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• Autodetect Presence of CSV Headers in a File

  - by banzaimonkey

  Short question: How do I automatically detect whether a CSV file has headers in the first row? Details: I've written a small CSV parsing engine that places the data into an object that I can access as (approximately) an in-memory database. The original code was written to parse third-party CSV with a predictable format, but I'd like to be able to use this code more generally. I'm trying to figure out a reliable way to automatically detect the presence of CSV headers, so the script can decide whether to use the first row of the CSV file as keys / column names or start parsing data immediately. Since all I need is a boolean test, I could easily specify an argument after inspecting the CSV file myself, but I'd rather not have to (go go automation). I imagine I'd have to parse the first 3 to ? rows of the CSV file and look for a pattern of some sort to compare against the headers. I'm having nightmares of three particularly bad cases in which: The headers include numeric data for some reason The first few rows (or large portions of the CSV) are null There headers and data look too similar to tell them apart If I can get a "best guess" and have the parser fail with an error or spit out a warning if it can't decide, that's OK. If this is something that's going to be tremendously expensive in terms of time or computation (and take more time than it's supposed to save me) I'll happily scrap the idea and go back to working on "important things". I'm working with PHP, but this strikes me as more of an algorithmic / computational question than something that's implementation-specific. If there's a simple algorithm I can use, great. If you can point me to some relevant theory / discussion, that'd be great, too. If there's a giant library that does natural language processing or 300 different kinds of parsing, I'm not interested.

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• need help passing multiple variables from foreach loop to test in switch case statement

  - by Brad

  $list_of_groups = array("FACULTY","STAFF"); foreach ($list_of_groups as $i => $group) { $user_in_group = $adldap->user_ingroup($username,$group); print "<h2>Group: ".$group." user in group? ".$user_in_group."</h2>"; // if 1, means yes } Need to print run the appropriate function based on what returns true. There are user's that are members of both FACULTY and STAFF groups, so I want to check for those users and display the appropriate content for them. So if the user is both faculty and staff, then display this, if they are only of staff, display that, same for faculty, might not make sense, but I will write out some code "in theory" that will help you understand what I am trying to do switch(Get group membership of user) { case "FACULTY": print "Faculty group member"; break; case "STAFF": print "Staff group member"; break; case "FACULTY and STAFF": print "Member of both faculty and staff"; break; } I am unsure on how it will check if they are members of both groups and run that thru the case statement to display the appropriate message. The foreach look currently runs thru every group the user belongs to, prints out the ones from the $list_of_groups and the number 1 to the right of it, signifying they belong to it. The problem I have is trying to use that information to run thru the case statement, I am unsure of how to go about that. This is what it prints out for the user currently passed thru the foreach loop: Group: FACULTY user in group? 1 Group: STAFF user in group? 1 Any help is appreciated.

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• CSS sliding-door buttons center alignment

  - by rochal

  Hi guys, I need help to align CSS buttons. I tried many different variations and I just cannot center my button the way I want. Firstly, have a look at this url: http://www.front-end-developer.net/cssbuttons/example.htm I'm using 2 images to form a button (this could be done on 1 image, but in this case we've got two). Everything works as expected as long as we apply float:left or float:right to the parent div element, to 'limit' width of the div and close it as soon as the content of the div ends. You can remove float:left from the button to see what I mean. But what about center positioned buttons? I cannot add float:left/right because I want align it in the middle. In theory, I could set { width:XXpx; margin:0 auto; } And I will get what you can see on this picture: But I don't know the length of the text inside. Having different translations my button can be very short, or 5 times that long. I also tried to use <span> instead of <div>, but unfortunately nested inline elements don't respect their padding correctly... And yes, I must use <a> inside, so buttons can be accessed by web crawlers. I'm really stuck on this one.

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• My PreferenceActivity does not show up, even though it is in my manifest file

