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• Need help figuring out scala compiler errors.

  - by klactose

  Hello all, I have been working on a project in scala, but I am getting some error messages that I don't quite understand. The classes that I am working with are relatively simple. For example: abstract class Shape case class Point(x: Int, y: Int) extends Shape case class Polygon(points: Point*) extends Shape Now suppose that I create a Polygon: val poly = new Polygon(new Point(2,5), new Point(7,0), new Point(3,1)) Then if I attempt to determine the location and size of the smallest possible rectangle that could contain the polygon, I get various errors that I don't quite understand. Below are snippets of different attempts and the corresponding error messages that they produce. val upperLeftX = poly.points.reduceLeft(Math.min(_.x, _.x)) Gives the error: "missing parameter type for expanded function ((x$1) = x$1.x)" val upperLeftX = poly.points.reduceLeft((a: Point, b: Point) => (Math.min(a.x, b.x))) Gives this error: "type mismatch; found : (Point, Point) = Int required: (Any, Point) = Any" I am very confused about both of these error messages. If anyone could explain more clearly what I am doing incorrectly, I would really appreciate it. Yes, I see that the second error says that I need type "Any" but I don't understand exactly how to implement a change that would work as I need it. Obviously simply changing "a: Point" to "a: Any" is not a viable solution, so what am I missing?

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• Generating equals / hashcode / toString using annotation

  - by Bruno Bieth

  I believe I read somewhere people generating equals / hashcode / toString methods during compile time (using APT) by identifying which fields should be part of the hash / equality test. I couldn't find anything like that on the web (I might have dreamed it ?) ... That could be done like that : public class Person { @Id @GeneratedValue private Integer id; @Identity private String firstName, lastName; @Identity private Date dateOfBirth; //... } For an entity (so we want to exlude some fields, like the id). Or like a scala case class i.e a value object : @ValueObject public class Color { private int red, green, blue; } Not only the file becomes more readable and easier to write, but it also helps ensuring that all the attributes are part of the equals / hashcode (in case you add another attribute later on, without updating the methods accordingly). I heard APT isn't very well supported in IDE but I wouldn't see that as a major issue. After all, tests are mainly run by continuous integration servers. Any idea if this has been done already and if not why ? Thanks

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• Help me create a Firefox extension (Javascript XPCOM Component)

  - by Johnny Grass

  I've been looking at different tutorials and I know I'm close but I'm getting lost in implementation details because some of them are a little bit dated and a few things have changed since Firefox 3. I have already written the javascript for the firefox extension, now I need to make it into an XPCOM component. This is the functionality that I need: My Javascript file is simple, I have two functions startServer() and stopServer. I need to run startServer() when the browser starts and stopServer() when firefox quits. Edit: I've updated my code with a working solution (thanks to Neil). The following is in MyExtension/components/myextension.js. Components.utils.import("resource://gre/modules/XPCOMUtils.jsm"); const CI = Components.interfaces, CC = Components.classes, CR = Components.results; // class declaration function MyExtension() {} MyExtension.prototype = { classDescription: "My Firefox Extension", classID: Components.ID("{xxxx-xxxx-xxx-xxxxx}"), contractID: "@example.com/MyExtension;1", QueryInterface: XPCOMUtils.generateQI([CI.nsIObserver]), // add to category manager _xpcom_categories: [{ category: "profile-after-change" }], // start socket server startServer: function () { /* socket initialization code */ }, // stop socket server stopServer: function () { /* stop server */ }, observe: function(aSubject, aTopic, aData) { var obs = CC["@mozilla.org/observer-service;1"].getService(CI.nsIObserverService); switch (aTopic) { case "quit-application": this.stopServer(); obs.removeObserver(this, "quit-application"); break; case "profile-after-change": this.startServer(); obs.addObserver(this, "quit-application", false); break; default: throw Components.Exception("Unknown topic: " + aTopic); } } }; var components = [MyExtension]; function NSGetModule(compMgr, fileSpec) { return XPCOMUtils.generateModule(components); }

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• Am I under risk of CSRF attacks in a POST form that doesn't require the user to be logged in?

