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  • Func<T> injecting with Windsor container

    - by yang
    Here is a code excerpt from AspComet project that works with Autofac. public MessageBus(IClientRepository clientRepository, Func<IMessagesProcessor> messagesProcessorFactoryMethod) { this.clientRepository = clientRepository; this.messagesProcessorFactoryMethod = messagesProcessorFactoryMethod; } How can I inject "Func<IMessagesProcessor> messagesProcessorFactoryMethod" with Windsor, is it possible? Thanks.

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  • Using Func<...> and params?

    - by grady
    Hello, I wrote this code: public static bool MyMethod(int someid, params string[] types) {...} How could I write that using Func? public static Func < int, ?params?, bool > MyMethod = ??? Thanks :-)

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  • two threads going to do func()

    - by nisnis84
    2 threads going to use the same func(). The 2 threads should be mutually exclusive. How do I get it to work properly? (output should be "abcdeabcde") char arr[] = "ABCDE"; int len = 5; void func(){ for(int i = 0; i <len;i++) printf("%c,arr[i]); }

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  • understanding func<T, TResult> C#

    - by Satish Raj
    Hi I am trying to refactor some of my code to use Func I have created a sample to try to understand how it works but I am getting compilation error. In the e.g. below when I am trying to access the parameter attributes or return the return value the compiler complain. Clarifications please. using System; namespace chsarp { class Program { static void Main(string[] args) { ParamInput input = new ParamInput(); input.ReservationID = 10; Test testMethod = new Test(); Func<ParamInput, ReservationResult> methodToInvoke = testMethod.GetStatus; ReservationResult result = TestFn(methodToInvoke, input); } static Result TestFn<Param, Result>(Func<Param, Result> methodToInvoke, Param parameter) where Result : new() { Result result = new Result(); try { result = methodToInvoke(parameter); } catch (Exception exception) { result.status = string.Format("Error-{0} during reserving {1}", parameter.ReservationID, exception.Message); } return result; } } class Test { public ReservationResult GetStatus(ParamInput msg) { ReservationResult result = new ReservationResult(); result.status = string.Format("The ReservationID-{0}", msg.ReservationID); return result; } } class ParamInput { public int ReservationID { get; set; } } class ReservationResult { public string status { get; set; } } }

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  • Generic Func<> as parameter to base method

    - by WestDiscGolf
    I might be losing the plot, but I hope someone can point me in the right direction. What am I trying to do? I'm trying to write some base methods which take Func< and Action so that these methods handle all of the exception handling etc. so its not repeated all over the place but allow the derived classes to specify what actions it wants to execute. So far this is the base class. public abstract class ServiceBase<T> { protected T Settings { get; set; } protected ServiceBase(T setting) { Settings = setting; } public void ExecAction(Action action) { try { action(); } catch (Exception exception) { throw new Exception(exception.Message); } } public TResult ExecFunc<T1, T2, T3, TResult>(Func<T1, T2, T3, TResult> function) { try { /* what goes here?! */ } catch (Exception exception) { throw new Exception(exception.Message); } } } I want to execute an Action in the following way in the derived class (this seems to work): public void Delete(string application, string key) { ExecAction(() => Settings.Delete(application, key)); } And I want to execute a Func in a similar way in the derived class but for the life of me I can't seem to workout what to put in the base class. I want to be able to call it in the following way (if possible): public object Get(string application, string key, int? expiration) { return ExecFunc(() => Settings.Get(application, key, expiration)); } Am I thinking too crazy or is this possible? Thanks in advance for all the help.

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  • autofac's Func<T> to resolve named service

    - by ppiotrowicz
    Given registered services: builder.RegisterType<Foo1>().Named<IFoo>("one").As<IFoo>(); builder.RegisterType<Foo2>().Named<IFoo>("two").As<IFoo>(); builder.RegisterType<Foo3>().Named<IFoo>("three").As<IFoo>(); Can I retrieve named implementations of IFoo interface by injecting something like Func<string, IFoo ? public class SomeClass(Func<string, IFoo> foo) { var f = foo("one"); Debug.Assert(f is Foo1); var g = foo("two"); Debug.Assert(g is Foo2); var h = foo("three"); Debug.Assert(h is Foo3); } I know I can do it with Meta<, but I don't want to use it.