  - by Charlie

  So I am modifying the Cube live wallpaper example. I have a class that extends PreferenceActivity, and I added the Activity in my manifest file. I keep getting ActivityNotFoundExceptions. Here is my preference class : public class MySettingsActivity extends PreferenceActivity implements SharedPreferences.OnSharedPreferenceChangeListener { @Override protected void onCreate(Bundle bundle) { super.onCreate(bundle); getPreferenceManager().setSharedPreferencesName( ParticleCandy.SHARED_PREFS_NAME); addPreferencesFromResource(R.xml.settings); getPreferenceManager().getSharedPreferences().registerOnSharedPreferenceChangeListener( this); } @Override protected void onResume() { super.onResume(); } @Override protected void onDestroy() { getPreferenceManager().getSharedPreferences().unregisterOnSharedPreferenceChangeListener( this); super.onDestroy(); } public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) { } } And here is my manifest file <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.pixel.theory.wallpapers.mywallpaper" android:versionCode="1" android:versionName="1.0"> <application android:icon="@drawable/icon" android:label="@string/app_name"> <service android:label="@string/app_name" android:name="MyWallpaper" android:permission="android.permission.BIND_WALLPAPER" > <intent-filter> <action android:name="android.service.wallpaper.WallpaperService"> </action> </application> <uses-sdk android:minSdkVersion="7" /> <uses-feature android:name="android.software.live_wallpaper" /> </manifest> Any ideas why my preferences activity doesn't get read in from the manifest?

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• how to queue function behind ajax request

  - by user1052335

  What I'm asking is conceptual rather than why my code doesn't work. I'm trying to make a web app that displays content fetched from a database in a sequence, one at a time, and then waits for a response from the user before continuing to the next one. I'm working with javascript on the client side with the JQuery library and php on the server side. In theory, there's time while waiting for the user's input to fetch information from the server using an AJAX request and have it ready for the use by the time he clicks the button, but there's also a chance that such an AJAX request hasn't completed when he clicks the button. So I need something like pseudocode: display current information fetch next data point from the server in the background onUserInput { if ( ajax request complete) { present the information fetched in this request } else if (ajax request not complete) { wait for ajax request complete present information to user } My question is this: how does one implement this " else if (ajax request not complete) { wait for ajax request complete " part. I'm currently using JQuery for my AJAX needs. I'm somewhat new to working with AJAX, and I did search around, but I didn't find anything that seemed on point. I don't know what tools I should use for this. Some kind of queue maybe? I don't need to be spoon fed. I just need to know how this is done, using what tools or if my desired outcome would be accomplished in some other way entirely. Thanks.

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• thread reaches end but isn't removed

  - by pstanton

  I create a bunch of threads to do some processing: new Thread("upd-" + id){ @Override public void run(){ try{ doSomething(); } catch (Throwable e){ LOG.error("error", e); } finally{ LOG.debug("thread death"); } } }.start(); I know i should be using a threadPool but i need to understand the following problem before i change it: I'm using eclipse's debugger and looking at the threads in the debug pane which lists active threads. Many of them complete as you would expect, and are removed from the debug pane, however some seem to stay in the list of active threads even though the log shows the "thread death" entry for these. When i attempt to debug these threads, they either do not pause for debugging or show an error dialog: "A timeout occurred while retrieving stack frames for thread: upd-...". there is some synchronization going on within the doSomething() call but i'm fairly sure it's ok and since the "thread death" log is being called i'm assuming these threads aren't deadlocked in that method. i don't do any Thread.join()s, however i do call a third party API but doubt they do either. Can anyone think of another reason these threads are lingering? Thanks. EDIT: I created this test to check the Garbage Collection theory: Thread thread = new Thread("!!!!!!!!!!!!!!!!") { @Override public void run() { System.out.println("running"); ThreadUs.sleepQuiet(5000); System.out.println("finished"); // <-- thread removed from list here } }; thread.start(); ThreadUs.sleepQuiet(10000); System.out.println(thread.isAlive()); // <-- thread already removed from list but hasn't been GC'd ThreadUs.sleepQuiet(10000); this proves that it is nothing to do with garbage collection as eclipse removes the thread from the thread list as soon as it completes and isn't waiting for the object to be de-referenced/GC'd.

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• What is the correct way to implement a massive hierarchical, geographical search for news?

