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• Quickest algorithm for finding sets with high intersection

  - by conradlee

  I have a large number of user IDs (integers), potentially millions. These users all belong to various groups (sets of integers), such that there are on the order of 10 million groups. To simplify my example and get to the essence of it, let's assume that all groups contain 20 user IDs (i.e., all integer sets have a cardinality of 100). I want to find all pairs of integer sets that have an intersection of 15 or greater. Should I compare every pair of sets? (If I keep a data structure that maps userIDs to set membership, this would not be necessary.) What is the quickest way to do this? That is, what should my underlying data structure be for representing the integer sets? Sorted sets, unsorted---can hashing somehow help? And what algorithm should I use to compute set intersection)? I prefer answers that relate C/C++ (especially STL), but also any more general, algorithmic insights are welcome. Update Also, note that I will be running this in parallel in a shared memory environment, so ideas that cleanly extend to a parallel solution are preferred.

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• T-SQL - Left Outer Joins - Fileters in the where clause versus the on clause.

  - by Greg Potter

  I am trying to compare two tables to find rows in each table that is not in the other. Table 1 has a groupby column to create 2 sets of data within table one. groupby number ----------- ----------- 1 1 1 2 2 1 2 2 2 4 Table 2 has only one column. number ----------- 1 3 4 So Table 1 has the values 1,2,4 in group 2 and Table 2 has the values 1,3,4. I expect the following result when joining for Group 2: `Table 1 LEFT OUTER Join Table 2` T1_Groupby T1_Number T2_Number ----------- ----------- ----------- 2 2 NULL `Table 2 LEFT OUTER Join Table 1` T1_Groupby T1_Number T2_Number ----------- ----------- ----------- NULL NULL 3 The only way I can get this to work is if I put a where clause for the first join: PRINT 'Table 1 LEFT OUTER Join Table 2, with WHERE clause' select table1.groupby as [T1_Groupby], table1.number as [T1_Number], table2.number as [T2_Number] from table1 LEFT OUTER join table2 --****************************** on table1.number = table2.number --****************************** WHERE table1.groupby = 2 AND table2.number IS NULL and a filter in the ON for the second: PRINT 'Table 2 LEFT OUTER Join Table 1, with ON clause' select table1.groupby as [T1_Groupby], table1.number as [T1_Number], table2.number as [T2_Number] from table2 LEFT OUTER join table1 --****************************** on table2.number = table1.number AND table1.groupby = 2 --****************************** WHERE table1.number IS NULL Can anyone come up with a way of not using the filter in the on clause but in the where clause? The context of this is I have a staging area in a database and I want to identify new records and records that have been deleted. The groupby field is the equivalent of a batchid for an extract and I am comparing the latest extract in a temp table to a the batch from yesterday stored in a partioneds table, which also has all the previously extracted batches as well. Code to create table 1 and 2: create table table1 (number int, groupby int) create table table2 (number int) insert into table1 (number, groupby) values (1, 1) insert into table1 (number, groupby) values (2, 1) insert into table1 (number, groupby) values (1, 2) insert into table2 (number) values (1) insert into table1 (number, groupby) values (2, 2) insert into table2 (number) values (3) insert into table1 (number, groupby) values (4, 2) insert into table2 (number) values (4)

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• Using ARIMA to model and forecast stock prices using user-friendly stats program

  - by Brian

  Hi people, Can anyone please offer some insight into this for me? I'm coming from a functional magnetic resonance imaging research background where I analyzed a lot of time series data, and I'd like to analyze the time series of stock prices (or returns) by: 1) modeling a successful stock in a particular market sector and then cross-correlating the time series of this historically successful stock with that of other newer stocks to look for significant relationships; 2) model a stock's price time series and use forecasting (e.g., exponential smoothing) to predict future values of it. I'd like to use non-linear modeling methods (ARIMA and ARCH) to do this. Several questions: How often do ARIMA and ARCH modeling methods (given that the individual who implements them does so accurately) actually fit the stock time series data they target, and what is the optimal fit I can expect? Is the extent to which this model fits the data commensurate with the extent to which it predicts this stock time series' future values? Rather than randomly selecting stocks to compare or model, if profit is my goal, what is an efficient approach, if any, to selecting the stocks I'm going to analyze? Which stats program is the most user-friendly for this? Any thoughts on this would be great and would go a long way for me. Thanks, Brian