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  • C# delegate or Func for 'all methods'?

    - by Michel
    Hi, i've read something about Func's and delegates and that they can help you to pass a method as a parameter. Now i have a cachingservice, and it has this declaration: public static void AddToCache<T>(T model, double millisecs, string cacheId) where T : class public static T GetFromCache<T>(string cacheId) where T : class So in a place where i want to cache some data, i check if it exists in the cache (with GetFromCache) and if not, get the data from somewhere, and the add it to the cache (with AddToCache) Now i want to extend the AddToCache method with a parameter, which is the class+method to call to get the data Then the declaration would be like this public static void AddToCache<T>(T model, double millisecs, string cacheId, Func/Delegate methode) where T : class Then this method could check wether the cache has data or not, and if not, get the data itself via the method it got provided. Then in the calling code i could say: AddToCache<Person>(p, 10000, "Person", new PersonService().GetPersonById(1)); AddToCache<Advert>(a, 100000, "Advert", new AdvertService().GetAdverts(3)); What i want to achieve is that the 'if cache is empty get data and add to cache' logic is placed on only one place. I hope this makes sense :) Oh, by the way, the question is: is this possible?

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  • OrderBy Linq.Expression as parameter = (Of Func(Of T,IComparable)) to perform LinqToEntity is not working

    - by NicoJuicy
    I'd like to get this working: Call: (Count & Page are used for pagination, so Count = 20 and Page = 1 for example, for the first 20 values). Sorting should be by name LeverancierService.GetLeveranciers(Function(el) el.Name, Count, Page) Equivalent in c#: LeverancierService.GetLeveranciers(el= el.Name, Count, Page) Method that gives an error (parameters shown above): Public Overridable Function GetAllPaged(orderby As Expression(Of Func(Of T, IComparable)), ByVal Count As Integer, ByVal Page As Integer) As IEnumerable(Of T) Return dbset.OrderBy(orderby).Skip((Page - 1) * Count).Take(Count).ToList() End Function Already tried changing it to this, but it gives the same error: Public Overridable Function GetAllPaged(Of TOrderBy)(orderby As Expression(Of Func(Of T, TOrderBy)), ByVal Count As Integer, ByVal Page As Integer) As IEnumerable(Of T) Return dbset.OrderBy(orderby).Skip((Page - 1) * Count).Take(Count).ToList() End Function Error: Unable to cast the type 'System.String' to type 'System.IComparable'. LINQ to Entities only supports casting Entity Data Model primitive types. Any idea how to do this? Extra info: I'm in a DDD-layered application, so the parameter should stay the same as the called method is an overridden interface (eg. if i change this, i have to do this for 200 times or so, because it's in VB.Net and not in C# (= 1 change) ) I know there is a way to change the expression to a string and then use DLinq (= Dynamic Linq), but that's not how it should be.

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  • Get the property, as a string, from an Expression<Func<TModel,TProperty>>