  - by Philip Brocoum

  The company I work for is in the business of sending press releases. We want to make it possible for interested parties to search for press releases based on a number of criteria, the most important being location. For example, someone might search for all news sent to New York City, Massachusetts, or ZIP code 89134, sent from a governmental institution, under the topic of "traffic". Or whatever. The problem is, we've sent, literally, hundreds of thousands of press releases. Searching is slow and complex. For example, a press release sent to Queens, NY should show up in the search I mentioned above even though it wasn't specifically sent to New York City, because Queens is a subset of New York City. We may also want to implement "and" and "or" and negation and text search to the query to create complex searches. These searches also have to be fast enough to function as dynamic RSS feeds. I really don't know anything about search theory, or how it's properly done. The way we are getting by right now is using a data mart to store the locations the releases were sent to in a single table. However, because of the subset thing mentioned above, the data mart is gigantic with millions of rows. And we haven't even implemented cities yet, and there are about 50,000 cities in the United States, which will exponentially increase the size of the data mart by so much I'm afraid it just won't work anymore. Anyway, I realize this is not a simple question and there won't be a "do this" answer. However, I'm hoping one of you can point me in the right direction where I can learn about how massive searches are done? Because I really know nothing about it. And such a search engine is turning out to be incredibly difficult to make. Thanks! I know there must be a way because if Google can search the entire internet we must be able to search our own database :-)

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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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• Ninject InThreadScope Binding

  - by e36M3

  I have a Windows service that contains a file watcher that raises events when a file arrives. When an event is raised I will be using Ninject to create business layer objects that inside of them have a reference to an Entity Framework context which is also injected via Ninject. In my web applications I always used InRequestScope for the context, that way within one request all business layer objects work with the same Entity Framework context. In my current Windows service scenario, would it be sufficient to switch the Entity Framework context binding to a InThreadScope binding? In theory when an event handler in the service triggers it's executed under some thread, then if another file arrives simultaneously it will be executing under a different thread. Therefore both events will not be sharing an Entity Framework context, in essence just like two different http requests on the web. One thing that bothers me is the destruction of these thread scoped objects, when you look at the Ninject wiki: .InThreadScope() - One instance of the type will be created per thread. .InRequestScope() - One instance of the type will be created per web request, and will be destroyed when the request ends. Based on this I understand that InRequestScope objects will be destroyed (garbage collected?) when (or at some point after) the request ends. This says nothing however on how InThreadScope objects are destroyed. To get back to my example, when the file watcher event handler method is completed, the thread goes away (back to the thread pool?) what happens to the InThreadScope-d objects that were injected? EDIT: One thing is clear now, that when using InThreadScope() it will not destroy your object when the handler for the filewatcher exits. I was able to reproduce this by dropping many files in the folder and eventually I got the same thread id which resulted in the same exact Entity Framework context as before, so it's definitely not sufficient for my applications. In this case a file that came in 5 minutes later could be using a stale context that was assigned to the same thread before.

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• SQL 2008: Using separate tables for each datatype to return single row

  - by Thomas C

  Hi all I thought I'd be flexible this time around and let the users decide what contact information the wish to store in their database. In theory it would look as a single row containing, for instance; name, adress, zipcode, Category X, Listitems A. Example FieldType table defining the datatypes available to a user: FieldTypeID, FieldTypeName, TableName 1,"Integer","tblContactInt" 2,"String50","tblContactStr50" ... A user the define his fields in the FieldDefinition table: FieldDefinitionID, FieldTypeID, FieldDefinitionName 11,2,"Name" 12,2,"Adress" 13,1,"Age" Finally we store the actual contact data in separate tables depending on its datatype. Master table, only contains the ContactID tblContact: ContactID 21 22 tblContactStr50: ContactStr50ID,ContactID,FieldDefinitionID,ContactStr50Value 31,21,11,"Person A" 32,21,12,"Adress of person A" 33,22,11,"Person B" tblContactInt: ContactIntID,ContactID,FieldDefinitionID,ContactIntValue 41,22,13,27 Question: Is it possible to return the content of these tables in two rows like this: ContactID,Name,Adress,Age 21,"Person A","Adress of person A",NULL 22,"Person B",NULL,27 I have looked into using the COALESCE and Temp tables, wondering if this is at all possible. Even if it is: maybe I'm only adding complexity whilst sacrificing performance for benefit in datastorage and user definition option. What do you think? Best Regards /Thomas C

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• Removing a view from it's superview causes memory error - why?

  - by mystify

  Xcode is throwing an error at me: malloc: * error for object 0x103f000: pointer being freed was not allocated * set a breakpoint in malloc_error_break to debug I tracked down the code until a line where I do this: - (void)inputValueCommitted:(NSString *)animationID finished:(BOOL)finished context:(void *)context { // retainCount of myView is 2! (one for the retain-property, one for beeing a subview) [self.myView removeFromSuperview]; // ERROR-LINE !! self.myView = nil; } When I remove that errorful line, the error is gone. So in conclusion: I can't get rid of my view! It's an UIImageView with nothing else inside, just showing an image. What I do is this: I create an UIView Animation Block, create that UIImageView, assign it to an retain-property with self.myView = ..., and after the animation is done, I just want to get rid of that view. So I remove it from it's superview and then set my property to nil, which lets it go away - in theory. Did anyone else encounter such issues? iPhone SDK 3.0.

