old?

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• Rending 2D Tile World (With Player In The Middle)

  - by Mick

  What I have at the moment is a series of data structures I'm using, and I would like to render the world onto the screen (just the visible parts). I've actually already done this several times (lots of rewrites), but it's a bit buggy (rounding seems to make the screen jump ever so slightly every x tiles the player walks past). Basically I've been confusing myself heavily on what I feel should be a pretty simple problem... so here I am asking for some help! OK! So I have a 50x50 array holding the tiles of the world. I have the player position as 2 floats, x ([0, 49]) and y ([0, 49]) in that array. I have the application size exactly in pixels (x and y). I have an arbitrary TILE_SIZE static int (based on screen pixels). What I think is heavily confusing me is using a 2d orthogonal projection in opengl which maps (0,0) to the top left of the screen and (SCREEN_SIZE_X, SCREEN_SIZE_Y) to the bottom right of the screen. gl.glMatrixMode(GL.GL_PROJECTION); gl.glLoadIdentity(); glu.gluOrtho2D(0, getActualWidth(), getActualHeight(), 0); gl.glMatrixMode(GL.GL_MODELVIEW); gl.glLoadIdentity(); The map tiles are set so that the (0,0) in the array is the bottom left. And the player has to be in the middle on the screen (SCREEN_SIZE_X/2, SCREEN_SIZE_Y/2). What I've been doing so far is trying to render 1-2 tiles more all around what would be displayed on the screen so that I don't have to worry about figuring out rendering half a tile from the top left, depending where the player is. It seems like such an easy problem but after spending about 40+hours on it rewriting it many times I think I'm at a point where I just can't think clearly anymore... Any help would be appreciated. It would be great if someone can provide some very basic pseudo code on keeping the player in the middle when your projection is mapped to screen coordinates and only rendering basically the tiles that you would be any be see. Thanks!

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• Checking timeouts made more readable

  - by Markus

  I have several situations where I need to control timeouts in a technical application. Either in a loop or as a simple check. Of course – handling this is really easy, but none of these is looking cute. To clarify, here is some C# (Pseudo) code: private DateTime girlWentIntoBathroom; girlWentIntoBathroom = DateTime.Now; do { // do something } while (girlWentIntoBathroom.AddSeconds(10) > DateTime.Now); or if (girlWentIntoBathroom.AddSeconds(10) > DateTime.Now) MessageBox.Show("Wait a little longer"); else MessageBox.Show("Knock louder"); Now I was inspired by something a saw in Ruby on StackOverflow: Now I’m wondering if this construct can be made more readable using extension methods. My goal is something that can be read like “If girlWentIntoBathroom is more than 10 seconds ago” 1st attempt if (girlWentIntoBathroom > (10).Seconds().Ago()) MessageBox.Show("Wait a little longer"); else MessageBox.Show("Knock louder"); So I wrote an extension for integer that converts the integer into a TimeSpan public static TimeSpan Seconds(this int amount) { return new TimeSpan(0, 0, amount); } After that, I wrote an extension for TimeSpan like this: public static DateTime Ago(this TimeSpan diff) { return DateTime.Now.Add(-diff); } This works fine so far, but has a great disadvantage. The logic is inverted! Since girlWentIntoBathroom is a timestamp in the past, the right side of the equation needs to count backwards: impossible. Just inverting the equation is no solution, because it will invert the read sentence as well. 2nd attempt So I tried something new: if (girlWentIntoBathroom.IsMoreThan(10).SecondsAgo()) MessageBox.Show("Knock louder"); else MessageBox.Show("Wait a little longer"); IsMoreThan() needs to transport the past timestamp as well as the span for the extension SecondsAgo(). It could be: public static DateWithIntegerSpan IsMoreThan(this DateTime baseTime, int span) { return new DateWithIntegerSpan() { Date = baseTime, Span = span }; } Where DateWithIntegerSpan is simply: public class DateWithIntegerSpan { public DateTime Date {get; set;} public int Span { get; set; } } And SecondsAgo() is public static bool SecondsAgo(this DateWithIntegerSpan dateAndSpan) { return dateAndSpan.Date.Add(new TimeSpan(0, 0, dateAndSpan.Span)) < DateTime.Now; } Using this approach, the English sentence matches the expected behavior. But the disadvantage is, that I need a helping class (DateWithIntegerSpan). Has anyone an idea to make checking timeouts look more cute and closer to a readable sentence? Am I a little too insane thinking about something minor like this?

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• Tiling Problem Solutions for Various Size "Dominoes"

