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  • Extending existing data structure in Scala.

    - by Lukasz Lew
    I have a normal tree defined in Scala. sealed abstract class Tree case class Node (...) extends Tree case class Leaf (...) extends Tree Now I want to add a member variable to all nodes and leaves in the tree. Is it possible with extend keyword or do I have to modify the tree classes by adding [T]?

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  • lazyinializationexception with transactional annotation in messageconvert

    - by Karl
    Hi, I have a Rest-Service exposed through spring-mvc. I have a particular method which is correctly mapped and called through a http-call. My spring application contains the hibernatetransactionmanager and transactions are configured through @Transactional-annotations. I annotated the method with @Transactional. @Transactional(readOnly = true) @Override @RequestMapping(value = "/start", method = RequestMethod.GET) @ResponseBody public List start(....) Whenever I call the http-method I get org.hibernate.LazyInitializationException from my org.springframework.http.converter.json.MappingJacksonHttpMessageConverter which is bound in my application context. Is the @Transactional annotation valid for the MessageConverter as well?

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  • What does the MVC Controller.UpdateModel<T>(T) actually try to do?

    - by unanswered
    When I submit my MVC Page I get an IvalidOperationException from System.Web.Mvc Controller object in the UpdateModel method. the MSDN documentation states that this method does the following: Updates the specified model instance using values from the controller's current value provider. Is the value provider referencing the current Request object? Or where exactly does it get the values that it is using to update the model? And what specifically does the UpdateModel method check and what does it 'mean' when it says that The model of type 'abcXYZ' was not successfully updated Thanks

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  • What happens if a bean attempts to load the Spring application context in its constructor?

    - by Derek Mahar
    Given the following Spring application context and class A, what happens when you run class A? applicationContext.xml (in classpath): <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"> <bean name="a" class="A"/> </beans> A.java: class A { private ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml"); public static void main(String[] args) { A a = new A(); } }

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  • Remove some tags in jquery

    - by user201140
    I would like to use jquery to remove some tags inside mainclass, so that this - <div class='mainclass'> <div class='inclass'> <a href='#'>Some text</a> </div> </div> Becomes this - <div class='mainclass'> Some text </div> Thanks in advance.

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  • Does "delegate" mean a type or an object?

    - by Michal Czardybon
    Reading from MSDN: "A delegate is a type that references a method. Once a delegate is assigned a method, it behaves exactly like that method." Does then "delegate" mean a type or an object?! ...It cannot be both. It seems to me that the single word is used in two different meanings: a type containing a reference to a method of some specified signature, an object of that type, which can be actually called like a method. I would prefer a more precise vocabulary and use "delegate type" for the first case. I have been recently reading a lot about events and delegates and that ambiguity was making me confused many times. Some other uses of "delegate" word in MSDN in the first meaning: "Custom event delegates are needed only when an event generates event data" "A delegate declaration defines a class that is derived from the class System.Delegate" Some other uses of "delegate" word in MSDN in the second meaning: "specify a delegate that will be called upon the occurrence of some event" "Delegates are objects that refer to methods. They are sometimes described as type-safe function pointers" What do you think? Why did people from Microsoft introduced this ambiguity? Am I the only person to have conceptual problems with different notions being referenced with the same word.

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  • CSS overflow : list in a div

    - by Felicita
    I have an image gallery and I dont want give an extra class to third list item: <div class="row"> <ul class="rowUl"> <li>ssss</li> <li>ssss</li> <li>ssss</li> </ul> </div> and css .row { width: 620px; clear: both; overflow: hidden; } .rowUl { width: 645px; float: left; } .rowUl li { width: 220px; float: left; } but the third list item drop in other row. How can I solve this without extra class?

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  • How to make Event visible?

