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  • Is it possible to match with decomposed sequences in F#?

    - by Ball
    I seem to remember an older version of F# allowing structural decomposition when matching sequences just like lists. Is there a way to use the list syntax while keeping the sequence lazy? I'm hoping to avoid a lot of calls to Seq.head and Seq.skip 1. I'm hoping for something like: let decomposable (xs:seq<'a>) = match xs with | h :: t -> true | _ -> false seq{ 1..100 } |> decomposable But this only handles lists and gives a type error when using sequences. When using List.of_seq, it seems to evaluate all the elements in the sequence, even if it is infinite.

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  • L2S DataContext out of synch: row not found or changed

    - by awrigley
    The Problem I am getting a number of errors that imply that the DataContext, or rather, the way I am using the DataContext is getting out of synch. The error occurs on db.SubmitChanges() where db is my DataContext instance. The error is: Row not found or changed. The problem only occurs intermitently, for example, adding a row then deleting it. If I stop the dev server and restart, the added row is there and I can delete it no problem. Ie, it seems that the problem is related to the DataContext losing track of the rows that have been added. IMPORTANT: Before anyone votes to close this thread, on the basis of it being a duplicate, I have checked the sql server profiler and there is no "Where 0 = 1" in the SQL. I have also recreated the dbml file, so am satisfied that the database schema is in synch with the schema represented by the dbml file. Ie, no cases of mismatched nullable/not nullable columns, etc. My Diagnosis (for what it is worth): It seems to be a problem related to how I am using the DataContext. I am new to MVC, Repositories and Services patterns, so suspect that I have wired things up wrong. The Setup Simple eLearning app in its early stages. Pupils need to be able to add and delete courses (Courses table) to their UserCourses. To do this, I have a service that gets a specific DataContext instance Dependency Injected into its constructor. Service Class Constructor: public class SqlPupilBlockService : IPupilBlockService { DataContext db; public SqlPupilBlockService(DataContext db) { this.db = db; CoursesRepository = new SqlRepository<Course>(db); UserCoursesRepository = new SqlRepository<UserCourse>(db); } // Etc, etc } The CoursesRepository and UserCoursesRepository are both private properties of the service class that are of Type IRepository (just a simple generic repository interface). Sql Respoitory Code: public class SqlRepository<T> : IRepository<T> where T : class { DataContext db; public SqlRepository(DataContext db) { this.db = db; } #region IRepository<T> Members public IQueryable<T> Query { get { return db.GetTable<T>(); } } public List<T> FetchAll() { return Query.ToList(); } public void Add(T entity) { db.GetTable<T>().InsertOnSubmit(entity); } public void Delete(T entity) { db.GetTable<T>().DeleteOnSubmit(entity); } public void Save() { db.SubmitChanges(); } #endregion } The two methods for adding and deleting UserCourses are: Service Methods for Adding and Deleting UserCourses: public void AddUserCourse(int courseId) { UserCourse uc = new UserCourse(); uc.IdCourse = courseId; uc.IdUser = UserId; uc.DateCreated = DateTime.Now; uc.DateAmended = DateTime.Now; uc.Role = "Pupil"; uc.CourseNotes = string.Empty; uc.ActiveStepIndex = 0; UserCoursesRepository.Add(uc); UserCoursesRepository.Save(); } public void DeleteUserCourse(int courseId) { var uc = (UserCoursesRepository.Query.Where(x => x.IdUser == UserId && x.IdCourse == courseId)).Single(); UserCoursesRepository.Delete(uc); UserCoursesRepository.Save(); } Ajax I am using Ajax via Ajax.BeginForm I don't think that is relevant. ASP.NET MVC 3 I am using mvc3, but don't think that is relevant: the errors are related to model code.

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  • How to do rolling balances in Linq2SQL

    - by David Liddle
    Given an account with a list of transactions I would like to output a query that shows each transaction with the rolling balance (just like you would see on an online banking account). TRANSACTIONS - ID - DATE - AMOUNT Here is what I created in T-SQL however was wondering if this can be translated to linq2sql code? select T.ID, convert(char(10), T.DATE, 101) as 'DATE', T.AMOUNT, (select sum(O.AMOUNT) from TRANSACTIONS O where O.DATE < T.DATE or (O.DATE = T.DATE and O.ID <= T.ID)) 'BALANCE' from TRANSACTIONS as T where T.DATE between @pStartDate and @pEndDate order by T.DATE, T.ID Alternatively I guess my other option is to just call a stored procedure for these kind of results. However, I have Services which call Repositories and didn't really want to put the sproc call in the Repository.