  - by user67081

  I've got an interesting tiling problem, I have a large square image (size 128k so 131072 squares) with dimensons 256x512... I want to fill this image with certain grain types (a 1x1 tile, a 1x2 strip, a 2x1 strip, and 2x2 square) and have no overlap, no holes, and no extension past the image boundary. Given some probability for each of these grain types, a list of the number required to be placed is generated for each. Obviously an iterative/brute force method doesn't work well here if we just randomly place the pieces, instead a certain algorithm is required. 1) all 2x2 square grains are randomly placed until exhaustion. 2) 1x2 and 2x1 grains are randomly placed alternatively until exhaustion 3) the remaining 1x1 tiles are placed to fill in all holes. It turns out this algorithm works pretty well for some cases and has no problem filling the entire image, however as you might guess, increasing the probability (and thus number) of 1x2 and 2x1 grains eventually causes the placement to stall (since there are too many holes created by the strips and not all them can be placed). My approach to this solution has been as follows: 1) Create a mini-image of size 8x8 or 16x16. 2) Fill this image randomly and following the algorithm specified above so that the desired probability of the entire image is realized in the mini-image. 3) Create N of these mini-images and then randomly successively place them in the large image. Unfortunately there are some downfalls to this simplification. 1) given the small size of the mini-images, nailing an exact probability for the entire image is not possible. Example if I want p(2x1)=P(1x2)=0.4, the mini image may only give 0.41 as the closes probability. 2) The mini-images create a pseudo boundary where no overlaps occur which isn't really descriptive of the model this is being used for. 3) There is only a fixed number of mini-images so i'm not sure how random this really is. I'm really just looking to brainstorm about possible solutions to this. My main concern is really to nail down closer probabilities, now one might suggest I just increase the mini-image size. Well I have, and it turns out that in certain cases(p(1x2)=p(2x1)=0.5) the mini-image 16x16 isn't even iteratively solvable.. So it's pretty obvious how difficult it is to randomly solve this for anything greater than 8x8 sizes.. So I'd love to hear some ideas. Thanks

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• Reasons NOT to use JSF [closed]

  - by Vain Fellowman

  I am new to StackExchange, but I figured you would be able to help me. We're crating a new Java Enterprise application, replacing an legacy JSP solution. Due to many many changes, the UI and parts of the business logic will completely be rethought and reimplemented. Our first thought was JSF, as it is the standard in Java EE. At first I had a good impression. But now I am trying to implement a functional prototype, and have some really serious concerns about using it. First of all, it creates the worst, most cluttered invalid pseudo-HTML/CSS/JS mix I've ever seen. It violates every single rule I learned in web-development. Furthermore it throws together, what never should be so tightly coupled: Layout, Design, Logic and Communication with the server. I don't see how I would be able to extend this output comfortably, whether styling with CSS, adding UI candy (like configurable hot-keys, drag-and-drop widgets) or whatever. Secondly, it is way too complicated. Its complexity is outstanding. If you ask me, it's a poor abstraction of basic web technologies, crippled and useless in the end. What benefits do I have? None, if you think about. Hundreds of components? I see ten-thousands of HTML/CSS snippets, ten-thousands of JavaScript snippets and thousands of jQuery plug-ins in addition. It solves really many problems - we wouldn't have if we wouldn't use JSF. Or the front-controller pattern at all. And Lastly, I think we will have to start over in, say 2 years. I don't see how I can implement all of our first GUI mock-up (Besides; we have no JSF Expert in our team). Maybe we could hack it together somehow. And then there will be more. I'm sure we could hack our hack. But at some point, we'll be stuck. Due to everything above the service tier is in control of JSF. And we will have to start over. My suggestion would be to implement a REST api, using JAX-RS. Then create a HTML5/Javascript client with client side MVC. (or some flavor of MVC..) By the way; we will need the REST api anyway, as we are developing a partial Android front-end, too. I doubt, that JSF is the best solution nowadays. As the Internet is evolving, I really don't see why we should use this 'rake'. Now, what are pros/cons? How can I emphasize my point to not use JSF? What are strong points to use JSF over my suggestion?

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• How to avoid the Portlet Skin mismatch

