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A Tour of the Scala Programming Language

Scalaツアー

Scala is a modern multi-paradigm programming language designed to express common programming patterns in a concise, elegant, and type-safe way.

Scalaはモダンなデザインのマルチパラダイムプログラミング言語で、簡潔、エレガントかつ型に安全な方法で一般的なプログラミングパターンを表現するためにデザインされています。

It smoothly integrates features of object-oriented and functional languages.

また、オブジェクト指向言語と関数型言語をスムースに統合しています。

Scala is the successor of Funnel, a language based on join calculus.

Scalaはjoin算法に基づいた言語であるFunnelの後継の言語に当たります。

Scala is object-oriented

Scalaはオブジェクト指向である

Scala is a pure object-oriented language in the sense that every value is an object.

Scalaはすべての値がオブジェクトである、という点において純粋なオブジェクト指向です。

Types and behavior of objects are described by classes and traits.

オブジェクトの型と振舞は、classとtraitに記述されます。

Class abstractions are extended by subclassing and a flexible mixin-based composition mechanism as a clean replacement for multiple inheritance.

クラスの抽象化はサブクラスと（多重継承のクリーンな代替としての）フレキシブルなMix-inベースの構成メカニズムによって拡張されます。

Scala is functional

Scalaは関数型でもある。

Scala is also a functional language in the sense that every function is a value.

Scala provides a lightweight syntax for defining anonymous functions, it supports higher-order functions, it allows functions to be nested, and supports currying.

Scala's case classes and its built-in support for pattern matching model algebraic types used in many functional programming languages.

Furthermore, Scala's notion of pattern matching naturally extends to the processing of XML data with the help of right-ignoring sequence patterns.

In this context, sequence comprehensions are useful for formulating queries.

These features make Scala ideal for developing applications like web services (external link).

Scala is statically typed

Scala is equipped with an expressive type system that enforces statically that abstractions are used in a safe and coherent manner. In particular, the type system supports:

   * generic classes,
   * variance annotations,
   * upper and lower type bounds,
   * inner classes and abstract types as object members,
   * compound types,
   * explicitly typed self references,
   * views, and
   * polymorphic methods.

A local type inference mechanism takes care that the user is not required to annotate the program with redundant type information. In combination, these features provide a powerful basis for the safe reuse of programming abstractions and for the type-safe extension of software.

Scala is extensible

The design of Scala acknowledges the fact that in practice, the development of domain-specific applications often requires domain-specific language extensions. Scala provides a unique combination of language mechanisms that make it easy to smoothly add new language constructs in form of libraries:

   * any method may be used as an infix or postfix operator, and
   * closures are constructed automatically depending on the expected type (target typing).

A joint use of both features facilitates the definition of new statements without extending the syntax and without using macro-like meta-programming facilities.

Scala interoperates with Java and .NET

Scala is designed to interoperate well with popular programming environments like the Java 2 Runtime Environment (JRE) and the .NET Framework (CLR). In particular, the interaction with mainstream object-oriented languages like Java and C# is as smooth as possible. Scala has the same compilation model (separate compilation, dynamic class loading) like Java and C# and allows access to thousands of high-quality libraries.

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