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| Ruby | |
|---|---|
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| Paradigm | multi-paradigm |
| Appeared in | 1995 |
| Designed by | Yukihiro Matsumoto |
| Developer | Yukihiro Matsumoto (among others) |
| Latest release | 1.9.0/ December 25 2007 |
| Typing discipline | dynamic ("duck") |
| Major implementations | Ruby, JRuby, Rubinius |
| Influenced by | Smalltalk, Perl, Lisp, Scheme, Python, CLU, Eiffel, Ada, Dylan |
| Influenced | Groovy |
| OS | Cross-platform |
| License | Ruby License GNU General Public License |
| Website | www.ruby-lang.org |
Ruby is a dynamic, reflective, general purpose object-oriented programming language. Originating in Japan in the mid 1990s, Ruby was initially developed and designed by Yukihiro "Matz" Matsumoto and combines syntax inspired by Perl with Smalltalk-like object-oriented features.
Ruby supports multiple programming paradigms (including functional, object oriented and imperative), and features a dynamic type system and automatic memory management; it is therefore similar in varying respects to Python, Perl, Lisp, Dylan, and CLU.
In its current, official implementation, written in C, Ruby is a single-pass interpreted language. As of 2008, there are a number of alternative implementations of the Ruby language, including Rubinius, JRuby and IronRuby, each of which takes a different approach, with JRuby providing just-in-time compilation functionality.
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Yukihiro Matsumoto, the creator of Ruby.
The language was created by Yukihiro Matsumoto, who started working on Ruby on February 24, 1993, and released it to the public in 1995. "Ruby" was named as a gemstone because of a joke within Matsumoto\'s circle of friends alluding to the name of the Perl programming language An Interview with the Creator of Ruby.
As of December 2007, the latest stable version is 1.8.6. Ruby 1.9.0 was released in December, but it is considered a development release. Several virtual machines are being developed for Ruby. These include JRuby, a port of Ruby to the Java platform, IronRuby, an implementation for the .NET Framework produced by Microsoft, and Rubinius, an interpreter modeled after self-hosting Smalltalk virtual machines. The main developers have thrown their weight behind the virtual machine provided by the YARV project, which was merged into the Ruby source tree on 31 December 2006, and released as part of Ruby 1.9.
The language\'s creator, Yukihiro "Matz" Matsumoto, has said that Ruby is designed for programmer productivity and fun, following the principles of good user interface design.The Ruby Programming Language by Yukihiro Matsumoto on 2000-06-12 (informit.com) He stresses that systems design needs to emphasize human, rather than computer, needs The Philosophy of Ruby, A Conversation with Yukihiro Matsumoto, Part I by Bill Venners on 2003-09-29 (Artima Developer):
| “ | Often people, especially computer engineers, focus on the machines. They think, "By doing this, the machine will run faster. By doing this, the machine will run more effectively. By doing this, the machine will something something something." They are focusing on machines. But in fact we need to focus on humans, on how humans care about doing programming or operating the application of the machines. We are the masters. They are the slaves. | ” |
Ruby is said to follow the principle of least surprise (POLS), meaning that the language should behave in such a way as to minimize confusion for experienced users. Matsumoto has said his primary design goal was to make a language which he himself enjoyed using, by minimizing programmer work and possible confusion. He has said he hadn\'t applied the principle of least surprise to the design of Ruby,The Philosophy of Ruby, A Conversation with Yukihiro Matsumoto, Part I by Bill Venners on 2003-09-29 (Artima Developer) but nevertheless the phrase has come to be closely associated with the Ruby programming language. The phrase has itself been a source of surprise, as novice users may take it to mean that Ruby\'s behaviors try to closely match behaviors familiar from other languages. In a May 2005 discussion on the comp.lang.ruby newsgroup, Matsumoto attempted to distance Ruby from POLS, explaining that because any design choice will be surprising to someone, he uses a personal standard in evaluating surprise. If that personal standard remains consistent there will be few surprises for those familiar with the standard. [1]
Matsumoto defined it this way in an interview [2]:
| “ | Everyone has an individual background. Someone may come from Python, someone else may come from Perl, and they may be surprised by different aspects of the language. Then they come up to me and say, \'I was surprised by this feature of the language, so Ruby violates the principle of least surprise.\' Wait. Wait. The principle of least surprise is not for you only. The principle of least surprise means principle of least my surprise. And it means the principle of least surprise after you learn Ruby very well. For example, I was a C++ programmer before I started designing Ruby. I programmed in C++ exclusively for two or three years. And after two years of C++ programming, it still surprises me. | ” |
Ruby is object oriented: every data type is an object, including even classes and types which many other languages designate as primitives (such as integers, booleans, and "nil"). Every function is a method. Named values (variables) always designate references to objects, not the objects themselves. Ruby supports inheritance with dynamic dispatch, mixins and singleton methods (belonging to, and defined for, a single instance rather than being defined on the class). Though Ruby does not support multiple inheritance, classes can import modules as mixins. Procedural syntax is supported, but all methods defined outside of the scope of a particular object are actually methods of the Object class. Since this class is parent to every other class, the changes become visible to all classes and objects.