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• Join + IEqualityComparer<T> and HashCode

  - by Jesus Rodriguez

  Im writing my own LINQ reference but Im getting troubles with some of the more complicated operators implementations. There is a Join implementation that takes a IEqualityComparer Im getting just crazy. Im trying to understand it first before I write (obviously) Image this two lists: List<string> initials = new List<string> {"A", "B", "C", "D", "E"}; List<string> words = new List<string> {"Ant", "Crawl", "Pig", "Boat", "Elephant", "Arc"}; Nothing weird here. I want to join both lists by the Initial, something like: Initial=A Word=Ant Initial=A Word=Arc Initial=B Word=Boat ... I need a comparator, I wrote this: public class InitialComparator : IEqualityComparer<string> { public bool Equals(string x, string y) { return x.StartsWith(y); } public int GetHashCode(string obj) { return obj[0].GetHashCode(); } } The Join itself: var blah = initials.Join(words, initial => initial, word => word, (initial, word) => new {Initial = initial, Word = word}, new InitialComparator()); It's the first time Im using HashCodes, after a good session of debugging I see that every word go to the comparator and look at its HashCode, if another word has the same HashCode it calls equals. Since I want to compare just the initial I though that I just need the first letter Hash (Am I wrong?) The thing is that this is not working correctly. Its says that "Ant" and "Arc" are equals, Ok, its comparing every word in the same list or not, But it adds only the last word it finds, in this case Arc, ignoring Ant and Ant is equals to "A" too... If I put "Ant" and "Ant" it add both. In short, What is the way of doing something like that? I know that Im doing something wrong. Thank you.

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• OpenCV shape matching

  - by MAckerman

  I'm new to OpenCV (am actually using Emgu CV C# wrapper) and am attempting to do some object detection. I'm attempting to determine if an object matches a predefined set of objects (that I will have to define). The background is well lit and does not move. My objects that I am starting with are bottles and cans. My current approach is: Do absDiff with a previously taken background image to separate the background. Then dilate 4x to make the lighter areas (in labels) shrink. Then I do a binary threshold to get a big blog, followed by finding contours in this image. I then take the largest contour and draw it, which becomes my shape to either save to the accepted set or compare with the accepted set. Currently I'm using cvMatchShapes, but the double return value seems to vary widely. I'm guessing it is because it doesn't take into account rotation. Is this approach a good one? It isn't working well for glass bottles since the edges are hard to find... I've read about haar classifiers, but thinking that might be overkill for my task.

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• Search book by title, and author

  - by Swoosh

  I got a table with columns: author firstname, author lastname, and booktitle Multiple users are inserting in the database, through an import, and I'd like to avoid duplicates. So I'm trying to do something like this: I have a record in the db: First Name: "Isaac" Last Name: "Assimov" Title: "I, Robot" If the user tries to add it again, it would be basically a non-split-text (would not be split up into author firstname, author lastname, and booktitle) So it would basically look like this: "Isaac Asimov - I Robot" or "Asimov, Isaac - I Robot" or "I Robot by Isaac Asimov" You see where I am getting at? (I cannot force the user to split up all the books into into author firstname, author lastname, and booktitle, and I don't even like the idea to force the user, because it's not too user-friendly) What is the best way (in SQL) to compare all this possible bookdata scenarios to what I have in the database, not to add the same book twice. I was thinking about a possibility of suggesting the user: "is THIS the book you are trying to add?" (imagine a list instead of the THIS word, just like on stackoverflow - ask question - Related Questions. I was thinking about soundex and maybe even the like operators, but so far i didn't get the results i was hoping.

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• magento, making a grouped product show on sale based on product children prices

  - by thrice801

  Hi, Question regarding Magento and sale items. So I have to use grouped items to link multiple items which are the same style but different colors, these are the items I have showing on my search results/category pages. - I am trying to figure out how I can make the master sku, show as on sale, when the children items are marked on sale. I am able to make it show up on the product page, but anytime I have tried calling any of the getchildren methods outside of grouped.phtml, I have failed, horribly. I think I worked on that method for probably 36 hours unsuccessfully calling it from any other page. So, I thought I would ask here. Does anyone know how I could call the getchildskus or whatever it is method, from the category page, so that I can do something like, for each child product, compare sale price with active price, if there is a difference, calculate the percentage off, and display the largest difference as "ON SALE, UP TO 30% OFF!", or whatever it may be? Any help would be much appreciated. (oh, and I cant set a price on the main group sku, I sell sunglasses and watches mainly and many times a different color will differ in price quite significantly.)