    - by Jaxidian
    I use some strongly-typed expressions that get serialized to allow my UI code to have strongly-typed sorting and searching expressions. These are of type Expression<Func<TModel,TProperty>> and are used as such: SortOption.Field = (p => p.FirstName);. I've gotten this working perfectly for this simple case. The code that I'm using for parsing the "FirstName" property out of there is actually reusing some existing functionality in a third-party product that we use and it works great, until we start working with deeply-nested properties(SortOption.Field = (p => p.Address.State.Abbreviation);). This code has some very different assumptions in the need to support deeply-nested properties. As for what this code does, I don't really understand it and rather than changing that code, I figured I should just write from scratch this functionality. However, I don't know of a good way to do this. I suspect we can do something better than doing a ToString() and performing string parsing. So what's a good way to do this to handle the trivial and deeply-nested cases? Requirements: Given the expression p => p.FirstName I need a string of "FirstName". Given the expression p => p.Address.State.Abbreviation I need a string of "Address.State.Abbreviation" While it's not important for an answer to my question, I suspect my serialization/deserialization code could be useful to somebody else who finds this question in the future, so it is below. Again, this code is not important to the question - I just thought it might help somebody. Note that DynamicExpression.ParseLambda comes from the Dynamic LINQ stuff and Property.PropertyToString() is what this question is about. /// <summary> /// This defines a framework to pass, across serialized tiers, sorting logic to be performed. /// </summary> /// <typeparam name="TModel">This is the object type that you are filtering.</typeparam> /// <typeparam name="TProperty">This is the property on the object that you are filtering.</typeparam> [Serializable] public class SortOption<TModel, TProperty> : ISerializable where TModel : class { /// <summary> /// Convenience constructor. /// </summary> /// <param name="property">The property to sort.</param> /// <param name="isAscending">Indicates if the sorting should be ascending or descending</param> /// <param name="priority">Indicates the sorting priority where 0 is a higher priority than 10.</param> public SortOption(Expression<Func<TModel, TProperty>> property, bool isAscending = true, int priority = 0) { Property = property; IsAscending = isAscending; Priority = priority; } /// <summary> /// Default Constructor. /// </summary> public SortOption() : this(null) { } /// <summary> /// This is the field on the object to filter. /// </summary> public Expression<Func<TModel, TProperty>> Property { get; set; } /// <summary> /// This indicates if the sorting should be ascending or descending. /// </summary> public bool IsAscending { get; set; } /// <summary> /// This indicates the sorting priority where 0 is a higher priority than 10. /// </summary> public int Priority { get; set; } #region Implementation of ISerializable /// <summary> /// This is the constructor called when deserializing a SortOption. /// </summary> protected SortOption(SerializationInfo info, StreamingContext context) { IsAscending = info.GetBoolean("IsAscending"); Priority = info.GetInt32("Priority"); // We just persisted this by the PropertyName. So let's rebuild the Lambda Expression from that. Property = DynamicExpression.ParseLambda<TModel, TProperty>(info.GetString("Property"), default(TModel), default(TProperty)); } /// <summary> /// Populates a <see cref="T:System.Runtime.Serialization.SerializationInfo"/> with the data needed to serialize the target object. /// </summary> /// <param name="info">The <see cref="T:System.Runtime.Serialization.SerializationInfo"/> to populate with data. </param> /// <param name="context">The destination (see <see cref="T:System.Runtime.Serialization.StreamingContext"/>) for this serialization. </param> public void GetObjectData(SerializationInfo info, StreamingContext context) { // Just stick the property name in there. We'll rebuild the expression based on that on the other end. info.AddValue("Property", Property.PropertyToString()); info.AddValue("IsAscending", IsAscending); info.AddValue("Priority", Priority); } #endregion }

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  • Generate dynamic UPDATE command from Expression<Func<T, T>>

    - by Rui Jarimba
    I'm trying to generate an UPDATE command based on Expression trees (for a batch update). Assuming the following UPDATE command: UPDATE Product SET ProductTypeId = 123, ProcessAttempts = ProcessAttempts + 1 For an expression like this: Expression<Func<Product, Product>> updateExpression = entity => new Product() { ProductTypeId = 123, ProcessAttempts = entity.ProcessAttempts + 1 }; How can I generate the SET part of the command? SET ProductTypeId = 123, ProcessAttempts = ProcessAttempts + 1

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  • Consolidating coding styles: Funcs, private method, single method classes

