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• Panning with the OpenGL Camera / View Matrix

  - by Pris

  I'm gonna try this again I've been trying to setup a simple camera class with OpenGL but I'm completely lost and I've made zero progress creating anything useful. I'm using modern OpenGL and the glm library for matrix math. To get the most basic thing I can think of down, I'd like to pan an arbitrarily positioned camera around. That means move it along its own Up and Side axes. Here's a picture of a randomly positioned camera looking at an object: It should be clear what the Up (Green) and Side (Red) vectors on the camera are. Even though the picture shows otherwise, assume that the Model matrix is just the identity matrix. Here's what I do to try and get it to work: Step 1: Create my View/Camera matrix (going to refer to it as the View matrix from now on) using glm::lookAt(). Step 2: Capture mouse X and Y positions. Step 3: Create a translation matrix mapping changes in the X mouse position to the camera's Side vector, and mapping changes in the Y mouse position to the camera's Up vector. I get the Side vector from the first column of the View matrix. I get the Up vector from the second column of the View matrix. Step 4: Apply the translation: viewMatrix = glm::translate(viewMatrix,translationVector); But this doesn't work. I see that the mouse movement is mapped to some kind of perpendicular axes, but they're definitely not moving as you'd expect with respect to the camera. Could someone please explain what I'm doing wrong and point me in the right direction with this camera stuff?

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• How to fix issue with my 3D first person camera?

  - by dxCUDA

  My camera moves and rotates, but relative to the worlds origin, instead of the players. I am having difficulty rotating the camera and then translating the camera in the direction relative to the camera facing angle. I have been able to translate the camera and rotate relative to the players origin, but not then rotate and translate in the direction relative to the cameras facing direction. My goal is to have a standard FPS-style camera. float yaw, pitch, roll; D3DXMATRIX rotationMatrix; D3DXVECTOR3 Direction; D3DXMATRIX matRotAxis,matRotZ; D3DXVECTOR3 RotAxis; // Set the yaw (Y axis), pitch (X axis), and roll (Z axis) rotations in radians. pitch = m_rotationX * 0.0174532925f; yaw = m_rotationY * 0.0174532925f; roll = m_rotationZ * 0.0174532925f; up = D3DXVECTOR3(0.0f, 1.0f, 0.0f);//Create the up vector //Build eye ,lookat and rotation vectors from player input data eye = D3DXVECTOR3(m_fCameraX, m_fCameraY, m_fCameraZ); lookat = D3DXVECTOR3(m_fLookatX, m_fLookatY, m_fLookatZ); rotation = D3DXVECTOR3(m_rotationX, m_rotationY, m_rotationZ); D3DXVECTOR3 camera[3] = {eye,//Eye lookat,//LookAt up };//Up RotAxis.x = pitch; RotAxis.y = yaw; RotAxis.z = roll; D3DXVec3Normalize(&Direction, &(camera[1] - camera[0]));//Direction vector D3DXVec3Cross(&RotAxis, &Direction, &camera[2]);//Strafe vector D3DXVec3Normalize(&RotAxis, &RotAxis); // Create the rotation matrix from the yaw, pitch, and roll values. D3DXMatrixRotationYawPitchRoll(&matRotAxis, pitch,yaw, roll); //rotate direction D3DXVec3TransformCoord(&Direction,&Direction,&matRotAxis); //Translate up vector D3DXVec3TransformCoord(&camera[2], &camera[2], &matRotAxis); //Translate in the direction of player rotation D3DXVec3TransformCoord(&camera[0], &camera[0], &matRotAxis); camera[1] = Direction + camera[0];//Avoid gimble locking D3DXMatrixLookAtLH(&in_viewMatrix, &camera[0], &camera[1], &camera[2]);

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• Getting Started with TypeScript – Classes, Static Types and Interfaces

  - by dwahlin

  I had the opportunity to speak on different JavaScript topics at DevConnections in Las Vegas this fall and heard a lot of interesting comments about JavaScript as I talked with people. The most frequent comment I heard from people was, “I guess it’s time to start learning JavaScript”. Yep – if you don’t already know JavaScript then it’s time to learn it. As HTML5 becomes more and more popular the amount of JavaScript code written will definitely increase. After all, many of the HTML5 features available in browsers have little to do with “tags” and more to do with JavaScript (web workers, web sockets, canvas, local storage, etc.). As the amount of JavaScript code being used in applications increases, it’s more important than ever to structure the code in a way that’s maintainable and easy to debug. While JavaScript patterns can certainly be used (check out my previous posts on the subject or my course on Pluralsight.com), several alternatives have come onto the scene such as CoffeeScript, Dart and TypeScript. In this post I’ll describe some of the features TypeScript offers and the benefits that they can potentially offer enterprise-scale JavaScript applications. It’s important to note that while TypeScript has several great features, it’s definitely not for everyone or every project especially given how new it is. The goal of this post isn’t to convince you to use TypeScript instead of standard JavaScript….I’m a big fan of JavaScript. Instead, I’ll present several TypeScript features and let you make the decision as to whether TypeScript is a good fit for your applications. TypeScript Overview Here’s the official definition of TypeScript from the http://typescriptlang.org site: “TypeScript is a language for application-scale JavaScript development. TypeScript is a typed superset of JavaScript that compiles to plain JavaScript. Any browser. Any host. Any OS. Open Source.” TypeScript was created by Anders Hejlsberg (the creator of the C# language) and his team at Microsoft. To sum it up, TypeScript is a new language that can be compiled to JavaScript much like alternatives such as CoffeeScript or Dart. It isn’t a stand-alone language that’s completely separate from JavaScript’s roots though. It’s a superset of JavaScript which means that standard JavaScript code can be placed in a TypeScript file (a file with a .ts extension) and used directly. That’s a very important point/feature of the language since it means you can use existing code and frameworks with TypeScript without having to do major code conversions to make it all work. Once a TypeScript file is saved it can be compiled to JavaScript using TypeScript’s tsc.exe compiler tool or by using a variety of editors/tools. TypeScript offers several key features. First, it provides built-in type support meaning that you define variables and function parameters as being “string”, “number”, “bool”, and more to avoid incorrect types being assigned to variables or passed to functions. Second, TypeScript provides a way to write modular code by directly supporting class and module definitions and it even provides support for custom interfaces that can be used to drive consistency. Finally, TypeScript integrates with several different tools such as Visual Studio, Sublime Text, Emacs, and Vi to provide syntax highlighting, code help, build support, and more depending on the editor. Find out more about editor support at http://www.typescriptlang.org/#Download. TypeScript can also be used with existing JavaScript frameworks such as Node.js, jQuery, and others and even catch type issues and provide enhanced code help. Special “declaration” files that have a d.ts extension are available for Node.js, jQuery, and other libraries out-of-the-box. Visit http://typescript.codeplex.com/SourceControl/changeset/view/fe3bc0bfce1f#samples%2fjquery%2fjquery.d.ts for an example of a jQuery TypeScript declaration file that can be used with tools such as Visual Studio 2012 to provide additional code help and ensure that a string isn’t passed to a parameter that expects a number. Although declaration files certainly aren’t required, TypeScript’s support for declaration files makes it easier to catch issues upfront while working with existing libraries such as jQuery. In the future I expect TypeScript declaration files will be released for different HTML5 APIs such as canvas, local storage, and others as well as some of the more popular JavaScript libraries and frameworks. Getting Started with TypeScript To get started learning TypeScript visit the TypeScript Playground available at http://www.typescriptlang.org. Using the playground editor you can experiment with TypeScript code, get code help as you type, and see the JavaScript that TypeScript generates once it’s compiled. Here’s an example of the TypeScript playground in action:   One of the first things that may stand out to you about the code shown above is that classes can be defined in TypeScript. This makes it easy to group related variables and functions into a container which helps tremendously with re-use and maintainability especially in enterprise-scale JavaScript applications. While you can certainly simulate classes using JavaScript patterns (note that ECMAScript 6 will support classes directly), TypeScript makes it quite easy especially if you come from an object-oriented programming background. An example of the Greeter class shown in the TypeScript Playground is shown next: class Greeter { greeting: string; constructor (message: string) { this.greeting = message; } greet() { return "Hello, " + this.greeting; } } Looking through the code you’ll notice that static types can be defined on variables and parameters such as greeting: string, that constructors can be defined, and that functions can be defined such as greet(). The ability to define static types is a key feature of TypeScript (and where its name comes from) that can help identify bugs upfront before even running the code. Many types are supported including primitive types like string, number, bool, undefined, and null as well as object literals and more complex types such as HTMLInputElement (for an <input> tag). Custom types can be defined as well. The JavaScript output by compiling the TypeScript Greeter class (using an editor like Visual Studio, Sublime Text, or the tsc.exe compiler) is shown next: var Greeter = (function () { function Greeter(message) { this.greeting = message; } Greeter.prototype.greet = function () { return "Hello, " + this.greeting; }; return Greeter; })(); Notice that the code is using JavaScript prototyping and closures to simulate a Greeter class in JavaScript. The body of the code is wrapped with a self-invoking function to take the variables and functions out of the global JavaScript scope. This is important feature that helps avoid naming collisions between variables and functions. In cases where you’d like to wrap a class in a naming container (similar to a namespace in C# or a package in Java) you can use TypeScript’s module keyword. The following code shows an example of wrapping an AcmeCorp module around the Greeter class. In order to create a new instance of Greeter the module name must now be used. This can help avoid naming collisions that may occur with the Greeter class.   module AcmeCorp { export class Greeter { greeting: string; constructor (message: string) { this.greeting = message; } greet() { return "Hello, " + this.greeting; } } } var greeter = new AcmeCorp.Greeter("world"); In addition to being able to define custom classes and modules in TypeScript, you can also take advantage of inheritance by using TypeScript’s extends keyword. The following code shows an example of using inheritance to define two report objects:   class Report { name: string; constructor (name: string) { this.name = name; } print() { alert("Report: " + this.name); } } class FinanceReport extends Report { constructor (name: string) { super(name); } print() { alert("Finance Report: " + this.name); } getLineItems() { alert("5 line items"); } } var report = new FinanceReport("Month's Sales"); report.print(); report.getLineItems();   In this example a base Report class is defined that has a variable (name), a constructor that accepts a name parameter of type string, and a function named print(). The FinanceReport class inherits from Report by using TypeScript’s extends keyword. As a result, it automatically has access to the print() function in the base class. In this example the FinanceReport overrides the base class’s print() method and adds its own. The FinanceReport class also forwards the name value it receives in the constructor to the base class using the super() call. TypeScript also supports the creation of custom interfaces when you need to provide consistency across a set of objects. The following code shows an example of an interface named Thing (from the TypeScript samples) and a class named Plane that implements the interface to drive consistency across the app. Notice that the Plane class includes intersect and normal as a result of implementing the interface.   interface Thing { intersect: (ray: Ray) => Intersection; normal: (pos: Vector) => Vector; surface: Surface; } class Plane implements Thing { normal: (pos: Vector) =>Vector; intersect: (ray: Ray) =>Intersection; constructor (norm: Vector, offset: number, public surface: Surface) { this.normal = function (pos: Vector) { return norm; } this.intersect = function (ray: Ray): Intersection { var denom = Vector.dot(norm, ray.dir); if (denom > 0) { return null; } else { var dist = (Vector.dot(norm, ray.start) + offset) / (-denom); return { thing: this, ray: ray, dist: dist }; } } } }   At first glance it doesn’t appear that the surface member is implemented in Plane but it’s actually included automatically due to the public surface: Surface parameter in the constructor. Adding public varName: Type to a constructor automatically adds a typed variable into the class without having to explicitly write the code as with normal and intersect. TypeScript has additional language features but defining static types and creating classes, modules, and interfaces are some of the key features it offers. So is TypeScript right for you and your applications? That’s a not a question that I or anyone else can answer for you. You’ll need to give it a spin to see what you think. In future posts I’ll discuss additional details about TypeScript and how it can be used with enterprise-scale JavaScript applications. In the meantime, I’m in the process of working with John Papa on a new Typescript course for Pluralsight that we hope to have out in December of 2012.