  - by Martin Deh

  here are probably many on going debates whether to use portlets or taskflows in a WebCenter custom portal application.  Usually the main battle on which side to take in these debates are centered around which technology enables better performance.  The good news is that both of my colleagues, Maiko Rocha and George Maggessy have posted their respective views on this topic so I will not have to further the discussion.  However, if you do plan to use portlets in a WebCenter custom portal application, this post will help you not have the "portlet skin mismatch" issue.   An example of the presence of the mismatch can be view from the applications log: The skin customsharedskin.desktop specified on the requestMap will be used even though the consumer's skin's styleSheetDocumentId on the requestMap does not match the local skin's styleSheetDocument's id. This will impact performance since the consumer and producer stylesheets cannot be shared. The producer styleclasses will not be compressed to avoid conflicts. A reason the ids do not match may be the jars are not identical on the producer and the consumer. For example, one might have trinidad-skins.xml's skin-additions in a jar file on the class path that the other does not have. Notice that due to the mismatch the portlet's CSS will not be able to be compressed, which will most like impact performance in the portlet's consuming portal. The first part of the blog will define the portlet mismatch and cover some debugging tips that can help you solve the portlet mismatch issue.  Following that I will give a complete example of the creating, using and sharing a shared skin in both a portlet producer and the consumer application. Portlet Mismatch Defined  In general, when you consume/render an ADF page (or task flow) using the ADF Portlet bridge, the portlet (producer) would try to use the skin of the consumer page - this is called skin-sharing. When the producer cannot match the consumer skin, the portlet would generate its own stylesheet and reference it from its markup - this is called mismatched-skin. This can happen because: The consumer and producer use different versions of ADF Faces, or The consumer has additional skin-additions that the producer doesn't have or vice-versa, or The producer does not have the consumer skin For case (1) & (2) above, the producer still uses the consumer skin ID to render its markup. For case (3), the producer would default to using portlet skin. If there is a skin mis-match then there may be a performance hit because: The browser needs to fetch this extra stylesheet (though it should be cached unless expires caching is turned off) The generated portlet markup uses uncompressed styles resulting in a larger markup It is often not obvious when a skin mismatch occurs, unless you look for either of these indicators: The log messages in the producer log, for example: The skin blafplus-rich.desktop specified on the requestMap will not be used because the styleSheetDocument id on the requestMap does not match the local skin's styleSheetDocument's id. It could mean the jars are not identical. For example, one might have trinidad-skins.xml's skin-additions in a jar file on the class path that the other does not have. View the portlet markup inside the iframe, there should be a <link> tag to the portlet stylesheet resource like this (note the CSS is proxied through consumer's resourceproxy): <link rel=\"stylesheet\" charset=\"UTF-8\" type=\"text/css\" href=\"http:.../resourceproxy/portletId...252525252Fadf%252525252Fstyles%252525252Fcache%252525252Fblafplus-rich-portlet-d1062g-en-ltr-gecko.css... Using HTTP monitoring tool (eg, firebug, httpwatch), you can see a request is made to the portlet stylesheet resource (see URL above) There are a number of reasons for mismatched-skin. For skin to match the producer and consumer must match the following configurations: The ADF Faces version (different versions may have different style selectors) Style Compression, this is defined in the web.xml (default value is false, i.e. compression is ON) Tonal styles or themes, also defined in the web.xml via context-params The same skin additions (jars with skin) are available for both producer and consumer.  Skin additions are defined in the trinidad-skins.xml, using the <skin-addition> tags. These are then aggregated from all the jar files in the classpath. If there's any jar that exists on the producer but not the consumer, or vice veras, you get a mismatch. Debugging Tips  Ensure the style compression and tonal styles/themes match on the consumer and producer, by looking at the web.xml documents for the consumer & producer applications It is bit more involved to determine if the jars match.  However, you can enable the Trinidad logging to show which skin-addition it is processing.  To enable this feature, update the logging.xml log level of both the producer and consumer WLS to FINEST.  For example, in the case of the WebLogic server used by JDeveloper: $JDEV_USER_DIR/system<version number>/DefaultDomain/config/fmwconfig/servers/DefaultServer/logging.xml Add a new entry: <logger name="org.apache.myfaces.trinidadinternal.skin.SkinUtils" level="FINEST"/> Restart WebLogic.  Run the consumer page, you should see the following logging in both the consumer and producer log files. Any entries that don't match is the cause of the mismatch.  The following is an example of what the log will produce with this setting: [SRC_CLASS: org.apache.myfaces.trinidadinternal.skin.SkinUtils] [APP: WebCenter] [SRC_METHOD: _getMetaInfSkinsNodeList] Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.skin/in1ar8/APP-INF/lib/announcement-skin.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.skin/in1ar8/APP-INF/lib/calendar-skin.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.skin/in1ar8/APP-INF/lib/custComps-skin.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.skin/in1ar8/APP-INF/lib/forum-skin.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.skin/in1ar8/APP-INF/lib/page-service-skin.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.skin/in1ar8/APP-INF/lib/peopleconnections-kudos-skin.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.skin/in1ar8/APP-INF/lib/peopleconnections-wall-skin.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.skin/in1ar8/APP-INF/lib/portlet-client-adf-skin.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.skin/in1ar8/APP-INF/lib/rtc-skin.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.skin/in1ar8/APP-INF/lib/serviceframework-skin.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.skin/in1ar8/APP-INF/lib/smarttag-skin.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.skin/in1ar8/APP-INF/lib/spaces-service-skins.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/oracle.webcenter.composer/3yo7j/WEB-INF/lib/custComps-skin.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/adf.oracle.domain.webapp/q433f9/WEB-INF/lib/adf-richclient-impl-11.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/adf.oracle.domain.webapp/q433f9/WEB-INF/lib/dvt-faces.jar!/META-INF/trinidad-skins.xml Processing skin URL:zip:/tmp/_WL_user/adf.oracle.domain.webapp/q433f9/WEB-INF/lib/dvt-trinidad.jar!/META-INF/trinidad-skins.xml   The Complete Example The first step is to create the shared library.  The WebCenter documentation covering this is located here in section 15.7.  In addition, our ADF guru Frank Nimphius also covers this in hes blog.  Here are my steps (in JDeveloper) to create the skin that will be used as the shared library for both the portlet producer and consumer. Create a new Generic Application Give application name (i.e. MySharedSkin) Give a project name (i.e. MySkinProject) Leave Project Technologies blank (none selected), and click Finish Create the trinidad-skins.xml Right-click on the MySkinProject node in the Application Navigator and select "New" In the New Galley, click on "General", select "File" from the Items, and click OK In the Create File dialog, name the file trinidad-skins.xml, and (IMPORTANT) give the directory path to MySkinProject\src\META-INF In the trinidad-skins.xml, complete the skin entry.  for example: <?xml version="1.0" encoding="windows-1252" ?