    - by eflles
    Inside a Silverlight library project I have a public event, which is not visible for other classes. How can I make the event visible? When I try the following code, I can not locate the event in the "ReceivingClass". .dll - file: Public Class MyClass Public Event MyEvent(ByVal sender As Object, ByVal e As EventArgs) Public Sub OnStart() RaiseEvent MyEvent(Me, new EventArgs) End Sub End Class Silverlight app: Imports MyClass Public Class ReceivingClass Public Sub New() Dim myClass As new MyClass AddHandler myClass.MyEvent, AddressOf Me.EventHandler End Sub Private Sub EventHandler(ByVal sender As Object, ByVal e As EventArgs) 'Handle Event End Sub End Class

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  • Using group_by with fields_for and accepts_nested_attributes_for

    - by Derek
    I have a the following rails models: class Release < ActiveRecord::Base has_many :release_questionnaires, :dependent => :destroy accepts_nested_attributes_for :release_questionnaires ... end class class ReleaseQuestionnaire < ActiveRecord::Base belongs_to :release belongs_to :milestone ... end class In my view code, I have the following form. <% form_for @release, ... do |f| %> ... <table class="questionnaires"> <% f.fields_for :release_questionnaires, @release.release_questionnaires.sort_by{|ra| ra.questionnaire.name} do |builder| %> ... <% end %> </table> <% end %> This works and allows me to view and edit the questionnaires as desired. However, I have an additional requirement to break the questionnaires out into their own tables grouped by the milestone they are associated to, rather than in a single table. It appears as though the group_by method is design to accomplish this, but I cannot get it to work as desired inside the tag. It may be that I'm missing something obvious, as I am a beginner... Any help is appreciated.

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  • Why are we getting a WCF "Framing error" on some machines but not others

    - by Ian Ringrose
    We have just found we are getting “framing errors” (as reported by the WCF logs) when running our system on some customer test machine. It all works ok on our development machines. We have an abstract base class, with KnownType attributes for all its sub classes. One of it’s subclass is missing it’s DataContract attribute. However it all worked on our test machine! On the customers test machine, we got “framing error” showing up the WCF logs, this is not the error message I have seen in the past when missing a DataContract attribute, or a KnownType attribute. I wish to get to the bottom of this, as we can no longer have confidence in our ability to test the system before giving it to the customer until we can make our machines behave the some as the customer’s machines. Code that try to show what I am talking about, (not the real code) [DataContract()] [KnownType(typeof(SubClass1))] [KnownType(typeof(SubClass2))] // other subclasses with data members public abstract class Base { [DataMember] public int LotsMoreItemsThenThisInRealLife; } /// <summary> /// This works on some machines (not not others) when passed to Contract::DoIt, /// note the missing [DataContract()] /// </summary> public class SubClass1 : Base { // has no data members } /// <summary> /// This works in all cases when passed to Contract::DoIt /// </summary> [DataContract()] public class SubClass2 : Base { // has no data members } public interface IContract { void DoIt(Base[] items); } public static class MyProgram { public static IContract ConntectToServerOverWCF() { // lots of code ... return null; } public static void Startup() { IContract server = ConntectToServerOverWCF(); // this works all of the time server.DoIt(new Base[]{new SubClass2(){LotsMoreItemsThenThisInRealLife=2}}); // this works "in develperment" e.g. on our machines, but not on the customer's test machines! server.DoIt(new Base[] { new SubClass1() { LotsMoreItemsThenThisInRealLife = 2 } }); } }

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  • VS2010 final does only link project on "rebuild all", not on "build changed"