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• Fun with Aggregates

  - by Paul White

  There are interesting things to be learned from even the simplest queries.  For example, imagine you are given the task of writing a query to list AdventureWorks product names where the product has at least one entry in the transaction history table, but fewer than ten. One possible query to meet that specification is: SELECT p.Name FROM Production.Product AS p JOIN Production.TransactionHistory AS th ON p.ProductID = th.ProductID GROUP BY p.ProductID, p.Name HAVING COUNT_BIG(*) < 10; That query correctly returns 23 rows (execution plan and data sample shown below): The execution plan looks a bit different from the written form of the query: the base tables are accessed in reverse order, and the aggregation is performed before the join.  The general idea is to read all rows from the history table, compute the count of rows grouped by ProductID, merge join the results to the Product table on ProductID, and finally filter to only return rows where the count is less than ten. This ‘fully-optimized’ plan has an estimated cost of around 0.33 units.  The reason for the quote marks there is that this plan is not quite as optimal as it could be – surely it would make sense to push the Filter down past the join too?  To answer that, let’s look at some other ways to formulate this query.  This being SQL, there are any number of ways to write logically-equivalent query specifications, so we’ll just look at a couple of interesting ones.  The first query is an attempt to reverse-engineer T-SQL from the optimized query plan shown above.  It joins the result of pre-aggregating the history table to the Product table before filtering: SELECT p.Name FROM ( SELECT th.ProductID, cnt = COUNT_BIG(*) FROM Production.TransactionHistory AS th GROUP BY th.ProductID ) AS q1 JOIN Production.Product AS p ON p.ProductID = q1.ProductID WHERE q1.cnt < 10; Perhaps a little surprisingly, we get a slightly different execution plan: The results are the same (23 rows) but this time the Filter is pushed below the join!  The optimizer chooses nested loops for the join, because the cardinality estimate for rows passing the Filter is a bit low (estimate 1 versus 23 actual), though you can force a merge join with a hint and the Filter still appears below the join.  In yet another variation, the < 10 predicate can be ‘manually pushed’ by specifying it in a HAVING clause in the “q1” sub-query instead of in the WHERE clause as written above. The reason this predicate can be pushed past the join in this query form, but not in the original formulation is simply an optimizer limitation – it does make efforts (primarily during the simplification phase) to encourage logically-equivalent query specifications to produce the same execution plan, but the implementation is not completely comprehensive. Moving on to a second example, the following query specification results from phrasing the requirement as “list the products where there exists fewer than ten correlated rows in the history table”: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) < 10 ); Unfortunately, this query produces an incorrect result (86 rows): The problem is that it lists products with no history rows, though the reasons are interesting.  The COUNT_BIG(*) in the EXISTS clause is a scalar aggregate (meaning there is no GROUP BY clause) and scalar aggregates always produce a value, even when the input is an empty set.  In the case of the COUNT aggregate, the result of aggregating the empty set is zero (the other standard aggregates produce a NULL).  To make the point really clear, let’s look at product 709, which happens to be one for which no history rows exist: -- Scalar aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709;   -- Vector aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709 GROUP BY th.ProductID; The estimated execution plans for these two statements are almost identical: You might expect the Stream Aggregate to have a Group By for the second statement, but this is not the case.  The query includes an equality comparison to a constant value (709), so all qualified rows are guaranteed to have the same value for ProductID and the Group By is optimized away. In fact there are some minor differences between the two plans (the first is auto-parameterized and qualifies for trivial plan, whereas the second is not auto-parameterized and requires cost-based optimization), but there is nothing to indicate that one is a scalar aggregate and the other is a vector aggregate.  This is something I would like to see exposed in show plan so I suggested it on Connect.  Anyway, the results of running the two queries show the difference at runtime: The scalar aggregate (no GROUP BY) returns a result of zero, whereas the vector aggregate (with a GROUP BY clause) returns nothing at all.  Returning to our EXISTS query, we could ‘fix’ it by changing the HAVING clause to reject rows where the scalar aggregate returns zero: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) BETWEEN 1 AND 9 ); The query now returns the correct 23 rows: Unfortunately, the execution plan is less efficient now – it has an estimated cost of 0.78 compared to 0.33 for the earlier plans.  Let’s try adding a redundant GROUP BY instead of changing the HAVING clause: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY th.ProductID HAVING COUNT_BIG(*) < 10 ); Not only do we now get correct results (23 rows), this is the execution plan: I like to compare that plan to quantum physics: if you don’t find it shocking, you haven’t understood it properly :)  The simple addition of a redundant GROUP BY has resulted in the EXISTS form of the query being transformed into exactly the same optimal plan we found earlier.  What’s more, in SQL Server 2008 and later, we can replace the odd-looking GROUP BY with an explicit GROUP BY on the empty set: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ); I offer that as an alternative because some people find it more intuitive (and it perhaps has more geek value too).  Whichever way you prefer, it’s rather satisfying to note that the result of the sub-query does not exist for a particular correlated value where a vector aggregate is used (the scalar COUNT aggregate always returns a value, even if zero, so it always ‘EXISTS’ regardless which ProductID is logically being evaluated). The following query forms also produce the optimal plan and correct results, so long as a vector aggregate is used (you can probably find more equivalent query forms): WHERE Clause SELECT p.Name FROM Production.Product AS p WHERE ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) < 10; APPLY SELECT p.Name FROM Production.Product AS p CROSS APPLY ( SELECT NULL FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ) AS ca (dummy); FROM Clause SELECT q1.Name FROM ( SELECT p.Name, cnt = ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) FROM Production.Product AS p ) AS q1 WHERE q1.cnt < 10; This last example uses SUM(1) instead of COUNT and does not require a vector aggregate…you should be able to work out why :) SELECT q.Name FROM ( SELECT p.Name, cnt = ( SELECT SUM(1) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID ) FROM Production.Product AS p ) AS q WHERE q.cnt < 10; The semantics of SQL aggregates are rather odd in places.  It definitely pays to get to know the rules, and to be careful to check whether your queries are using scalar or vector aggregates.  As we have seen, query plans do not show in which ‘mode’ an aggregate is running and getting it wrong can cause poor performance, wrong results, or both. © 2012 Paul White Twitter: @SQL_Kiwi email: [email protected]