    - by jdoig
    Hi all, We currently have 3 devs with, some, conflicting styles and I'm looking for a way to bring peace to the kingdom... The Coders: Foo 1: Likes to use Func's & Action's inside public methods. He uses actions to alias off lengthy method calls and Func's to perform simple tasks that can be expressed in 1 or 2 lines and will be used frequently through out the code Pros: The main body of his code is succinct and very readable, often with only one or 2 public methods per class and rarely any private methods. Cons: The start of methods contain blocks of lambda rich code that other developers don't enjoy reading; and, on occasion, can contain higher order functions that other dev's REALLY don't like reading. Foo 2: Likes to create a private method for (almost) everything the public method will have to do . Pros: Public methods remain small and readable (to all developers). Cons: Private methods are numerous. With private methods that call into other private methods, that call into... etc, etc. Making code hard to navigate. Foo 3: Likes to create a public class with a, single, public method for every, non-trivial, task that needs performing, then dependency inject them into other objects. Pros: Easily testable, easy to understand (one object, one responsibility). Cons: project gets littered by classes, opening multiple class files to understand what code does makes navigation awkward. It would be great to take the best of all these techniques... Foo-1 Has really nice, readable (almost dsl-like) code... for the most part, except for all the Action and Func lambda shenanigans bulked together at the start of a method. Foo-3 Has highly testable and extensible code that just feels a bit "belt-&-braces" for some solutions and has some code-navigation niggles (constantly hitting F12 in VS and opening 5 other .cs files to find out what a single method does). And Foo-2... Well I'm not sure I like anything about the one-huge .cs file with 2 public methods and 12 private ones, except for the fact it's easier for juniors to dig into. I admit I grossly over-simplified the explanations of those coding styles; but if any one knows of any patterns, practices or diplomatic-manoeuvres that can help unite our three developers (without just telling any of them to just "stop it!") that would be great. From a feasibility standpoint : Foo-1's style meets with the most resistance due to some developers finding lambda and/or Func's hard to read. Foo-2's style meets with a less resistance as it's just so easy to fall into. Foo-3's style requires the most forward thinking and is difficult to enforce when time is short. Any ideas on some coding styles or conventions that can make this work?

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  • What is user gcc's purpose in requesting code possibly like this?

    - by James Morris
    In the question between syntax, are there any equal function the user gcc is requesting only what I can imagine to be the following code: #include <stdio.h> #include <string.h> /* estimated magic values */ #define MAXFUNCS 8 #define MAXFUNCLEN 3 int the_mainp_compare_func(char** mainp) { char mainp0[MAXFUNCS][MAXFUNCLEN] = { 0 }; char mainp1[MAXFUNCS][MAXFUNCLEN] = { 0 }; char* psrc, *pdst; int i = 0; int func = 0; psrc = mainp[0]; printf("scanning mainp[0] for functions...\n"); while(*psrc) { if (*psrc == '\0') break; else if (*psrc == ',') ++psrc; else { mainp0[func][0] = *psrc++; if (*psrc == ',') { mainp0[func][1] = '\0'; psrc++; } else if (*psrc !='\0') { mainp0[func][1] = *psrc++; mainp0[func][2] = '\0'; } printf("function: '%s'\n", mainp0[func]); } ++func; } printf("\nscanning mainp[1] for functions...\n"); psrc = mainp[1]; func = 0; while(*psrc) { if (*psrc == '\0') break; else if (*psrc == ',') ++psrc; else { mainp1[func][0] = *psrc++; if (*psrc == ',') { mainp1[func][1] = '\0'; psrc++; } else if (*psrc !='\0') { mainp1[func][1] = *psrc++; mainp1[func][2] = '\0'; } printf("function: '%s'\n", mainp1[func]); } ++func; } printf("\ncomparing functions in '%s' with those in '%s'\n", mainp[0], mainp[1] ); int func2; func = 0; while (*mainp0[func] != '\0') { func2 = 0; while(*mainp1[func2] != '\0') { printf("comparing %s with %s\n", mainp0[func], mainp1[func2]); if (strcmp(mainp0[func], mainp1[func2++]) == 0) return 1; /* not sure what to return here */ } ++func; } /* no matches == failure */ return -1; /* not sure what to return on failure */ } int main(int argc, char** argv) { char* mainp[] = { "P,-Q,Q,-R", "R,A,P,B,F" }; if (the_mainp_compare_func(mainp) == 1) printf("a match was found, but I don't know what to do with it!\n"); else printf("no match found, and I'm none the wiser!\n"); return 0; } My question is, what is it's purpose?

