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  • Lambda Expressions for a 5th Grader

    - by Randy Minder
    If you had to explain Lambda expressions to a 5th grader, how would you do it? And what examples might you give, or resources might you point them to? I may be finding myself in the position of having to teach this to 5th grade level developers and could use some assistance. Thanks very much.

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  • regular expressions for class name

    - by user576701
    i need a regular expressions string to get all anchor tags in a page with a specific css class name, in c#/vb.net this is what i got so far "<a.*?href=""(.*?)"".*?>(.*?)</a>" but my attempts to add "class=name" isnt working, also is it possible to find links where the class name appears either before or after the href with one expression ? i am familiar with 3rd party html libraries, but thats an overkill for what i have in mind, so is the webbrowser control.

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  • nginx dynamic servername with regular expression doesn't work for co.uk

    - by redn0x
    I'm trying to setup a nginx server which dynamically loads content from a folder for a domain. To do this I'm using regular expressions in the server name like so: server_name ((?<subdomain>.+)\.)?(?<domain>.+)\.(?<tld>.*); This will create a 3 variables for nginx to use later on, for example when using the following url: test.foo.example.com this will evaluate to: $subdomain = test.foo $domain = example $tld = com The problem arises when the co.uk top-level domain is used. In this case when using the url test.foo.example.co.ukit will evaluate to: $subdomain = test.foo.cedira $domain = co $tld = uk How can I edit the regular expression so that it will also work for co.uk?

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  • Entity Framework many-to-many using VB.Net Lambda

    - by bgs264
    Hello, I'm a newbie to StackOverflow so please be kind ;) I'm using Entity Framework in Visual Studio 2010 Beta 2 (.NET framework 4.0 Beta 2). I have created an entity framework .edmx model from my database and I have a handful of many-to-many relationships. A trivial example of my database schema is Roles (ID, Name, Active) Members (ID, DateOfBirth, DateCreated) RoleMembership(RoleID, MemberID) I am now writing the custom role provider (Inheriting System.Configuration.Provider.RoleProvider) and have come to write the implementation of IsUserInRole(username, roleName). The LINQ-to-Entity queries which I wrote, when SQL-Profiled, all produced CROSS JOIN statements when what I want is for them to INNER JOIN. Dim query = From m In dc.Members From r In dc.Roles Where m.ID = 100 And r.Name = "Member" Select m My problem is almost exactly described here: http://stackoverflow.com/questions/553918/entity-framework-and-many-to-many-queries-unusable I'm sure that the solution presented there works well, but whilst I studied Java at uni and I can mostly understand C# I cannot understand this Lambda syntax provided and I need to get a similar example in VB. I've looked around the web for the best part of half a day but I'm not closer to my answer. So please can somebody advise how, in VB, I can construct a LINQ statement which would do this equivalent in SQL: SELECT rm.RoleID FROM RoleMembership rm INNER JOIN Roles r ON r.ID = rm.RoleID INNER JOIN Members m ON m.ID = rm.MemberID WHERE r.Name = 'Member' AND m.ID = 101 I would use this query to see if Member 101 is in Role 3. (I appreciate I probably don't need the join to the Members table in SQL but I imagine in LINQ I'd need to bring in the Member object?) UPDATE: I'm a bit closer by using multiple methods: Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load Dim count As Integer Using dc As New CBLModel.CBLEntities Dim persons = dc.Members.Where(AddressOf myTest) count = persons.Count End Using System.Diagnostics.Debugger.Break() End Sub Function myTest(ByVal m As Member) As Boolean Return m.ID = "100" AndAlso m.Roles.Select(AddressOf myRoleTest).Count > 0 End Function Function myRoleTest(ByVal r As Role) As Boolean Return r.Name = "Member" End Function SQL Profiler shows this: SQL:BatchStarting SELECT [Extent1].[ID] AS [ID], ... (all columns from Members snipped for brevity) ... FROM [dbo].[Members] AS [Extent1] RPC:Completed exec sp_executesql N'SELECT [Extent2].[ID] AS [ID], [Extent2].[Name] AS [Name], [Extent2].[Active] AS [Active] FROM [dbo].[RoleMembership] AS [Extent1] INNER JOIN [dbo].[Roles] AS [Extent2] ON [Extent1].[RoleID] = [Extent2].[ID] WHERE [Extent1].[MemberID] = @EntityKeyValue1',N'@EntityKeyValue1 int',@EntityKeyValue1=100 SQL:BatchCompleted SELECT [Extent1].[ID] AS [ID], ... (all columns from Members snipped for brevity) ... FROM [dbo].[Members] AS [Extent1] I'm not certain why it is using sp_execsql for the inner join statement and why it's still running a select to select ALL members though. Thanks. UPDATE 2 I've written it by turning the above "multiple methods" into lambda expressions then all into one query, like this: Dim allIDs As String = String.Empty Using dc As New CBLModel.CBLEntities For Each retM In dc.Members.Where(Function(m As Member) m.ID = 100 AndAlso m.Roles.Select(Function(r As Role) r.Name = "Doctor").Count > 0) allIDs &= retM.ID.ToString & ";" Next End Using But it doesn't seem to work: "Doctor" is not a role that exists, I just put it in there for testing purposes, yet "allIDs" still gets set to "100;" The SQL in SQL Profiler this time looks like this: SELECT [Project1].* FROM ( SELECT [Extent1].*, (SELECT COUNT(1) AS [A1] FROM [dbo].[RoleMembership] AS [Extent2] WHERE [Extent1].[ID] = [Extent2].[MemberID]) AS [C1] FROM [dbo].[Members] AS [Extent1] ) AS [Project1] WHERE (100 = [Project1].[ID]) AND ([Project1].[C1] > 0) For brevity I turned the list of all the columns from the Members table into * As you can see it's just ignoring the "Role" query... :/