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• Cladogram, tree of life, cladistics, taxonomy in JS or canvas?

  - by boblet

  Good people - I need some help to find a way to create an interactive cladogram or phylogenetic tree (yes, I have read all related posts, and do not find what I am looking for). The thing is, I need the nodes to be name-able. An example would be something like this Most scripts I find are either applets, flash, or simply do not show the node classification, ie it would skip "feliformia" in this example. This is useless to me, as I would then end up with carnivore - anonymous node - anonymous node - anonymous node - tiger, and that is not good. This tree will in theory cover all life, so it could get rather large, and get links and names in english and latin from database. So: no flash, no applets. It must be horizontal, no supertrees (circular). I have gone through this http://bioinfo.unice.fr/biodiv/Tree_editors.html but most of them seems to be either old, not displaying sub-node levels, applets, or way too complex. I imagine this would be a delightful job for canvas/jQuery..? And chances are, someone got there before me? Any pointers much appreciated. Note: if anyone out there would like to do something like this as a project, I will be happy to help, even though it would not benefit me for this project.This type of taxonomy is not as simple as it may seem, and I would be happy see this happen.

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• MS Surface Tag Visualizer steals contact events

  - by Isak Savo

  I'm struggling with the TagVisualizer control on an MS Surface project. In theory the control seems great, allowing you to respond to input from real world physical objects The problem is that the control will cover the entire screen (since I want to capture tags on the entire screen) and as such, no other controls in my app will receive the touch events. (Unless, they are direct ascendants in the visual tree). In my app, I want to have a "layer" type of a approach, where each layer can respond to (contact) input: Window `- Grid `- LayersPanel `- TagVisualizer `- Layer 1 `- Layer 2 `- Layer 3 `- Layer 4 Now it doesn't matter where I put the tag visualizer, it's always going to steal contact events from all or some of the other layers. (due to the nature of RoutedEvents) To me, it seems like the control is completely useless in practice as it will always interfere with your application's other controls. What am I missing here? So my questions are: Any suggestions on how to work around this? Has anyone used TagVisualizers in a similar scenario? If so, how did you solve this? By the way, the layers all work fine, since they will only steal events that are directly on top of their sub elements (the rest of the layer is invisible to hit testing)

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• PHP database simulation

  - by Emdiesse

  I have a PHP script that works by calling items from a database based upon the time they were placed in there and it deletes them if they are older than 5 minutes. Basically, I want to now simulate what would happen if this database was being updated regularly. So I was considering sticking in some code that loads an XML file then goes through and parses that into the database based upon the time data located within a node of the xml data... but the problem there is I want it to continually loop through an enter this data so it'll never actually run the other processes So I was thinking of having another PHP script do that that could do this independantly of the php script that is going to display this data... In theory: I am looking to have a button that I can press and it will then run some php code to load up an XML file from a directory on my web server and then iterate though the data sending the data, to a database, based upon the time within a node in the PHP script and when the script was first called So back to my page that displayed the data... if I continually hit refresh it will contain different results each time because data is being added by the other process and this php script removes the older data when it is refreshed Any information on this? Is there a way I can silently, and safely, run a php script without it being loaded into a browser... like a thread!?

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• What is faster- Java or C# (Or good old C)?

  - by Rexsung

  I'm currently deciding on a platform to build a scientific computational product on, and am deciding on either C#, Java, or plain C with Intels compiler on Core2 Quad CPU's. It's mostly integer arithmetic. My benchmarks so far show Java and C are about on par with each other, and dotNET/C# trails by about 5%- however a number of my coworkers are claiming that dotNET with the right optimizations will beat both of these given enough time for the JIT to do its work. I always assume that the JIT would have done it's job within a few minutes of the app starting (Probably a few seconds in my case, as it's mostly tight loops), so I'm not sure whether to believe them Can anyone shed any light on the situation? Would dotNET beat Java? (Or am I best just sticking with C at this point?). The code is highly multithreaded and data sets are several terabytes in size. Haskell/erlang etc are not options in this case as there is a significant quantity of existing legacy C code that will be ported to the new system, and porting C to Java/C# is a lot simpler than to Haskell or Erlang. (Unless of course these provide a significant speedup). Edit: We are considering moving to C# or Java because they may, in theory, be faster. Every percent we can shave off our processing time saves us tens of thousands of dollars per year. At this point we are just trying to evaluate whether C, Java, or c# would be faster.