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  • LINQ Expression help with Func TEntity,TType

    - by Chris Conway
    I have a repository method that accepts an order by parameter in the form: public IEnumerable<TEntity> Get<TEntity>(Expression<Func<TEntity,string>> orderBy) Now that works fine when trying to sort by a property of type string, var entities = rep.Get(x => x.Name); but what if i want to sort by double or int or any other type. Doing something like var entities = rep.Get(x => x.Price); obviously throws a compile error saying I can't convert double to string. How can I make this more generic so I can sort by any property in my entity, or at least the properties where the type implements IComparable or something similar?

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  • why is this legal, c++ typedef func

    - by acidzombie24
    i did this in msvc 2005. typedef void (*cleanup_t)(); void func(cleanup_t clean) { cleanup_t(); } Why does this compile? and not give me a warning? ok, it gave me a unreferenced formal parameter warning but originally i did this when clean was in a class no there was no unreferenced formal parameter when this code gave me problems. What is cleanup_t(); really doing and what is the point? now for laughs i tried int() and that worked also.

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  • get look up a string given a func<T,object> param

    - by Sammy
    given this code namespace GridTests { public class Grid<T> { IEnumerable<T> DataSource { get; set; } IList<Column> Columns = new List<Column>(); class Column { public string DisplayText { get; set; } Func<T, object> Rowdata { get; set; } } } } I need to be able to loop through the columns collection and get the Rowdata's object value using the DisplayText. Thanks

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  • Multiple generic types in one container

    - by Lirik
    I was looking at the answer of this question regarding multiple generic types in one container and I can't really get it to work: the properties of the Metadata class are not visible, since the abstract class doesn't have them. Here is a slightly modified version of the code in the original question: public abstract class Metadata { } public class Metadata<T> : Metadata { // ... some other meta data public T Function{ get; set; } } List<Metadata> metadataObjects; metadataObjects.Add(new Metadata<Func<double,double>>()); metadataObjects.Add(new Metadata<Func<int,double>>()); metadataObjects.Add(new Metadata<Func<double,int>>()); foreach( Metadata md in metadataObjects) { var tmp = md.Function; // <-- Error: does not contain a definition for Function } The exact error is: error CS1061: 'Metadata' does not contain a definition for 'Function' and no extension method 'Function' accepting a first argument of type 'Metadata' could be found (are you missing a using directive or an assembly reference?) I believe it's because the abstract class does not define the property Function, thus the whole effort is completely useless. Is there a way that we can get the properties?

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  • C# style Action<T>, Func<T,T>, etc in C++0x

    - by Austin Hyde
    C# has generic function types such as Action<T> or Func<T,U,V,...> With the advent of C++0x and the ability to have template typedef's and variadic template parameters, it seems this should be possible. The obvious solution to me would be this: template <typename T> using Action<T> = void (*)(T); however, this does not accommodate for functors or C++0x lambdas, and beyond that, does not compile with the error "expected unqualified-id before 'using'" My next attempt was to perhaps use boost::function: template <typename T> using Action<T> = boost::function<void (T)>; This doesn't compile either, for the same reason. My only other idea would be STL style template arguments: template <typename T, typename Action> void foo(T value, Action f) { f(value); } But this doesn't provide a strongly typed solution, and is only relevant inside the templated function. Now, I will be the first to admit that I am not the C++ wiz I prefer to think I am, so it's very possible there is an obvious solution I'm not seeing. Is it possible to have C# style generic function types in C++?

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  • Extract information from a Func<bool, T> or alike lambda

    - by Syska
    I''m trying to build a generic cache layer. ICacheRepository Say I have the following: public class Person { public int PersonId { get; set; } public string Firstname { get; set; } public string Lastname { get; set; } public DateTime Added { get; set; } } And I have something like this: list.Where(x => x.Firstname == "Syska"); Here I want to extract the above information, to see if the query supplied the "PersonId" which it did not, so I dont want to cache it. But lets say I run a query like this: list.Where(x => x.PersonId == 10); Since PersonId is my key ... I want to cache it. with the key like "Person_10" and I later can fetch it from the cache. I know its possible to extract the information with Expression<Func<>> but there seems to be a big overhead of doing this (when running compile and extract the Constant values etc. and a bunch of cache to be sure to parse right) Are there a framework for this? Or some smart/golden way of doing this ?

