是什么声明和必要的程序之间的差异 [英] What is the difference between declarative and imperative programming

问题描述

我一直在网上搜索寻找的声明和必要程序的定义，将一些启发我。然而，在一些我已经找到了资源使用的语言是艰巨的 - 比如在维基百科。
没有任何一个有一个真实的例子，他们可以告诉我，可能会带来一些观点这个主题......也许在C＃。

I have been searching the web looking for a definition for declarative and imperative programming that would shed some light for me. However the language used at some of the resources that I have found is daunting - for instance at Wikipedia. Does any one have a real world example that they could show me that might bring some perspective to this subject... perhaps in C#.

推荐答案

声明与命令式编程的一个很好的C＃示例是LINQ。

A great C# example of declarative vs. imperative programming is LINQ.

是必须编程，你要发生，一步步什么告诉编译器。

With imperative programming, you tell the compiler what you want to happen, step by step.

例如，让我们开始这个集合，然后选择单号：

For example, let's start with this collection, and choose the odd numbers:

List<int> collection = new List<int> { 1, 2, 3, 4, 5 };

使用命令式编程，我们会一步通过这一点，并决定我们想要什么：

With imperative programming, we'd step through this, and decide what we want:

List<int> results = new List<int>();
foreach(var num in collection)
{
    if (num % 2 != 0)
          results.Add(num);
}

在这里，我们说：

Here, we're saying:

1. 创建一个结果集


2. 通过每个步骤号集合中


3. 检查的数量，如果是奇数，将它添加到结果

是声明节目，在另一方面，你写code，描述你想要什么，但不一定如何得到它（声明您预期的效果，但不是一步-step）：

With declarative programming, on the other hand, you write code that describes what you want, but not necessarily how to get it (declare your desired results, but not the step-by-step):

var results = collection.Where( num => num % 2 != 0);

在这里，我们说给我们的一切在这里很奇怪，而不是通过收集步骤检查这个项目，如果是奇数，将它添加到结果集。

Here, we're saying "Give us everything where it's odd", not "Step through the collection. Check this item, if it's odd, add it to a result collection."

在很多情况下，code将两种设计的混合物，也因此它并不总是黑色和白色。

In many cases, code will be a mixture of both designs, too, so it's not always black-and-white.

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