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  • Is It possible to use the second part of this code for repository patterns and generics

    - by newToCSharp
    Is there any issues in using version 2,to get the same results as version 1. Or is this just bad coding. Any Ideas public class Customer { public int CustomerID { get; set; } public string EmailAddress { get; set; } int Age { get; set; } } public interface ICustomer { void AddNewCustomer(Customer Customer); void AddNewCustomer(string EmailAddress, int Age); void RemoveCustomer(Customer Customer); } public class BALCustomer { private readonly ICustomer dalCustomer; public BALCustomer(ICustomer dalCustomer) { this.dalCustomer = dalCustomer; } public void Add_A_New_Customer(Customer Customer) { dalCustomer.AddNewCustomer(Customer); } public void Remove_A_Existing_Customer(Customer Customer) { dalCustomer.RemoveCustomer(Customer); } } public class CustomerDataAccess : ICustomer { public void AddNewCustomer(Customer Customer) { // MAKE DB CONNECTION AND EXECUTE throw new NotImplementedException(); } public void AddNewCustomer(string EmailAddress, int Age) { // MAKE DB CONNECTION AND EXECUTE throw new NotImplementedException(); } public void RemoveCustomer(Customer Customer) { // MAKE DB CONNECTION AND EXECUTE throw new NotImplementedException(); } } // VERSION 2 public class Customer_New : DataRespository<CustomerDataAccess> { public int CustomerID { get; set; } public string EmailAddress { get; set; } public int Age { get; set; } } public class DataRespository<T> where T:class,new() { private T item = new T(); public T Execute { get { return item; } set { item = value; } } public void Update() { //TO BE CODED } public void Save() { //TO BE CODED } public void Remove() { //TO BE CODED } } class Program { static void Main(string[] args) { Customer_New cus = new Customer_New() { Age = 10, EmailAddress = "[email protected]" }; cus.Save(); cus.Execute.RemoveCustomer(new Customer()); // Repository Version Customer customer = new Customer() { EmailAddress = "[email protected]", CustomerID = 10 }; BALCustomer bal = new BALCustomer(new CustomerDataAccess()); bal.Add_A_New_Customer(customer); } } }

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  • How can I detect common substrings in a list of strings

    - by danio
    Given a set of strings, for example: EFgreen EFgrey EntireS1 EntireS2 J27RedP1 J27GreenP1 J27RedP2 J27GreenP2 JournalP1Black JournalP1Blue JournalP1Green JournalP1Red JournalP2Black JournalP2Blue JournalP2Green I want to be able to detect that these are three sets of files: EntireS[1,2] J27[Red,Green]P[1,2] JournalP[1,2][Red,Green,Blue] Are there any known ways of approaching this problem - any published papers I can read on this? The approach I am considering is for each string look at all other strings and find the common characters and where differing characters are, trying to find sets of strings that have the most in common, but I fear that this is not very efficient and may give false positives. Note that this is not the same as 'How do I detect groups of common strings in filenames' because that assumes that a string will always have a series of digits following it. [Edited 15/09/09 to add more sample strings]

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  • BlockingQueue decorator that logs removed objects

    - by scompt.com
    I have a BlockingQueue that's being used in a producer-consumer situation. I would like to decorate this queue so that every object that's taken from it is logged. I know what the straightforward implementation would look like: simply implement BlockingQueue and accept a BlockingQueue in the constructor to which all of the methods would delegate. Is there another way that I'm missing? A library perhaps? Something with a callback interface?

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  • Optimising ruby regexp -- lots of match groups