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  • Weak event handler model for use with lambdas

    - by Benjol
    OK, so this is more of an answer than a question, but after asking this question, and pulling together the various bits from Dustin Campbell, Egor, and also one last tip from the 'IObservable/Rx/Reactive framework', I think I've worked out a workable solution for this particular problem. It may be completely superseded by IObservable/Rx/Reactive framework, but only experience will show that. I've deliberately created a new question, to give me space to explain how I got to this solution, as it may not be immediately obvious. There are many related questions, most telling you you can't use inline lambdas if you want to be able to detach them later: Weak events in .Net? Unhooking events with lambdas in C# Can using lambdas as event handlers cause a memory leak? How to unsubscribe from an event which uses a lambda expression? Unsubscribe anonymous method in C# And it is true that if YOU want to be able to detach them later, you need to keep a reference to your lambda. However, if you just want the event handler to detach itself when your subscriber falls out of scope, this answer is for you.

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  • List<object>.RemoveAll - How to create an appropriate Predicate

    - by CJM
    This is a bit of noob question - I'm still fairly new to C# and generics and completely new to predicates, delegates and lamda expressions... I have a class 'Enquiries' which contains a generic list of another class called 'Vehicles'. I'm building up the code to add/edit/delete Vehicles from the parent Enquiry. And at the moment, I'm specifically looking at deletions. From what I've read so far, it appears that I can use Vehicles.RemoveAll() to delete an item with a particular VehicleID or all items with a particular EnquiryID. My problem is understanding how to feed .RemoveAll the right predicate - the examples I have seen are too simplistic (or perhaps I am too simplistic given my lack of knowledge of predicates, delegates and lambda expressions). So if I had a List<Of Vehicle> Vehicles where each Vehicle had an EnquiryID, how would I use Vehicles.RemoveAll() to remove all vehicles for a given EnquiryID? I understand there are several approaches to this so I'd be keen to hear the differences between approaches - as much as I need to get something working, this is also a learning exercise. As an supplementary question, is a Generic list the best repository for these objects? My first inclination was towards a Collection, but it appears I am out of date. Certainly Generics seem to be preferred, but I'm curious as to other alternatives. Thanks

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  • GridView ObjectDataSource LINQ Paging and Sorting using multiple table query.