  - by Monika Sulik

  I'm probably being a total noob here, but I'm still uncertain about what a CSRF (Cross-Site Request Forgery) attack is exactly. So lets look at three situations... 1) I have a POST form that I use to edit data on my site. I want this data to be edited only by users that are logged in. 2) I have a site, which can be used by both users who are logged in as well as guests. Parts of the site are for logged in users only, but there are also POST forms that can be used by all users - anonymous and not (for example a standard contact form). Should the contact form be safeguarded against CSRF attacks? 3) I have a site which doesn't have an authentication system at all (well, perhaps that's unrealistic, so lets say it has an admin site which is separate from the rest of it and the admin part is properly safeguarded). The main part of the site is only used by anonymous users. Do the POST forms on it need to be safeguarded? In the case of 1) the answer is clearly yes. But in the case of 2 and 3 I don't know (and is the difference between 2 and 3 even significant?).

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• error handler isn't called when file is uploaded via ajax using jQuery form plugin

  - by scompt.com

  Here's my test case. If the form is posted, a 500 error response is sent. If not, the form is sent. If the file input tag is commented out, the error handler is called. If the file input tag is present, the error handler isn't called. I think this might have something to do with the fact that jQuery needs to use an iframe to handle the upload and iframes don't seem to respond to the error handler. Edit: If I add iframe: true to the options passed to ajaxSubmit to force the use of an iframe, the non-file-upload case stops working also, so it definitely has to do with the iframe. Edit2: I'm using the jQuery Form Plugin. <?php if($_SERVER['REQUEST_METHOD'] == 'POST') { header('HTTP/1.1 500 Internal Server Error'); die; } else {?> <html><head> <script type='text/javascript' src='http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js?ver=2.9.2'></script> <script type='text/javascript' src='http://github.com/malsup/form/raw/master/jquery.form.js?v2.43'></script> <script type="text/javascript"> jQuery(document).ready(function() { jQuery('a').click(function() {jQuery('form').ajaxSubmit({error: function(){alert('error handler called');}})}); }); </script> </head><body> <form method="POST"> <input type="text" name="mytext" /> <input type="file" name="myfile" /><!-- comment this element out --> <input type="hidden" name="blah" value="blah" /> <a>submit</a> </form> </body></html> <?php } Is there any way to get the error handler to be called in both situations?

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• Manipulate score/rank on query results from NHibernate.Search

  - by Fernando Figueiredo

  I've been working with NHibernate, NHibernate.Search and Lucene.Net to improve the search engine used on the website I develop. Basically, I use it to search contents of corporations specification documents. This is not to be confused with Lucene's notion of documents: in my case, a specification document (which I'll hereafter call a "specdoc") can contain many pages, and the content of these pages are the ones that are actually indexed (thus, the pages themselves are the ones that fall into Lucene's concept of documents). So, the pages belong to a specdoc, that in turn belong to a corporation (so, a corporation can have many specdocs). I'm using NHibernate.Search "IndexEmbedded" and "ContainedIn" attributes to associate the pages with their specdoc and the specdocs to their corporations, so I can query for terms in specdoc pages and have Lucene/NH.Search return either the pages themselves, the specdocs, or the corporations that match the query on the pages. I can query this way and get ranked results, thus presenting results (that is, corporations, specdocs or pages) by relevance, which is great. But now I need something more. Specifically in the case where I query terms and have NH.Search return the corporations that match, I need to manually/artificially tune the score of some of the results, because there are corporations that I want to show up on the top of the result set - think of "sponsored results". I'm thinking of doing it on my application, maybe creating an entity/database table that contain an association to the corporation entity, and a score boost value. But I don't know how to feed this to Lucene and have it boost the results accordingly at search time. Initially I thought about deriving a Similarity class to do this, but it doesn't look like Similarity can be used to modify result sets at search time. As per this page, it looks like what I need is to mess around with weight or scoring. But the docs are a little superficial in that there are no examples on how to implement a custom scoring, let alone integrate it with NH.Search. So, does anyone know how to do this, or point me to some documentation or working example on how to do something similar? Thanks!

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• intelligent path truncation/ellipsis for display

  - by peterchen

  I am looking for an existign path truncation algorithm (similar to what the Win32 static control does with SS_PATHELLIPSIS) for a set of paths that should focus on the distinct elements. For example, if my paths are like this: Unit with X/Test 3V/ Unit with X/Test 4V/ Unit with X/Test 5V/ Unit without X/Test 3V/ Unit without X/Test 6V/ Unit without X/2nd Test 6V/ When not enough display space is available, they should be truncated to something like this: ...with X/...3V/ ...with X/...4V/ ...with X/...5V/ ...without X/...3V/ ...without X/...6V/ ...without X/2nd ...6V/ (Assuming that an ellipsis generally is shorter than three letters). This is just an example of a rather simple, ideal case (e.g. they'd all end up at different lengths now, and I wouldn't know how to create a good suggestion when a path "Thingie/Long Test/" is added to the pool). There is no given structure of the path elements, they are assigned by the user, but often items will have similar segments. It should work for proportional fonts, so the algorithm should take a measure function (and not call it to heavily) or generate a suggestion list. Data-wise, a typical use case would contain 2..4 path segments anf 20 elements per segment. I am looking for previous attempts into that direction, and if that's solvable wiht sensible amount of code or dependencies.