> <skins xmlns="http://myfaces.apache.org/trinidad/skin">   <skin>     <id>mysharedskin.desktop</id>     <family>mysharedskin</family>     <extends>fusionFx-v1.desktop</extends>     <style-sheet-name>css/mysharedskin.css</style-sheet-name>   </skin> </skins> Create CSS file In the Application Navigator, right click on the META-INF folder (where the trinidad-skins.xml is located), and select "New" In the New Gallery, select Web-Tier-> HTML, CSS File from the the Items and click OK In the Create Cascading Style Sheet dialog, give the name (i.e. mysharedskin.css) Ensure that the Directory path is the under the META-INF (i.e. MySkinProject\src\META-INF\css) Once the new CSS opens in the editor, add in a style selector.  For example, this selector will style the background of a particular panelGroupLayout: af|panelGroupLayout.customPGL{     background-color:Fuchsia; } Create the MANIFEST.MF (used for deployment JAR) In the Application Navigator, right click on the META-INF folder (where the trinidad-skins.xml is located), and select "New" In the New Galley, click on "General", select "File" from the Items, and click OK In the Create File dialog, name the file MANIFEST.MF, and (IMPORTANT) ensure that the directory path is to MySkinProject\src\META-INF Complete the MANIFEST.MF, where the extension name is the shared library name Manifest-Version: 1.1 Created-By: Martin Deh Implementation-Title: mysharedskin Extension-Name: mysharedskin.lib.def Specification-Version: 1.0.1 Implementation-Version: 1.0.1 Implementation-Vendor: MartinDeh Create new Deployment Profile Right click on the MySkinProject node, and select New From the New Gallery, select General->Deployment Profiles, Shared Library JAR File from Items, and click OK In the Create Deployment Profile dialog, give name (i.e.mysharedskinlib) and click OK In the Edit JAR Deployment dialog, un-check Include Manifest File option  Select Project Output->Contributors, and check Project Source Path Select Project Output->Filters, ensure that all items under the META-INF folder are selected Click OK to exit the Project Properties dialog Deploy the shared lib to WebLogic (start server before steps) Right click on MySkin Project and select Deploy For this example, I will deploy to JDeverloper WLS In the Deploy dialog, select Deploy to Weblogic Application Server and click Next Choose IntegratedWebLogicServer and click Next Select Deploy to selected instances in the domain radio, select Default Server (note: server must be already started), and ensure Deploy as a shared Library radio is selected Click Finish Open the WebLogic console to see the deployed shared library The following are the steps to create a simple test Portlet Create a new WebCenter Portal - Portlet Producer Application In the Create Portlet Producer dialog, select default settings and click Finish Right click on the Portlets node and select New IIn the New Gallery, select Web-Tier->Portlets, Standards-based Java Portlet (JSR 286) and click OK In the General Portlet information dialog, give portlet name (i.e. MyPortlet) and click Next 2 times, stopping at Step 3 In the Content Types, select the "view" node, in the Implementation Method, select the Generate ADF-Faces JSPX radio and click Finish Once the portlet code is generated, open the view.jspx in the source editor Based on the simple CSS entry, which sets the background color of a panelGroupLayout, replace the <af:form/> tag with the example code <af:form>         <af:panelGroupLayout id="pgl1" styleClass="customPGL">           <af:outputText value="background from shared lib skin" id="ot1"/>         </af:panelGroupLayout>  </af:form> Since this portlet is to use the shared library skin, in the generated trinidad-config.xml, remove both the skin-family tag and the skin-version tag In the Application Resources view, under Descriptors->META-INF, double-click to open the weblogic-application.xml Add a library reference to the shared skin library (note: the library-name must match the extension-name declared in the MANIFEST.MF):  <library-ref>     <library-name>mysharedskin.lib.def</library-name>  </library-ref> Notice that a reference to oracle.webcenter.skin exists.  This is important if this portlet is going to be consumed by a WebCenter Portal application.  If this tag is not present, the portlet skin mismatch will happen.  Configure the portlet for deployment Create Portlet deployment WAR Right click on the Portlets node and select New In the New Gallery, select Deployment Profiles, WAR file from Items and click OK In the Create Deployment Profile dialog, give name (i.e. myportletwar), click OK Keep all of the defaults, however, remember the Context Root entry (i.e. MyPortlet4SharedLib-Portlets-context-root, this will be needed to obtain the producer WSDL URL) Click OK, then OK again to exit from the Properties dialog Since the weblogic-application.xml has to be included in the deployment, the portlet must be deployed as a WAR, within an EAR In the Application dropdown, select Deploy->New Deployment Profile... By default EAR File has been selected, click OK Give Deployment Profile (EAR) a name (i.e. MyPortletProducer) and click OK In the Properties dialog, select Application Assembly and ensure that the myportletwar is checked Keep all of the other defaults and click OK For this demo, un-check the Auto Generate ..., and all of the Security Deployment Options, click OK Save All In the Application dropdown, select Deploy->MyPortletProducer In the Deployment Action, select Deploy to Application Server, click Next Choose IntegratedWebLogicServer and click Next Select Deploy to selected instances in the domain radio, select Default Server (note: server must be already started), and ensure Deploy as a standalone Application radio is selected The select deployment type (identifying the deployment as a JSR 286 portlet) dialog appears.  Keep default radio "Yes" selection and click OK Open the WebLogic console to see the deployed Portlet The last step is to create the test portlet consuming application.  This will be done using the OOTB WebCenter Portal - Framework Application.  Create the Portlet Producer Connection In the JDeveloper Deployment log, copy the URL of the portlet deployment (i.e. http://localhost:7101/MyPortlet4SharedLib-Portlets-context-root Open a browser and paste in the URL.  The Portlet information page should appear.  Click on the WSRP v2 WSDL link Copy the URL from the browser (i.e. http://localhost:7101/MyPortlet4SharedLib-Portlets-context-root/portlets/wsrp2?WSDL) In the Application Resources view, right click on the Connections folder and select New Connection->WSRP Connection Give the producer a name or accept the default, click Next Enter (paste in) the WSDL URL, click Next If connection to Portlet is succesful, Step 3 (Specify Additional ...) should appear.  Accept defaults and click Finish Add the portlet to a test page Open the home.jspx.  Note in the visual editor, the orange dashed border, which identifies the panelCustomizable tag. From the Application Resources. select the MyPortlet portlet node, and drag and drop the node into the panelCustomizable section.  A Confirm Portlet Type dialog appears, keep default ADF Rich Portlet and click OK Configure the portlet to use the shared skin library Open the weblogic-application.xml and add the library-ref entry (mysharedskin.lib.def) for the shared skin library.  See create portlet example above for the steps Since by default, the custom portal using a managed bean to (dynamically) determine the skin family, the default trinidad-config.xml will need to be altered Open the trinidad-config.xml in the editor and replace the EL (preferenceBean) for the skin-family tag, with mysharedskin (this is the skin-family named defined in the trinidad-skins.xml) Remove the skin-version tag Right click on the index.html to test the application   Notice that the JDeveloper log view does not have any reporting of a skin mismatch.  In addition, since I have configured the extra logging outlined in debugging section above, I can see the processed skin jar in both the producer and consumer logs: <SkinUtils> <_getMetaInfSkinsNodeList> Processing skin URL:zip:/JDeveloper/system11.1.1.6.38.61.92/DefaultDomain/servers/DefaultServer/upload/mysharedskin.lib.def/[email protected]/app/mysharedskinlib.jar!/META-INF/trinidad-skins.xml 

