Scala入门教程：12步带你领略编程语言精华

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本篇文章是《Scala基础教程》，由Bill Venners、Martin Odersky和Lex Spoon共同撰写，发布于2007年5月9日。该教程旨在引导读者逐步了解Scala编程语言，帮助新手掌握基本技能。Scala是一种静态类型、面向对象的语言，它巧妙地融合了命令式（imperative）和函数式编程风格，使其在现代虚拟机上运行得非常顺畅，特别是在Java虚拟机（JVM）上。 Scala设计初衷是为了与Java和其他平台如.NET世界无缝集成。主Scala编译器`scalac`生成的是可以在JVM上运行的Java字节码。此外，还存在另一个编译器，可以将Scala代码编译成可以在.NET Common Language Runtime（CLR）上运行的二进制文件，这体现了Scala跨平台的特性。教程共分为12个步骤，每一步都精心设计，确保学习者能逐步熟悉Scala的关键概念，包括但不限于： 1. **静态类型和类型推断**：Scala强调类型系统的重要性，同时允许编译器自动推断类型，减少了冗余的类型声明。 2. **面向对象编程**：讲解Scala中的类、对象、继承、封装和多态等面向对象编程的核心概念。 3. **函数式编程**：介绍Scala的高阶函数、lambda表达式和模式匹配，展示其函数式编程的一面。 4. **可扩展性和模块化**：如何使用trait、case class和特质（traits）来创建可复用的模块和灵活的设计。 5. **集合和并行计算**：Scala强大的集合库以及如何利用并行性进行高效编程。 6. **交互式编程环境**：scala REPL的使用，即交互式编程环境，方便快速试验和学习。 7. **编译器和工具链**：理解如何安装和配置Scala环境，以及使用`scalac`编译器和相关IDE（如IntelliJ IDEA或Eclipse插件）。 8. **JVM和.NET互操作**：Scala在两种不同平台上的应用策略，包括JVM与.NET之间的桥梁。通过这些步骤，初学者不仅能掌握Scala语言的基础，还能了解到它与其他语言（如Java）的协作方式，以及如何利用其特性在实际项目中发挥效用。学习过程中，读者可以结合实际编写小项目来加深理解和熟练度。这是一个全面且实用的Scala入门指南，适合想要踏入这个现代编程语言世界的读者。

2014年7月26日 First Steps to Scala

http://www.artima.com/scalazine/articles/steps.html 5/25

unnamed7: Unit = ()

scala> greet

Hello, world!

unnamed8: Unit = ()

The recommended style guideline for such method invocations is that if the method may have

side effects

, you should provide the parentheses even if the compiler doesn't require them.

Thus in this case, since the greet method prints to the standard output, it has side effects

and you should invoke it with parentheses to alert programmers looking at the code.

Step 5. Write some Scala scripts

Although Scala is designed to help developers build large systems, it also scales down nicely

such that it feels natural to write scripts in it. A script is just a sequence of statements in a file

that will be executed sequentially. (By the way, if you're still running the scala interpreter, you

can exit it by entering the :quit command.) Put this into a file named hello.scala:

println("Hello, world, from a script!")

then run:

>scala hello.scala

And you should get yet another greeting:

Hello, world, from a script!

Command line arguments to a Scala script are available via a Scala array named args. In

Scala, arrays are zero based, as in Java, but you access an element by specifying an index

in parentheses rather than square brackets. So the first element in a Scala array named

steps is steps(0), not steps[0]. To try this out, type the following into a new file named

helloarg.scala:

// Say hello to the first argument

println("Hello, " + args(0) + "!")

then run:

>scala helloarg.scala planet

In this command, "planet" is passed as a command line argument, which is accessed in

the script as args(0). Thus, you should see:

Hello, planet!

Note also that this script included a comment. As with Java, the Scala compiler will ignore

characters between // and the next end of line, as well as any characters between /* and

*/. This example also shows strings being concatenated with the + operator. This works as

you'd expect. The expression "Hello, " + "world!" will result in the string "Hello,

world!".

By the way, if you're on some flavor of Unix, you can run a Scala script as a shell script by

prepending a “pound bang” directive at the top of the file. For example, type the following into

a file named helloarg:

#!/bin/sh

exec scala $0 $@

// Say hello to the first argument

println("Hello, " + args(0) + "!")

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