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• Fun with Aggregates

  - by Paul White

  There are interesting things to be learned from even the simplest queries.  For example, imagine you are given the task of writing a query to list AdventureWorks product names where the product has at least one entry in the transaction history table, but fewer than ten. One possible query to meet that specification is: SELECT p.Name FROM Production.Product AS p JOIN Production.TransactionHistory AS th ON p.ProductID = th.ProductID GROUP BY p.ProductID, p.Name HAVING COUNT_BIG(*) < 10; That query correctly returns 23 rows (execution plan and data sample shown below): The execution plan looks a bit different from the written form of the query: the base tables are accessed in reverse order, and the aggregation is performed before the join.  The general idea is to read all rows from the history table, compute the count of rows grouped by ProductID, merge join the results to the Product table on ProductID, and finally filter to only return rows where the count is less than ten. This ‘fully-optimized’ plan has an estimated cost of around 0.33 units.  The reason for the quote marks there is that this plan is not quite as optimal as it could be – surely it would make sense to push the Filter down past the join too?  To answer that, let’s look at some other ways to formulate this query.  This being SQL, there are any number of ways to write logically-equivalent query specifications, so we’ll just look at a couple of interesting ones.  The first query is an attempt to reverse-engineer T-SQL from the optimized query plan shown above.  It joins the result of pre-aggregating the history table to the Product table before filtering: SELECT p.Name FROM ( SELECT th.ProductID, cnt = COUNT_BIG(*) FROM Production.TransactionHistory AS th GROUP BY th.ProductID ) AS q1 JOIN Production.Product AS p ON p.ProductID = q1.ProductID WHERE q1.cnt < 10; Perhaps a little surprisingly, we get a slightly different execution plan: The results are the same (23 rows) but this time the Filter is pushed below the join!  The optimizer chooses nested loops for the join, because the cardinality estimate for rows passing the Filter is a bit low (estimate 1 versus 23 actual), though you can force a merge join with a hint and the Filter still appears below the join.  In yet another variation, the < 10 predicate can be ‘manually pushed’ by specifying it in a HAVING clause in the “q1” sub-query instead of in the WHERE clause as written above. The reason this predicate can be pushed past the join in this query form, but not in the original formulation is simply an optimizer limitation – it does make efforts (primarily during the simplification phase) to encourage logically-equivalent query specifications to produce the same execution plan, but the implementation is not completely comprehensive. Moving on to a second example, the following query specification results from phrasing the requirement as “list the products where there exists fewer than ten correlated rows in the history table”: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) < 10 ); Unfortunately, this query produces an incorrect result (86 rows): The problem is that it lists products with no history rows, though the reasons are interesting.  The COUNT_BIG(*) in the EXISTS clause is a scalar aggregate (meaning there is no GROUP BY clause) and scalar aggregates always produce a value, even when the input is an empty set.  In the case of the COUNT aggregate, the result of aggregating the empty set is zero (the other standard aggregates produce a NULL).  To make the point really clear, let’s look at product 709, which happens to be one for which no history rows exist: -- Scalar aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709;   -- Vector aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709 GROUP BY th.ProductID; The estimated execution plans for these two statements are almost identical: You might expect the Stream Aggregate to have a Group By for the second statement, but this is not the case.  The query includes an equality comparison to a constant value (709), so all qualified rows are guaranteed to have the same value for ProductID and the Group By is optimized away. In fact there are some minor differences between the two plans (the first is auto-parameterized and qualifies for trivial plan, whereas the second is not auto-parameterized and requires cost-based optimization), but there is nothing to indicate that one is a scalar aggregate and the other is a vector aggregate.  This is something I would like to see exposed in show plan so I suggested it on Connect.  Anyway, the results of running the two queries show the difference at runtime: The scalar aggregate (no GROUP BY) returns a result of zero, whereas the vector aggregate (with a GROUP BY clause) returns nothing at all.  Returning to our EXISTS query, we could ‘fix’ it by changing the HAVING clause to reject rows where the scalar aggregate returns zero: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) BETWEEN 1 AND 9 ); The query now returns the correct 23 rows: Unfortunately, the execution plan is less efficient now – it has an estimated cost of 0.78 compared to 0.33 for the earlier plans.  Let’s try adding a redundant GROUP BY instead of changing the HAVING clause: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY th.ProductID HAVING COUNT_BIG(*) < 10 ); Not only do we now get correct results (23 rows), this is the execution plan: I like to compare that plan to quantum physics: if you don’t find it shocking, you haven’t understood it properly :)  The simple addition of a redundant GROUP BY has resulted in the EXISTS form of the query being transformed into exactly the same optimal plan we found earlier.  What’s more, in SQL Server 2008 and later, we can replace the odd-looking GROUP BY with an explicit GROUP BY on the empty set: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ); I offer that as an alternative because some people find it more intuitive (and it perhaps has more geek value too).  Whichever way you prefer, it’s rather satisfying to note that the result of the sub-query does not exist for a particular correlated value where a vector aggregate is used (the scalar COUNT aggregate always returns a value, even if zero, so it always ‘EXISTS’ regardless which ProductID is logically being evaluated). The following query forms also produce the optimal plan and correct results, so long as a vector aggregate is used (you can probably find more equivalent query forms): WHERE Clause SELECT p.Name FROM Production.Product AS p WHERE ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) < 10; APPLY SELECT p.Name FROM Production.Product AS p CROSS APPLY ( SELECT NULL FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ) AS ca (dummy); FROM Clause SELECT q1.Name FROM ( SELECT p.Name, cnt = ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) FROM Production.Product AS p ) AS q1 WHERE q1.cnt < 10; This last example uses SUM(1) instead of COUNT and does not require a vector aggregate…you should be able to work out why :) SELECT q.Name FROM ( SELECT p.Name, cnt = ( SELECT SUM(1) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID ) FROM Production.Product AS p ) AS q WHERE q.cnt < 10; The semantics of SQL aggregates are rather odd in places.  It definitely pays to get to know the rules, and to be careful to check whether your queries are using scalar or vector aggregates.  As we have seen, query plans do not show in which ‘mode’ an aggregate is running and getting it wrong can cause poor performance, wrong results, or both. © 2012 Paul White Twitter: @SQL_Kiwi email: [email protected]

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• Complex event system for DungeonKeeper like game

  - by paul424

  I am working on opensource GPL3 game. http://opendungeons.sourceforge.net/ , new coders would be welcome. Now there's design question regarding Event System: We want to improve the game logic, that is program a new event system. I will just repost what's settled up already on http://forum.freegamedev.net/viewtopic.php?f=45&t=3033. From the discussion came the idea of the Publisher / Subscriber pattern + "domains": My current idea is to use the subscirbers / publishers model. Its similar to Observable pattern, but instead one subscribes to Events types, not Object's Events. For each Event would like to have both static and dynamic type. Static that is its's type would be resolved by belonging to the proper inherited class from Event. That is from Event we would have EventTile, EventCreature, EvenMapLoader, EventGameMap etc. From that there are of course subtypes like EventCreature would be EventKobold, EventKnight, EventTentacle etc. The listeners would collect the event from publishers, and send them subcribers , each of them would be a global singleton. The Listeners type hierachy would exactly mirror the type hierarchy of Events. In each constructor of Event type, the created instance would notify the proper listeners. That is when calling EventKnight the proper ctor would notify the Listeners : EventListener, CreatureLisener and KnightListener. The default action for an listner would be to notify all subscribers, but there would be some exceptions , like EventAttack would notify AttackListener which would dispatch event by the dynamic part ( that is the Creature pointer or hash). Any comments ? #include <vector> class Subscriber; class SubscriberAttack; class Event{ private: int foo; int bar; protected: // static std::vector<Publisher*> publishersList; static std::vector<Subscriber*> subscribersList; static std::vector<Event*> eventQueue; public: Event(){ eventQueue.push_back(this); } static int subscribe(Subscriber* ss); static int unsubscribe(Subscriber* ss); //static int reg_publisher(Publisher* pp); //static int unreg_publisher(Publisher* pp); }; // class Publisher{ // }; class Subscriber{ public: int (*newEvent) (Event* ee); Subscriber( ){ Event::subscribe(this); } Subscriber( int (*fp) (Event* ee) ):newEvent(fp){ Subscriber(); } ~Subscriber(){ Event::unsubscribe(this); } }; class EventAttack: Event{ private: int foo; int bar; protected: // static std::vector<Publisher*> publishersList; static std::vector<SubscriberAttack*> subscribersList; static std::vector<EventAttack*> eventQueue; public: EventAttack(){ eventQueue.push_back(this); } static int subscribe(SubscriberAttack* ss); static int unsubscribe(SubscriberAttack* ss); //static int reg_publisher(Publisher* pp); //static int unreg_publisher(Publisher* pp); }; class AttackSubscriber :Subscriber{ public: int (*newEvent) (EventAttack* ee); AttackSubscriber( ){ EventAttack::subscribe(this); } AttackSubscriber( int (*fp) (EventAttack* ee) ):newEventAttack(fp){ AttackSubscriber(); } ~AttackSubscriber(){ EventAttack::unsubscribe(this); } }; From that point, others wanted the Subject-Observer pattern, that is one would subscribe to all event types produced by particular object. That way it came out to add the domain system : Huh, to meet the ability to listen to particular game's object events, I though of introducing entity domains . Domains are trees, which nodes are labeled by unique names for each level. ( like the www addresses ). Each Entity wanting to participate in our event system ( that is be able to publish / produce events ) should at least now its domain name. That would end up in Player1/Room/Treasury/#24 or Player1/Creature/Kobold/#3 producing events. The subscriber picks some part of a tree. For example by specifiing subtree with the root in one of the nodes like Player1/Room/* ,would subscribe us to all Players1's room's event, and Player1/Creature/Kobold/#3 would subscribe to Players' third kobold's event. Does such event system make sense to you ? I have many implementation details to ask as well, but first let's start some general discussion. Note1: Notice that in the case of a fight between two creatues fight , the creature being attacked would have to throw an event, becuase it is HE/SHE/IT who have its domain address. So that would be BeingAttackedEvent() etc. I will edit that post if some other reflections on this would come out. Note2: the existing class hierarchy might be used to get the domains addresses being build in constructor . In a ctor you would just add + ."className" to domain address. If you are in a class'es hierarchy leaf constructor one might use nextID , hash or any other charactteristic, just to make the addresses distinguishable . Note3:subscribing to all entity's Events would require knowledge of all possible events produced by this entity . This could be done in one function call, but information on E produced would have to be handled for every Entity. SmartNote4 : Finding proper subscribers in a tree would be easy. One would start in particular Leaf for example Player1/Creature/Kobold/#3 and go up one parent a time , notifiying each Subscriber in a Node ie. : Player1/Creature/Kobold/* , Player1/Creature/* , Player1/* etc, , up to a root that is /* .<<<< Note5: The Event system was needed to have some way of incorporating Angelscript code into application. So the Event dispatcher was to be a gate to A-script functions. But it came out to this one.