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• Java Simple Calculator

  - by Lahiru Kavinda

  I have made this calculator program in Java. This works well only when two numbers are calculated at one time. That means to get the sum of 1+2+3 you have to go this way : press 1 press + press 2 press = press + press 3 press = and it calculates it as 6. But I want to program this so that I can get the answer by: press 1 press + press 2 press + press 3 press = but this gives the answer 5!!! How to code this so that it works like an ordinary calculator? Here is my code: import java.awt.*; import java.awt.event.*; import javax.swing.*; public class cal1 extends JFrame { double op1 = 0d, op2 = 0d; double result = 0d; char action; boolean b = false; boolean pressequal = false; public cal1() { makeUI(); } private void makeUI() { setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setSize(400, 400); b0 = new JButton("0"); b1 = new JButton("1"); b2 = new JButton("2"); b3 = new JButton("3"); b4 = new JButton("4"); b5 = new JButton("5"); b6 = new JButton("6"); b7 = new JButton("7"); b8 = new JButton("8"); b9 = new JButton("9"); bDot = new JButton("."); bMul = new JButton("*"); bDiv = new JButton("/"); bPlus = new JButton("+"); bMinus = new JButton("-"); bEq = new JButton("="); t = new JTextField(12); t.setFont(new Font("Tahoma", Font.PLAIN, 24)); t.setHorizontalAlignment(JTextField.RIGHT); numpad = new JPanel(); display = new JPanel(); numpad.add(b7); numpad.add(b8); numpad.add(b9); numpad.add(bMul); numpad.add(b4); numpad.add(b5); numpad.add(b6); numpad.add(bDiv); numpad.add(b1); numpad.add(b2); numpad.add(b3); numpad.add(bMinus); numpad.add(bDot); numpad.add(b0); numpad.add(bEq); numpad.add(bPlus); numpad.setLayout(new GridLayout(4, 5, 5, 4)); display.add(t); add(display, BorderLayout.NORTH); add(numpad, BorderLayout.CENTER); t.addKeyListener(new KeyAdapter() { @Override public void keyTyped(KeyEvent e) { typeOnt(e); } }); b0.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b0pressed(e); } }); b1.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b1pressed(e); } }); b2.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b2pressed(e); } }); b3.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b3pressed(e); } }); b4.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b4pressed(e); } }); b5.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b5pressed(e); } }); b6.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b6pressed(e); } }); b7.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b7pressed(e); } }); b8.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b8pressed(e); } }); b9.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { b9pressed(e); } }); bDot.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { bDotpressed(e); } }); bPlus.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { bPlusPressed(e); } }); bMinus.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { bMinusPressed(e); } }); bMul.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { bMulPressed(e); } }); bDiv.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { bDivPressed(e); } }); bEq.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { bEqpressed(e); } }); } void typeOnt(KeyEvent e) { e.consume(); } void b0pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "0"); } else { t.setText(t.getText() + "0"); } } void b1pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "1"); } else { t.setText(t.getText() + "1"); } } void b2pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "2"); } else { t.setText(t.getText() + "2"); } } void b3pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "3"); } else { t.setText(t.getText() + "3"); } } void b4pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "4"); } else { t.setText(t.getText() + "4"); } } void b5pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "5"); } else { t.setText(t.getText() + "5"); } } void b6pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "6"); } else { t.setText(t.getText() + "6"); } } void b7pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "7"); } else { t.setText(t.getText() + "7"); } } void b8pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "8"); } else { t.setText(t.getText() + "8"); } } void b9pressed(ActionEvent e) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "9"); } else { t.setText(t.getText() + "9"); } } void bDotpressed(ActionEvent e) { if (!t.getText().contains(".")) { if (b) { t.setText(null); b = false; t.setText(t.getText() + "0."); } else if (t.getText().isEmpty()) { t.setText("0."); } else { t.setText(t.getText() + "."); } } } void bPlusPressed(ActionEvent e) { b = true; action = '+'; op1 = Double.parseDouble(t.getText()); } void bMinusPressed(ActionEvent e) { b = true; action = '-'; op1 = Double.parseDouble(t.getText()); } void bMulPressed(ActionEvent e) { b = true; action = '*'; op1 = Double.parseDouble(t.getText()); } void bDivPressed(ActionEvent e) { b = true; action = '/'; op1 = Double.parseDouble(t.getText()); } void bEqpressed(ActionEvent e) { op2 = Double.parseDouble(t.getText()); doCal(); } void doCal() { switch (action) { case '+': result = op1 + op2; break; case '-': result = op1 - op2; break; case '*': result = op1 * op2; break; case '/': result = op1 / op2; break; } t.setText(String.valueOf(result)); } public static void main(String[] args) { new cal1().setVisible(true); } JButton b0; JButton b1; JButton b2; JButton b3; JButton b4; JButton b5; JButton b6; JButton b7; JButton b8; JButton b9; JButton bDot; JButton bPlus; JButton bMinus; JButton bMul; JButton bDiv; JButton bEq; JPanel display; JPanel numpad; JTextField t; }