    - by Sam
    I've just migrated a solution containing c++ and c# projects from VS2008 to VS2010 and got a strange problem. When I select "rebuild all", everything compiles and links as I would expect it to do. Then I change some c++ source file (just add a space), build the project, I get several thousands of linking errors like these: GDlgPackerListe.obj : error LNK2028: Nicht aufgelöstes Token (0A0000C7) ""public: bool __thiscall LList::Add(class LBString const &)" (?Add@LList@@$$FQAE_NABVLBString@@@Z)", auf das in Funktion ""public: virtual void __thiscall LRcPackerListe::HookRunReport(class LFortschritt &)" (?HookRunReport@LRcPackerListe@@$$FUAEXAAVLFortschritt@@@Z)" verwiesen wird. Db_Lieferschein2.obj : error LNK2020: Nicht aufgelöstes Token (0A0000E6) "public: bool __thiscall LList::Add(class LBString const &)" (?Add@LList@@$$FQAE_NABVLBString@@@Z). bmed.obj : error LNK2028: Nicht aufgelöstes Token (0A00014D) ""public: bool __thiscall LList::Add(class LBString const &)" (?Add@LList@@$$FQAE_NABVLBString@@@Z)", auf das in Funktion ""public: virtual long __thiscall MENUKB::Methode(long,long)" (?Methode@MENUKB@@$$FUAEJJJ@Z)" verwiesen wird. GDlgPackerListe.obj : error LNK2028: Nicht aufgelöstes Token (0A0000C9) ""public: void __thiscall LList::Sort(void)" (?Sort@LList@@$$FQAEXXZ)", auf das in Funktion ""public: virtual void __thiscall LRcPackerListe::HookRunReport(class LFortschritt &)" (?HookRunReport@LRcPackerListe@@$$FUAEXAAVLFortschritt@@@Z)" verwiesen wird. Dlg_Gutschrift.obj : error LNK2020: Nicht aufgelöstes Token (0A000128) "public: virtual __thiscall LBaseType::~LBaseType(void)" (??1LBaseType@@$$FUAE@XZ). Module_Damals.lib(svSuchAltLink.obj) : error LNK2001: Nicht aufgelöstes externes Symbol ""public: __thiscall SView::SView(void)" (??0SView@@QAE@XZ)". Module_Damals.lib(svShowEMF.obj) : error LNK2001: Nicht aufgelöstes externes Symbol ""public: virtual void __thiscall SView::HookValueChanged(unsigned __int64)" (?HookValueChanged@SView@@UAEX_K@Z)". When I hit "rebuild all" it recompiles and links without any errors or even warnings and produces a working exe. I'm using Visual Studio 2010 final (german edition). Whats going on here? Or, more important: how do I get the linker to work correctly??

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  • What reasons are there to place member functions before member variables or vice/versa?

    - by Cory Klein
    Given a class, what reasoning is there for either of the two following code styles? Style A: class Foo { private: doWork(); int bar; } Style B: class Foo { private: int bar; doWork(); } For me, they are a tie. I like Style A because the member variables feel more fine-grained, and thus would appear past the more general member functions. However, I also like Style B, because the member variables seem to determine, in a OOP-style way, what the class is representing. Are there other things worth considering when choosing between these two styles?

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  • Can I make PDOStatement->fetchObject not use non-member variables?

    - by threendib
    Lets say I have a class like this: Class User { var $id var $name; } And I run a query using PDO in php like so: $stm = $db->prepare('select * from users where id = :id'); $r = $stm->execute(array(':id' => $id)); $user = $r->fetchObject('User'); If I vardump my user object it has all kinds of other fields in it that I have not defined in the User class. Obviously I could make my query specific so that it only gives me back the fields I need/want. But if I don't want to do that is there any way to make this work the way I want it to? I like the idea of fetchObject, because it's one line of code to create this object and set member variables for me. I just don't want it to set variables I haven't defined in my class.

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  • Is a many-to-many relationship with extra fields the right tool for my job?