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• Re: Help with Boost Grammar

  - by Decmac04

  I have redesigned and extended the grammar I asked about earlier as shown below: // BIFAnalyser.cpp : Defines the entry point for the console application. // // /*============================================================================= Copyright (c) Temitope Jos Onunkun 2010 http://www.dcs.kcl.ac.uk/pg/onun/ Use, modification and distribution is subject to the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) =============================================================================*/ //////////////////////////////////////////////////////////////////////////// // // // B Machine parser using the Boost "Grammar" and "Semantic Actions". // // // //////////////////////////////////////////////////////////////////////////// include include include include include include //////////////////////////////////////////////////////////////////////////// using namespace std; using namespace boost::spirit; //////////////////////////////////////////////////////////////////////////// // // Semantic Actions // //////////////////////////////////////////////////////////////////////////// // // namespace { //semantic action function on individual lexeme void do_noint(char const* start, char const* end) { string str(start, end); if (str != "NAT1") cout << "PUSH(" << str << ')' << endl; } //semantic action function on addition of lexemes void do_add(char const*, char const*) { cout << "ADD" << endl; // for(vector::iterator vi = strVect.begin(); vi < strVect.end(); ++vi) // cout << *vi << " "; } //semantic action function on subtraction of lexemes void do_subt(char const*, char const*) { cout << "SUBTRACT" << endl; } //semantic action function on multiplication of lexemes void do_mult(char const*, char const*) { cout << "\nMULTIPLY" << endl; } //semantic action function on division of lexemes void do_div(char const*, char const*) { cout << "\nDIVIDE" << endl; } // // vector flowTable; //semantic action function on simple substitution void do_sSubst(char const* start, char const* end) { string str(start, end); //use boost tokenizer to break down tokens typedef boost::tokenizer Tokenizer; boost::char_separator sep(" -+/*:=()",0,boost::drop_empty_tokens); // char separator definition Tokenizer tok(str, sep); Tokenizer::iterator tok_iter = tok.begin(); pair dependency; //create a pair object for dependencies //create a vector object to store all tokens vector dx; // int counter = 0; // tracks token position for(tok.begin(); tok_iter != tok.end(); ++tok_iter) //save all tokens in vector { dx.push_back(*tok_iter ); } counter = dx.size(); // vector d_hat; //stores set of dependency pairs string dep; //pairs variables as string object // dependency.first = *tok.begin(); vector FV; for(int unsigned i=1; i < dx.size(); i++) { // if(!atoi(dx.at(i).c_str()) && (dx.at(i) !=" ")) { dependency.second = dx.at(i); dep = dependency.first + "|-" + dependency.second + " "; d_hat.push_back(dep); vector<string> row; row.push_back(dependency.first); //push x_hat into first column of each row for(unsigned int j=0; j<2; j++) { row.push_back(dependency.second);//push an element (column) into the row } flowTable.push_back(row); //Add the row to the main vector } } //displays internal representation of information flow table cout << "\n****************\nDependency Table\n****************\n"; cout << "X_Hat\tDx\tG_Hat\n"; cout << "-----------------------------\n"; for(unsigned int i=0; i < flowTable.size(); i++) { for(unsigned int j=0; j<2; j++) { cout << flowTable[i][j] << "\t "; } if (*tok.begin() != "WHILE" ) //if there are no global flows, cout << "\t{}"; //display empty set cout << "\n"; } cout << "***************\n\n"; for(int unsigned j=0; j < FV.size(); j++) { if(FV.at(j) != dependency.second) dep = dependency.first + "|-" + dependency.second + " "; d_hat.push_back(dep); } cout << "PUSH(" << str << ')' << endl; cout << "\n*******\nDependency pairs\n*******\n"; for(int unsigned i=0; i < d_hat.size(); i++) cout << d_hat.at(i) << "\n...\n"; cout << "\nSIMPLE SUBSTITUTION\n\n"; } //semantic action function on multiple substitution void do_mSubst(char const* start, char const* end) { string str(start, end); cout << "PUSH(" << str << ')' << endl; //cout << "\nMULTIPLE SUBSTITUTION\n\n"; } //semantic action function on unbounded choice substitution void do_mChoice(char const* start, char const* end) { string str(start, end); cout << "PUSH(" << str << ')' << endl; cout << "\nUNBOUNDED CHOICE SUBSTITUTION\n\n"; } void do_logicExpr(char const* start, char const* end) { string str(start, end); //use boost tokenizer to break down tokens typedef boost::tokenizer Tokenizer; boost::char_separator sep(" -+/*=:()<",0,boost::drop_empty_tokens); // char separator definition Tokenizer tok(str, sep); Tokenizer::iterator tok_iter = tok.begin(); //pair dependency; //create a pair object for dependencies //create a vector object to store all tokens vector dx; for(tok.begin(); tok_iter != tok.end(); ++tok_iter) //save all tokens in vector { dx.push_back(*tok_iter ); } for(unsigned int i=0; i cout << "PUSH(" << str << ')' << endl; cout << "\nPREDICATE\n\n"; } void do_predicate(char const* start, char const* end) { string str(start, end); cout << "PUSH(" << str << ')' << endl; cout << "\nMULTIPLE PREDICATE\n\n"; } void do_ifSelectPre(char const* start, char const* end) { string str(start, end); //if cout << "PUSH(" << str << ')' << endl; cout << "\nPROTECTED SUBSTITUTION\n\n"; } //semantic action function on machine substitution void do_machSubst(char const* start, char const* end) { string str(start, end); cout << "PUSH(" << str << ')' << endl; cout << "\nMACHINE SUBSTITUTION\n\n"; } } //////////////////////////////////////////////////////////////////////////// // // Machine Substitution Grammar // //////////////////////////////////////////////////////////////////////////// // Simple substitution grammar parser with integer values removed struct Substitution : public grammar { template struct definition { definition(Substitution const& ) { machine_subst = ( (simple_subst) | (multi_subst) | (if_select_pre_subst) | (unbounded_choice) )[&do_machSubst] ; unbounded_choice = str_p("ANY") ide_list str_p("WHERE") predicate str_p("THEN") machine_subst str_p("END") ; if_select_pre_subst = ( ( str_p("IF") predicate str_p("THEN") machine_subst *( str_p("ELSIF") predicate machine_subst ) !( str_p("ELSE") machine_subst) str_p("END") ) | ( str_p("SELECT") predicate str_p("THEN") machine_subst *( str_p("WHEN") predicate machine_subst ) !( str_p("ELSE") machine_subst) str_p("END")) | ( str_p("PRE") predicate str_p("THEN") machine_subst str_p("END") ) )[&do_ifSelectPre] ; multi_subst = ( (machine_subst) *( ( str_p("||") (machine_subst) ) | ( str_p("[]") (machine_subst) ) ) ) [&do_mSubst] ; simple_subst = (identifier str_p(":=") arith_expr) [&do_sSubst] ; expression = predicate | arith_expr ; predicate = ( (logic_expr) *( ( ch_p('&') (logic_expr) ) | ( str_p("OR") (logic_expr) ) ) )[&do_predicate] ; logic_expr = ( identifier (str_p("<") arith_expr) | (str_p("<") arith_expr) | (str_p("/:") arith_expr) | (str_p("<:") arith_expr) | (str_p("/<:") arith_expr) | (str_p("<<:") arith_expr) | (str_p("/<<:") arith_expr) | (str_p("<=") arith_expr) | (str_p("=") arith_expr) | (str_p("=") arith_expr) | (str_p("=") arith_expr) ) [&do_logicExpr] ; arith_expr = term *( ('+' term)[&do_add] | ('-' term)[&do_subt] ) ; term = factor ( ('' factor)[&do_mult] | ('/' factor)[&do_div] ) ; factor = lexeme_d[( identifier | +digit_p)[&do_noint]] | '(' expression ')' | ('+' factor) ; ide_list = identifier *( ch_p(',') identifier ) ; identifier = alpha_p +( alnum_p | ch_p('_') ) ; } rule machine_subst, unbounded_choice, if_select_pre_subst, multi_subst, simple_subst, expression, predicate, logic_expr, arith_expr, term, factor, ide_list, identifier; rule<ScannerT> const& start() const { return predicate; //return multi_subst; //return machine_subst; } }; }; //////////////////////////////////////////////////////////////////////////// // // Main program // //////////////////////////////////////////////////////////////////////////// int main() { cout << "*********************************\n\n"; cout << "\t\t...Machine Parser...\n\n"; cout << "*********************************\n\n"; // cout << "Type an expression...or [q or Q] to quit\n\n"; string str; int machineCount = 0; char strFilename[256]; //file name store as a string object do { cout << "Please enter a filename...or [q or Q] to quit:\n\n "; //prompt for file name to be input //char strFilename[256]; //file name store as a string object cin strFilename; if(*strFilename == 'q' || *strFilename == 'Q') //termination condition return 0; ifstream inFile(strFilename); // opens file object for reading //output file for truncated machine (operations only) if (inFile.fail()) cerr << "\nUnable to open file for reading.\n" << endl; inFile.unsetf(std::ios::skipws); Substitution elementary_subst; // Simple substitution parser object string next; while (inFile str) { getline(inFile, next); str += next; if (str.empty() || str[0] == 'q' || str[0] == 'Q') break; parse_info< info = parse(str.c_str(), elementary_subst !end_p, space_p); if (info.full) { cout << "\n-------------------------\n"; cout << "Parsing succeeded\n"; cout << "\n-------------------------\n"; } else { cout << "\n-------------------------\n"; cout << "Parsing failed\n"; cout << "stopped at: " << info.stop << "\"\n"; cout << "\n-------------------------\n"; } } } while ( (*strFilename != 'q' || *strFilename !='Q')); return 0; } However, I am experiencing the following unexpected behaviours on testing: The text files I used are: f1.txt, ... containing ...: debt:=(LoanRequest+outstandingLoan1)*20 . f2.txt, ... containing ...: debt:=(LoanRequest+outstandingLoan1)*20 || newDebt := loanammount-paidammount || price := purchasePrice + overhead + bb . f3.txt, ... containing ...: yy < (xx+7+ww) . f4.txt, ... containing ...: yy < (xx+7+ww) & yy : NAT . When I use multi_subst as start rule both files (f1 and f2) are parsed correctly; When I use machine_subst as start rule file f1 parse correctly, while file f2 fails, producing the error: “Parsing failed stopped at: || newDebt := loanammount-paidammount || price := purchasePrice + overhead + bb” When I use predicate as start symbol, file f3 parse correctly, but file f4 yields the error: “ “Parsing failed stopped at: & yy : NAT” Can anyone help with the grammar, please? It appears there are problems with the grammar that I have so far been unable to spot.