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• check status application pool iis7 with csharp (access-denied)

  - by jack

  I need to monitor the status of an application in the applications pool of IIS 7 from an other machine on the same domain. My monitoring application must be in C# and running as a Windows service. On my server, I create a user with administration rights and I execute the command aspnet_regiis -ga machine\username wich worked succesfully. My problem is when I try to access the application pool i still get COMExcepttion "Access denied". What did i do wrong or wich step did i miss? I used code from http://patelshailesh.com/index.php/create-a-website-application-pool-programmatically-using-csharp as example. int status = 0; string ipAddress = "10.20.2.13"; string username = "username"; string password = "password"; try { DirectoryEntry de = new DirectoryEntry(string.Format("IIS://{0}/W3SVC/AppPools/MyAppPoolName", ipAddress), username, password); //the exception is thron here. status = (int)de.InvokeGet("AppPoolState"); switch (status) { case 2: //Runnig break; case 4: //Stopped break; default: break; } } catch (Exception ex) { }

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• Android SQLite database locale, locking, and version

  - by gdoten

  In some books and online I see these method calls being made after a database is created: db.setLocale(Locale.getDefault()); db.setLockingEnabled(true); db.setVersion(DB_VERSION); Why is this done? As far as I can tell, after creating a new database, the system adds a table named android_metadata with one field named locale and that table has one row with the locale field set to "en_US". Now I assume the column has that value because I am using a U.S. phone, and if I were using a phone from a different region then the locale field would be set appropriately. Can anyone confirm this? I'm guessing that the setLocale method would only be useful in the case that you install a pre-built database onto a phone and then want to change the locale to match the phone's locale. Sound right? The documentation for setLockingEnabled says it defaults to true so there's no need to make that call, right? Lastly, what's with the call to setVersion? I can't find a table that contains this information so I've been assuming that the database file itself stores the version number somewhere. So when I create a database, which requires you to have already specified the version number in the call to the SQLiteOpenHelper constructor, there's no point in calling setVersion. Again, perhaps this method exists for the case of installing a pre-built database to a device and you then wish to change the database's version (though I can't think of when doing this would make sense). Thanks for any insight!

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• In JSF How can I understand of multi checkboxes whether all of them is checked or not?

  - by Bariscan

  As you understand from the title above, I have a datatable and checkboxes in each row. I want to enable a button when at least one checkbox is selected, and disable it when there is no selected checkboxes (I mean all of them is unselected). I could achieve this as like if one of the checkboxes is selected, the button becomes enable. However, the reversable case I have to do is when the checkboxes is being unselected, when the last selected checbox becomes unselected, the button immediately must become disabled... BTW, I must do it without using a setter method nor a backing bean. Can I perform it by using jquery or a jsfunction, richfaces, etc? As a result, I want to learn how I can disable a button at the moment when all of the checkboxes are unselected? In order to clarify the case, here is my code below; <h:selectBooleanCheckbox id="selectionCheck" onclick="document.getElementById('form1:button1').disabled=false" value="#{_apiV2Product.selectValue}" > </h:selectBooleanCheckbox> Any help would be appreciated, Many thanks, Baris

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• Keyword 'this'(Me) is not available calling the base constructor