    - by whichhand
    Previously had a go at asking a more specific version of this question, but had trouble articulating what my question was. On reflection that made me doubt if my chosen solution was correct for the problem, so this time I will explain the problem and ask if a) I am on the right track and b) if there is a way around my current brick wall. I am currently building a web interface to enable an existing database to be interrogated by (a small number of) users. Sticking with the analogy from the docs, I have models that look something like this: class Musician(models.Model): first_name = models.CharField(max_length=50) last_name = models.CharField(max_length=50) dob = models.DateField() class Album(models.Model): artist = models.ForeignKey(Musician) name = models.CharField(max_length=100) class Instrument(models.Model): artist = models.ForeignKey(Musician) name = models.CharField(max_length=100) Where I have one central table (Musician) and several tables of associated data that are related by either ForeignKey or OneToOneFields. Users interact with the database by creating filtering criteria to select a subset of Musicians based on data the data on the main or related tables. Likewise, the users can then select what piece of data is used to rank results that are presented to them. The results are then viewed initially as a 2 dimensional table with a single row per Musician with selected data fields (or aggregates) in each column. To give you some idea of scale, the database has ~5,000 Musicians with around 20 fields of related data. Up to here is fine and I have a working implementation. However, it is important that I have the ability for a given user to upload there own annotation data sets (more than one) and then filter and order on these in the same way they can with the existing data. The way I had tried to do this was to add the models: class UserDataSets(models.Model): user = models.ForeignKey(User) name = models.CharField(max_length=100) description = models.CharField(max_length=64) results = models.ManyToManyField(Musician, through='UserData') class UserData(models.Model): artist = models.ForeignKey(Musician) dataset = models.ForeignKey(UserDataSets) score = models.IntegerField() class Meta: unique_together = (("artist", "dataset"),) I have a simple upload mechanism enabling users to upload a data set file that consists of 1 to 1 relationship between a Musician and their "score". Within a given user dataset each artist will be unique, but different datasets are independent from each other and will often contain entries for the same musician. This worked fine for displaying the data, starting from a given artist I can do something like this: artist = Musician.objects.get(pk=1) dataset = UserDataSets.objects.get(pk=5) print artist.userdata_set.get(dataset=dataset.pk) However, this approach fell over when I came to implement the filtering and ordering of query set of musicians based on the data contained in a single user data set. For example, I could easily order the query set based on all of the data in the UserData table like this: artists = Musician.objects.all().order_by(userdata__score) But that does not help me order by the results of a given single user dataset. Likewise I need to be able to filter the query set based on the "scores" from different user data sets (eg find all musicians with a score 5 in dataset1 and < 2 in dataset2). Is there a way of doing this, or am I going about the whole thing wrong?

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  • Is there a g++ equivalent to Visual Studio's __declspec(novtable)?

    - by ceretullis
    Is there a g++ equivalent to Visual Studio's __declspec(novtable) argument? Basically, in a pure virtual base class the __declspec(novtable) argument can be used to suppress the creation of a vtable for the base class as well as vtable initialization/deinitialization code in the contstructor/destructor respectively. E.g., class __declspec(novtable) PureVirtualBaseClass { public: PureVirtualBaseClass(){} virtual ~PureVirtualBaseClass() = 0; }; See Paul DiLascia's article for more info. Also see my related question.

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  • Questions about use lib for perl

    - by Tyug
    I use use lib "./DIR" to grab a library from a folder elsewhere. However, it doesn't seem to work on my server, but it works fine on my local desktop. Any particular reasons? And one more question, does use lib get propagated within several modules? Two situations: Say I make a base class that requires a few libraries, but I know that it needs to be extended and the extended class will need to use another library. Can I put the use lib command in the base class? or will I need to put it in every extending class? Finally, can I just have a use package where package contains a bunch of use lib, will it propagate the use lib statements over to my current module? <-- I don't think so, but asking anyways Thanks in advance! Tyug

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  • C++ app fails to initialize (0xc0000005), when using C# dll

    - by Simon
    Hi, I have a C# DLL, which I call from a native C++ programm. As I use Qt and /clr compiler option did not work I followed this tutorial for a bridge. So I have a VS2008 project (compiled with /clr), which links to the C# DLL and contains the bridge class and the native class, which exposes interfaces to my C++ programm. Another VS2008 project (no .net stuff) calls the native class (statically linked). I had some issues, but now the programm at least compiles. However, if I try to run this programm, I get a (0xc0000005) error on initialization, when I try to use the native class. As this happens on initialization, I don't even see, which DLLs fail to initialize. All DLLs should be in the right place. Any hints? Thank you.