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• Help with Boost Grammar

  - by Decmanc04

  I have been using the following win32 console code to try to parse a B Machine Grammar embedded within C++ using Boost Spirit grammar template. I am a relatively new Boost user. The code compiles, but when I run the .exe file produced by VC++2008, the program partially parses the input file. I believe the problem is with my grammar definition or the functions attached as semantic atctions. The code is given below: // BIFAnalyser.cpp : Defines the entry point for the console application. // // /*============================================================================= Copyright (c) Temitope Jos Onunkun 2010 http://www.dcs.kcl.ac.uk/pg/onun/ Use, modification and distribution is subject to the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) =============================================================================*/ //////////////////////////////////////////////////////////////////////////// // // // B Machine parser using the Boost "Grammar" and "Semantic Actions". // // // //////////////////////////////////////////////////////////////////////////// #include <boost/spirit/core.hpp> #include <boost/tokenizer.hpp> #include <iostream> #include <string> #include <fstream> #include <vector> #include <utility> /////////////////////////////////////////////////////////////////////////////////////////// using namespace std; using namespace boost::spirit; /////////////////////////////////////////////////////////////////////////////////////////// // // Semantic actions // //////////////////////////////////////////////////////////////////////////// vector<string> strVect; namespace { //semantic action function on individual lexeme void do_noint(char const* str, char const* end) { string s(str, end); if(atoi(str)) { ; } else { strVect.push_back(s); cout << "PUSH(" << s << ')' << endl; } } //semantic action function on addition of lexemes void do_add(char const*, char const*) { cout << "ADD" << endl; for(vector<string>::iterator vi = strVect.begin(); vi < strVect.end(); ++vi) cout << *vi << " "; } //semantic action function on subtraction of lexemes void do_subt(char const*, char const*) { cout << "SUBTRACT" << endl; for(vector<string>::iterator vi = strVect.begin(); vi < strVect.end(); ++vi) cout << *vi << " "; } //semantic action function on multiplication of lexemes void do_mult(char const*, char const*) { cout << "\nMULTIPLY" << endl; for(vector<string>::iterator vi = strVect.begin(); vi < strVect.end(); ++vi) cout << *vi << " "; cout << "\n"; } //semantic action function on division of lexemes void do_div(char const*, char const*) { cout << "\nDIVIDE" << endl; for(vector<string>::iterator vi = strVect.begin(); vi < strVect.end(); ++vi) cout << *vi << " "; } //semantic action function on simple substitution void do_sSubst(char const* str, char const* end) { string s(str, end); //use boost tokenizer to break down tokens typedef boost::tokenizer<boost::char_separator<char> > Tokenizer; boost::char_separator<char> sep("-+/*:=()"); // default char separator Tokenizer tok(s, sep); Tokenizer::iterator tok_iter = tok.begin(); pair<string, string > dependency; //create a pair object for dependencies //save first variable token in simple substitution dependency.first = *tok.begin(); //create a vector object to store all tokens vector<string> dx; // for( ; tok_iter != tok.end(); ++tok_iter) //save all tokens in vector { dx.push_back(*tok_iter ); } vector<string> d_hat; //stores set of dependency pairs string dep; //pairs variables as string object for(int unsigned i=1; i < dx.size()-1; i++) { dependency.second = dx.at(i); dep = dependency.first + "|->" + dependency.second + " "; d_hat.push_back(dep); } cout << "PUSH(" << s << ')' << endl; for(int unsigned i=0; i < d_hat.size(); i++) cout <<"\n...\n" << d_hat.at(i) << " "; cout << "\nSIMPLE SUBSTITUTION\n"; } //semantic action function on multiple substitution void do_mSubst(char const* str, char const* end) { string s(str, end); //use boost tokenizer to break down tokens typedef boost::tokenizer<boost::char_separator<char> > Tok; boost::char_separator<char> sep("-+/*:=()"); // default char separator Tok tok(s, sep); Tok::iterator tok_iter = tok.begin(); // string start = *tok.begin(); vector<string> mx; for( ; tok_iter != tok.end(); ++tok_iter) //save all tokens in vector { mx.push_back(*tok_iter ); } mx.push_back("END\n"); //add a marker "end" for(unsigned int i=0; i<mx.size(); i++) { // if(mx.at(i) == "END" || mx.at(i) == "||" ) // break; // else if( mx.at(i) == "||") // do_sSubst(str, end); // else // { // do_sSubst(str, end); // } cout << "\nTokens ... " << mx.at(i) << " "; } cout << "PUSH(" << s << ')' << endl; cout << "MULTIPLE SUBSTITUTION\n"; } } //////////////////////////////////////////////////////////////////////////// // // Simple Substitution Grammar // //////////////////////////////////////////////////////////////////////////// // Simple substitution grammar parser with integer values removed struct Substitution : public grammar<Substitution> { template <typename ScannerT> struct definition { definition(Substitution const& ) { multi_subst = (simple_subst [&do_mSubst] >> +( str_p("||") >> simple_subst [&do_mSubst]) ) ; simple_subst = (Identifier >> str_p(":=") >> expression)[&do_sSubst] ; Identifier = alpha_p >> +alnum_p//[do_noint] ; expression = term >> *( ('+' >> term)[&do_add] | ('-' >> term)[&do_subt] ) ; term = factor >> *( ('*' >> factor)[&do_mult] | ('/' >> factor)[&do_div] ) ; factor = lexeme_d[( (alpha_p >> +alnum_p) | +digit_p)[&do_noint]] | '(' >> expression >> ')' | ('+' >> factor) ; } rule<ScannerT> expression, term, factor, Identifier, simple_subst, multi_subst ; rule<ScannerT> const& start() const { return multi_subst; } }; }; //////////////////////////////////////////////////////////////////////////// // // Main program // //////////////////////////////////////////////////////////////////////////// int main() { cout << "************************************************************\n\n"; cout << "\t\t...Machine Parser...\n\n"; cout << "************************************************************\n\n"; // cout << "Type an expression...or [q or Q] to quit\n\n"; //prompt for file name to be input cout << "Please enter a filename...or [q or Q] to quit:\n\n "; char strFilename[256]; //file name store as a string object cin >> strFilename; ifstream inFile(strFilename); // opens file object for reading //output file for truncated machine (operations only) Substitution elementary_subst; // Simple substitution parser object string str, next; // inFile.open(strFilename); while (inFile >> str) { getline(cin, next); str += next; if (str.empty() || str[0] == 'q' || str[0] == 'Q') break; parse_info<> info = parse(str.c_str(), elementary_subst, space_p); if (info.full) { cout << "\n-------------------------\n"; cout << "Parsing succeeded\n"; cout << "\n-------------------------\n"; } else { cout << "\n-------------------------\n"; cout << "Parsing failed\n"; cout << "stopped at: \": " << info.stop << "\"\n"; cout << "\n-------------------------\n"; } } cout << "Please enter a filename...or [q or Q] to quit\n"; cin >> strFilename; return 0; } The contents of the file I tried to parse, which I named "mf7.txt" is given below: debt:=(LoanRequest+outstandingLoan1)*20 || newDebt := loanammount-paidammount The output when I execute the program is: ************************************************************ ...Machine Parser... ************************************************************ Please enter a filename...or [q or Q] to quit: c:\tplat\mf7.txt PUSH(LoanRequest) PUSH(outstandingLoan1) ADD LoanRequest outstandingLoan1 MULTIPLY LoanRequest outstandingLoan1 PUSH(debt:=(LoanRequest+outstandingLoan1)*20) ... debt|->LoanRequest ... debt|->outstandingLoan1 SIMPLE SUBSTITUTION Tokens ... debt Tokens ... LoanRequest Tokens ... outstandingLoan1 Tokens ... 20 Tokens ... END PUSH(debt:=(LoanRequest+outstandingLoan1)*20) MULTIPLE SUBSTITUTION ------------------------- Parsing failedstopped at: ": " ------------------------- My intention is to capture only the variables in the file, which I managed to do up to the "||" string. Clearly, the program is not parsing beyond the "||" string in the input file. I will appreciate assistance to fix the grammar. SOS, please.