  - by serhio

  In the inherited class I use the base constructor, but can't use class's members calling this base constructor. In this example I have a PicturedLabel that knows it's own color and has a image. A TypedLabel : PictureLabel knows it's type but uses the base color. The (base)image that uses TypedLabel should be colored with the (base)color, however, I can't obtain this color: Error: Keyword 'this' is not available in the current context A workaround? /// base class public class PicturedLabel : Label { PictureBox pb = new PictureBox(); public Color LabelColor; public PicturedLabel() { // initialised here in a specific way LabelColor = Color.Red; } public PicturedLabel(Image img) : base() { pb.Image = img; this.Controls.Add(pb); } } public enum LabelType { A, B } /// derived class public class TypedLabel : PicturedLabel { public TypedLabel(LabelType type) : base(GetImageFromType(type, this.LabelColor)) //Error: Keyword 'this' is not available in the current context { } public static Image GetImageFromType(LabelType type, Color c) { Image result = new Bitmap(10, 10); Rectangle rec = new Rectangle(0, 0, 10, 10); Pen pen = new Pen(c); Graphics g = Graphics.FromImage(result); switch (type) { case LabelType.A: g.DrawRectangle(pen, rec); break; case LabelType.B: g.DrawEllipse(pen, rec); break; } return result; } }

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• Best pratice: How do I implement a list that can be rendered both server-side and client-side?

  - by André Pena

  Technologies involved: ASP.NET Web-forms Javascript (jQuery for instance) Case To make it clearer let's give the Stackoverflow authors list as an example. This list can be manipulated at client-side. I can search, page and so forth. So obviously we would need to call jQuery.ajax to retrieve the HTML of each page given a search. Alright. Now this leaves me with the first question: What is the best way to render the response for the jQuery.ajax at server-side? I can't use templates I suppose, so the most obvious solution I think is to create the HTML tags as server-controls and render them as the result of an ASHX request? Is this is best approach? Nice. That solved we have yet another problem: When the user first enters the Authors List the first list page should already come from the server completely rendered alright? Of course we could render the first page as well as an ajax call but I don't think it's better. This time I CAN use templates to render the list but this template couldn't be reused in case 1. What do I do? Now the final question: Now we have 2 rendering strategies: 1) Client and 2) Server. How do I reuse code for the 2 renderings? What are the best pratices for solving these problems?

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• Solving problems involving more complex data structures with CUDA

  - by Nils

  So I read a bit about CUDA and GPU programming. I noticed a few things such that access to global memory is slow (therefore shared memory should be used) and that the execution path of threads in a warp should not diverge. I also looked at the (dense) matrix multiplication example, described in the programmers manual and the nbody problem. And the trick with the implementation seems to be the same: Arrange the calculation in a grid (which it already is in case of the matrix mul); then subdivide the grid into smaller tiles; fetch the tiles into shared memory and let the threads calculate as long as possible, until it needs to reload data from the global memory into shared memory. In case of the nbody problem the calculation for each body-body interaction is exactly the same (page 682): bodyBodyInteraction(float4 bi, float4 bj, float3 ai) It takes two bodies and an acceleration vectors. The body vector has four components it's position and the weight. When reading the paper, the calculation is understood easily. But what is if we have a more complex object, with a dynamic data structure? For now just assume that we have an object (similar to the body object presented in the paper) which has a list of other objects attached and the number of objects attached is different in each thread. How could I implement that without having the execution paths of the threads to diverge? I'm also looking for literature which explains how different algorithms involving more complex data structures can be effectively implemented in CUDA.

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• Disabling redraw in WinForms app

  - by Ryan

  I'm working on a C#.Net application which has a somewhat annoying bug in it. The main window has a number of tabs, each of which has a grid on it. When switching from one tab to another, or selecting a different row in a grid, it does some background processing, and during this the menu flickers as it's redrawn (File, Help, etc menu items as well as window icon and title). I tried disabling the redraw on the window while switching tabs/rows (WM_SETREDRAW message) at first. In one case, it works perfectly. In the other, it solves the immediate bug (title/menu flicker), but between disabling the redraw and enabling it again, the window is "transparent" to mouse clicks - there's a small window (<1 sec) in which I can click and it will, say, highlight an icon on my desktop, as if the app wasn't there at all. If I have something else running in the background (Firefox, say) it will actually get focus when clicked (and draw part of the browser, say the address bar.) Here's code I added. m = new Message(); m.HWnd = System.Windows.Forms.Application.OpenForms[0].Handle; //top level m.WParam = (IntPtr)0; //disable redraw m.LParam = (IntPtr)0; //unused m.Msg = 11; //wm_setredraw WndProc(ref m); <snip - Application ignores clicks while in this section (in one case) m = new Message(); m.HWnd = System.Windows.Forms.Application.OpenForms[0].Handle; //top level m.WParam = (IntPtr)1; //enable m.LParam = (IntPtr)0; //unused m.Msg = 11; //wm_setredraw WndProc(ref m); System.Windows.Forms.Application.OpenForms[0].Refresh(); Does anyone know if a) there's a way to fix the transparent-application problem here, or b) if I'm doing it wrong in the first place and this should be fixed some other way?