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• Table valued function only returns CLR error

  - by Anthony

  I have read-only access to a database that was set up for a third-party, closed-source app. Once group of (hopefully) useful table functions only returns the error: Failed to initialize the Common Language Runtime (CLR) v2.0.50727 with HRESULT 0x80131522. You need to restart SQL server to use CLR integration features. (severity 16) But in theory, the third-party app should be able to use the function (either directly or indirectly), so I'm convinced I'm not setting things up right. I'm very new to SQL Server, so I could be missing something obvious. Or I could be missing something really slight, I have no idea. Here is an example of a query that returns the above error: SELECT * FROM dbo.UncompressDataDateRange(4,'Apr 24 2010 12:00AM','Apr 30 2010 12:00AM') Where the function takes three parameters: The Data Set (int) -- basically the data has 6 classifications, and the giant table this should be pulling from has a column to indicate which is which. startDate (smalldatetime) endDate (smalldatetime) There are other, similar functions that expand on the same idea, all returning the same error. Quick Note: I'm not sure if this is relevant, but I was able to connect to the database via SQL Studio (but without the privs to script the functions as code), and a checked the dependency for the above sample function. It turns out that it is a dependent of a view that I have gotten to work, and that view is dependent of the larger, much-hairier data-table. This makes me think I should somehow be pointing the function at the results of the view, but I'm not seeing any documentation that shows how that is done.

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• Is a confirmation screen necessary for an order form?

  - by abeger

  In a discussion about how to streamline an order form on our site, the idea of eliminating the confirmation screen. So, instead of filling out the form, clicking "Submit", seeing a summary on a confirmation screen and clicking "Confirm", the user would simply fill out the form, hit "Submit", and the order's done. The theory is that fewer clicks and fewer screens means less time to order and therefore the ordering experience is easier. The opposing opinion says that without the confirmation screen, user error increases and people just end up canceling/changing orders after the fact. I'm looking for more input from the SO community. Have you ever done this? How has it worked out, compared to a traditional confirmation screen setup? Are there examples of a true "one click and done" setup on the web (does Amazon's 1-click have a confirmation screen? I've never been courageous enough to try it)? EDIT: Just to clarify, when I say "confirmation screen", I mean a second step where the customer reviews the order before placing it. Even if we did do away with it, the user would still receive a message saying "your order has been placed".

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• HTTP POST prarameters order / REST urls

  - by pq

  Let's say that I'm uploading a large file via a POST HTTP request. Let's also say that I have another parameter (other than the file) that names the resource which the file is updating. The resource cannot be not part of the URL the way you can do it with REST (e.g. foo.com/bar/123). Let's say this is due to a combination of technical and political reasons. The server needs to ignore the file if the resource name is invalid or, say, the IP address and/or the logged in user are not authorized to update the resource. Looks like, if this POST came from an HTML form that contains the resource name first and file field second, for most (all?) browsers, this order is preserved in the POST request. But it would be naive to fully rely on that, no? In other words the order of HTTP parameters is insignificant and a client is free to construct the POST in any order. Isn't that true? Which means that, at least in theory, the server may end up storing the whole large file before it can deny the request. It seems to me that this is a clear case where RESTful urls have an advantage, since you don't have to look at the POST content to perform certain authorization/error checking on the request. Do you agree? What are your thoughts, experiences?

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• Getting started with massive data

  - by Max

  I'm a math guy and occasionally do some statistics/machine learning analysis consulting projects on the side. The data I have access to are usually on the smaller side, at most a couple hundred of megabytes (and almost always far less), but I want to learn more about handling and analyzing data on the gigabyte/terabyte scale. What do I need to know and what are some good resources to learn from? Hadoop/MapReduce is one obvious start. Is there a particular programming language I should pick up? (I primarily work now in Python, Ruby, R, and occasionally Java, but it seems like C and Clojure are often used for large-scale data analysis?) I'm not really familiar with the whole NoSQL movement, except that it's associated with big data. What's a good place to learn about it, and is there a particular implementation (Cassandra, CouchDB, etc.) I should get familiar with? Where can I learn about applying machine learning algorithms to huge amounts of data? My math background is mostly on the theory side, definitely not on the numerical or approximation side, and I'm guessing most of the standard ML algorithms don't really scale. Any other suggestions on things to learn would be great!