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• KD-Trees and missing values (vector comparison)

  - by labratmatt

  I have a system that stores vectors and allows a user to find the n most similar vectors to the user's query vector. That is, a user submits a vector (I call it a query vector) and my system spits out "here are the n most similar vectors." I generate the similar vectors using a KD-Tree and everything works well, but I want to do more. I want to present a list of the n most similar vectors even if the user doesn't submit a complete vector (a vector with missing values). That is, if a user submits a vector with three dimensions, I still want to find the n nearest vectors (stored vectors are of 11 dimensions) I have stored. I have a couple of obvious solutions, but I'm not sure either one seem very good: Create multiple KD-Trees each built using the most popular subset of dimensions a user will search for. That is, if a user submits a query vector of thee dimensions, x, y, z, I match that query to my already built KD-Tree which only contains vectors of three dimensions, x, y, z. Ignore KD-Trees when a user submits a query vector with missing values and compare the query vector to the vectors (stored in a table in a DB) one by one using something like a dot product. This has to be a common problem, any suggestions? Thanks for the help.

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• Help to Install Eclipse for A Netbeans Users

  - by Yan Cheng CHEOK

  I had been using Netbeans all the while to develop Swing application. So far, I am a Happy Netbeans User Currently, I had a project (GWT, J2EE and Swing), which I need to use Eclipse (Please do not ask Why) Here is the step I had been taken. Download Eclipse IDE for Java EE Developers (190 MB) from http://www.eclipse.org/downloads/ I thought this should be the correct choice, as I see most features are found in that edition http://www.eclipse.org/downloads/packages/compare-packages After struggling a while to get use to the user interface of Eclipse, I still cannot find a Visual GUI Editor! After doing some Googling, I realize I need to install something called Plugins However, tones of plugins which had similar features has confused me, as I found http://www.cloudgarden.com/jigloo/index.html http://www.eclipse.org/vep/WebContent/main.php http://code.google.com/p/visualswing4eclipse/ This makes me even more confuse? Which plugin I should use to develop a Swing based application? Most of them seems not up-to-dated. Or, is there any complete bundle I can download, where 1 click, will install all the necessary Swing development tools for me? I just miss my Netbeans :( I really appreciate their team, who make the installation work so easy. One click button install, all the necessary tools just come to me

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• Conversion failed: SqlParameter and DateTime

  - by Tim

  I'm changing old,vulnerable sqlcommands with SqlParameters but get a SqlException: System.Data.SqlClient.SqlException {"Conversion failed when converting datetime from character string."} on sqlCommand.ExecuteScalar() Dim sqlString As String = _ "SELECT TOP 1 " & _ "fiSL " & _ "FROM " & _ "tabData AS D " & _ "WHERE " & _ "D.SSN_Number = '@SSN_Number' " & _ "AND D.fiProductType = 1 " & _ "AND D.Repair_Completion_Date > '@Repair_Completion_Date' " & _ "ORDER BY " & _ "D.Repair_Completion_Date ASC" Dim obj As Object Dim sqlCommand As SqlCommand Try sqlCommand = New SqlCommand(sqlString, Common.MyDB.SqlConn_RM2) sqlCommand.CommandTimeout = 120 sqlCommand.Parameters.AddWithValue("@SSN_Number", myClaim.SSNNumber) sqlCommand.Parameters.AddWithValue("@Repair_Completion_Date", myClaim.RepairCompletionDate) If Common.MyDB.SqlConn_RM2.State <> System.Data.ConnectionState.Open Then Common.MyDB.SqlConn_RM2.Open() obj = sqlCommand.ExecuteScalar() Catch ex As Exception Dim debug As String = ex.ToString Finally Common.MyDB.SqlConn_RM2.Close() End Try myClaim.RepairCompletionDate is a SQLDateTime. Do i have to remove the quotes in the sqlString to compare Date columns? But then i dont get a exception but incorrect results.

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• How can I apply a PSSM efficiently?