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• GRAPH PROBLEM: find an algorithm to determine the shortest path from one point to another in a recta

  - by newba

  I'm getting such an headache trying to elaborate an appropriate algorithm to go from a START position to a EXIT position in a maze. For what is worth, the maze is rectangular, maxsize 500x500 and, in theory, is resolvable by DFS with some branch and bound techniques ... 10 3 4 7 6 3 3 1 2 2 1 0 2 2 2 4 2 2 5 2 2 1 3 0 2 2 2 2 1 3 3 4 2 3 4 4 3 1 1 3 1 2 2 4 2 2 1 Output: 5 1 4 2 Explanation: Our agent looses energy every time he gives a step and he can only move UP, DOWN, LEFT and RIGHT. Also, if the agent arrives with a remaining energy of zero or less, he dies, so we print something like "Impossible". So, in the input 10 is the initial agent's energy, 3 4 is the START position (i.e. column 3, line 4) and we have a maze 7x6. Think this as a kind of labyrinth, in which I want to find the exit that gives the agent a better remaining energy (shortest path). In case there are paths which lead to the same remaining energy, we choose the one which has the small number of steps, of course. I need to know if a DFS to a maze 500x500 in the worst case is feasible with these limitations and how to do it, storing the remaining energy in each step and the number of steps taken so far. The output means the agent arrived with remaining energy= 5 to the exit pos 1 4 in 2 steps. If we look carefully, in this maze it's also possible to exit at pos 3 1 (column 3, row 1) with the same energy but with 3 steps, so we choose the better one. With these in mind, can someone help me some code or pseudo-code? I have troubles working this around with a 2D array and how to store the remaining energy, the path (or number of steps taken)....

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• CIE XYZ colorspace: is it RGBA or XYZA?

  - by Tronic

  I plan to write a painting program based on linear combinations of xy plane points (0,1), (1,0 ) and (0,0). Such system works identically to RGB, except that the primaries are not within the gamut but at the corners of a triangle that encloses the entire gamut, therefore allowing for all colors to be reproduced. I have seen the three points being referred to as X, Y and Z (upper case) somewhere, but I cannot find the page anymore. My pixel format stores the intensity of each of those three components the same way as RGB does, together with alpha value. This allows using pretty much any image manipulation operation designed for RGBA without modifying the code. What is my format called? Is it XYZA, RGBA or something else? Google doesn't seem to know of XYZA and RGBA will get confused with sRGB + alpha (which I also need to use in the same program). Notice that the primaries X, Y and Z and their intensities have little to do with the x, y and z coordinates (lower case) that are more commonly used.

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• When should I be cautious using about data binding in .NET?

  - by Ben McCormack

  I just started working on a small team of .NET programmers about a month ago and recently got in a discussion with our team lead regarding why we don't use databinding at all in our code. Every time we work with a data grid, we iterate through a data table and populate the grid row by row; the code usually looks something like this: Dim dt as DataTable = FuncLib.GetData("spGetTheData ...") Dim i As Integer For i = 0 To dt.Rows.Length - 1 '(not sure why we do not use a for each here)' gridRow = grid.Rows.Add() gridRow(constantProductID).Value = dt("ProductID").Value gridRow(constantProductDesc).Value = dt("ProductDescription").Value Next '(I am probably missing something in the code, but that is basically it)' Our team lead was saying that he got burned using data binding when working with Sheridan Grid controls, VB6, and ADO recordsets back in the nineties. He's not sure what the exact problem was, but he remembers that binding didn't work as expected and caused him some major problems. Since then, they haven't trusted data binding and load the data for all their controls by hand. The reason the conversation even came up was because I found data binding to be very simple and really liked separating the data presentation (in this case, the data grid) from the in-memory data source (in this case, the data table). "Loading" the data row by row into the grid seemed to break this distinction. I also observed that with the advent of XAML in WPF and Silverlight, data-binding seems like a must-have in order to be able to cleanly wire up a designer's XAML code with your data. When should I be cautious of using data-binding in .NET?