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• GWT : Internet Explorer transparency issue

  - by dindeman

  This post concerns only IE. The last line of the following code is causing the issue. int width = 200; int height = 200; int overHeight = 40; AbsolutePanel absPanel = new AbsolutePanel(); absPanel.setSize(width + "px", height + "px"); SimplePanel underPanel = new SimplePanel(); underPanel.setWidth(width + "px"); underPanel.setHeight(height + "px"); underPanel.getElement().getStyle().setBackgroundColor("red"); SimplePanel overPanel = new SimplePanel(); overPanel.setWidth(width + "px"); overPanel.setHeight(overHeight + "px"); overPanel.getElement().getStyle().setBackgroundColor("black"); //Setting the IE opacity to 20% on the black element in order to obtain the see through effect. overPanel.getElement().getStyle().setProperty("filter", "alpha(opacity=20)"); absPanel.add(underPanel, 0, 0); absPanel.add(overPanel, 0, 0); RootPanel.get("test").add(absPanel); //The next line causes the problem. absPanel.getElement().getStyle().setProperty("filter", "alpha(opacity=100)"); So basically this code should display a red square of 200px by 200px (see underPanel in the code) and on top of it a black rectangle of 200px by 40px (see overPanel in the code). However the black rectangle is partially see through since its transparency is set to 20%, therefore it should appear in red, but of a darker red than the rectangle sitting under since it is actually a faded black item. Some rendering problem occurs because of the last line of code that sets the opacity of the containing AbsolutePanel to 100% (which in theory should not affect the visual result). Indeed in that case the panel lying over remains still see through but straight through the background colour of the page! It's like if the panel sitting under was not there at all... Any ideas? This is under GWT 2.0 and IE7.

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• Help needed in grokking password hashes and salts

  - by javafueled

  I've read a number of SO questions on this topic, but grokking the applied practice of storing a salted hash of a password eludes me. Let's start with some ground rules: a password, "foobar12" (we are not discussing the strength of the password). a language, Java 1.6 for this discussion a database, postgreSQL, MySQL, SQL Server, Oracle Several options are available to storing the password, but I want to think about one (1): Store the password hashed with random salt in the DB, one column Found on SO and elsewhere is the automatic fail of plaintext, MD5/SHA1, and dual-columns. The latter have pros and cons MD5/SHA1 is simple. MessageDigest in Java provides MD5, SHA1 (through SHA512 in modern implementations, certainly 1.6). Additionally, most RDBMSs listed provide methods for MD5 encryption functions on inserts, updates, etc. The problems become evident once one groks "rainbow tables" and MD5 collisions (and I've grokked these concepts). Dual-column solutions rest on the idea that the salt does not need to be secret (grok it). However, a second column introduces a complexity that might not be a luxury if you have a legacy system with one (1) column for the password and the cost of updating the table and the code could be too high. But it is storing the password hashed with a random salt in single DB column that I need to understand better, with practical application. I like this solution for a couple of reasons: a salt is expected and considers legacy boundaries. Here's where I get lost: if the salt is random and hashed with the password, how can the system ever match the password? I have theory on this, and as I type I might be grokking the concept: Given a random salt of 128 bytes and a password of 8 bytes ('foobar12'), it could be programmatically possible to remove the part of the hash that was the salt, by hashing a random 128 byte salt and getting the substring of the original hash that is the hashed password. Then re hashing to match using the hash algorithm...??? So... any takers on helping. :) Am I close?

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• Flipping View transition becomes clunky when using UIPickerViews with a large number of elements

  - by user302246

  I have a very simple app created with the Utility Application project template on XCode. My MainView has two UIPickerView components and two buttons. The FlipSideView has another UIPickerView. The pickers on the main view each have 4 segments and each segment has 8 rows. The picker on the flip side has just 1 segment with 8 rows. All rows on all pickers are just text. With just this setup, pressing the button to flip the view back and forth displays a noticeable delay before the animation actually starts, and then the animation actually seems to go faster than what it should, like it's trying to make up for the lost time. I removed the pickers in interface builder and loaded the app on the phone and the animation now seems natural. I also tried just one picker (the flipside one) and things still seem normal. So my current theory is that the number of objects involved in the main view is the cause. The thing is that I don't think it's that many (4 x 8 x 2 = 64), but I could be completely wrong. This is pretty much my first app so maybe I'm just doing something grossly wrong, or maybe the phone is has a lot more limited processing than I thought. I am thinking of creating the picker views with pickerView:viewForRow:forComponent:reusingView: to see if this hopefully performs better, but I'm not sure if this is just a waste of time. Any suggestions? Thanks Ruy P.S.: Testing on a 3G phone on 3.1.2

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• How to restrain one's self from the overwhelming urge to rewrite everything?

