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  • Abstract Factory Method and Polymorphism

    - by Scotty C.
    Being a PHP programmer for the last couple of years, I'm just starting to get into advanced programming styles and using polymorphic patterns. I was watching a video on polymorphism the other day, and the guy giving the lecture said that if at all possible, you should get rid of if statements in your code, and that a switch is almost always a sign that polymorphism is needed. At this point I was quite inspired and immediately went off to try out these new concepts, so I decided to make a small caching module using a factory method. Of course the very first thing I have to do is create a switch to decide what file encoding to choose. DANG! class Main { public static function methodA($parameter='') { switch ($parameter) { case 'a': $object = new \name\space\object1(); break; case 'b': $object = new \name\space\object2(); break; case 'c': $object = new \name\space\object3(); break; default: $object = new \name\space\object1(); } return (sekretInterface $object); } } At this point I'm not really sure what to do. As far as I can tell, I either have to use a different pattern and have separate methods for each object instance, or accept that a switch is necessary to "switch" between them. What do you guys think?

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  • I've been told that Exceptions should only be used in exceptional cases. How do I know if my case is exceptional?

    - by tieTYT
    My specific case here is that the user can pass in a string into the application, the application parses it and assigns it to structured objects. Sometimes the user may type in something invalid. For example, their input may describe a person but they may say their age is "apple". Correct behavior in that case is roll back the transaction and to tell the user an error occurred and they'll have to try again. There may be a requirement to report on every error we can find in the input, not just the first. In this case, I argued we should throw an exception. He disagreed, saying, "Exceptions should be exceptional: It's expected that the user may input invalid data, so this isn't an exceptional case" I didn't really know how to argue that point, because by definition of the word, he seems to be right. But, it's my understanding that this is why Exceptions were invented in the first place. It used to be you had to inspect the result to see if an error occurred. If you failed to check, bad things could happen without you noticing. Without exceptions every level of the stack needs to check the result of the methods they call and if a programmer forgets to check in one of these levels, the code could accidentally proceed and save invalid data (for example). Seems more error prone that way. Anyway, feel free to correct anything I've said here. My main question is if someone says Exceptions should be exceptional, how do I know if my case is exceptional?

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  • When to use functional programming approach and when not? (in Java)

    - by john smith optional
    let's assume I have a task to create a Set of class names. To remove duplication of .getName() method calls for each class, I used org.apache.commons.collections.CollectionUtils and org.apache.commons.collections.Transformer as follows: Snippet 1: Set<String> myNames = new HashSet<String>(); CollectionUtils.collect( Arrays.<Class<?>>asList(My1.class, My2.class, My3.class, My4.class, My5.class), new Transformer() { public Object transform(Object o) { return ((Class<?>) o).getName(); } }, myNames); An alternative would be this code: Snippet 2: Collections.addAll(myNames, My1.class.getName(), My2.class.getName(), My3.class.getName(), My4.class.getName(), My5.class.getName()); So, when using functional programming approach is overhead and when it's not and why? Isn't my usage of functional programming approach in snippet 1 is an overhead and why?

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  • Code Line Delimiter [closed]

    - by John Isaiah Carmona
    Possible Duplicate: Why are statements in many programming languages terminated by semicolons? I just found out that R Programming Language, which is somewhat belong to the C family (I'm not sure about this but it uses {} instead of begin end), uses a new line as a delimiter for a new line of code instead of the semi-colon ;. Why is some programming language designed to use a new line instead of a symbol like semi-colon which I think will make the code more readable? Phyton total = item_one + \ item_two + \ item_three C total = item_one + item_two + item_three;

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  • Dependency Injection Confusion

    - by James
    I think I have a decent grasp of what Dependency Inversion principle (DIP) is, my confusion is more around dependency injection. My understanding is the whole point of DI is to decouple parts of an application, to allow changes in one part without effecting another, assuming the interface does not change. For examples sake, we have this public class MyClass(IMyInterface interface) { public MyClass { interface.DoSomething(); } } public interface IMyInterface { void DoSomething(); } How is this var iocContainer = new UnityContainer(); iocContainer.Resolve<MyClass>(); better practice than doing this //if multiple implementations are possible, could use a factory here. IMyInterface interface = new InterfaceImplementation(); var myClass = new MyClass(interface); It may be I am missing a very important point, but I am failing to see what is gained. I am aware that using an IOC container I can easily handle an objects life cycle, which is a +1 but I don't think that is core to what IOC is about.