  - by flies

  I am fitting for position specific scoring matrices (PSSM aka Position Specific Weight Matrices). The fit I'm using is like simulated annealing, where I the perturb the PSSM, compare the prediction to experiment and accept the change if it improves agreement. This means I apply the PSSM millions of times per fit; performance is critical. In my particular problem, I'm applying a PSSM for an object of length L (~8 bp) at every position of a DNA sequence of length M (~30 bp) (so there are M-L+1 valid positions). I need an efficient algorithm to apply a PSSM. Can anyone help improve performance? My best idea is to convert the DNA into some kind of a matrix so that applying the PSSM is matrix multiplication. There are efficient linear algebra libraries out there (e.g. BLAS), but I'm not sure how best to turn an M-length DNA sequence into a matrix M x 4 matrix and then apply the PSSM at each position. The solution needs to work for higher order/dinucleotide terms in the PSSM - presumably this means representing the sequence-matrix for mono-nucleotides and separately for dinucleotides. My current solution iterates over each position m, then over each letter in word from m to m+L-1, adding the corresponding term in the matrix. I'm storing the matrix as a multi-dimensional STL vector, and profiling has revealed that a lot of the computation time is just accessing the elements of the PSSM (with similar performance bottlenecks accessing the DNA sequence). If someone has an idea besides matrix multiplication, I'm all ears.

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• Missing Intellisense While Describing Custom Control Properties Declaratively

  - by Albert Bori

  So, I've been working on this project for a few days now, and have been unable to resolve the issue of getting intellisense support for my custom-defined inner properties for a user control (ascx, mind you). I have seen the solution to this (using server controls, .cs mind you) many times. Spelled out in this article very well. Everything works for me while using ascx controls except intellisense. Here's the outline of my code: [PersistChildren(true)] [ParseChildren(typeof(BreadCrumbItem))] [ControlBuilder(typeof(BreadCrumbItem))] public partial class styledcontrols_buttons_BreadCrumb : System.Web.UI.UserControl { ... [PersistenceMode(PersistenceMode.InnerDefaultProperty)] public List<BreadCrumbItem> BreadCrumbItems { get { return _breadCrumbItems; } set { _breadCrumbItems = value; } } ... protected override void AddParsedSubObject(object obj) { base.AddParsedSubObject(obj); if (obj is BreadCrumbItem) BreadCrumbItems.Add(obj as BreadCrumbItem); } ... public class BreadCrumbItem : ControlBuilder { public string Text { get; set; } public string NavigateURL { get; set; } public override Type GetChildControlType(string tagName, System.Collections.IDictionary attribs) { if (String.Compare(tagName, "BreadCrumbItem", true) == 0) { return typeof(BreadCrumbItem); } return null; } } } Here's my mark up (which works fine, just no intellisense on the child object declarations): <%@ Register src="../styledcontrols/buttons/BreadCrumb.ascx" tagname="BreadCrumb" tagprefix="uc1" %> ... <uc1:BreadCrumb ID="BreadCrumb1" runat="server" BreadCrumbTitleText="Current Page"> <BreadCrumbItem Text="Home Page" NavigateURL="~/test/breadcrumbtest.aspx?iwentsomewhere=1" /> <BreadCrumbItem Text="Secondary Page" NavigateURL="~/test/breadcrumbtest.aspx?iwentsomewhere=1" /> </uc1:BreadCrumb> I think the issue lies with how the intellisense engine traverses supporting classes. All the working examples I see of this are not ascx, but Web Server Controls (cs, in a compiled assembly). If anyone could shed some light on how to accomplish this with ascx controls, I'd appreciate it.

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• Fast Lightweight Image Comparisson Metric Algorithm

  - by gav

  Hi All, I am developing an application for the Android platform which contains 1000+ image filters that have been 'evolved'. When a user selects a photo I want to present the most relevant filters first. This 'relevance' should be dependent on previous use cases. I have already developed tools that register when a filtered image is saved; this combination of filter and image can be seen as the training data for my system. The issue is that the comparison must occur between selecting an image and the next screen coming up. From a UI point of view I need the whole process to take less that 4 seconds; select an image- obtain a metric to use for similarity - check against use cases - return 6 closest matches. I figure with 4 seconds I can use animations and progress dialogs to keep the user happy. Due to platform contraints I am fairly limited in the computational expense of the algorithm. I have implemented a technique adapted from various online tutorials for running C code on the G1 and hence this language is available Specific Constraints; Qualcomm® MSM7201A™, 528 MHz Processor 320 x 480 Pixel bitmap in 32 bit ARGB ~ 2 seconds computational time for the native method to get the metric ~ 2 seconds to compare the metric of the current image with training data This is an academic project so all ideas are welcome, anything you can think of or have heard about would be of interest to me. My ideas; I want to keep the complexity down (O(n*m)?) by using pixel data only rather than a neighbourhood function I was looking at using the Colour historgram/Greyscale histogram/Texture/Entropy of the image, combining them to make the measure. There will be an obvious loss of information but I need the resultant metric to be substantially smaller than the memory footprint of the image (~0.512 MB) As I said, any ideas to direct my research would be fantastic. Kind regards, Gavin

