c# - Difference between Covariance & Contra-variance -


I am having trouble understanding the difference between empathy and immorality.

The question is, "What is the difference between sympathy and corruption?"

Sovereignty and depravity are the properties of a mapping function that connects one member of a set with another. More specifically, a mapping can be a cult or anti in relation to relationship on that set.

Consider the following two subsets of the set of all C # types. First: 

  {animal, tiger, fruit, banana}.

And secondly, this is clearly related to the set: 

  {IEnumerable & lt; Animals>, IEnumerable & lt; Tiger & gt;, IEnumerable & lt; Feet & gt ;, IEnumerable & lt; Banana & gt; }

There is an mapping operation from the first set to the second set. For each T in the first set, in the second set related type IEnumerable & lt; T & gt; . Or, in a nutshell, mapping T → IE & lt; T & gt; . Note that this is a "thin arrow".

So far with me?

Now we consider an relationship . In the first set, there is an assignment consistency relationship between pairs. A value of type tiger can be assigned to a variable of animal , so these types are called "assignment compatible". Let us type "a value of type X can be specified as a lower type in y " " X . That's a "fat arrow".

So in our first subset, here are all assignment compatibility relationships: 

  Tiger ⇒ Tiger Tiger ⇒ Animal Animal ⇒ Animal Creation ⇒ Banana made ⇒ fruit fruits ⇒ fruit

In C # 4, supporting the co-sensitive sensitivity of some interfaces, the type of pair in the second set The Quick Assignment Compatibility Relationship is: 

  IE> Tiger> ⇒ IE  IE & LT; Tiger & gt; ⇒ IE & lt; Animals & gt; IE & LT; Animals> ⇒ IE & lt; Animals & gt; IE & LT; Banana> ⇒ IE & lt; Banana & gt; IE & LT; Banana & gt; ⇒ IE & lt; Fruits & gt; ; IE & LT; Fruits & gt; ⇒ IE & lt; fruit & gt;

Note that mapping T → IE > Assignment preserves the existence and direction of compatibility That is, if X ⇒ Y , then it is also true that IE ⇒ ⇒ IE & lt; Y & gt;

If we have two things on both sides of the fat arrow, then we can turn both sides towards the right hand of a thin arrow.

Mapping This property is called "sympathetic mapping" in relation to a particular relationship. It should be understood: where the sequence of tigers can be used, where the sequence of animals is but the opposite is not true. A sequence of animals can not be needed where a series of tigers are required.

This community is now considering this subset of all types of sets: 

  {ICemperable & lt; Tiger & gt;, ICemperable & lt; Animals>, IComperbol & lt; Fert>, IComperbal & lt; Banana & gt; }

We now have the third set T → IC & lt; T & gt; There is a mapping on .

In C # 4:

IC < Tiger & gt; ⇒ IC & lt; Tiger & gt; IC & LT; Animals & gt; ⇒ IC & lt; Tiger & gt; Backwards! IC & LT; Animals & gt; ⇒ IC & lt; Animals & gt; IC & LT; Banana & gt; ⇒ IC & lt; Banana & gt; IC & LT; Fruit & gt; ⇒ IC & lt; Banana & gt; Backwards! IC & LT; Fruit & gt; ⇒ IC & lt; Fruit & gt;

That is, the mapping T → IC & lt; T & gt; has preserved existence but direction of compatibility assignment is the same, if x ⇒ y , then ic < X & gt; A mapping that holds , but goes back is a relation called contravariant mapping.

P> Again, this should be clearly correct. A device that can compare two animals, can also compare two tigers, but a device that can compare two tigers does not necessarily compare any two animals.

Therefore there is a difference between sovereignty and corruption in C # 4. > Maintenance direction of assignment In contrast, behind


Comments

Post a Comment

Popular posts from this blog

sql - dynamically varied number of conditions in the 'where' statement using LINQ -

I am using my first project LINQ (in mvc), so maybe there's something very simple that I remember. However, a day of searching and experimenting does not work, so it works. I am trying to write a LINQ query (Linux to SQL) in which in many cases where the statement is different from an OR or an AND. We do not know how many conditions are going in the query till runtime. This search is for filter control, where the user can choose multiple criteria for filtering. Select from table where table.col = 1 or table.col = 2 or table.col = 7 .... 'Other number of conditions Before I just create the SQL query as a string, while looping over all the situations. However, it seems that there should be a good way to do this in LINQ. I tried to use Expression trees, but they had a second thought for this moment on my head, where the lambda function was to be executed inside the statement such as: values ​​for matchingRows = matchingRows for each value Where (function (row) row.c...
Read more

asp.net mvc - Dynamically Generated Ajax.BeginForm -

I have a problem with ASP.NET MVC Ajax forms. I generate many Ajax form in a table such as: & Lt; Input type = "submit" name = "activity" value = "add activity" / & gt; & Lt;%}% & gt; & Lt; / TD & gt; & Lt; / TR & gt; & Lt;%}% & gt; So far so good. When I post one of those forms, it gives a partial view in a div, and in this new partial view a new Ajax Beginnform (which is not in Genesis form) This second Ajax Beginnorf is exactly like the ones I got on the table, but when I post it, I do not get the "Ajax Post", but a normal post that sends me to a new page, I do not know whether the two Ajax forms What is the reason for the difference between, why is it the "dynamically generated" Ajax form behaves like a normal HTML form? By the way, I know that I can do it in different ways using javascript, but I would like to understand whether it can only be done using MVC helplars and Ajax lib...
Read more

Debug on symbian -

I am using trk for phone debug This works well for the Holorld project But when I start the project in phone debug mode 1) the load failed 2) TrkProtocolPlugin: to target the specified file Failure (please verify If any body understands what problem I am experiencing, then this problem helps me Pre-release If the application has the privileges assigned (with the appropriate certificate) itemprop = "text" > In your case, I will check: / li> If there is no conflict of application ID with any other application of device If there are problematic commands in the installation package (for example copy copy for non-accessible directories)
Read more