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  • What's the best way to expose a Model object in a ViewModel?

    - by Angel
    In a WPF MVVM application, I exposed my model object into my viewModel by creating an instance of Model class (which cause dependency) into ViewModel. Instead of creating separate VM properties, I wrap the Model properties inside my ViewModel Property. My model is just an entity framework generated proxy class: public partial class TblProduct { public TblProduct() { this.TblPurchaseDetails = new HashSet<TblPurchaseDetail>(); this.TblPurchaseOrderDetails = new HashSet<TblPurchaseOrderDetail>(); this.TblSalesInvoiceDetails = new HashSet<TblSalesInvoiceDetail>(); this.TblSalesOrderDetails = new HashSet<TblSalesOrderDetail>(); } public int ProductId { get; set; } public string ProductCode { get; set; } public string ProductName { get; set; } public int CategoryId { get; set; } public string Color { get; set; } public Nullable<decimal> PurchaseRate { get; set; } public Nullable<decimal> SalesRate { get; set; } public string ImagePath { get; set; } public bool IsActive { get; set; } public virtual TblCompany TblCompany { get; set; } public virtual TblProductCategory TblProductCategory { get; set; } public virtual TblUser TblUser { get; set; } public virtual ICollection<TblPurchaseDetail> TblPurchaseDetails { get; set; } public virtual ICollection<TblPurchaseOrderDetail> TblPurchaseOrderDetails { get; set; } public virtual ICollection<TblSalesInvoiceDetail> TblSalesInvoiceDetails { get; set; } public virtual ICollection<TblSalesOrderDetail> TblSalesOrderDetails { get; set; } } Here is my ViewModel: public class ProductViewModel : WorkspaceViewModel { #region Constructor public ProductViewModel() { StartApp(); } #endregion //Constructor #region Properties private IProductDataService _dataService; public IProductDataService DataService { get { if (_dataService == null) { if (IsInDesignMode) { _dataService = new ProductDataServiceMock(); } else { _dataService = new ProductDataService(); } } return _dataService; } } //Get and set Model object private TblProduct _product; public TblProduct Product { get { return _product ?? (_product = new TblProduct()); } set { _product = value; } } #region Public Properties public int ProductId { get { return Product.ProductId; } set { if (Product.ProductId == value) { return; } Product.ProductId = value; RaisePropertyChanged("ProductId"); } } public string ProductName { get { return Product.ProductName; } set { if (Product.ProductName == value) { return; } Product.ProductName = value; RaisePropertyChanged(() => ProductName); } } private ObservableCollection<TblProduct> _productRecords; public ObservableCollection<TblProduct> ProductRecords { get { return _productRecords; } set { _productRecords = value; RaisePropertyChanged("ProductRecords"); } } //Selected Product private TblProduct _selectedProduct; public TblProduct SelectedProduct { get { return _selectedProduct; } set { _selectedProduct = value; if (_selectedProduct != null) { this.ProductId = _selectedProduct.ProductId; this.ProductCode = _selectedProduct.ProductCode; } RaisePropertyChanged("SelectedProduct"); } } #endregion //Public Properties #endregion // Properties #region Commands private ICommand _newCommand; public ICommand NewCommand { get { if (_newCommand == null) { _newCommand = new RelayCommand(() => ResetAll()); } return _newCommand; } } private ICommand _saveCommand; public ICommand SaveCommand { get { if (_saveCommand == null) { _saveCommand = new RelayCommand(() => Save()); } return _saveCommand; } } private ICommand _deleteCommand; public ICommand DeleteCommand { get { if (_deleteCommand == null) { _deleteCommand = new RelayCommand(() => Delete()); } return _deleteCommand; } } #endregion //Commands #region Methods private void StartApp() { LoadProductCollection(); } private void LoadProductCollection() { var q = DataService.GetAllProducts(); this.ProductRecords = new ObservableCollection<TblProduct>(q); } private void Save() { if (SelectedOperateMode == OperateModeEnum.OperateMode.New) { //Pass the Model object into Dataservice for save DataService.SaveProduct(this.Product); } else if (SelectedOperateMode == OperateModeEnum.OperateMode.Edit) { //Pass the Model object into Dataservice for Update DataService.UpdateProduct(this.Product); } ResetAll(); LoadProductCollection(); } #endregion //Methods } Here is my Service class: class ProductDataService:IProductDataService { /// <summary> /// Context object of Entity Framework model /// </summary> private MaizeEntities Context { get; set; } public ProductDataService() { Context = new MaizeEntities(); } public IEnumerable<TblProduct> GetAllProducts() { using(var context=new R_MaizeEntities()) { var q = from p in context.TblProducts where p.IsDel == false select p; return new ObservableCollection<TblProduct>(q); } } public void SaveProduct(TblProduct _product) { using(var context=new R_MaizeEntities()) { _product.LastModUserId = GlobalObjects.LoggedUserID; _product.LastModDttm = DateTime.Now; _product.CompanyId = GlobalObjects.CompanyID; context.TblProducts.Add(_product); context.SaveChanges(); } } public void UpdateProduct(TblProduct _product) { using (var context = new R_MaizeEntities()) { context.TblProducts.Attach(_product); context.Entry(_product).State = EntityState.Modified; _product.LastModUserId = GlobalObjects.LoggedUserID; _product.LastModDttm = DateTime.Now; _product.CompanyId = GlobalObjects.CompanyID; context.SaveChanges(); } } public void DeleteProduct(int _productId) { using (var context = new R_MaizeEntities()) { var product = (from c in context.TblProducts where c.ProductId == _productId select c).First(); product.LastModUserId = GlobalObjects.LoggedUserID; product.LastModDttm = DateTime.Now; product.IsDel = true; context.SaveChanges(); } } } I exposed my model object in my viewModel by creating an instance of it using new keyword, also I instantiated my DataService class in VM. I know this will cause a strong dependency. So: What's the best way to expose a Model object in a ViewModel? What's the best way to use DataService in VM?