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• How to compile a C++ source code written for Linux/Unix on Windows Vista (code given)

  - by HTMZ

  I have a c++ source code that was written in linux/unix environment by some other author. It gives me errors when i compile it in windows vista environment. I am using Bloodshed Dev C++ v 4.9. please help. #include <iostream.h> #include <map> #include <vector> #include <string> #include <string.h> #include <strstream> #include <unistd.h> #include <stdlib.h> using namespace std; template <class T> class PrefixSpan { private: vector < vector <T> > transaction; vector < pair <T, unsigned int> > pattern; unsigned int minsup; unsigned int minpat; unsigned int maxpat; bool all; bool where; string delimiter; bool verbose; ostream *os; void report (vector <pair <unsigned int, int> > &projected) { if (minpat > pattern.size()) return; // print where & pattern if (where) { *os << "<pattern>" << endl; // what: if (all) { *os << "<freq>" << pattern[pattern.size()-1].second << "</freq>" << endl; *os << "<what>"; for (unsigned int i = 0; i < pattern.size(); i++) *os << (i ? " " : "") << pattern[i].first; } else { *os << "<what>"; for (unsigned int i = 0; i < pattern.size(); i++) *os << (i ? " " : "") << pattern[i].first << delimiter << pattern[i].second; } *os << "</what>" << endl; // where *os << "<where>"; for (unsigned int i = 0; i < projected.size(); i++) *os << (i ? " " : "") << projected[i].first; *os << "</where>" << endl; *os << "</pattern>" << endl; } else { // print found pattern only if (all) { *os << pattern[pattern.size()-1].second; for (unsigned int i = 0; i < pattern.size(); i++) *os << " " << pattern[i].first; } else { for (unsigned int i = 0; i < pattern.size(); i++) *os << (i ? " " : "") << pattern[i].first << delimiter << pattern[i].second; } *os << endl; } } void project (vector <pair <unsigned int, int> > &projected) { if (all) report(projected); map <T, vector <pair <unsigned int, int> > > counter; for (unsigned int i = 0; i < projected.size(); i++) { int pos = projected[i].second; unsigned int id = projected[i].first; unsigned int size = transaction[id].size(); map <T, int> tmp; for (unsigned int j = pos + 1; j < size; j++) { T item = transaction[id][j]; if (tmp.find (item) == tmp.end()) tmp[item] = j ; } for (map <T, int>::iterator k = tmp.begin(); k != tmp.end(); ++k) counter[k->first].push_back (make_pair <unsigned int, int> (id, k->second)); } for (map <T, vector <pair <unsigned int, int> > >::iterator l = counter.begin (); l != counter.end (); ) { if (l->second.size() < minsup) { map <T, vector <pair <unsigned int, int> > >::iterator tmp = l; tmp = l; ++tmp; counter.erase (l); l = tmp; } else { ++l; } } if (! all && counter.size () == 0) { report (projected); return; } for (map <T, vector <pair <unsigned int, int> > >::iterator l = counter.begin (); l != counter.end(); ++l) { if (pattern.size () < maxpat) { pattern.push_back (make_pair <T, unsigned int> (l->first, l->second.size())); project (l->second); pattern.erase (pattern.end()); } } } public: PrefixSpan (unsigned int _minsup = 1, unsigned int _minpat = 1, unsigned int _maxpat = 0xffffffff, bool _all = false, bool _where = false, string _delimiter = "/", bool _verbose = false): minsup(_minsup), minpat (_minpat), maxpat (_maxpat), all(_all), where(_where), delimiter (_delimiter), verbose (_verbose) {}; ~PrefixSpan () {}; istream& read (istream &is) { string line; vector <T> tmp; T item; while (getline (is, line)) { tmp.clear (); istrstream istrs ((char *)line.c_str()); while (istrs >> item) tmp.push_back (item); transaction.push_back (tmp); } return is; } ostream& run (ostream &_os) { os = &_os; if (verbose) *os << transaction.size() << endl; vector <pair <unsigned int, int> > root; for (unsigned int i = 0; i < transaction.size(); i++) root.push_back (make_pair (i, -1)); project (root); return *os; } void clear () { transaction.clear (); pattern.clear (); } }; int main (int argc, char **argv) { extern char *optarg; unsigned int minsup = 1; unsigned int minpat = 1; unsigned int maxpat = 0xffffffff; bool all = false; bool where = false; string delimiter = "/"; bool verbose = false; string type = "string"; int opt; while ((opt = getopt(argc, argv, "awvt:M:m:L:d:")) != -1) { switch(opt) { case 'a': all = true; break; case 'w': where = true; break; case 'v': verbose = true; break; case 'm': minsup = atoi (optarg); break; case 'M': minpat = atoi (optarg); break; case 'L': maxpat = atoi (optarg); break; case 't': type = string (optarg); break; case 'd': delimiter = string (optarg); break; default: cout << "Usage: " << argv[0] << " [-m minsup] [-M minpat] [-L maxpat] [-a] [-w] [-v] [-t type] [-d delimiter] < data .." << endl; return -1; } } if (type == "int") { PrefixSpan<unsigned int> prefixspan (minsup, minpat, maxpat, all, where, delimiter, verbose); prefixspan.read (cin); prefixspan.run (cout); }else if (type == "short") { PrefixSpan<unsigned short> prefixspan (minsup, minpat, maxpat, all, where, delimiter, verbose); prefixspan.read (cin); prefixspan.run (cout); } else if (type == "char") { PrefixSpan<unsigned char> prefixspan (minsup, minpat, maxpat, all, where, delimiter, verbose); prefixspan.read (cin); prefixspan.run (cout); } else if (type == "string") { PrefixSpan<string> prefixspan (minsup, minpat, maxpat, all, where, delimiter, verbose); prefixspan.read (cin); prefixspan.run (cout); } else { cerr << "Unknown Item Type: " << type << " : choose from [string|int|short|char]" << endl; return -1; } return 0; }

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• Find vertices of a convex hull

  - by Jeff Bullard

  I am attempting to do this within CGAL. From a 3D point cloud, find the convex hull, then loop over the finite facets of the convex hull and print each facet's vertices. It seems like there should be a straightforward way to do this; I would have expected that 3D polyhedra would own a vector of facet objects, each of which in turn would own a vector of its edges, each of which in turn would own a vector of its vertices, and that their would be some access through this hierarchy using iterators. But so far I have been unable to find a simple way to navigate through this hierarchy (if it exists).