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• iPhone Multithreaded Search

  - by Kulpreet

  I'm sort of new to any sort of multithreading and simply can't seem to get a simple search method working on a background thread properly. Everything seems to be in order with an NSAutoreleasePool and the UI being updated on the main thread. The app doesn't crash and does perform a search in the background but the search results yield the several of the same items several times depending on how fast I type it in. The search works properly without the multithreading (which is commented out), but is very slow because of the large amounts of data I am working with. Here's the code: - (void)filterContentForSearchText:(NSString*)searchText { isSearching = YES; NSAutoreleasePool *apool = [[NSAutoreleasePool alloc] init]; /* Update the filtered array based on the search text and scope. */ //[self.filteredListContent removeAllObjects]; // First clear the filtered array. for (Entry *entry in appDelegate.entries) { NSComparisonResult result = [entry.gurmukhiEntry compare:searchText options:(NSCaseInsensitiveSearch|NSDiacriticInsensitiveSearch) range:NSMakeRange(0, [searchText length])]; if (result == NSOrderedSame) { [self.filteredListContent addObject:entry]; } } [self.searchDisplayController.searchResultsTableView performSelectorOnMainThread:(@selector(reloadData)) withObject:nil waitUntilDone:NO]; //[self.searchDisplayController.searchResultsTableView reloadData]; [apool drain]; isSearching = NO; } - (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString { if (!isSearching) { [self.filteredListContent removeAllObjects]; // First clear the filtered array. [self performSelectorInBackground:(@selector(filterContentForSearchText:)) withObject:searchString]; } //[self filterContentForSearchText:searchString]; return NO; // Return YES to cause the search result table view to be reloaded. }

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• Why does the Java Collections Framework offer two different ways to sort?

  - by dvanaria

  If I have a list of elements I would like to sort, Java offers two ways to go about this. For example, lets say I have a list of Movie objects and I’d like to sort them by title. One way I could do this is by calling the one-argument version of the static java.util.Collections.sort( ) method with my movie list as the single argument. So I would call Collections.sort(myMovieList). In order for this to work, the Movie class would have to be declared to implement the java.lang.Comparable interface, and the required method compareTo( ) would have to be implemented inside this class. Another way to sort is by calling the two-argument version of the static java.util.Collections.sort( ) method with the movie list and a java.util.Comparator object as it’s arguments. I would call Collections.sort(myMovieList, titleComparator). In this case, the Movie class wouldn’t implement the Comparable interface. Instead, inside the main class that builds and maintains the movie list itself, I would create an inner class that implements the java.util.Comparator interface, and implement the one required method compare( ). Then I'd create an instance of this class and call the two-argument version of sort( ). The benefit of this second method is you can create an unlimited number of these inner class Comparators, so you can sort a list of objects in different ways. In the example above, you could have another Comparator to sort by the year a movie was made, for example. My question is, why bother to learn both ways to sort in Java, when the two-argument version of Collections.sort( ) does everything the first one-argument version does, but with the added benefit of being able to sort the list’s elements based on several different criteria? It would be one less thing to have to keep in your mind while coding. You’d have one basic mechanism of sorting lists in Java to know.