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• Using VLOOKUP in Excel

  - by Mark Virtue

  VLOOKUP is one of Excel’s most useful functions, and it’s also one of the least understood.  In this article, we demystify VLOOKUP by way of a real-life example.  We’ll create a usable Invoice Template for a fictitious company. So what is VLOOKUP?  Well, of course it’s an Excel function.  This article will assume that the reader already has a passing understanding of Excel functions, and can use basic functions such as SUM, AVERAGE, and TODAY.  In its most common usage, VLOOKUP is a database function, meaning that it works with database tables – or more simply, lists of things in an Excel worksheet.  What sort of things?   Well, any sort of thing.  You may have a worksheet that contains a list of employees, or products, or customers, or CDs in your CD collection, or stars in the night sky.  It doesn’t really matter. Here’s an example of a list, or database.  In this case it’s a list of products that our fictitious company sells: Usually lists like this have some sort of unique identifier for each item in the list.  In this case, the unique identifier is in the “Item Code” column.  Note:  For the VLOOKUP function to work with a database/list, that list must have a column containing the unique identifier (or “key”, or “ID”), and that column must be the first column in the table.  Our sample database above satisfies this criterion. The hardest part of using VLOOKUP is understanding exactly what it’s for.  So let’s see if we can get that clear first: VLOOKUP retrieves information from a database/list based on a supplied instance of the unique identifier. Put another way, if you put the VLOOKUP function into a cell and pass it one of the unique identifiers from your database, it will return you one of the pieces of information associated with that unique identifier.  In the example above, you would pass VLOOKUP an item code, and it would return to you either the corresponding item’s description, its price, or its availability (its “In stock” quantity).  Which of these pieces of information will it pass you back?  Well, you get to decide this when you’re creating the formula. If all you need is one piece of information from the database, it would be a lot of trouble to go to to construct a formula with a VLOOKUP function in it.  Typically you would use this sort of functionality in a reusable spreadsheet, such as a template.  Each time someone enters a valid item code, the system would retrieve all the necessary information about the corresponding item. Let’s create an example of this:  An Invoice Template that we can reuse over and over in our fictitious company. First we start Excel… …and we create ourselves a blank invoice: This is how it’s going to work:  The person using the invoice template will fill in a series of item codes in column “A”, and the system will retrieve each item’s description and price, which will be used to calculate the line total for each item (assuming we enter a valid quantity). For the purposes of keeping this example simple, we will locate the product database on a separate sheet in the same workbook: In reality, it’s more likely that the product database would be located in a separate workbook.  It makes little difference to the VLOOKUP function, which doesn’t really care if the database is located on the same sheet, a different sheet, or a completely different workbook. In order to test the VLOOKUP formula we’re about to write, we first enter a valid item code into cell A11: Next, we move the active cell to the cell in which we want information retrieved from the database by VLOOKUP to be stored.  Interestingly, this is the step that most people get wrong.  To explain further:  We are about to create a VLOOKUP formula that will retrieve the description that corresponds to the item code in cell A11.  Where do we want this description put when we get it?  In cell B11, of course.  So that’s where we write the VLOOKUP formula – in cell B11. Select cell B11: We need to locate the list of all available functions that Excel has to offer, so that we can choose VLOOKUP and get some assistance in completing the formula.  This is found by first clicking the Formulas tab, and then clicking Insert Function:   A box appears that allows us to select any of the functions available in Excel.  To find the one we’re looking for, we could type a search term like “lookup” (because the function we’re interested in is a lookup function).  The system would return us a list of all lookup-related functions in Excel.  VLOOKUP is the second one in the list.  Select it an click OK… The Function Arguments box appears, prompting us for all the arguments (or parameters) needed in order to complete the VLOOKUP function.  You can think of this box as the function is asking us the following questions: What unique identifier are you looking up in the database? Where is the database? Which piece of information from the database, associated with the unique identifier, do you wish to have retrieved for you? The first three arguments are shown in bold, indicating that they are mandatory arguments (the VLOOKUP function is incomplete without them and will not return a valid value).  The fourth argument is not bold, meaning that it’s optional:   We will complete the arguments in order, top to bottom. The first argument we need to complete is the Lookup_value argument.  The function needs us to tell it where to find the unique identifier (the item code in this case) that it should be retuning the description of.  We must select the item code we entered earlier (in A11). Click on the selector icon to the right of the first argument: Then click once on the cell containing the item code (A11), and press Enter: The value of “A11” is inserted into the first argument. Now we need to enter a value for the Table_array argument.  In other words, we need to tell VLOOKUP where to find the database/list.  