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• What's the most efficient way to find barycentric coordinates?

  - by bobobobo

  In my profiler, finding barycentric coordinates is apparently somewhat of a bottleneck. I am looking to make it more efficient. It follows the method in shirley, where you compute the area of the triangles formed by embedding the point P inside the triangle. Code: Vector Triangle::getBarycentricCoordinatesAt( const Vector & P ) const { Vector bary ; // The area of a triangle is real areaABC = DOT( normal, CROSS( (b - a), (c - a) ) ) ; real areaPBC = DOT( normal, CROSS( (b - P), (c - P) ) ) ; real areaPCA = DOT( normal, CROSS( (c - P), (a - P) ) ) ; bary.x = areaPBC / areaABC ; // alpha bary.y = areaPCA / areaABC ; // beta bary.z = 1.0f - bary.x - bary.y ; // gamma return bary ; } This method works, but I'm looking for a more efficient one!

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• Confusion about Rotation matrices from Euler Angles

  - by xEnOn

  I am trying to learn more about Euler Angles so as to help myself in understanding how I can control my camera better in the game. I came across the following formula that converts Euler Angles to rotation matrices: In the equation, I could see that the first matrix from the left is the rotation matrix about x-axis, the second is about y-axis and the third is about z-axis. From my understanding about ordinary matrix transformations, the later transformation is always applied to the right hand side. And if I'm right about this, then the above equation should have a rotation order starting from rotating about z-axis, y-axis, then finally x-axis. But, from the symbols it seems that the rotation order start rotating about x-axis, then y-axis, then finally z-axis. What should the actual order of the rotation be? Also, I am confuse about if the input vector, in this case, would be a row vector on the left, or a column vector on the right?

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• How access PhysicalMaterial from Actor Class?

  - by EmAdpres

  I use Projectile for my weapon system and UDKProjectile has two main function to handle Hit of projectiles(=bullet of my weapon): simulated function ProcessTouch(Actor Other, Vector HitLocation, Vector HitNormal) // For Actors simulated event HitWall(vector HitNormal, actor Wall, PrimitiveComponent WallComp) // Everything except Actors ( I guess) the first method, the function just give me the actor which I hit and my question is How I can get that actor's physical material by first parameter ( Other ), in order to make a proper react about it ( for example a proper Sound of collide ) ... A tricky (but hateful ) way which I knew works is, make a Trace from a little back of that actor to that actor, and use HitInfo parameter which include physical Material ! But there should be a more standard way !

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• Several classes need to access the same data, where should the data be declared?

  - by Juicy

  I have a basic 2D tower defense game in C++. Each map is a separate class which inherits from GameState. The map delegates the logic and drawing code to each object in the game and sets data such as the map path. In pseudo-code the logic section might look something like this: update(): for each creep in creeps: creep.update() for each tower in towers: tower.update() for each missile in missiles: missile.update() The objects (creeps, towers and missiles) are stored in vector-of-pointers. The towers must have access to the vector-of-creeps and the vector-of-missiles to create new missiles and identify targets. The question is: where do I declare the vectors? Should they be members of the Map class, and passed as arguments to the tower.update() function? Or declared globally? Or are there other solutions I'm missing entirely?

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• box2d and constant movement

  - by Arnas

  i'm developing a game with a top down view, the players body is a circle. To move the character you need to tap on the screen and it moves to the spot. To achieve this i'm saving the coordinate of the touch and call a method every frame which applies linear velocity to the body with a vector of the direction the body should go _body->SetLinearVelocity(b2Vec2((a.x - currPos.x)/SPEED_RATIO,(size.height - a.y - currPos.y)/SPEED_RATIO)); //click position - current position, screen height - click position (since the y axis is flipped, (0,0) is in the bottom left ) - current position = vector of the direction we want to go now the problem with this is that the body slows down until it finally stops when getting closer to the point we want it to go, since the closer we are to that point the lenght of the vector gets smaller. Besides that i've read that it's bad practice to set linear velocity in box2d and i should use apply force instead, but that way the forces would add up and overshoot the target where it's supposed to stop. So what i'm asking is how to move a box2d body to a coordinate in constant speed.

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• Elastic Collision Formula in Java

  - by Shijima

  I'm trying to write a Java formula based on this tutorial: 2-D elastic collisions without Trigonometry. I am in the section "Elastic Collisions in 2 Dimensions". In step 1, it mentions "Next, find the unit vector of n, which we will call un. This is done by dividing by the magnitude of n". My below code represents the normal vector of 2 objects (I'm using a simple array to represent the normal vector), but I am not really sure what the tutorial means by dividing the magnitude of n to get the un. int[] normal = new int[2]; normal[0] = ball2.x - ball1.x; normal[1] = ball2.y - ball1.y; Can anyone please explain what un is, and how I can calculate it with my array in Java?

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• How can I have multiple layers in my map array?

  - by Manl400

  How do I load Levels in my game, as in Layer 1 would be Objects, Layer 2 would be Characters and so on. I only need 3 layers, and they will all be put on top of each other. i.e having a flower with a transparent background to be put on grass or dirt on the layer below.I would like to Read From the same file too. How would i go about doing this? Any help would be appreciated. I load the map from a level file which are just numbers corresponding to a tile in the tilesheet. Here is the level file [Layer1] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 [Layer2] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 [Layer3] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 And here is the code that interprets it void LoadMap(const char *filename, std::vector< std::vector <int> > &map) { std::ifstream openfile(filename); if(openfile.is_open()) { std::string line, value; int space; while(!openfile.eof()) { std::getline(openfile, line); if(line.find("[TileSet]") != std::string::npos) { state = TileSet; continue; } else if (line.find("[Layer1]") != std::string::npos) { state = Map; continue; } switch(state) { case TileSet: if(line.length() > 0) tileSet = al_load_bitmap(line.c_str()); break; case Map: std::stringstream str(line); std::vector<int> tempVector; while(!str.eof()) { std::getline(str, value, ' '); if(value.length() > 0) tempVector.push_back(atoi(value.c_str())); } map.push_back(tempVector); break; } } } else { } } and this is how it draws the map. Also the tile sheet is 1280 by 1280 and the tilesizeX and tilesizeY is 64 void DrawMap(std::vector <std::vector <int> > map) { int mapRowCount = map.size(); for(int i, j = 0; i < mapRowCount; i ++) { int mapColCount = map[i].size(); for (int j = 0; j < mapColCount; ++j) { int tilesetIndex = map[i][j]; int tilesetRow = floor(tilesetIndex / TILESET_COLCOUNT); int tilesetCol = tilesetIndex % TILESET_COLCOUNT; al_draw_bitmap_region(tileSet, tilesetCol * TileSizeX, tilesetRow * TileSizeY, TileSizeX, TileSizeY, j * TileSizeX, i * TileSizeX, NULL); } } } EDIT: http://i.imgur.com/Ygu0zRE.jpg

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• OO Design - polymorphism - how to design for handing streams of different file types

  - by Kache4

  I've little experience with advanced OO practices, and I want to design this properly as an exercise. I'm thinking of implementing the following, and I'm asking if I'm going about this the right way. I have a class PImage that holds the raw data and some information I need for an image file. Its header is currently something like this: #include <boost/filesytem.hpp> #include <vector> namespace fs = boost::filesystem; class PImage { public: PImage(const fs::path& path, const unsigned char* buffer, int bufferLen); const vector<char> data() const { return data_; } const char* rawData() const { return &data_[0]; } /*** other assorted accessors ***/ private: fs::path path_; int width_; int height_; int filesize_; vector<char> data_; } I want to fill the width_ and height_ by looking through the file's header. The trivial/inelegant solution would be to have a lot of messy control flow that identifies the type of image file (.gif, .jpg, .png, etc) and then parse the header accordingly. Instead of using vector<char> data_, I was thinking of having PImage use a class, RawImageStream data_ that inherits from vector<char>. Each type of file I plan to support would then inherit from RawImageStream, e.g. RawGifStream, RawPngStream. Each RawXYZStream would encapsulate the respective header-parsing functions, and PImage would only have to do something like height_ = data_.getHeight();. Am I thinking this through correctly? How would I create the proper RawImageStream subclass for data_ to be in the PImage ctor? Is this where I could use an object factory? Anything I'm forgetting?

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• rand() generating the same number – even with srand(time(NULL)) in my main!