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• Using Hidden Markov Model for designing AI mp3 player

  - by Casper Slynge

  Hey guys. Im working on an assignment, where I want to design an AI for a mp3 player. The AI must be trained and designed with the use of a HMM method. The mp3 player shall have the functionality of adapting to its user, by analyzing incoming biological sensor data, and from this data the mp3 player will choose a genre for the next song. Given in the assignment is 14 samples of data: One sample consist of Heart Rate, Respiration, Skin Conductivity, Activity and finally the output genre. Below is the 14 samples of data, just for you to get an impression of what im talking about. Sample HR RSP SC Activity Genre S1 Medium Low High Low Rock S2 High Low Medium High Rock S3 High High Medium Low Classic S4 High Medium Low Medium Classic S5 Medium Medium Low Low Classic S6 Medium Low High High Rock S7 Medium High Medium Low Classic S8 High Medium High Low Rock S9 High High Low Low Classic S10 Medium Medium Medium Low Classic S11 Medium Medium High High Rock S12 Low Medium Medium High Classic S13 Medium High Low Low Classic S14 High Low Medium High Rock My time of work regarding HMM is quite low, so my question to you is if I got the right angle on the assignment. I have three different states for each sensor: Low, Medium, High. Two observations/output symbols: Rock, Classic In my own opinion I see my start probabilities as the weightened factors for either a Low, Medium or High state in the Heart Rate. So the ideal solution for the AI is that it will learn these 14 sets of samples. And when a users sensor input is received, the AI will compare the combination of states for all four sensors, with the already memorized samples. If there exist a matching combination, the AI will choose the genre, and if not it will choose a genre according to the weightened transition probabilities, while simultaniously updating the transition probabilities with the new data. Is this a right approach to take, or am I missing something ? Is there another way to determine the output probability (read about Maximum likelihood estimation by EM, but dont understand the concept)? Best regards, Casper

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• How do I write test code to exercise a C# generic Pair<TKey, TValue> ?

  - by Scott Davies

  Hi, I am reading through Jon Skeet's "C# in Depth", first edition (which is a great book). I'm in section 3.3.3, page 84, "Implementing Generics". Generics always confuse me, so I wrote some code to exercise the sample. The code provided is: using System; using System.Collections.Generic; public sealed class Pair<TFirst, TSecond> : IEquatable<Pair<TFirst, TSecond>> { private readonly TFirst first; private readonly TSecond second; public Pair(TFirst first, TSecond second) { this.first = first; this.second = second; } ...property getters... public bool Equals(Pair<TFirst, TSecond> other) { if (other == null) { return false; } return EqualityComparer<TFirst>.Default.Equals(this.First, other.First) && EqualityComparer<TSecond>.Default.Equals(this.Second, other.Second); } My code is: class MyClass { public static void Main (string[] args) { // Create new pair. Pair thePair = new Pair(new String("1"), new String("1")); // Compare a new pair to previous pair by generating a second pair. if (thePair.Equals(new Pair(new string("1"), new string("1")))) System.Console.WriteLine("Equal"); else System.Console.WriteLine("Not equal"); } } The compiler complains: "Using the generic type 'ManningListing36.Paie' requires 2 type argument(s) CS0305" What am I doing wrong ? Thanks, Scott

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• Advantages/Disadvantages of different implementations for Comparing Objects using .NET

  - by Kevin Crowell

  This questions involves 2 different implementations of essentially the same code. First, using delegate to create a Comparison method that can be used as a parameter when sorting a collection of objects: class Foo { public static Comparison<Foo> BarComparison = delegate(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); }; } I use the above when I want to have a way of sorting a collection of Foo objects in a different way than my CompareTo function offers. For example: List<Foo> fooList = new List<Foo>(); fooList.Sort(BarComparison); Second, using IComparer: public class BarComparer : IComparer<Foo> { public int Compare(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); } } I use the above when I want to do a binary search for a Foo object in a collection of Foo objects. For example: BarComparer comparer = new BarComparer(); List<Foo> fooList = new List<Foo>(); Foo foo = new Foo(); int index = fooList.BinarySearch(foo, comparer); My questions are: What are the advantages and disadvantages of each of these implementations? What are some more ways to take advantage of each of these implementations? Is there a way to combine these implementations in such a way that I do not need to duplicate the code? Can I achieve both a binary search and an alternative collection sort using only 1 of these implementations?

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• php user authentication libraries / frameworks ... what are the options?