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• compact Number formatting behavior in Java (automatically switch between decimal and scientific notation)

  - by kostmo

  I am looking for a way to format a floating point number dynamically in either standard decimal format or scientific notation, depending on the value of the number. For moderate magnitudes, the number should be formatted as a decimal with trailing zeros suppressed. If the floating point number is equal to an integral value, the decimal point should also be suppressed. For extreme magnitudes (very small or very large), the number should be expressed in scientific notation. Alternately stated, if the number of characters in the expression as standard decimal notation exceeds a certain threshold, switch to scientific notation. I should have control over the maximum number of digits of precision, but I don't want trailing zeros appended to express the minimum precision; all trailing zeros should be suppressed. Basically, it should optimize for compactness and readability. 2.80000 - 2.8 765.000000 - 765 0.0073943162953 - 0.00739432 (limit digits of precision—to 6 in this case) 0.0000073943162953 - 7.39432E-6 (switch to scientific notation if the magnitude is small enough—less than 1E-5 in this case) 7394316295300000 - 7.39432E+6 (switch to scientific notation if the magnitude is large enough—for example, when greater than 1E+10) 0.0000073900000000 - 7.39E-6 (strip trailing zeros from significand in scientific notation) 0.000007299998344 - 7.3E-6 (rounding from the 6-digit precision limit causes this number to have trailing zeros which are stripped) Here's what I've found so far: The .toString() method of the Number class does most of what I want, except it doesn't upconvert to integer representation when possible, and it will not express large integral magnitudes in scientific notation. Also, I'm not sure how to adjust the precision. The "%G" format string to the String.format(...) function allows me to express numbers in scientific notation with adjustable precision, but does not strip trailing zeros. I'm wondering if there's already some library function out there that meets these criteria. I guess the only stumbling block for writing this myself is having to strip the trailing zeros from the significand in scientific notation produced by %G.

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• "Ambigous type variable" error when defining custom "read" function

  - by Tener

  While trying to compile the following code, which is enhanced version of read build on readMay from Safe package. readI :: (Typeable a, Read a) => String -> a readI str = case readMay str of Just x -> x Nothing -> error ("Prelude.read failed, expected type: " ++ (show (typeOf > (undefined :: a))) ++ "String was: " ++ str) I get an error from GHC: WavefrontSimple.hs:54:81: Ambiguous type variable `a' in the constraint: `Typeable a' arising from a use of `typeOf' at src/WavefrontSimple.hs:54:81-103 Probable fix: add a type signature that fixes these type variable(s)` I don't understand why. What should be fixed to get what I meant? EDIT: Ok, so the solution to use ScopedTypeVariables and forall a in type signature works. But why the following produces very similar error to the one above? The compiler should infer the right type since there is asTypeOf :: a -> a -> a used. readI :: (Typeable a, Read a) => String -> a readI str = let xx = undefined in case readMay str of Just x -> x `asTypeOf` xx Nothing -> error ("Prelude.read failed, expected type: " ++ (show (typeOf xx)) ++ "String was: " ++ str)

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• Correct method to search for AD user by email address from .NET

  - by BrianLy

  I'm having some issues with code that is intended to find a user in Active Directory by searching on their email address. I have tried 2 methods but I'm sometimes finding that the FindOne() method will not return any results on some occasions. If I look up the user in the GAL in Outlook I see the SMTP email address listed. My end goal is to confirm that the user exists in AD. I only have the email address as search criteria, so no way to use first or last name. Method 1: Using mail property: DirectorySearcher search = new DirectorySearcher(entry); search.Filter = "(mail=" + email + ")"; search.PropertiesToLoad.Add("mail"); SearchResult result = search.FindOne(); Method 2: proxyAddresses property: DirectorySearcher search = new DirectorySearcher(entry); search.Filter = "(proxyAddresses=SMTP:" + email + ")"; // I've also tried with =smtp: search.PropertiesToLoad.Add("mail"); SearchResult result = search.FindOne(); I've tried changing the case of the email address input but it still does not return a result. Is there a problem here with case sensitivity? If so, what is the best way to resolve it?

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• Using git pull to track a remote branch without merging

  - by J Barlow

  I am using git to track content which is changed by some people and shared "read-only" with others. The "readers" may from time to time need to make a change, but mostly they will not. I want to allow for the git "writers" to rebase pushed branches** if need be, and ensure that the "readers" never accidentally get a merge. That's normally easy enough. git pull origin +master There's one case that seems to cause problems. If a reader makes a local change, the command above will merge. I want pull to be fully automatic if the reader has not made local changes, while if they have made local changes, it should stop and ask for input. I want to track any upstream changes while being careful about merging downstream changes. In a way, I don't really want to pull. I want to track the master branch exactly. ** (I know this is not a best practice, but it seems necessary in our case: we have one main branch that contains most of the work and some topic branches for specific customers with minor changes that need to be isolated. It seems easiest to frequently rebase to keep the topics up to date.)