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  • How can you predict the time it will take for two processes in two different machines in a cluster to communicate?

    - by Dokkat
    I am trying to develop a computing application which needs a lot of memory (500gb). Buying a single machine for that is overly expensive. I can, though, buy ~100 small instances on Digital Ocean or similar, divide the memory in blocks and use TCP to emulate shared memory between the instances. Now, my question is: how can I measure/predict the time it will take for two processes in two different machines like that to share information, in comparison to IPC and shared memory? Are there rules of thumb? I don't want exact values, but knowing more or less how much faster one is would be very helpful in visualising the feasibility of this approach.

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  • Why are most websites optimized for viewing in portrait mode?

    - by NVM
    I simply cannot figure this out. Almost all monitors have an aspect ratio where width is much bigger than the height and yet almost all websites are designed exactly for the other way round? I am not really a web developer and am just experimenting stuff at the moment but this madness baffles me!!! Edit: The point is not that I would like to limit the height of a website. The point is that I'd wat it to somehow fill all available space when I have my 1920x1080 in landscape mode. Edit 2: See this to understand what I am saying

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  • How stable are Single Page Application (SPA) build with Microsoft .Net for enterprise application [on hold]

    - by Husrat Mehmood
    Imagine a situation where you have your data loading to your application via REST Api,you are building a responsive application(ajax request) for an Enterprise. What potential problems might I run into for a single page application(SPA) using Microsoft Asp.Net Web application build using MVC template? Are there advantages to just designing a multi-page application using asp.net mvc 5 remember I am using SPA for an Enterprise Application where there are role based views for the users.?