  - by es11

  I am using PHP and the codeigniter framework for a project I am working on, and require a user login/authentication system. For now I'd rather not use SSL (might be overkill and the fact that I am using shared hosting discourages this). I have considered using openID but decided that since my target audience is generally not technical, it might scare users away (not to mention that it requires mirroring of login information etc.). I know that I could write a hash based authentication (such as sha1) since there is no sensitive data being passed (I'd compare the level of sensitivity to that of stackoverflow). That being said, before making a custom solution, it would be nice to know if there are any good libraries or packages out there that you have used to provide semi-secure authentication? I am new to codeigniter, but something that integrates well with it would be preferable. Any ideas? (i'm open to criticism on my approach and open to suggestions as to why I might be crazy not to just use ssl). Thanks in advance. Update: I've looked into some of the suggestions. I am curious to try out zend-auth since it seems well supported and well built. Does anyone have experience with using zend-auth in codeigniter (is it too bulky?) and do you have a good reference on integrating it with CI? I do not need any complex authentication schemes..just a simple login/logout/password-management authorization system. Also, dx_auth seems interesting as well, however I am worried that it is too buggy. Has anybody else had success with this? I realized that I would also like to manage guest users (i.e. users that do not login/register) in a similar way to stackoverflow..so any suggestions that have this functionality would be great

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• MySQL GIS and Spatial Extensions - how to map regions and query against them

  - by chibineku

  I am trying to make a smartphone app which will return a list of users within a certain proximity, say 100m. It's easy to get the coordinates of my BlackBerry and write them to a database, but in order to return a list of other users within 100m, I need to pull every other record from the database and compare the distance between the two points, checking to see if it's within range, before outputting that user's information. This is going to be time consuming if there are many users involved. So I would like to map areas (countries, cities, I'm not yet sure of the resolution I'll need) so that I can first target a smaller subset of all users. This will save on processing time. I have read the basics of GIS and spatial querying on the mysql website but to be honest the query is over my head and I hate copying and pasting code without understanding it. Plus it only checks for proximity - I want to first check if a coordinate falls within a certain area. Does anyone have any experience of such matters and feel like giving me some pointers? Resources such as any preexisting databases of points describing countries as polygons would be really helpful too. Many thanks to anyone who takes the time :)

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• linq - how to sort a list

  - by Billy Logan

  Hello everyone, I have a linq query that populates a list of designers. since i am using the filters below my sorting is not functioning properly. My question is with the given code below how can i best sort this List after the fact or sort while querying? I have tried to sort the list after the fact using the following script but i receive a compiler error: List<TBLDESIGNER> designers = new List<TBLDESIGNER>(); designers = 'calls my procedure below and comes back with an unsorted list of designers' designers.Sort((x, y) => string.Compare(x.FIRST_NAME, y.LAST_NAME)); Query goes as follows: List<TBLDESIGNER> designer = null; using (SOAE strikeOffContext = new SOAE()) { //Invoke the query designer = AdminDelegates.selectDesignerDesigns.Invoke(strikeOffContext).ByActive(active).ByAdmin(admin).ToList(); } Delegate: public static Func<SOAE, IQueryable<TBLDESIGNER>> selectDesignerDesigns = CompiledQuery.Compile<SOAE, IQueryable<TBLDESIGNER>>( (designer) => from c in designer.TBLDESIGNER.Include("TBLDESIGN") orderby c.FIRST_NAME ascending select c); Filter ByActive: public static IQueryable<TBLDESIGNER> ByActive(this IQueryable<TBLDESIGNER> qry, bool active) { //Return the filtered IQueryable object return from c in qry where c.ACTIVE == active select c; } Filter ByAdmin: public static IQueryable<TBLDESIGNER> ByAdmin(this IQueryable<TBLDESIGNER> qry, bool admin) { //Return the filtered IQueryable object return from c in qry where c.SITE_ADMIN == admin select c; } Thanks in advance, Billy

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• Unit testing opaque structure based C API

  - by Nicolas Goy

  I have a library I wrote with API based on opaque structures. Using opaque structures has a lot of benefits and I am very happy with it. Now that my API are stable in term of specifications, I'd like to write a complete battery of unit test to ensure a solid base before releasing it. My concern is simple, how do you unit test API based on opaque structures where the main goal is to hide the internal logic? For example, let's take a very simple object, an array with a very simple test: WSArray a = WSArrayCreate(); int foo = 5; WSArrayAppendValue(a, &foo); int *bar = WSArrayGetValueAtIndex(a, 0); if(&foo != bar) printf("Eroneous value returned\n"); else printf("Good value returned\n"); WSRelease(a); Of course, this tests some facts, like the array actually acts as wanted with 1 value, but when I write unit tests, at least in C, I usualy compare the memory footprint of my datastructures with a known state. In my example, I don't know if some internal state of the array is broken. How would you handle that? I'd really like to avoid adding codes in the implementation files only for unit testings, I really emphasis loose coupling of modules, and injecting unit tests into the implementation would seem rather invasive to me. My first thought was to include the implementation file into my unit test, linking my unit test statically to my library. For example: #include <WS/WS.h> #include <WS/Collection/Array.c> static void TestArray(void) { WSArray a = WSArrayCreate(); /* Structure members are available because we included Array.c */ printf("%d\n", a->count); } Is that a good idea? Of course, the unit tests won't benefit from encapsulation, but they are here to ensure it's actually working.