Click on the selector icon next to the second argument: Now locate the database/list and select the entire list – not including the header line.  The database is located on a separate worksheet, so we first click on that worksheet tab: Next we select the entire database, not including the header line: …and press Enter.  The range of cells that represents the database (in this case “’Product Database’!A2:D7”) is entered automatically for us into the second argument. Now we need to enter the third argument, Col_index_num.  We use this argument to specify to VLOOKUP which piece of information from the database, associate with our item code in A11, we wish to have returned to us.  In this particular example, we wish to have the item’s description returned to us.  If you look on the database worksheet, you’ll notice that the “Description” column is the second column in the database.  This means that we must enter a value of “2” into the Col_index_num box: It is important to note that that we are not entering a “2” here because the “Description” column is in the B column on that worksheet.  If the database happened to start in column K of the worksheet, we would still enter a “2” in this field. Finally, we need to decide whether to enter a value into the final VLOOKUP argument, Range_lookup.  This argument requires either a true or false value, or it should be left blank.  When using VLOOKUP with databases (as is true 90% of the time), then the way to decide what to put in this argument can be thought of as follows: If the first column of the database (the column that contains the unique identifiers) is sorted alphabetically/numerically in ascending order, then it’s possible to enter a value of true into this argument, or leave it blank. If the first column of the database is not sorted, or it’s sorted in descending order, then you must enter a value of false into this argument As the first column of our database is not sorted, we enter false into this argument: That’s it!  We’ve entered all the information required for VLOOKUP to return the value we need.  Click the OK button and notice that the description corresponding to item code “R99245” has been correctly entered into cell B11: The formula that was created for us looks like this: If we enter a different item code into cell A11, we will begin to see the power of the VLOOKUP function:  The description cell changes to match the new item code: We can perform a similar set of steps to get the item’s price returned into cell E11.  Note that the new formula must be created in cell E11.  The result will look like this: …and the formula will look like this: Note that the only difference between the two formulae is the third argument (Col_index_num) has changed from a “2” to a “3” (because we want data retrieved from the 3rd column in the database). If we decided to buy 2 of these items, we would enter a “2” into cell D11.  We would then enter a simple formula into cell F11 to get the line total: =D11*E11 …which looks like this… Completing the Invoice Template We’ve learned a lot about VLOOKUP so far.  In fact, we’ve learned all we’re going to learn in this article.  It’s important to note that VLOOKUP can be used in other circumstances besides databases.  This is less common, and may be covered in future How-To Geek articles. Our invoice template is not yet complete.  In order to complete it, we would do the following: We would remove the sample item code from cell A11 and the “2” from cell D11.  This will cause our newly created VLOOKUP formulae to display error messages: We can remedy this by judicious use of Excel’s IF() and ISBLANK() functions.  We change our formula from this…       =VLOOKUP(A11,’Product Database’!A2:D7,2,FALSE) …to this…       =IF(ISBLANK(A11),”",VLOOKUP(A11,’Product Database’!A2:D7,2,FALSE)) We would copy the formulas in cells B11, E11 and F11 down to the remainder of the item rows of the invoice.  Note that if we do this, the resulting formulas will no longer correctly refer to the database table.  We could fix this by changing the cell references for the database to absolute cell references.  Alternatively – and even better – we could create a range name for the entire product database (such as “Products”), and use this range name instead of the cell references.  The formula would change from this…       =IF(ISBLANK(A11),”",VLOOKUP(A11,’Product Database’!A2:D7,2,FALSE)) …to this…       =IF(ISBLANK(A11),”",VLOOKUP(A11,Products,2,FALSE)) …and then copy the formulas down to the rest of the invoice item rows. We would probably “lock” the cells that contain our formulae (or rather unlock the other cells), and then protect the worksheet, in order to ensure that our carefully constructed formulae are not accidentally overwritten when someone comes to fill in the invoice. We would save the file as a template, so that it could be reused by everyone in our company If we were feeling really clever, we would create a database of all our customers in another worksheet, and then use the customer ID entered in cell F5 to automatically fill in the customer’s name and address in cells B6, B7 and B8. If you would like to practice with VLOOKUP, or simply see our resulting Invoice Template, it can be downloaded from here. Similar Articles Productive Geek Tips Make Excel 2007 Print Gridlines In Workbook FileMake Excel 2007 Always Save in Excel 2003 FormatConvert Older Excel Documents to Excel 2007 FormatImport Microsoft Access Data Into ExcelChange the Default Font in Excel 2007 TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Classic Cinema Online offers 100’s of OnDemand Movies OutSync will Sync Photos of your Friends on Facebook and Outlook Windows 7 Easter Theme YoWindoW, a real time weather screensaver Optimize your computer the Microsoft way Stormpulse provides slick, real time weather data

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• getting at a UIButton with the tag property IPhone