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  • How to copy or replicate a complex website to local file and modify then

    - by Andre Chenier
    I am not good at designing the visual side of a website. I found a website which I gave 10 over 10 because its functionality suits my aims and also it seems very esthetical. I know HTML, PHP, mySQL and some degree of CSS. I don't know JS, Ajax, Jquery. So I want to replicate this web site (save completely) on my local and then modify it. (content, colors, icons etc.) I saved this web site in Chrome and IE. After clicking the site from my local folder, a saw an ugly & non-working site. My aim is to understand the functions of the parts that I don't know. For example when I delete a js in its page what will happen as the result of the deletion operation. Since the page is too complex it has lots of css, js files to download inside. I don't want to deal it manually. Is there any alternative and easy way to get the web page completely to my local which also works like a charm from local? regards

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  • How do you save/export changes made in Firebug?

    - by blunders
    Using Firebug to edit CSS, how do I save/export changes made to the CSS? TOOLS: Firefox, Firebug MAJOR UPDATE: If you know of a way to lock the forward/back/refresh on a FireFox tab, please let me know. Otherwise, I've given up on using FireBug/FireDiff as an IDE for CSS, it's nice, but lol... press backspace at the wrong time and ALL your work is gone... funny. So, really like the browser highlighting to CSS/HTML in Firebug. Know any good CSS editors that do this? Really had hope FireBug would work, but for now only see it as being good for ad-hoc inspection and test; meaning using it for what it's made for. UPDATES: @Lèse majesté: Just as an update, "Web Developer add-on" does let you edit CSS, but it does not let you edit/save CSS changes made by Firebug. Meaning you use Firebug to ID and maybe test changes, but it does not let you save the changes from Firebug. Here's a "how to" covering how to use them together: FF + FB + WD @Lèse majesté: Still playing around with FireDiff. It works okay, found one bug already (although I'm just working around it), and there's no "how to" I've been able to find, so I'm just trying every feature and clicking around... (for example, to export a diff you must be over the last item in the list, right click, and select as "Save Diff". The ".diff" is just a text file, no idea why at this point the ext is .diff.

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  • Is there a simple isometric graphical game engine (using vectors?) that could be used for a (multiplayer) crafting/farming game? [closed]

    - by Renier Wijnen
    Possible Duplicate: Good, free isometric game engine? With little game development experience (albeit having graphical skills and some programming knowledge) a group currently working on a game used to explain permaculture through interaction would like to create a simple concept game. Is there a specific engine or set of tools we could used to achieve this? Being able to make it an (online) multiplayer game would be much preferred. Thank you in advance for your input.

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  • Query something and return the reason if nothing has been found

    - by Daniel Hilgarth
    Assume I have a Query - as in CQS that is supposed to return a single value. Let's assume that the case that no value is found is not exceptional, so no exception will be thrown in this case. Instead, null is returned. However, if no value has been found, I need to act according to the reason why no value has been found. Assuming that the Query knows the reason, how would I communicate it to the caller of the Query? A simple solution would be not return the value directly but a container object that contains the value and the reason: public class QueryResult { public TValue Value { get; private set; } public TReason ReasonForNoValue { get; private set; } } But that feels clumsy, because if a value is found, ReasonForNoValue makes no sense and if no value has been found, Value makes no sense. What other options do I have to communicate the reason? What do you think of one event per reason? For reference: This is going to be implemented in C#.

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  • Best Option for Creating A Small Church Website

    - by Jim
    I've been asked to create a website for a small church. Their prior site was hosted on geocities which is no longer. They are not looking for anything robust, just an informational site with a calendar and maybe a contact form. The church would also like to be able to administer the site with little technical know-how. Cost is also an issue. Given these requirements, something like sites.google.com seems like a good option. However, my main concern is that Sites will suffer the same fate as geocities. It is definitely not a flagship Google product. Are there other good alternatives that fit the requirements?

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  • How to verify the Liskov substitution principle in an inheritance hierarchy?

