definition | 易学教程

What is data serialization ?

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问题 First of all, I could not able to get clear definition of it from WikiPedia or even from serialize function in the PHP manual. I need to know some cases we need the term serialization and how things are going without it? In other word, Where you must need serialization and without it your code will be missing some important feature. 回答1: What serialization is? Serialization is objects encoding into other language. For example you have an array in PHP like this: $array = array("a" => 1, "b" =>

HTTPbis - what does bis mean?

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I've often seen "bis" appended to versions of protocols (eg v.34bis or httpbis). What does "bis" mean or stand for? A telecom engineer I know thinks it might be French in origin. As others have already said, "bis" comes from "twice" or "repeat" . It's used to indicate a second variant of something (although usually with only minor variations that don't warrant a new name). In the context of HTTP, HTTPbis is the name of the working group in charge of refining HTTP. According to its charter : HTTP is one of the most successful and widely-used protocols on the Internet today. However, its

Simple definition of “semantics” as it is commonly used in relation to programming languages/APIs?

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It occurred to me today that although I've adopted and don't infrequently use the term "semantics" when referring to language elements and naming conventions, I don't have any sense of a formal definition. My attempt to find a formal definition in the programming domain made my eyes glaze over. I have a sense of its meaning from the contexts in which I've encountered it, and from its more common usage with respect to linguistics, and I typically use the term to refer to the meaning or expressiveness of the language element, or the fidelity of nomenclature to the intent, behaviour, or function

Defining a class within a namespace

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问题 Is there a more succinct way to define a class in a namespace than this: namespace ns { class A {}; } I was hoping something like class ns::A {}; would work, but alas not. 回答1: You're close, you can forward declare the class in the namespace and then define it outside if you want: namespace ns { class A; // just tell the compiler to expect a class def } class ns::A { // define here }; What you cannot do is define the class in the namespace without members and then define the class again

What does “in constant time” imply?

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问题 I work as a programmer, but have no computer science background, so recently I've been following along with the excellent MIT OpenCourseWare intro to Computer Science and Programming. In the course of which, the question is asked: "will any program written using only function definitions and calls, the basic arithmetic operators, assignment and conditionals run in constant time?" I thought the answer was yes, since all of these operations seem pretty simple. But as you smart people probably

REST - What exactly is meant by Uniform Interface?

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问题 Wikipedia has: Uniform interface The uniform interface constraint is fundamental to the design of any REST service.[14] The uniform interface simplifies and decouples the architecture, which enables each part to evolve independently. The four guiding principles of this interface are: Identification of resources Individual resources are identified in requests, for example using URIs in web-based REST systems. The resources themselves are conceptually separate from the representations that are

How to show zsh function definition (like bash “type myfunc”)?

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问题 How do I show the definition of a function in zsh? type foo doesn't give the definition. In bash: bash$ function foo() { echo hello; } bash$ foo hello bash$ type foo foo is a function foo () { echo hello } In zsh: zsh$ function foo() { echo hello; } zsh$ foo hello zsh$ type foo foo is a shell function 回答1: The zsh idiom is whence , the -f flag prints function definitions: zsh$ whence -f foo foo () { echo hello } zsh$ In zsh, type is defined as equivalent to whence -v , so you can continue to

Enum inside class (TypeScript definition file)

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I've searched around but can't seem to find an answer for this, hopefully you can help. How can I add an enum to Image? This is what I would like ideally but I get an error. declare module 'Lib' { export module Graphics { export class Image { enum State {} static STATE_IDLE: State; static STATE_LOADING: State; static STATE_READY: State; static STATE_ERROR: State; constructor(); } } } If I move State into the Graphics module it works but now State belong to Graphics...which is incorrect, it needs to be part of Image. Any ideas? Thanks I also bumped into this problem recently. This is what I am

What does the term “Tuple” Mean in Relational Databases?

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问题 Please explain what is meant by tuples in sql?Thanks.. 回答1: Most of the answers here are on the right track. However, a row is not a tuple . Tuples * are unordered sets of known values with names. Thus, the following tuples are the same thing (I'm using an imaginary tuple syntax since a relational tuple is largely a theoretical construct): (x=1, y=2, z=3) (z=3, y=2, x=1) (y=2, z=3, x=1) ...assuming of course that x, y, and z are all integers. Also note that there is no such thing as a

What is the difference between a heuristic and an algorithm?

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问题 What is the difference between a heuristic and an algorithm? 回答1: An algorithm is the description of an automated solution to a problem . What the algorithm does is precisely defined. The solution could or could not be the best possible one but you know from the start what kind of result you will get. You implement the algorithm using some programming language to get (a part of) a program . Now, some problems are hard and you may not be able to get an acceptable solution in an acceptable time