    - by Farcaller
    I'm working on a ruby baser lexer. To improve performance, I joined up all tokens' regexps into one big regexp with match group names. The resulting regexp looks like: /\A(?<__anonymous_-1038694222803470993>(?-mix:\n+))|\A(?<__anonymous_-1394418499721420065>(?-mix:\/\/[\A\n]*))|\A(?<__anonymous_3077187815313752157>(?-mix:include\s+"[\A"]+"))|\A(?<LET>(?-mix:let\s))|\A(?<IN>(?-mix:in\s))|\A(?<CLASS>(?-mix:class\s))|\A(?<DEF>(?-mix:def\s))|\A(?<DEFM>(?-mix:defm\s))|\A(?<MULTICLASS>(?-mix:multiclass\s))|\A(?<FUNCNAME>(?-mix:![a-zA-Z_][a-zA-Z0-9_]*))|\A(?<ID>(?-mix:[a-zA-Z_][a-zA-Z0-9_]*))|\A(?<STRING>(?-mix:"[\A"]*"))|\A(?<NUMBER>(?-mix:[0-9]+))/ I'm matching it to my string producing a MatchData where exactly one token is parsed: bigregex =~ "\n ... garbage" puts $~.inspect Which outputs #<MatchData "\n" __anonymous_-1038694222803470993:"\n" __anonymous_-1394418499721420065:nil __anonymous_3077187815313752157:nil LET:nil IN:nil CLASS:nil DEF:nil DEFM:nil MULTICLASS:nil FUNCNAME:nil ID:nil STRING:nil NUMBER:nil> So, the regex actually matched the "\n" part. Now, I need to figure the match group where it belongs (it's clearly visible from #inspect output that it's _anonymous-1038694222803470993, but I need to get it programmatically). I could not find any option other than iterating over #names: m.names.each do |n| if m[n] type = n.to_sym resolved_type = (n.start_with?('__anonymous_') ? nil : type) val = m[n] break end end which verifies that the match group did have a match. The problem here is that it's slow (I spend about 10% of time in the loop; also 8% grabbing the @input[@pos..-1] to make sure that \A works as expected to match start of string (I do not discard input, just shift the @pos in it). You can check the full code at GH repo. Any ideas on how to make it at least a bit faster? Is there any option to figure the "successful" match group easier?

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  • Repository, Service or Domain object - where does logic belong?

    - by betitall
    Take this simple, contrived example: UserRepository.GetAllUsers(); UserRepository.GetUserById(); Inevitably, I will have more complex "queries", such as: //returns users where active=true, deleted=false, and confirmed = true GetActiveUsers(); I'm having trouble determining where the responsibility of the repository ends. GetActiveUsers() represents a simple "query". Does it belong in the repository? How about something that involves a bit of logic, such as: //activate the user, set the activationCode to "used", etc. ActivateUser(string activationCode);

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  • C++ inheritance question

    - by user233973
    Hi guys, I have a C++ inheritance related question. I have a set of classes like this (I have not given the complete class structure coz I am lazy :) ). I want to access chiComponent class public methods using com pointer. How should I go about it? Note that I am having to change the object which "com" is pointing to in a lot of places. So I do not think I can have another chiComponent *ccom = <some_cast> com; ccom.chiComponentMethod() How should I go about it? class Component{ }; class chiComponent : public Component { public: void chiComponentMethod() { cout << "Hi! Chi component function called!!"; } } class parent { protected: Component *com; }; class child : public parent{ public: child() { com = new chiComponent(); } } Regards Arun

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  • Javascript regular expressions problem

    - by Patrick
    Hello! I am creating a small yatzy game and i have run into some regex problems. I need to verify certain criteria to see if they are met. The fields one to six is very straight forward the problem comes after that. Like trying to create a regex that matches the ladder. The Straight should contain one of the following characters 1-5. It must contain one of each to pass but i can't figure out how to check for it. I was thinking /1{1}2{1}3{1}4{1}5{1}/g; but that only matches if they come in order. How can i check if they don't come in the correct order?

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  • How should I be using IoC in this winform piece of code?

    - by Pure.Krome
    Hi folks, I've got a winform app in visual studio 2010. My app does the following Get a list of files which I need to read the data then insert into a database. For each file, read data and insert into DB. So .. this is the code i have. var list = _repository.GetFileList(); if (list != null) { int i = 0; foreach(var file in list) { i++; var service = new MyService(i, _repository); service.ParseAndSave(); } } So i was hoping to have a new repository for each 'service' i create. Firstly, i'm not sure if I should be using IoC in this case. I believe I should be because then i don't need to tightly couple this winform to a repository. Secondly, I've tried using a Singleton repo, which I don't want and can confirm that it kills that code (crashes with an exception). Some other notes (which shouldn't impact this question) - Using Entity Framework for ASP.NET 4. - Using StructureMap for IoC Can someone help, please?

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  • Unix: replace every odd | with \left| and every even | with \right|

    - by HH
    An enormous equation. You need to add \left| on the left side of corresponding |. The corresponding | you need to replace with \right|. Equation \begin{equation} | \Delta w_{0} | = \frac{|w_{0}|}{2} \left( |\frac{\Delta g}{g}|+|\frac{\Delta (\Delta r)}{\Delta r}| + |\frac{\Delta r}{r}| +|\frac{\Delta L}{L}| \right) \end{equation}

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  • Separating text and graphics in an image

    - by avd
    I dont know whether should I post this question here or not? But if someone knows it, please answer? What are the algorithms for determining which region in an image is text and which one is graphic? Means how to separate such regions? (figure or diagram)

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  • How to understand the output of the PHP regex matching below?