    - by user367426
    I am trying to create a pageing and sorting object data source that before execution returns all results, then sorts on these results before filtering and then using the take and skip methods with the aim of retrieving just a subset of results from the database (saving on database traffic). this is based on the following article: http://www.singingeels.com/Blogs/Nullable/2008/03/26/Dynamic_LINQ_OrderBy_using_String_Names.aspx Now I have managed to get this working even creating lambda expressions to reflect the sort expression returned from the grid even finding out the data type to sort for DateTime and Decimal. public static string GetReturnType<TInput>(string value) { var param = Expression.Parameter(typeof(TInput), "o"); Expression a = Expression.Property(param, "DisplayPriceType"); Expression b = Expression.Property(a, "Name"); Expression converted = Expression.Convert(Expression.Property(param, value), typeof(object)); Expression<Func<TInput, object>> mySortExpression = Expression.Lambda<Func<TInput, object>>(converted, param); UnaryExpression member = (UnaryExpression)mySortExpression.Body; return member.Operand.Type.FullName; } Now the problem I have is that many of the Queries return joined tables and I would like to sort on fields from the other tables. So when executing a query you can create a function that will assign the properties from other tables to properties created in the partial class. public static Account InitAccount(Account account) { account.CurrencyName = account.Currency.Name; account.PriceTypeName = account.DisplayPriceType.Name; return account; } So my question is, is there a way to assign the value from the joined table to the property of the current table partial class? i have tried using. from a in dc.Accounts where a.CompanyID == companyID && a.Archived == null select new { PriceTypeName = a.DisplayPriceType.Name}) but this seems to mess up my SortExpression. Any help on this would be much appreciated, I do understand that this is complex stuff.

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  • Will C++0x support __stdcall or extern "C" capture-nothing lambdas?

    - by Daniel Trebbien
    Yesterday I was thinking about whether it would be possible to use the convenience of C++0x lambda functions to write callbacks for Windows API functions. For example, what if I wanted to use a lambda as an EnumChildProc with EnumChildWindows? Something like: EnumChildWindows(hTrayWnd, CALLBACK [](HWND hWnd, LPARAM lParam) { // ... return static_cast<BOOL>(TRUE); // continue enumerating }, reinterpret_cast<LPARAM>(&myData)); Another use would be to write extern "C" callbacks for C routines. E.g.: my_class *pRes = static_cast<my_class*>(bsearch(&key, myClassObjectsArr, myClassObjectsArr_size, sizeof(my_class), extern "C" [](const void *pV1, const void *pV2) { const my_class& o1 = *static_cast<const my_class*>(pV1); const my_class& o2 = *static_cast<const my_class*>(pV2); int res; // ... return res; })); Is this possible? I can understand that lambdas that capture variables will never be compatible with C, but it at least seems possible to me that capture-nothing lambdas can be compatible.

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  • Python regular expressions matching variables to end of line

    - by None
    When you use variables (is that the correct word?) in python regular expressions like this: "blah (?P\w+)" ("value" would be the variable), how could you make the variable's value be the text after "blah " to the end of the line or to a certain character not paying any attention to the actual content of the variable. For example, this is pseudo-code for what I want: >>> import re >>> p = re.compile("say (?P<value>continue_until_text_after_assignment_is_recognized) endsay") >>> m = p.match("say Hello hi yo endsay") >>> m.group('value') 'Hello hi yo' Note: The title is probably not understandable. That is because I didn't know how to say it. Sorry if I caused any confusion.

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  • Common lisp error: "should be lambda expression"

    - by Zachary
    I just started learning Common Lisp a few days ago, and I'm trying to build a function that inserts a number into a tree. I'm getting an error, * - SYSTEM::%EXPAND-FORM: (CONS NIL LST) should be a lambda expression From googling around, it seems like this happens when you have too many sets of parenthesis, but after looking at this for an hour or so and changing things around, I can't figure out where I could be doing this. This is the code where it's happening: (defun insert (lst probe) (cond ((null lst) (cons probe lst)) ((equal (length lst) 1) (if (<= probe (first lst)) (cons probe lst) (append lst (list probe)))) ((equal (length lst) 2) ((cons nil lst) (append lst nil) (insertat nil lst 3) (cond ((<= probe (second lst)) (insert (first lst) probe)) ((> probe (fourth lst)) (insert (fifth lst) probe)) (t (insert (third lst) probe))))))) I'm pretty sure it's occurring after the ((equal (length lst) 2), where the idea is to insert an empty list into the existing list, then append an empty list onto the end, then insert an empty list into the middle.

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  • Regular expressions in URL Rewrite Module for IIS7

    - by TN
    I have following rewrite rule to append .aspx extension if url has no extension. <rule name="SimpleRewrite" stopProcessing="true"> <match url="^(.*(?&lt;=/)([^/.]*))$" /> <action type="Rewrite" url="{R:1}.aspx" /> </rule> However the rule is not working: Error HTTP 500.52 - URL Rewrite Module Error. The expression "^(.*(?<=/)([^/.]*))$" has an invalid syntax. However, this regular expression works in .NET. What regular expressions are supported by IIS Url Rewrite Module? How to make positive lookbehind assertion?