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• Can iPad/iPhone Touch Points be Wrong Due to Calibration?

  - by Kristopher Johnson

  I have an iPad application that uses the whole screen (that is, UIStatusBarHidden is set true in the Info.plist file). The main window's frame is set to (0, 0, 768, 1024), as is the main view in that frame. The main view has multitouch enabled. The view has code to handle touches: - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { for (UITouch *touch in touches) { CGPoint location = [touch locationInView:nil]; NSLog(@"touchesMoved at location %@", NSStringFromCGPoint(location)); } } When I run the app in the simulator, it works pretty much as expected. As I move the mouse from one edge of the screen to the other, reported X values go from 0 to 767. Reported Y values go from 20 to 1023, but it is a known issue that the simulator doesn't report touches in the top 20 pixels of the screen, even when there is no status bar. Here's what's weird: When I run the app on an actual iPad, the X values go from 0 to 767 as expected, but reported Y values go from -6 to 1017. The fact that it seems to work properly on the simulator leads me to suspect that real devices' touchscreens are not perfectly calibrated, and mine is simply reporting values six pixels too low. Can anyone verify that this is the case? Otherwise, is there anything else that could account for the Y values being six pixels off from what I expect? (In a few days, I should have a second iPad, so I can test this with another device and compare the results.)

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• Write a sql for updating data based on time

  - by Lu Lu

  Hello everyone, Because I am new with SQL Server and T-SQL, so I will need your help. I have 2 table: Realtime and EOD. To understand my question, I give example data for 2 tables: ---Realtime table--- Symbol Date Value ABC 1/3/2009 03:05:01 327 // this day is not existed in EOD -> inserting BBC 1/3/2009 03:05:01 458 // this day is not existed in EOD -> inserting ABC 1/2/2009 03:05:01 326 // this day is new -> updating BBC 1/2/2009 03:05:01 454 // this day is new -> updating ABC 1/2/2009 02:05:01 323 BBC 1/2/2009 02:05:01 453 ABC 1/2/2009 01:05:01 313 BBC 1/2/2009 01:05:01 423 ---EOD table--- Symbol Date Value ABC 1/2/2009 02:05:01 323 BBC 1/2/2009 02:05:01 453 I will need to create a store procedure to update value of symbols. If data in day of a symbol is new (compare between Realtime & EOD), it will update value and date for EOD at that day if existing, otherwise inserting. And store will update EOD table with new data: ---EOD table--- Symbol Date Value ABC 1/3/2009 03:05:01 327 BBC 1/3/2009 03:05:01 458 ABC 1/2/2009 03:05:01 326 BBC 1/2/2009 03:05:01 454 P/S: I use SQL Server 2005. And I have a similar answered question at here: http://stackoverflow.com/questions/2726369/help-to-the-way-to-write-a-query-for-the-requirement Please help me. Thanks.

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• How can I find out if two arguments are instances of the same, but unknown class?

  - by Ingmar

  Let us say we have a method which accepts two arguments o1 and o2 of type Object and returns a boolean value. I want this method to return true only when the arguments are instances of the same class, e.g.: foo(new Integer(4),new Integer(5)); Should return true, however: foo(new SomeClass(), new SubtypeSomeClass()); should return false and also: foo(new Integer(3),"zoo"); should return false. I believe one way is to compare the fully qualified class names: public boolean foo(Object o1, Object o2){ Class<? extends Object> c1 = o1.getClass(); Class<? extends Object> c2 = o2.getClass(); if(c1.getName().equals(c2.getName()){ return true;} return false; } An alternative conditional statement would be : if (c1.isAssignableFrom(c2) && c2.isAssignableFrom(c1)){ return true; } The latter alternative is rather slow. Are there other alternatives to this problem?

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