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  • ASP.NET MVC4: How do I keep from having multiple identical results in my lookup tables

    - by sehummel
    I'm new to ASP.NET so this may be an easy question. I'm seeding my database with several rows of dummy data. Here is one of my rows: new Software { Title = "Microsoft Office", Version = "2012", SerialNumber = "12346231434543", Platform = "PC", Notes = "Macs really rock!", PurchaseDate = "2011-12-04", Suite = true, SubscriptionEndDate = null, SeatCount = 0, SoftwareTypes = new List<SoftwareType> { new SoftwareType { Type="Suite" }}, Locations = new List<Location> { new Location { LocationName = "Paradise" }}, Publishers = new List<SoftwarePublisher> { new SoftwarePublisher { Publisher = "Microsoft" }}} But when I do this, a new row is created for each location, with the LocationName being set in each row like this. We only have two locations. How do I get it to create a LocationID property for the Software class and in my Locations class. Here is my Location class: public class Location { public int Id { get; set; } [Required] [StringLength(20)] public string LocationName { get; set; } public virtual Software Software { get; set; } } I have this line in my Software class to reference this table: public virtual List<Location> Locations { get; set; } Again, what I want when I am done is a Locations table with two entries, and a LocationID field in my Software table. How do I do this?

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  • Must parameter of assignment operator be reference?

    - by Tim
    When overloading assignment operator of a class in C++, must its parameter be reference? For example, class MyClass { public: ... MyClass & operator=(const MyClass &rhs); ... } Can it be class MyClass { public: ... MyClass & operator=(const MyClass rhs); ... } ? Thanks!

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  • Questions on using enums as parameters and if/else conditions

    - by dotnetdev
    Hi, Is it possible to do the following with an enum in C#?: Pass in to a method a selected value of the enum (eg if an enum has members such as Red, Green, Orange, I can pass in Colors.Red). In the method body of the above method which accepts an enum, I can say if (Enum == Colors.Red). What would be the syntax for this? I've always seemed to have stalled on this.

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  • python list/dict property best practice

    - by jterrace
    I have a class object that stores some properties that are lists of other objects. Each of the items in the list has an identifier that can be accessed with the id property. I'd like to be able to read and write from these lists but also be able to access a dictionary keyed by their identifier. Let me illustrate with an example: class Child(object): def __init__(self, id, name): self.id = id self.name = name class Teacher(object): def __init__(self, id, name): self.id = id self.name = name class Classroom(object): def __init__(self, children, teachers): self.children = children self.teachers = teachers classroom = Classroom([Child('389','pete')], [Teacher('829','bob')]) This is a silly example, but it illustrates what I'm trying to do. I'd like to be able to interact with the classroom object like this: #access like a list print classroom.children[0] #append like it's a list classroom.children.append(Child('2344','joe')) #delete from like it's a list classroom.children.pop(0) But I'd also like to be able to access it like it's a dictionary, and the dictionary should be automatically updated when I modify the list: #access like a dict print classroom.childrenById['389'] I realize I could just make it a dict, but I want to avoid code like this: classroom.childrendict[child.id] = child I also might have several of these properties, so I don't want to add functions like addChild, which feels very un-pythonic anyway. Is there a way to somehow subclass dict and/or list and provide all of these functions easily with my class's properties? I'd also like to avoid as much code as possible.