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  • generalizing the pumping lemma for UNIX-style regular expressions

    - by Avi
    Most UNIX regular expressions have, besides the usual *,+,? operators a backslash operator where \1,\2,... match whatever's in the last parentheses, so for example L=(a)b\1* matches the (non regular) language a^n b a^n On one hand, this seems to be pretty powerful since you can create (a*)b\1b\1 to match the language a^n b a^n b a^n which can't even be recognized by a stack automaton. On the other hand, I'm pretty sure a^n b^n cannot be expressed this way. Two questions: 1. Is there any literature on this family of languages (UNIX-y regular). In particular, is there a version of the pumping lemma for these? 2. Can someone prove (or perhaps disprove) that a^n b^n cannot be expressed this way? Thanks

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  • Fuzzy Regular Expressions

    - by Thomas Ahle
    In my work I have with great results used approximate string matching algorithms such as Damerau–Levenshtein distance to make my code less vulnerable to spelling mistakes. Now I have a need to match strings against simple regular expressions such TV Schedule for \d\d (Jan|Feb|Mar|...). This means that the string TV Schedule for 10 Jan should return 0 while T Schedule for 10. Jan should return 2. This could be done by generating all strings in the regex (in this case 100x12) and find the best match, but that doesn't seam practical. Do you have any ideas how to do this effectively?

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  • Using regular expressions to do mass replace in Notepad++

    - by user638820
    I've been trying to replace (and translate) this text, and i don't know what formula I should Use for thousands of places that I need to translate to Spanish. OKay this is what i want to do, i want to use regular expressions on Notepadd++. I give 4 variations, and in bold is what's supposed to go after the name of the place, in lower case and not to be confused with eg. Agency Village because that's its name. Missouri 5,988,927 Adrian City city 1,677 Advance city 1,347 Affton CDP 20,307 Agency Village village 684 Airport Drive village 698 To | [[Adrian City (Misuri)|Adrian City]] || ciudad || 1677 |- | [[Advance (Misuri)|Advance]] || ciudad || 1347 |- | [[Afton (Misuri)|Afton]] || CDP || 20307 |- | [[Agency Village (Misuri)|Agency Village]] || villa || 684 |- | [[Airport Drive (Misuri)|Airport Drive]] || villa || 698

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  • Rewriting VB.NET Lambda experession as a C# statement

    - by ChadD
    I downgraded my app from version 4 of the framework to version 4 and now I want to implement this VB.NET lambda function statement (which works on 3.5) Dim colLambda As ColumnItemValueAccessor = Function(rowItem As Object) General_ItemValueAccessor(rowItem, colName) and rewrite it in C#. This was my attempt: ColumnItemValueAccessor colLambda = (object rowItem) => General_ItemValueAccessor(rowItem, colName); When I did this, I get the following error: Error 14 One or more types required to compile a dynamic expression cannot be found. Are you missing references to Microsoft.CSharp.dll and System.Core.dll? C:\Source\DotNet\SqlSmoke\SqlSmoke\UserControls\ScriptUserControl.cs 84 73 SqlSmoke However, when I downgraded the app from version 4.0 of the framework to 3.5 (because our users only hae 3.5 and don't have rights to install 4.0). when I did this, the reference to "Microsoft.CSharp" was broken. Can I rewrite the VB.NET command in C# using syntax that is valid in C# 3.5 as I was able to in VB.NET? What would the syntax be?

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  • Regular Expressions

    - by Rocky
    Hello Everyone, I am new to Stackoverflow and I have a quick question. Let's assume we are given a large number of HTML files (large as in theoretically infinite). How can I use Regular Expressions to extract the list of Phone Numbers from all those files? Explanation/expression will be really appreciated. The Phone numbers can be any of the following formats: (123) 456 7899 (123).456.7899 (123)-456-7899 123-456-7899 123 456 7899 1234567899 Thanks a lot for all your help and have a good one!

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  • How to render Max(Substgring) with Lambda Extensions

    - by caifa
    Hi everybody. I'm using NHibernate with Lambda Extensions. I'd like to know how to nest a Max function with a Substring. The following statement retrieves Max("invoice_id") var ret = session .CreateCriteria<Invoice>() .SetProjection(Projections.Max("invoice_id")) .UniqueResult(); but in my case the field invoice_id is made in this way: 123452010 where 12345 is the invoice number, and 2010 is the current year. So I need to calculate the Max function only over the first 5 digits. How can I do it?