    - by smarty
    $file = '{include file="{$COMMON_TPL_PATH}common/header_admin.tpl"} {include file="{$mainPage}"} {include file="{$COMMON_TPL_PATH}common/footer_admin.tpl"}'; preg_match('/^(\{\})|^(\{\*([\S\s]*?)\*\})|^(<\?(?:php\w+|=|[a-zA-Z]+)?)|^([ ]*[ ]+[ ]*)|^(\{strip\})|^(\{\/strip\})|^(\{literal\})|^(\{\s{1,}\/)|^(\{\s{1,})|^(\{\/)|^(\{)|^(([\S\s]*?)(?=([ ]*[ ]+[ ]*|\{|<\?)))|^([\S\s]+)/', $file, $matches); var_dump($matches); Why the output is: array(13) { [0]=> string(1) "{" [1]=> string(0) "" [2]=> string(0) "" [3]=> string(0) "" [4]=> string(0) "" [5]=> string(0) "" [6]=> string(0) "" [7]=> string(0) "" [8]=> string(0) "" [9]=> string(0) "" [10]=> string(0) "" [11]=> string(0) "" [12]=> string(1) "{" } It seems to me that ^([\S\s]+) can match the whole string..

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  • How to match a variable list of items separated by commas

    - by user261915
    I want to turn something like this CS 240, CS 246, ECE 222, ... (more or less); Software Engineering students only into ('CS 240', 'CS 246', 'ECE 222', 'ECE 220') in Python, code that matches a single course looks like >>> re.search('([A-Z]{2,5} \d{3})', 'SE 112').groups() ('SE 112',) I prefer a regular expression only method because I have a bunch of other alternate reg exps using '|' to combine them. However, a method with split is acceptable.

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  • Sed: regular expression match lines without <!--

    - by sixtyfootersdude
    I have a sed command to comment out xml commands sed 's/^\([ \t]*\)\(.*[0-9a-zA-Z<].*\)$/\1<!-- Security: \2 -->/' web.xml Takes: <a> <!-- Comment --> <b> bla </b> </a> Produces: <!-- Security: <a> --> <!-- Security: <!-- Comment --> --> // NOTE: there are two end comments. <!-- Security: <b> --> <!-- Security: bla --> <!-- Security: </b> --> <!-- Security: </a> --> Ideally I would like to not use my sed script to comment things that are already commented. Ie: <!-- Security: <a> --> <!-- Comment --> <!-- Security: <b> --> <!-- Security: bla --> <!-- Security: </b> --> <!-- Security: </a> --> I could do something like this: sed 's/^\([ \t]*\)\(.*[0-9a-zA-Z<].*\)$/\1<!-- Security: \2 -->/' web.xml sed 's/^[ \t]*<!-- Security: \(<!--.*-->\) -->/\1/' web.xml but I think a one liner is cleaner (?) This is pretty similar: http://stackoverflow.com/questions/436850/matching-a-line-that-doesnt-contain-specific-text-with-regular-expressions

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  • How can I improve this regular expression?

    - by Michael Haren
    I want a regular expression to match valid input into a Tags input field with the following properties: 1-5 tags Each tag is 1-30 characters long Valid tag characters are [a-zA-Z0-9-] input and tags can be separated by any amount of whitespace Here's what I have so far--it seems to work but I'm interested how it could be simplified or if it has any major flaws: \s*[a-zA-Z0-9-]{1,30}(\s+[a-zA-Z0-9-]{1,30}){0,4}\s* // that is: \s* // match all beginning whitespace [a-zA-Z0-9-]{1,30} // match the first tag (\s+[a-zA-Z0-9-]{1,30}){0,4} // match all subsequent tags \s* // match all ending whitespace Preprocessing the input to make the whitespace issue easier isn't an option (e.g. trimming or adding a space). If it matters, this will be used in javascript. Any suggestions would be appreciated, thanks!

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  • How to prevent regex from stopping at the first match of alternatives ?

    - by miket2e
    If I have the string hello world , how can I modify the regex world|wo|w so that it will match all of "world", "wo" and "w" rather than just the single first match of "world" that it comes to ? If this is not possible directly, is there a good workaround ? I'm using C# if it makes a difference: Regex testRegex = new Regex("world|wo|w"); MatchCollection theMatches = testRegex.Matches("hello world"); foreach (Match thisMatch in theMatches) { ... }

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