self-reference | 易学教程

Is self-reference possible in MATLAB?

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As noted here , functions in packages, as well as static methods in classes, still need to use a packagename.functionname syntax or import packagename.* for each function (since the imports are part of the function workspace and not global). This means that changing the package/class name later on can become a tedious nuisance. Is there any way to do something like import this.* , i.e. a package/class name agnostic method to access all functions/static methods in the same package/class? So... doesn't this require importthis to also be imported? Or is importthis a function you always have in

How can I refer to the class type a interface is implementing in Java?

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I came to a problem with interfaces in a program I'm making. I want to create a interface which have one of its methods receiving/returning a reference to the type of the own object. It was something like: public interface I { ? getSelf(); } public class A implements I { A getSelf() { return this; } } public class B implements I { B getSelf() { return this; } } I can't use an "I" where it's a "?", because I don't want to return a reference to the interface, but the class. I searched and found that there are no way to "self-refer" in Java, so I can't just substitute that "?" in the example for

Self referencing / parent-child relationship in Entity Framework

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问题 I read quite a number of posts of programmers that run into the Unable to determine a valid ordering for dependent operations. Dependencies may exist due to foreign key constraints, model requirements, or store-generated values -exception when using a self-referencing relationship in Entity Framework. I am trying to get a parent-child relationship to work: public class Category { public int CategoryId { get; set; } public string Name { get; set; } public int ParentId { get; set; } public

Entity Framework 4.1 Code First Self-Referencing One-to-Many and Many-to-Many Associations

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问题 I have a User that can have collection of users he likes... Another user can have collection of users he likes.... If User A likes User B and if User B likes User A, then they get to hang out. I need to send each other their contact info. How do we represent such a model in Entity Framework Code First? public class User { public int UserId { get; set; } public int? UserLikeId { get; set; } public virtual UserLike UserLike { get; set; } } public class UserLike { public int UserLikeId { get;

Entity Framework Code First: how to map multiple self-referencing many-to-many relationships

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问题 I have created an entity type that has multiple collection properties that reference items of the same type. In other words, it reflects a single database table in which the rows are arbitrarily grouped, such that a row may appear in multiple groups. In the following simplified example, the Person class has Brothers and Sisters collection properties that also reference Person entities: public class Person { public Person() { Brothers = new Collection<Person>(); Sisters = new Collection<Person

TypeScript: self-referencing return type for static methods in inheriting classes

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问题 With Polymorphic this in TypeScript 1.7, as I discovered here, we can define a method in a class with a return type of this , and automatically, any classes that extend that class and inherit the methods, will have their return types set to their respective this type. Like so: class Model { save():this { // return type: Model // save the current instance and return it } } class SomeModel extends Model { // inherits the save() method - return type: SomeModel } However, what I'm after is to

Uses of self referencing lists

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问题 I know it is possible to create a self referencing list in languages like Python: >>> my_list = [1,2] >>> my_list.append(my_list) >>> print my_list [1,2,[...]] >>> print my_list[0] 1 >>> print my_list[2] [1,2,[...]] What algorithms benefit from self referencing lists? I cannot think of one. Thanks. 回答1: Self-referencing lists, and, generally speaking, circular data structures, can be caused when representing a graph using data structures. For example, consider this naive representation of a

R self reference

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In R I find myself doing something like this a lot: adataframe[adataframe$col==something]<-adataframe[adataframe$col==something)]+1 This way is kind of long and tedious. Is there some way for me to reference the object I am trying to change such as adataframe[adataframe$col==something]<-$self+1 ? Matt Dowle Try package data.table and its := operator. It's very fast and very short. DT[col1==something, col2:=col3+1] The first part col1==something is the subset. You can put anything here and use the column names as if they are variables; i.e., no need to use $ . Then the second part col2:=col3+1

R self reference

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问题 In R I find myself doing something like this a lot: adataframe[adataframe$col==something]<-adataframe[adataframe$col==something)]+1 This way is kind of long and tedious. Is there some way for me to reference the object I am trying to change such as adataframe[adataframe$col==something]<-$self+1 ? 回答1: Try package data.table and its := operator. It's very fast and very short. DT[col1==something, col2:=col3+1] The first part col1==something is the subset. You can put anything here and use the