    - by Songo
    Inspired by this answer: Liskov Substitution Principle requires that Preconditions cannot be strengthened in a subtype. Postconditions cannot be weakened in a subtype. Invariants of the supertype must be preserved in a subtype. History constraint (the "history rule"). Objects are regarded as being modifiable only through their methods (encapsulation). Since subtypes may introduce methods that are not present in the supertype, the introduction of these methods may allow state changes in the subtype that are not permissible in the supertype. The history constraint prohibits this. I was hoping if someone would post a class hierarchy that violates these 4 points and how to solve them accordingly. I'm looking for an elaborate explanation for educational purposes on how to identify each of the 4 points in the hierarchy and the best way to fix it. Note: I was hoping to post a code sample for people to work on, but the question itself is about how to identify the faulty hierarchies :)

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  • Should I close database connections after use in PHP?

    - by Sprottenwels
    I wonder if I should close any unnecessary database connection inside of my PHP scripts. I am aware of the fact that database connections are closed implicitly when the block stops executing and 'manually' closing the connections could kinda bloat the codebase with unnecessary code. But shouldn't I do so in order to make by code as readable and as easy understandable as possible, while also preventing several possible issues during run time? Also, if I would do, would it be enough to unset() my database object?

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  • generating maps

    - by gardian06
    This is a conglomeration question when answering please specify which part you are addressing. I am looking at creating a maze type game that utilizes elevation. I have a few features I would like to have, but am unsure as to some of the implementation. I have done work doing fileIO maze generation (using a key to read the file, and then generate the level based on that file), but I am unsure how to think about this with elevation in the mix. I think height maps might be a good approach, but don't know how to represent them effectively. for a height map which is more beneficial XML(containing h[u,v] data and key definition), CSV (item1 is key reference, item2 is elevation), or another approach that I have not thought of yet? When it comes to placing the elevation values themselves what kind of deltah values are appropriate to have it noticeable at about a 60degree angle while not really effecting gravity driven physics (assuming some effect while moving up/down hill)? I am thinking of maybe going to procedural generation at some point, but am wondering if it is practical to have a procedurally generated grid (wall squares possibly same dimensions as the open space squares), or if designing to a thin wall open spaces is better? this decision will effect the amount of work need on the graphics end for uniform vs. irregular walls. EDIT: game will be a elevation maze shooter. levels/maps will be mazes with elevation the player has to negotiate. elevations will have effects on "combat" vision, and movement

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  • How to store prices that have effective dates?

    - by lal00
    I have a list of products. Each of them is offered by N providers. Each providers quotes us a price for a specific date. That price is effective until that provider decides to set a new price. In that case, the provider will give the new price with a new date. The MySQL table header currently looks like: provider_id, product_id, price, date_price_effective Every other day, we compile a list of products/prices that are effective for the current day. For each product, the list contains a sorted list of the providers that have that particular product. In that way, we can order certain products from whoever happens to offer the best price. To get the effective prices, I have a SQL statement that returns all rows that have date_price_effective >= NOW(). That result set is processed with a ruby script that does the sorting and filtering necessary to obtain a file that looks like this: product_id_1,provider_1,provider_3,provider8,provider_10... product_id_2,provider_3,provider_2,provider1,provider_10... This works fine for our purposes, but I still have an itch that a SQL table is probably not the best way to store this kind of information. I have that feeling that this kind of problema has been solved previously in other more creative ways. Is there a better way to store this information other than in SQL? or, if using SQL, is there a better approach than the one I'm using?

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  • Best scripting language for project [on hold]

    - by Dave
    This is a subjective question, but I don't know where else to ask it. I'd appreciate it if someone could direct me to an appropriate scripting language for my project. I'm a little new at this so I'd appreciate any help. The project is a website that will display a list of photo subject groups (such as "nature" "people" "sports" etc) on the home page. The photos will all be in subdirectories of the main photo directory (photos) and each subject group will represent a subdirectory in photos. For example in directory photos there might be 3 subdirectories, "nature" "people" "sports" and in each of those subdirectories there will be the actual photos. The idea is that when the website owner wants to update/add/delete a subject group all he has to do is add, delete or update a subdirectory of the photos directory. This means, I think, that I need a scripting language that can read the directories and files in the website and then send a web page with the information in it. What is the simplest and easiest scripting language to do this in? Any ideas? Thanks

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  • How to had operation with character/items on binary with concrete operations on C++?