  - by Nick Sweet

  So, I'm trying to create a random vector (think geometry, not an expandable array), and every time I call my random vector function I get the same x value, thought y and z are different. int main () { srand ( (unsigned)time(NULL)); Vector<double> a; a.randvec(); cout << a << endl; return 0; } using the function //random Vector template <class T> void Vector<T>::randvec() { const int min=-10, max=10; int randx, randy, randz; const int bucket_size = RAND_MAX/(max-min); do randx = (rand()/bucket_size)+min; while (randx <= min && randx >= max); x = randx; do randy = (rand()/bucket_size)+min; while (randy <= min && randy >= max); y = randy; do randz = (rand()/bucket_size)+min; while (randz <= min && randz >= max); z = randz; } For some reason, randx will consistently return 8, whereas the other numbers seem to be following the (pseudo) randomness perfectly. However, if I put the call to define, say, randy before randx, randy will always return 8. Why is my first random number always 8? Am I seeding incorrectly?

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• Boost tuple + transform

  - by JH

  Is it possible to do the following. Say my boost tuple has <String, int> I would like to use std::transform + mem_fun to insert only the String element in a corresponding vector. Is it possible or are we required to use a loop and push_back(get<0) Ie the following doesn't like to compile... (unknown types...) result.resize(storage.size()) std::transform(storage.begin(), storage.end(), result.begin(), std::mem_fun(&boost::get<0>)); Here is an example (trying one of the comments): #include <boost/tuple/tuple.hpp> #include <vector> #include <string> #include <algorithm> int main(int argc, char**argv) { std::vector< boost::tuple<std::string, int> > storage; std::vector< std::string> result; result.resize(storage.size()); std::transform(storage.begin(), storage.end(), result.begin(), &boost::get<0, boost::tuple<std::string, int> >); return 0; } Output: g++ test.cpp /usr/include/boost/tuple/detail/tuple_basic.hpp: In instantiation of `boost::tuples::cons<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, TT>': /usr/include/boost/tuple/detail/tuple_basic.hpp:151: instantiated from `boost::tuples::element<0, boost::tuples::cons<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, TT> >' test.cpp:14: instantiated from here /usr/include/boost/tuple/detail/tuple_basic.hpp:329: error: `boost::tuples::cons<HT, TT>::tail' has incomplete type /usr/include/boost/tuple/detail/tuple_basic.hpp:329: error: invalid use of template type parameter test.cpp: In function `int main(int, char**)': test.cpp:14: error: no matching function for call to `transform(__gnu_cxx::__normal_iterator<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>*, std::vector<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, std::allocator<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > > >, __gnu_cxx::__normal_iterator<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>*, std::vector<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, std::allocator<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > > >, __gnu_cxx::__normal_iterator<std::string*, std::vector<std::string, std::allocator<std::string> > >, <unresolved overloaded function type>)'

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• C++ templates - matrix class

  - by lastOfMohicans

  Hi I'm learning templates in C++ so I decied to write matrix class which would be a template class. In Matrix.h file I wrote #pragma once #include "stdafx.h" #include <vector> using namespace std; template<class T> class Matrix { public: Matrix(); ~Matrix(); GetDataVector(); SetDataVector(vector<vector<T>> dataVector); bool operator == (Matrix* matrix); bool operator < (Matrix* matrix); bool operator <= (Matrix* matrix); bool operator > (Matrix* matrix); bool operator >= (Matrix* matrix); Matrix* operator + (Matrix* matrix); Matrix* operator - (Matrix* matrix); Matrix* operator * (Matrix* matrix); private: vector<vector<T>> datavector; int columns,rows; }; In Matrix cpp Visual Stuio automaticlly generated code for default constructors #include "StdAfx.h" #include "Matrix.h" Matrix::Matrix() { } Matrix::~Matrix() { } However if I want to compile this I get an error 'Matrix' : use of class template requires template argument list The error are in file Matrix.cpp in default constructors What may be the problem ??

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• Avoiding RTTI In Java

  - by destructo_gold

  Hi, If I have a superclass, say Animal, and two subclasses: Zebra and Giraffe, If I decide to define a Vector of Animals: Vector <Animal> animals = new Vector(); and I want to say: You can add Giraffes, but you must own at least one Zebra first. What is the best way to do this without using RTTI? (instanceof)

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• terminate called after throwing an instance of 'std::length_error'

  - by mark

  hello all, this is my first post here. As i am newbie, the problem might be stupid. I was writing a piece of code while the following error message shown, terminate called after throwing an instance of 'std::length_error' what(): basic_string::_S_create /home/gcj/finals /home/gcj/quals where Aborted the following is the offending code especially Line 39 to Line 52. It is weired for me as this block of code is almost same as the Line64 to Line79. int main(){ std::vector<std::string> dirs, need; std::string tmp_str; std::ifstream fp_in("small.in"); std::ofstream fp_out("output"); std::string::iterator iter_substr_begin, iter_substr_end; std::string slash("/"); int T, N, M; fp_in>>T; for (int t = 0; t < T; t++){ std::cout<<" time "<< t << std::endl; fp_in >> N >> M; for (int n =0; n<N; n++){ fp_in>>tmp_str; dirs.push_back(tmp_str); tmp_str.clear(); } for (int m=0; m<M; m++){ fp_in>>tmp_str; need.push_back(tmp_str); tmp_str.clear(); } for (std::vector<std::string>::iterator iter = dirs.begin(); iter!=dirs.end(); iter++){ for (std::string::iterator iter_str = (*iter).begin()+1; iter_str<(*iter).end(); ++iter_str){ if ((*iter_str)=='/') { std::string tmp_str2((*iter).begin(), iter_str); if (find(dirs.begin(), dirs.end(), tmp_str2)==dirs.end()) { dirs.push_back(tmp_str2); } } } } for (std::vector<std::string>::iterator iter_tmp = dirs.begin(); iter_tmp!= dirs.end(); ++iter_tmp) std::cout<<*iter_tmp<<" "; dirs.clear(); std::cout<<std::endl; std::cout<<" need "<<std::endl; //processing the next for (std::vector<std::string>::iterator iter_tmp = need.begin(); iter_tmp!=need.end(); ++iter_tmp) std::cout<<*iter_tmp<<" "; std::cout<<" where "; for (std::vector<std::string>::iterator iter = need.begin(); iter!=need.end(); iter++){ for (std::string::iterator iter_str = (*iter).begin()+1; iter_str<(*iter).end(); ++iter_str){ if ((*iter_str)=='/') { std::string tmp_str2((*iter).begin(), iter_str); if (find(need.begin(), need.end(), tmp_str2)==need.end()) { need.push_back(tmp_str2); } } } } for (std::vector<std::string>::iterator iter_tmp = need.begin(); iter_tmp!= need.end(); ++iter_tmp) std::cout<<*iter_tmp<<" "; need.clear(); std::cout<<std::endl; //finish processing the next } for (std::vector<std::string>::iterator iter= dirs.begin(); iter!=dirs.end(); iter++) std::cout<<*iter<<" "; std::cout<<std::endl; for (std::vector<std::string>::iterator iter= need.begin(); iter!=need.end(); iter++) std::cout<<*iter<<" "; std::cout<<std::endl; fp_out.close(); } best regards, Mark

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• Use of for_each on map elements

  - by Antonio

  I have a map where I'd like to perform a call on every data type object member function. I yet know how to do this on any sequence but, is it possible to do it on an associative container? The closest answer I could find was this: Boost.Bind to access std::map elements in std::for_each. But I cannot use boost in my project so, is there an STL alternative that I'm missing to boost::bind? If not possible, I thought on creating a temporary sequence for pointers to the data objects and then, call for_each on it, something like this: class MyClass { public: void Method() const; } std::map<int, MyClass> Map; //... std::vector<MyClass*> Vector; std::transform(Map.begin(), Map.end(), std::back_inserter(Vector), std::mem_fun_ref(&std::map<int, MyClass>::value_type::second)); std::for_each(Vector.begin(), Vector.end(), std::mem_fun(&MyClass::Method)); It looks too obfuscated and I don't really like it. Any suggestions?

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• ajax call to servlet puzzler

  - by vector

  Greetings! I'm having a problem getting a text value of a captcha from a servlet through ajax call. When my captcha gets created, its text value is written to session, but after refreshing the image itself though ajax call, I only get one old value of the text. Refreshing the image itself works ok, but I'm stuck getting the correct values from the session on subsequent call. On page reload I get both the new image and its new text value, no joy with ajax though. This works great for the image refresh: $("#asos").attr("src", "/ImageServlet?="+((new Date()).getTime()) ) This call to another method to get text value gives me old stuff: $.ajax({ url:"checkCaptcha", type:"GET", cache: false, success: function( data) { alert(data); } }); Any feedback will be appreciated. ps: here's the meat of the method getting the call: PrintWriter out = response.getWriter(); response.setContentType("text/html"); response.setDateHeader("Expires", 0 ); // Set standard HTTP/1.1 no-cache headers. response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate"); // Set IE extended HTTP/1.1 no-cache headers (use addHeader). response.addHeader("Cache-Control", "post-check=0, pre-check=0"); // Set standard HTTP/1.0 no-cache header. response.setHeader("Pragma", "no-cache"); out.print( request.getSession( ).getAttribute("randomPixValue") ); out.close();

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