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  • How to construct a flowchart/storyboard in a Func Spec

    - by PeterQ
    Hey I'm a bit embarrassed to write a post on this topic, but I would appreciate the help. At my school, the CS kids (myself included) have created a nice, little program that is built for incoming Chem/Bio students. It consists of several modules that reviews topics they should have a firm grasp on before they start their classes. It's a nice tool since it cuts down on reviewing the material in class but also allows the students to do a quick diagnostic to fix any problems. Now, I'm in charge of constructing a simple interface that reports on the progress of the group and individual students. The interface is pretty simple. It's just a window that pops up, and it has three tabs: the first tab is a "cumulative" report of all of students. The secnod tab has a drop down box that lists the students and once a student is selected, a report for him/her comes up. And the third tab is simply a description of all of the terms used in the 1st and 2nd tabs. Now, I'm trying to be a good CS student and write a func. spec for my interface. My problem comes with the fact that I'd like to insert a little flowchart using Visio. Problem is, and I'm quite embarrassed to admit this, I don't know how to construct the flowchart/storyboard. For instance, I know I start with a "Start/Click Icon" in a rectangle. Then where do I go? Do I draw three arrrows (one going to each tab) and then describing what goes on? In tab one, the only thing that happens is that the user will select a "sort" method in the drop down box. This will sort the list. The End. Similarly, if the user selects the second tab, then he will go to a drop down box with the student names. Selecting a name will bring up student info. And the third tab is just a list of unfamiliar terms coming from the first or second tab. I wanted to storyboard/flowchart what I'm doing, but I'm unclear how to go about it. Any help would be appreciated! (Just to clarify, I'm not having trouble with using Visio, but I don't know how one goes about construct a storyboard or determining the procedure for constructing one)