  - by dubbeat

  Hey There, I'm having a little trouble using the tag property to access a UIButton UIButton *randomButton = [[UIButton buttonWithType:UIButtonTypeRoundedRect ]retain]; randomButton.frame = CGRectMake(205, 145, 90, 22); // size and position of button [randomButton setTitle:@"Random" forState:UIControlStateNormal]; randomButton.backgroundColor = [UIColor clearColor]; randomButton.adjustsImageWhenHighlighted = YES; [randomButton addTarget:self action:@selector(getrandom:) forControlEvents:UIControlEventTouchUpInside]; randomButton.reversesTitleShadowWhenHighlighted=YES; randomButton.toggleButton [self.view addSubview:randomButton]; [randomButton release]; randomButton.tag=333; Then later on in code I try to get at the button in the following manner which gives me an error saying Incompatible Objective-C types initializing 'struct UIView *', expected 'struct UIButton *' UIButton *random = [self.view viewWithTag:333]; random.highlighted=NO;

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• How to add an onclick event to a joint.js element?

  - by ahalbert

  I have a joint.js element in a DAG, and would like to be able to trigger an event by clicking on it. I could use $(selector).click(...) to do it, but I was wondering if there was a joint.js specific way of handling it, since that would probobly be better. One event I decided was a candidate for onclick was 'batch:stop' My code: var variable = new joint.shapes.basic.Rect({ name : label, id: label, onclick : function () {alert("hello");}, size: { width: width, height: height }, attrs: { text: { text: label, 'font-size': letterSize, 'font-family': 'monospace' }, rect: { fill : fillColor, width: width, height: height, rx: 5, ry: 5, stroke: '#555' } } }); variable.on('batch:stop', function (element) {alert(""); toggleEvidence(element.name);}); return variable; How should I add an onclick event?

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• UITableViewController and viewForHeaderInSection problems

  - by Fiona

  Hello, So I need your help please! I've created a UITableViewController: ContactDetailViewController. In IB in the nib file, I've added a view ahead of the table view and hooked it up to headerView - a UIView declared in the .h file. I've also created a view: CustomerHeaderView However when I run the code below, Its throwing an exception at the following line: headerView = [[UIView alloc] initWithNibName:@"ContactHeaderDetail" bundle:nil]; The error being thrown is: 2010-05-20 10:59:50.405 OnePageCRM[19620:20b] * -[UIView initWithNibName:bundle:]: unrecognized selector sent to instance 0x3ca4fa0 2010-05-20 10:59:50.406 OnePageCRM[19620:20b] Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '** -[UIView initWithNibName:bundle:]: unrecognized selector sent to instance 0x3ca4fa0' So any ideas anyone? Many thanks, Fiona // // ContactDetailViewController.m // OnePageCRM // // Created by Fiona Tighe on 19/05/2010. // Copyright 2010 __MyCompanyName__. All rights reserved. // #import "ContactDetailViewController.h" #import "DisplayInfoViewController.h" #import "ActionViewController.h" #define SectionHeaderHeigth 200 @implementation ContactDetailViewController @synthesize name; @synthesize date; @synthesize headerView; @synthesize nextAction; @synthesize nameLabel; @synthesize usernameLabel; @synthesize nextActionTextField; @synthesize dateLabel; @synthesize notesTableView; @synthesize contactInfoButton; @synthesize backgroundInfoButton; @synthesize actionDoneButton; - (void)viewDidLoad { [super viewDidLoad]; // Uncomment the following line to display an Edit button in the navigation bar for this view controller. // self.navigationItem.rightBarButtonItem = self.editButtonItem; } - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc that aren't in use. } - (void)viewDidUnload { // Release any retained subviews of the main view. // e.g. self.myOutlet = nil; } #pragma mark Table view methods - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 2; } // Customize the number of rows in the table view. - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { int numOfRows; NSLog(@"section: %d", section); switch (section){ case 0: numOfRows = 0; break; case 1: numOfRows = 3; break; default: break; } return numOfRows; } - (UIView *) tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section { if (section == 0){ headerView = [[UIView alloc] initWithNibName:@"ContactHeaderDetail" bundle:nil]; // headerView = [[UIView alloc] initWithNibName:@"ContactHeaderDetail" bundle:nil]; return headerView; }else{ return nil; } } - (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section{ return SectionHeaderHeigth; } // Customize the appearance of table view cells. - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } // Set up the cell... return cell; } - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { // Navigation logic may go here. Create and push another view controller. // AnotherViewController *anotherViewController = [[AnotherViewController alloc] initWithNibName:@"AnotherView" bundle:nil]; // [self.navigationController pushViewController:anotherViewController]; // [anotherViewController release]; } /* // Override to support conditional editing of the table view. - (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath { // Return NO if you do not want the specified item to be editable. return YES; } */ /* // Override to support editing the table view. - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { // Delete the row from the data source [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES]; } else if (editingStyle == UITableViewCellEditingStyleInsert) { // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view } } */ /* // Override to support rearranging the table view. - (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath { } */ /* // Override to support conditional rearranging of the table view. - (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath { // Return NO if you do not want the item to be re-orderable. return YES; } */ -(IBAction)displayContactInfo:(id)sender{ DisplayInfoViewController *divc = [[DisplayInfoViewController alloc] init]; divc.textView = self.nextAction; divc.title = @"Contact Info"; [self.navigationController pushViewController:divc animated:YES]; [divc release]; } -(IBAction)displayBackgroundInfo:(id)sender{ DisplayInfoViewController *divc = [[DisplayInfoViewController alloc] init]; divc.textView = self.nextAction; divc.title = @"Background Info"; [self.navigationController pushViewController:divc animated:YES]; [divc release]; } -(IBAction)actionDone:(id)sender{ ActionViewController *avc = [[ActionViewController alloc] init]; avc.title = @"Action"; avc.nextAction = self.nextAction; [self.navigationController pushViewController:avc animated:YES]; [avc release]; } - (void)dealloc { [name release]; [date release]; [nextAction release]; [nameLabel release]; [usernameLabel release]; [nextActionTextField release]; [dateLabel release]; [notesTableView release]; [contactInfoButton release]; [backgroundInfoButton release]; [actionDoneButton release]; [headerView release]; [super dealloc]; } @end