    - by Piperoman
    I have the next problem. A item can had a lot of states: NORMAL = 0000000 DRY = 0000001 HOT = 0000010 BURNING = 0000100 WET = 0001000 COLD = 0010000 FROZEN = 0100000 POISONED= 1000000 A item can had some states at same time but not all of them Is impossible to be dry and wet at same time. If you COLD a WET item, it turns into FROZEN. If you HOT a WET item, it turns into NORMAL A item can be BURNING and POISON Etc. I have try to set binary flags to states, and use AND to set operation to combine different states, checking before if is possible or not to do it, or change to another status. Exist a concrete patron to solve this problem efficiently without had a interminable switch that check every states with everynew states? It is relative easy to check 2 different states, but if exist a third state it is not trivial to do.

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  • Truly useful UML diagrams

    - by eversor
    UML has a jungle of Diagrams. Profile Diagrams, Class Diagrams, Package Diagrams... However, (IMH-and-not-too-experienced-O) I quite see that doing each and every diagram is overkill. Therefore, which UML Diagrams are more suitable in a web context, more expecificly a blog (we want to build it from scratchs). I understand that just because I used UML Diagrams does not imply that our code would be great and brilliant... but, it certainly would be better than just unplanified code...

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  • Is it illegal to use content in such a way?

    - by MHZ
    I have a couple of questions about the legality of the content of some websites. I am currently working on two websites and I would like to make sure I am not breaking any laws, by using some content like I am... Do I need to get a license to use images from the Internet (such as google.images.com) in my site, assuming they aren't a company logo belonging to another company? If not, am I allowed to use it after I modify it with a image editing software? If content such as phone numbers, e-mail addresses, website addresses, and text from websites can be found for free online, and I gather this information for a search engine based site that I am working on and offering this information on a paid basis (similar to google, but more specialized), is something that is legal? Note: I am not 'copying' or redirecting business from anywhere, to my site. The exact opposite, the site I am working on actually helps advertise businesses and make it easier for customers to find them.

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  • Could someone explain in detail simplex /or perlin noise?

    - by Ryan Szemplinski
    I am really interested in perlin/simplex noise but I am having a difficult time understanding it. I am not very good at math but I am willing to learn because it interests me greatly. If someone is willing to dedicate there time into this I would be immensely appreciative of this. To be more concise, an explanation of functions and some calculation inside the functions would be nice to understand. Thanks in advance!

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  • Interface extension

    - by user877329
    Suppose that I have an input stream interface, which defines a method for reading data. I also have a seekable interface which defines a method for seeking. A natural way of defining a input file is then to implement both input stream and seekable. I want to construct a data decoder from the input stream interface so I can read data from a file or from another stream. The problem is that I also want to implement seek functionality to the data decoder, since I want to be able to step individual records not raw bytes. This is not possible if I only provide an input stream, which does not have the bytewise seek method. Should I skip the seekable interface and add the seek method to input stream instead and force all streams to at least leave it as a nop.

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  • Preferred lambda syntax?

    - by Roger Alsing
    I'm playing around a bit with my own C like DSL grammar and would like some oppinions. I've reserved the use of "(...)" for invocations. eg: foo(1,2); My grammar supports "trailing closures" , pretty much like Ruby's blocks that can be passed as the last argument of an invocation. Currently my grammar support trailing closures like this: foo(1,2) { //parameterless closure passed as the last argument to foo } or foo(1,2) [x] { //closure with one argument (x) passed as the last argument to foo print (x); } The reason why I use [args] instead of (args) is that (args) is ambigious: foo(1,2) (x) { } There is no way in this case to tell if foo expects 3 arguments (int,int,closure(x)) or if foo expects 2 arguments and returns a closure with one argument(int,int) - closure(x) So thats pretty much the reason why I use [] as for now. I could change this to something like: foo(1,2) : (x) { } or foo(1,2) (x) -> { } So the actual question is, what do you think looks best? [...] is somewhat wrist unfriendly. let x = [a,b] { } Ideas?

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