Book V: Web Programming in Java

Generating QR Code in Java Book V: Web Programming

Understanding the structure of a Ruby program Creating comments and declaring variables Using operators and data structures Branching and looping statements Creating functions and objects

he Ruby programming language was created by Yukihiro Matz Matsumoto, a Japanese programmer who named the language after a gemstone in reference to the Perl (pearl) programming language Although most languages focus on wringing out extra performance from computer hardware, Ruby focuses on a clean language syntax that s easy for programmers to understand and use Instead of trying to increase machine efficiency, Ruby tries to increase programmer efficiency The overriding principle of Ruby is to create a language of least surprise, meaning that after you re familiar with Ruby, you aren t suddenly surprised that its features can be used in an entirely different way, which often occurs with languages such as C++ Ruby is an interpreted, object-oriented language for creating interactive Web pages Although Ruby is similar to Perl and Python, Ruby abandons the Csyntax of Perl and more closely resembles the syntax of programming languages like Smalltalk or Ada Instead of enclosing blocks of commands in curly brackets like C or Perl, Ruby encloses blocks of commands with keywords like Ada or more modern versions of BASIC A programming framework, dubbed Ruby on Rails, makes it easy to manipulate databases through Web pages and has attracted the attention of many former Java programmers Like Ruby itself, Ruby on Rails is free, which has further fueled its growth Although still a relatively young language (created in 1995), Ruby has attracted a worldwide following and will likely play a major role in future applications developed for the Web Mac OS X and many Linux distributions include an interpreter for the Ruby language To get a copy of the free Ruby interpreter for other operating systems, visit the official Ruby Web site (wwwruby-langorg)

A Ruby program can consist of one or more commands:

print( What is your name ) myname = gets() puts( Welcome to Ruby, #{myname} )

Unlike other programming languages, Ruby programs don t need to define a main program, don t enclose blocks of commands with curly brackets, and don t end statements with a semicolon Type a command, and Ruby obeys without its syntax interfering with your thinking The preceding Ruby program simply asks the user to type in a name Whatever name the user types gets stored in the myname variable Then the last line prints the string Welcome to Ruby, followed by the contents of the myname variable

To write a comment in Ruby, use the # symbol Anything that appears to the right of the # symbol is considered a comment, which the computer ignores

# This is a comment print( What is your name ) myname = gets() # This is also a comment puts( Welcome to Ruby, #{myname} )

If you want to write a comment over multiple lines, define the start and end of a comment block with =begin and =end, such as

=begin This is a block of comments that make it easy to comment out multiple lines However, Ruby s block commenting is kind of ugly so it s rarely used =end print( What is your name ) myname = gets() puts( Welcome to Ruby, #{myname} )

Defining comments with the =begin and =end lines is often cumbersome, so it s more common for programmers to use multiple # symbols in front of each line instead like this:

# long time to write so maybe he deserves # a big fat raise or at least some extra # sick days so he can look for a better job print( What is your name ) myname = gets() puts( Welcome to Ruby, #{myname} )