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  • Functional Adaptation

    - by Charles Courchaine
    In real life and OO programming we’re often faced with using adapters, DVI to VGA, 1/4” to 1/8” audio connections, 110V to 220V, wrapping an incompatible interface with a new one, and so on.  Where the adapter pattern is generally considered for interfaces and classes a similar technique can be applied to method signatures.  To be fair, this adaptation is generally used to reduce the number of parameters but I’m sure there are other clever possibilities to be had.  As Jan questioned in the last post, how can we use a common method to execute an action if the action has a differing number of parameters, going back to the greeting example it was suggested having an AddName method that takes a first and last name as parameters.  This is exactly what we’ll address in this post. Let’s set the stage with some review and some code changes.  First, our method that handles the setup/tear-down infrastructure for our WCF service: 1: private static TResult ExecuteGreetingFunc<TResult>(Func<IGreeting, TResult> theGreetingFunc) 2: { 3: IGreeting aGreetingService = null; 4: try 5: { 6: aGreetingService = GetGreetingChannel(); 7: return theGreetingFunc(aGreetingService); 8: } 9: finally 10: { 11: CloseWCFChannel((IChannel)aGreetingService); 12: } 13: } Our original AddName method: 1: private static string AddName(string theName) 2: { 3: return ExecuteGreetingFunc<string>(theGreetingService => theGreetingService.AddName(theName)); 4: } Our new AddName method: 1: private static int AddName(string firstName, string lastName) 2: { 3: return ExecuteGreetingFunc<int>(theGreetingService => theGreetingService.AddName(firstName, lastName)); 4: } Let’s change the AddName method, just a little bit more for this example and have it take the greeting service as a parameter. 1: private static int AddName(IGreeting greetingService, string firstName, string lastName) 2: { 3: return greetingService.AddName(firstName, lastName); 4: } The new signature of AddName using the Func delegate is now Func<IGreeting, string, string, int>, which can’t be used with ExecuteGreetingFunc as is because it expects Func<IGreeting, TResult>.  Somehow we have to eliminate the two string parameters before we can use this with our existing method.  This is where we need to adapt AddName to match what ExecuteGreetingFunc expects, and we’ll do so in the following progression. 1: Func<IGreeting, string, string, int> -> Func<IGreeting, string, int> 2: Func<IGreeting, string, int> -> Func<IGreeting, int>   For the first step, we’ll create a method using the lambda syntax that will “eliminate” the last name parameter: 1: string lastNameToAdd = "Smith"; 2: //Func<IGreeting, string, string, int> -> Func<IGreeting, string, int> 3: Func<IGreeting, string, int> addName = (greetingService, firstName) => AddName(greetingService, firstName, lastNameToAdd); The new addName method gets us one step close to the signature we need.  Let’s say we’re going to call this in a loop to add several names, we’ll take the final step from Func<IGreeting, string, int> -> Func<IGreeting, int> in line as a lambda passed to ExecuteGreetingFunc like so: 1: List<string> firstNames = new List<string>() { "Bob", "John" }; 2: int aID; 3: foreach (string firstName in firstNames) 4: { 5: //Func<IGreeting, string, int> -> Func<IGreeting, int> 6: aID = ExecuteGreetingFunc<int>(greetingService => addName(greetingService, firstName)); 7: Console.WriteLine(GetGreeting(aID)); 8: } If for some reason you needed to break out the lambda on line 6 you could replace it with 1: aID = ExecuteGreetingFunc<int>(ApplyAddName(addName, firstName)); and use this method: 1: private static Func<IGreeting, int> ApplyAddName(Func<IGreeting, string, int> addName, string lastName) 2: { 3: return greetingService => addName(greetingService, lastName); 4: } Splitting out a lambda into its own method is useful both in this style of coding as well as LINQ queries to improve the debugging experience.  It is not strictly necessary to break apart the steps & functions as was shown above; the lambda in line 6 (of the foreach example) could include both the last name and first name instead of being composed of two functions.  The process demonstrated above is one of partially applying functions, this could have also been done with Currying (also see Dustin Campbell’s excellent post on Currying for the canonical curried add example).  Matthew Podwysocki also has some good posts explaining both Currying and partial application and a follow up post that further clarifies the difference between Currying and partial application.  In either technique the ultimate goal is to reduce the number of parameters passed to a function.  Currying makes it a single parameter passed at each step, where partial application allows one to use multiple parameters at a time as we’ve done here.  This technique isn’t for everyone or every problem, but can be extremely handy when you need to adapt a call to something you don’t control.

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  • OpenGl glutIdleFunc(void (*func)(void))

    - by PHENOMERICAN
    I'm trying to design very simple animation in OpenGL such as rotating and translating objects. In the red book, I found that using GLUT's glutIdleFunc() is okay for a simple animation. How many times does glutIdleFunc(...) call the function in one second? Thank you.

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  • Cannot Translate to SQL using Select(x => Func(x))

    - by Dan
    I'm slowly learning the ins and outs of LINQtoSQL, but this is confusing me. Here is the statement I have: IQueryable<IEvent> events = (from e in db.getEvents() select e).Select(x => SelectEvent(x, null)); What the SelectEvent does can be explained in this answer here. I am not using the .toList() function as I don't want potentially thousands of records brought into memory. public IEvent SelectEvent(SqlServer.Event ev, EventType? type) { // Create an object which implements IEvent // I don't have the code in front of me, so forgive the lack of code } My question is really for the Select() method. I get the "Cannot translate to SQL" error and the Select() is listed in the error message. Clueless on this one :-/.

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  • Meteor Deps - Running a Client Side Func

    - by Andrew Plummer
    I'm struggling to get a handle on Meteor deps, in order to be specific my use case is: 2) When collection is changed, I want to run a jQuery function on the client side I think deps are what I'm looking for, but at the moment I have only just used: Template.templateName.set () -> return Set.find({}) ...in terms of reactivity. A solution which simply console.log's the collection each time it is changed would be more that enough.

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