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• IE8 Jquery Javascript "Error: Object required" Bug

  - by thechrisvoth

  IE8 throws an "Error: Object required" message (error in the actual jquery library script, not my javascript file) when the switch statement in this function runs. This code works in IE6, IE7, FF3, and Safari... Any ideas? Does it have something to do with the '$(this)' selector in the switch? Thanks! function totshirts(){ $('.shirt-totals input').val('0'); var cxs = 0; var cs = 0; var cm = 0; $.each($('select.size'), function() { switch($(this).val()){ case "cxs": cxs ++; $('input[name="cxs"]').val(cxs); break; case "cs": cs ++; $('input[name="cs"]').val(cs); break; case "cm": cm ++; $('input[name="cm"]').val(cm); break; } }); }

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• iPhone Gameloop render update from a separate thread

  - by Rich

  Hi, I'm new to iPhone development. I have a game loop setup as follows. (void)CreateGameTick:(NSTimeInterval) in_time { [NSThread detachNewThreadSelector:@selector(GameTick) toTarget:self withObject:nil]; } My basic game tick/render looks like this (void)GameTick { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; CGRect wrect = [self bounds]; while( m_running ) { [self drawRect: wrect]; } [pool release]; } My render function gets called. However nothing gets drawn (I am using Core Graphics to draw some lines on a derived UIView). If I call my update via a timer then all is well and good. Can you tell me why the render fails when done via threads? And is it possible to make it work via threads? Thanks Rich

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• iphone custom navigation bar edit button

  - by Sarah

  Hi all, I use custom image for my navigation bar buttons using the following code, that allows me to make custom add button. I want to be able to do the same for the edit button item. UIImage *image=[UIImage imageNamed:@"Plus.png"]; UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom]; button.bounds = CGRectMake( 0, 0, image.size.width, image.size.height ); [button setBackgroundImage:image forState:UIControlStateNormal]; [button addTarget:self action:@selector(add) forControlEvents:UIControlEventTouchUpInside]; UIBarButtonItem *barButtonItem = [[UIBarButtonItem alloc] initWithCustomView:button]; self.navigationItem.rightBarButtonItem = barButtonItem; [barButtonItem release]; self.navigationItem.leftBarButtonItem = self.editButtonItem; I'm doing this because I want to change the button text color.I would appreciate your help, Sarah

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• FB.ui and setting popup size

  - by manuelpedrera

  I am using FB.ui with the display parameter set to popup. When the method is 'stream.publish', it autoresizes when the content is loaded. However, when using 'fbml.dialog' (in order to display a multi-friend selector) it shows a size that I'm not able to change (and the content is displayed cropped). I have tried with the following approaches, with no luck: FB.ui({ method: 'fbml.dialog', size: {width: 800, height: 500}, ... FB.ui({ method: 'fbml.dialog', width: 800, height: 500, ... Also I've been looking at the API source code, and it declares the method this way: Method declaration: 'fbml.dialog': { size : { width: 575, height: 300 }, url : 'render_fbml.php', loggedOutIframe : true }... Functions that executes the methods: // the basic call data var call = { cb : cb, id : id, size : method.size || {}, url : FB._domain.www + method.url, params : params }; Any help would be much appreciated...

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• Suppressing line specific XCode compiler warnings

  - by MrHen

  Similar to Ben Gottlieb's question, I have a handful of deprecated calls that are bugging me. Is there a way to suppress warnings by line? For instance: if([[UIApplication sharedApplication] respondsToSelector:@selector(setStatusBarHidden:withAnimation:)]) { [[UIApplication sharedApplication] setStatusBarHidden:YES withAnimation:UIStatusBarAnimationSlide]; } else { [[UIApplication sharedApplication] setStatusBarHidden:YES animated:NO]; //causes deprecation warning } All I care about is that line. I don't want to turn off all deprecation warnings. I would also rather not do something like suppress specific warnings by file. There have been a few other circumstances where I wanted to flag a specific line as okay even though the compiler generates a warning. I essentially want to let my team know that the problem has been handled and stop getting bugged about the same line over and over.

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• Are There Specific CSS Selectors Targeting IE10?

  - by kunambi

  Since IE is getting rid of conditional comments in version 10, I'm in dire need to find a "CSS hack" targeting IE10 specifically. NB! It has to be the selector that's getting "hacked" and not the CSS-properties. In Mozilla, you can use: @-moz-document url-prefix() { h1 { color: red; } } While in Webkit, you usually do: @media screen and (-webkit-min-device-pixel-ratio:0) { h1 { color: blue; } } How would I do something similar in IE10? TYIA.

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