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• Defining Light Coordinates

  - by Zachary

  I took a Computer Graphics exam a couple of days ago which had extra credit question like the following: A light can be defined in one of two ways. It can be defined in world coordinates, e.g. a street light, or in the viewer (eye coordinates), e.g., a head-lamp worn by a miner. In either case the viewpoint can freely change. Describe how the light should be transformed different in these two cases. Since I won't get to see the results of this until after spring break, I thought I would ask here. It seems like the analogies being used are misleading - could you not define a light source that is located at the viewers eye in world coordinates just as well as you could in eye coordinates? I've been doing some research on how OpenGL handles light, and it seems as though it always uses eye coordinates - the ModelView matrix would be applied to any light in world coordinates. In that case the answer may just be that you would have to transform light defined in world coordinates into eye coordinates using something like the ModelView matrix, while light defined in eye coordinates would only need to be transformed by the projection matrix. Then again I could be totally under thinking (or over thinking this). Another thought I had is that it determines which way you render shadows, but that has more to do with the location of the light and its type (point, directional, emission, etc) than what coordinates it is represented in. Any ideas?

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• WF performance with new 20,000 persisted workflow instances each month

  - by Nikola Stjelja

  Windows Workflow Foundation has a problem that is slow when doing WF instances persistace. I'm planning to do a project whose bussiness layer will be based on WF exposed WCF services. The project will have 20,000 new workflow instances created each month, each instance could take up to 2 months to finish. What I was lead to belive that given WF slownes when doing peristance my given problem would be unattainable given performance reasons. I have the following questions: Is this true? Will my performance be crap with that load(given WF persitance speed limitations) How can I solve the problem? We currently have two possible solutions: 1. Each new buisiness process request(e.g. Give me a new drivers license) will be a new WF instance, and the number of persistance operations will be limited by forwarding all status request operations to saved state values in a separate database. 2. Have only a small amount of Workflow Instances up at any give time, without any persistance ofso ever(only in case of system crashes etc.), by breaking each workflow stap in to a separate worklof and that workflow handling each business process request instance in the system that is at that current step(e.g. I'm submitting my driver license reques form, which is step one... we have 100 cases of that, and my step one workflow will handle every case simultaneusly). I'm very insterested in solution for that problem. If you want to discuss that problem pleas be free to mail me at [email protected]

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• Wrapping FUSE from Go

  - by Matt Joiner

  I'm playing around with wrapping FUSE with Go. However I've come stuck with how to deal with struct fuse_operations. I can't seem to expose the operations struct by declaring type Operations C.struct_fuse_operations as the members are lower case, and my pure-Go sources would have to use C-hackery to set the members anyway. My first error in this case is "can't set getattr" in what looks to be the Go equivalent of a default copy constructor. My next attempt is to expose an interface that expects GetAttr, ReadLink etc, and then generate C.struct_fuse_operations and bind the function pointers to closures that call the given interface. This is what I've got (explanation continues after code): package fuse // #include <fuse.h> // #include <stdlib.h> import "C" import ( //"fmt" "os" "unsafe" ) type Operations interface { GetAttr(string, *os.FileInfo) int } func Main(args []string, ops Operations) int { argv := make([]*C.char, len(args) + 1) for i, s := range args { p := C.CString(s) defer C.free(unsafe.Pointer(p)) argv[i] = p } cop := new(C.struct_fuse_operations) cop.getattr = func(*C.char, *C.struct_stat) int {} argc := C.int(len(args)) return int(C.fuse_main_real(argc, &argv[0], cop, C.size_t(unsafe.Sizeof(cop)), nil)) } package main import ( "fmt" "fuse" "os" ) type CpfsOps struct { a int } func (me *CpfsOps) GetAttr(string, *os.FileInfo) int { return -1; } func main() { fmt.Println(os.Args) ops := &CpfsOps{} fmt.Println("fuse main returned", fuse.Main(os.Args, ops)) } This gives the following error: fuse.go:21[fuse.cgo1.go:23]: cannot use func literal (type func(*_Ctype_char, *_Ctype_struct_stat) int) as type *[0]uint8 in assignment I'm not sure what to pass to these members of C.struct_fuse_operations, and I've seen mention in a few places it's not possible to call from C back into Go code. If it is possible, what should I do? How can I provide the "default" values for interface functions that acts as though the corresponding C.struct_fuse_operations member is set to NULL?

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