官术网_书友最值得收藏!

Abstractions

What do we mean by abstractions? Why are they important? To understand this, we will compare two approaches. First, the "go to the wall and pull at one of the wooden panels fitted into the rectangular hole" approach versus the "open the door, please" approach.

A door is an abstraction. We really don't care whether it is made of wood or some other material, or what type of a lock it has, or any other details. The details are important, but not always. If we worry about the details always, we would quickly get bogged down, and all the communication would effectively come to a halt.

A table is an abstraction, so is a chair, and so is a house. I hope you get the drift. We want to be selectively ignorant of the details at times, and selective ignorance is abstraction.

Now, you may ask why does it matter to us programmers? The reason is that it gets things done in a compact manner.

For example, let's look at the following Scala code, which is used to count the frequency of characters in a string:

scala> "hello world".toList.filter(_.isLetter).groupBy(x => x).map { y =>
 | y._1 -> y._2.size
 | }
res1: scala.collection.immutable.Map[Char,Int] = Map(e -> 1, l -> 3, h -> 1, r -> 1, w -> 1, o -> 2, d -> 1)

Isn't it compact?

On the Urban Dictionary website, http://www.urbandictionary.com/define.php?term=cutie, the term "cutie" is defined as compact beauty—the kind you just want to put in your pocket and keep beside you forever.

I was bowled over when I first saw it all. It is concise, short, packs a punch, and is elegant. The Type Less Do More philosophy. Gets a lot done with less...

Note

To run the code snippet, fire up the Scala REPL. This looks a lot like a command console, a prompt waiting for you to key in Scala code. In a command terminal, typing just Scala fires up the REPL:

~> scala

It will give the following output:

Welcome to Scala version 2.11.7 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_25).

You can type in expressions to have them evaluated and type help for more information. Let's try the following simple one line commands:

scala> 1 + 1
res2: Int = 2
scala> "hello".length
res4: Int = 5

For me, Scala brought the thrill back to programming... You can do a great deal by writing a few lines of code—less is more...

Scala gives you many tools, so the code is abstract and reusable...

主站蜘蛛池模板: 威信县| 陆川县| 临武县| 黄骅市| 西丰县| 南康市| 长乐市| 青阳县| 泽普县| 易门县| 民丰县| 广元市| 佳木斯市| 孟津县| 安远县| 时尚| 中江县| 宁陵县| 湖州市| 改则县| 阳东县| 龙陵县| 广昌县| 综艺| 明光市| 新晃| 长泰县| 临清市| 彩票| 东乡县| 宁蒗| 霞浦县| 东兴市| 若羌县| 集安市| 台前县| 江阴市| 阜宁县| 咸丰县| 柞水县| 于田县|