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# Preface

Ruby is the interpreted scripting language for quick and easy object-oriented programming. It has many features to process text files and to do system management tasks (as in Perl). It is simple, straight-forward, and extensible.

If you want a language for easy object-oriented programming, or you don't like the PERL ugliness, or you do like the concept of lisp, but don't like too much parentheses, Ruby may be the language of the choice.

Ruby's features are as follows:

> #### Interpretive

>   Ruby is the interpreted language, so you don't have to recompile to execute the program written in Ruby.

> #### Variables have no type (dynamic typing)

>   Variables in Ruby can contain data of any type. You don't have to worry about variable typing. Consequently, it has weaker compile time check.

> #### No declaration needed

>   You can use variables in your Ruby programs without any declarations. Variable name itself denotes its scope (local, global, instance, etc.)

> #### Simple syntax

>   Ruby has simple syntax influenced slightly from Eiffel.

> #### No user-level memory management

>   Ruby has automatic memory management. Objects no longer referenced from anywhere are automatically collected by the garbage collector built in the interpreter.

> #### Everything is object

>   Ruby is the pure object-oriented language from the beginning. Even basic data like integers are treated uniformly as objects.

> #### Class, inheritance, methods

>   Of course, as a O-O language, Ruby has basic features like classes, inheritance, methods, etc.

> #### Singleton methods

>   Ruby has the feature to define methods for certain specified object. For example, you can define a press-button action for certain GUI button by defining a singleton method for the button. Or, you can make up your own prototype based object system using singleton methods (if you want to).

> #### Mix-in by modules

>   Ruby does not have the multiple inheritance intentionally. IMO, It is the source of confusion. Instead, Ruby has modules to share the implementation across the inheritance tree. It is often called the "Mix-in."

> #### Iterators

>   Ruby has iterators for loop abstraction.

> #### Closures

>   In Ruby, you can objectify the procedure.

> #### Text processing and regular expression

>   Ruby has bunch of text processing features like in Perl.

> #### Bignums

>   With built-in bignums, you can calculate factorial(400), for example.

> #### Exception handling

>   As in Java(tm).

> #### Direct access to OS

>   Ruby can call most of system calls on UNIX boxes. It can be used in system programming.

> #### Dynamic loading

>   You can load object files into Ruby interpreter on-the-fly, on most of UNIXes.

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