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  • JPA entitylisteners and @embeddable

    - by seanizer
    I have a class hierarchy of JPA entities that all inherit from a BaseEntity class: @MappedSuperclass @EntityListeners( { ValidatorListener.class }) public abstract class BaseEntity implements Serializable { // other stuff } I want all entities that implement a given interface to be validated automatically on persist and/or update. Here's what I've got. My ValidatorListener: public class ValidatorListener { private enum Type { PERSIST, UPDATE } @PrePersist public void checkPersist(final Object entity) { if (entity instanceof Validateable) { this.check((Validateable) entity, Type.PERSIST); } } @PreUpdate public void checkUpdate(final Object entity) { if (entity instanceof Validateable) { this.check((Validateable) entity, Type.UPDATE); } } private void check(final Validateable entity, final Type persist) { switch (persist) { case PERSIST: if (entity instanceof Persist) { ((Persist) entity).persist(); } if (entity instanceof PersistOrUpdate) { ((PersistOrUpdate) entity).persistOrUpdate(); } break; case UPDATE: if (entity instanceof Update) { ((Update) entity).update(); } if (entity instanceof PersistOrUpdate) { ((PersistOrUpdate) entity).persistOrUpdate(); } break; default: break; } } } and here's my Validateable interface that it checks against (the outer interface is just a marker, the inner contain the methods): public interface Validateable { interface Persist extends Validateable { void persist(); } interface PersistOrUpdate extends Validateable { void persistOrUpdate(); } interface Update extends Validateable { void update(); } } All of this works, however I would like to extend this behavior to Embeddable classes. I know two solutions: call the validation method of the embeddable object manually from the entity validation method: public void persistOrUpdate(){ // validate my own properties first // then manually validate the embeddable property: myEmbeddable.persistOrUpdate(); // this works but I'd like something that I don't have to call manually } use reflection, checking all properties to see if their type is of one of their interface types. This would work, but it's not pretty. Is there a more elegant solution?

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  • Instance where embedded C++ compilers don't support multiple inheritance?

    - by Nathan
    I read a bit about a previous attempt to make a C++ standard for embedded platforms where they specifically said multiple inheritance was bad and thus not supported. From what I understand, this was never implemented as a mainstream thing and most embedded C++ compilers support most standard C++ constructs. Are there cases where a compiler on a current embedded platform (i.e. something not more than a few years old) absolutely does not support multiple inheritance? I don't really want to do multiple inheritance in a sense where I have a child with two full implementations of a class. What I am most interested in is inheriting from a single implementation of a class and then also inheriting one or more pure virtual classes as interfaces only. This is roughly equivalent to Java/.Net where I can extend only one class but implement as many interfaces as I need. In C++ this is all done through multiple inheritance rather than being able to specifically define an interface and declare a class implements it.

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  • Appropriate uses of Monad `fail` vs. MonadPlus `mzero`

    - by jberryman
    This is a question that has come up several times for me in the design code, especially libraries. There seems to be some interest in it so I thought it might make a good community wiki. The fail method in Monad is considered by some to be a wart; a somewhat arbitrary addition to the class that does not come from the original category theory. But of course in the current state of things, many Monad types have logical and useful fail instances. The MonadPlus class is a sub-class of Monad that provides an mzero method which logically encapsulates the idea of failure in a monad. So a library designer who wants to write some monadic code that does some sort of failure handling can choose to make his code use the fail method in Monad or restrict his code to the MonadPlus class, just so that he can feel good about using mzero, even though he doesn't care about the monoidal combining mplus operation at all. Some discussions on this subject are in this wiki page about proposals to reform the MonadPlus class. So I guess I have one specific question: What monad instances, if any, have a natural fail method, but cannot be instances of MonadPlus because they have no logical implementation for mplus? But I'm mostly interested in a discussion about this subject. Thanks! EDIT: One final thought occured to me. I recently learned (even though it's right there in the docs for fail) that monadic "do" notation is desugared in such a way that pattern match failures, as in (x:xs) <- return [] call the monad's fail. It seems like the language designers must have been strongly influenced by the prospect of some automatic failure handling built in to haskell's syntax in their inclusion of fail in Monad.

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