  - by Scott Saad

  Setup Have you ever had the experience of going into a piece of code to make a seemingly simple change and then realizing that you've just stepped into a wasteland that deserves some serious attention? This usually gets followed up with an official FREAK OUT moment, where the overwhelming feeling of rewriting everything in sight starts to creep up. It's important to note that this bad code does not necessarily come from others as it may indeed be something we've written or contributed to in the past. Problem It's obvious that there is some serious code rot, horrible architecture, etc. that needs to be dealt with. The real problem, as it relates to this question, is that it's not the right time to rewrite the code. There could be many reasons for this: Currently in the middle of a release cycle, therefore any changes should be minimal. It's 2:00 AM in the morning, and the brain is starting to shut down. It could have seemingly adverse affects on the schedule. The rabbit hole could go much deeper than our eyes are able to see at this time. etc... Question So how should we balance the duty of continuously improving the code, while also being a responsible developer? How do we refrain from contributing to the broken window theory, while also being aware of actions and the potential recklessness they may cause? Update Great answers! For the most part, there seems to be two schools of thought: Don't resist the urge as it's a good one to have. Don't give in to the temptation as it will burn you to the ground. It would be interesting to know if more people feel any balance exists.

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• How should I design my MYSQL table/s?

  - by yaya3

  I built a really basic php/mysql site for an architect that uses one 'projects' table. The website showcases various projects that he has worked on. Each project contained one piece of text and one series of images. Original projects table (create syntax): CREATE TABLE `projects` ( `project_id` int(11) NOT NULL auto_increment, `project_name` text, `project_text` text, `image_filenames` text, `image_folder` text, `project_pdf` text, PRIMARY KEY (`project_id`) ) ENGINE=MyISAM AUTO_INCREMENT=8 DEFAULT CHARSET=latin1; The client now requires the following, and I'm not sure how to handle the expansions in my DB. My suspicion is that I will need an additional table. Each project now have 'pages'. Pages either contain... One image One "piece" of text One image and one piece of text. Each page could use one of three layouts. As each project does not currently have more than 4 pieces of text (a very risky assumption) I have expanded the original table to accommodate everything. New projects table attempt (create syntax): CREATE TABLE `projects` ( `project_id` int(11) NOT NULL AUTO_INCREMENT, `project_name` text, `project_pdf` text, `project_image_folder` text, `project_img_filenames` text, `pages_with_text` text, `pages_without_img` text, `pages_layout_type` text, `pages_title` text, `page_text_a` text, `page_text_b` text, `page_text_c` text, `page_text_d` text, PRIMARY KEY (`project_id`) ) ENGINE=MyISAM AUTO_INCREMENT=8 DEFAULT CHARSET=latin1; In trying to learn more about MYSQL table structuring I have just read an intro to normalization and A Simple Guide to Five Normal Forms in Relational Database Theory. I'm going to keep reading! Thanks in advance

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• Debugging unexpected error message - possible memory management problem?

  - by Ben Packard

  I am trying to debug an application that is throwing up strange (to my untutored eyed) errors. When I try to simply log the count of an array... NSLog(@"Array has %i items", [[self startingPlayers] count]); ...I sometimes get an error: -[NSCFString count]: unrecognized selector sent to instance 0x1002af600 or other times -[NSConcreteNotification count]: unrecognized selector sent to instance 0x1002af600 I am not sending 'count' to any NSString or NSNotification, and this line of code works fine normally. A Theory... Although the error varies, the crash happens at predictable times, immediately after I have run through some other code where I'm thinking I might have a memory management issue. Is it possible that the object reference is still pointing to something that is meant to be destroyed? Sorry if my terms are off, but perhaps it's expecting the array at the address it calls 'count' on, but finds another previous object that shouldn't still be there (eg an NSString)? Would this cause the problem? If so, what is the most efficient way to debug and find out what is that address? Most of my debugging up until now involves inserting NSLogs, so this would be a good opportunity to learn how to use the debugger.

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