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  • Python regular expressions assigning to named groups

    - by None
    When you use variables (is that the correct word?) in python regular expressions like this: "blah (?P\w+)" ("value" would be the variable), how could you make the variable's value be the text after "blah " to the end of the line or to a certain character not paying any attention to the actual content of the variable. For example, this is pseudo-code for what I want: >>> import re >>> p = re.compile("say (?P<value>continue_until_text_after_assignment_is_recognized) endsay") >>> m = p.match("say Hello hi yo endsay") >>> m.group('value') 'Hello hi yo' Note: The title is probably not understandable. That is because I didn't know how to say it. Sorry if I caused any confusion.

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  • Building 'flat' rather than 'tree' LINQ expressions

    - by Ian Gregory
    I'm using some code (available here on MSDN) to dynamically build LINQ expressions containing multiple OR 'clauses'. The relevant code is var equals = values.Select(value => (Expression)Expression.Equal(valueSelector.Body, Expression.Constant(value, typeof(TValue)))); var body = equals.Aggregate<Expression>((accumulate, equal) => Expression.Or(accumulate, equal)); This generates a LINQ expression that looks something like this: (((((ID = 5) OR (ID = 4)) OR (ID = 3)) OR (ID = 2)) OR (ID = 1)) I'm hitting the recursion limit (100) when using this expression, so I'd like to generate an expression that looks like this: (ID = 5) OR (ID = 4) OR (ID = 3) OR (ID = 2) OR (ID = 1) How would I modify the expression building code to do this?

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  • combining dynamic text with regular expressions in php

    - by pfunc
    I am experimenting with finding popular keywords using curl, php and regular expressions. I have an array of non-specific nouns that I am matching my keyword search up. So I am looking for words like "the", "and", "that" etc. and taking them out of the keyword search. so I have an array of words like so: $wordArr = [the, and, at,....]; and then running something like: && preg_match('(\bmyword\w*\b)', $key) == false how do I combine these two so it loops through the array finding out if any of the words in the array match the regular expression? I guess I could just do a for loop, but though maybe I could use in_array($wordArr, $key).. or something like that.

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  • Python comparing string against several regular expressions

    - by maerics
    I'm pretty experienced with Perl and Ruby but new to Python so I'm hoping someone can show me the Pythonic way to accomplish the following task. I want to compare several lines against multiple regular expressions and retrieve the matching group. In Ruby it would be something like this: STDIN.each_line do |line| case line when /^A:(.*?)$/ then puts "FOO: #{$1}" when /^B:(.*?)$/ then puts "BAR: #{$1}" # when ... else puts "NO MATCH: #{line}" end end My attempts in Python are turning out pretty ugly because the matching group is returned from a call to match/search on a regular expression and Python has no assignment in conditionals or switch statements. What's the Pythonic way to do (or think!) about this problem?

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  • Given a Member Access lambda expression, convert it to a specific string representation with full ac

    - by Nathan
    Given an Expression<Func<T, object>> (e.g. x = x.Prop1.SubProp), I want to create a string "Prop1.SubProp" for as deep as necessary. In the case of a single access (e.g. x = x.Prop1), I can easily do this with: MemberExpression body = (expression.Body.NodeType == ExpressionType.Convert) ? (MemberExpression)((UnaryExpression)expression.Body).Operand : (MemberExpression)expression.Body; return body.Member.Name; However, if there is deeper nesting, e.g. x = x.Prop1.SubProp1, this only gets the most deeply nested name, e.g. "SubProp1" instead of "Prop1.SubProp1" Is there anyway to access the full property path of a lambda expression?

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  • JAVA: Build XML document using XPath expressions

    - by snoe
    I know this isn't really what XPath is for but if I have a HashMap of XPath expressions to values how would I go about building an XML document. I've found dom-4j's DocumentHelper.makeElement(branch, xpath) except it is incapable of creating attributes or indexing. Surely a library exists that can do this? Map xMap = new HashMap(); xMap.put("root/entity/@att", "fooattrib"); xMap.put("root/array[0]/ele/@att", "barattrib"); xMap.put("root/array[0]/ele", "barelement"); xMap.put("root/array[1]/ele", "zoobelement"); would result in: <root> <entity att="fooattrib"/> <array><ele att="barattrib">barelement</ele></array> <array><ele>zoobelement</ele></array> </root>

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