Ruby has been described as a multi-paradigm programming language: it allows procedural programming (defining functions/variables outside classes makes them part of the root, \'self\' Object), with object orientation (everything is an object) or functional programming (it has anonymous functions, closures, and continuations; statements all have values, and functions return the last evaluation). It has support for introspection, reflection and metaprogramming, as well as support for interpreter-basedGreen threads threads. Ruby features dynamic typing, and supports parametric polymorphism.
According to the Ruby FAQ Ruby FAQ, "If you like Perl, you will like Ruby and be right at home with its syntax. If you like Smalltalk, you will like Ruby and be right at home with its semantics. If you like Python, you may or may not be put off by the huge difference in design philosophy between Python and Ruby/Perl." How Does Ruby Compare With Python? (FAQ)
Ruby checks the type of each expression and sub-expression dynamically, as they are encountered during execution, and will raise a runtime error whenever a type error is found.
There is no universally agreed upon definition of type safe (see TypeSafe at C2.com Wiki), and in the case of Ruby, it depends on which definition one refers to.
One definition of type-safe language requires that "no operation will be applied to a variable of a wrong type." In this respect, Ruby is probably type safe (given Ruby\'s semantics, it would be very difficult to prove theoretically, but might be assumed as long as no contradictory code example is found).[citation needed]
Another definition of type-safe program requires that "the program will not have type errors when it runs". In this respect, Ruby is obviously not type safe, since it may by design raise type errors during execution.[citation needed]
Again, there is no universally agreed upon definition of Strongly Typed. C2.com Wiki lists at least 8 different definitions from different sources.
According to some of these definitions, Ruby is strongly typed, while according to others it is weakly typed:
Ruby currently lacks full support for Unicode, though it has partial support for UTF-8.
The Ruby official distribution also includes "irb", an interactive command-line interpreter which can be used to test code quickly. The following code fragment represents a sample session using irb:
The syntax of Ruby is broadly similar to Perl and Python. Class and method definitions are signaled by keywords. In contrast to Perl, variables are not obligatorily prefixed with a sigil. When used, the sigil changes the semantics of scope of the variable. The most striking difference from C and Perl is that keywords are typically used to define logical code blocks, without braces (i.e., pair of { and }). Line breaks are significant and taken as the end of a statement; a semicolon may be equivalently used. Unlike Python, indentation is not significant.
One of the differences of Ruby compared to Python and Perl is that Ruby keeps all of its instance variables completely private to the class and only exposes them through accessor methods (attr_writer, attr_reader, etc). Unlike the "getter" and "setter" methods of other languages like C++ or Java, accessor methods in Ruby can be written with a single line of code. As invocation of these methods does not require the use of parentheses, it is trivial to change an instance variable into a full function, without modifying a single line of code or having to do any refactoring achieving similar functionality to C# and VB.NET property members. Python\'s property descriptors are similar, but come with a tradeoff in the development process. If one begins in Python by using a publicly exposed instance variable and later changes the implementation to use a private instance variable exposed through a property descriptor, code internal to the class may need to be adjusted to use the private variable rather than the public property. Ruby removes this design decision by forcing all instance variables to be private, but also provides a simple way to declare set and get methods. This is in keeping with the idea that in Ruby, one never directly accesses the internal members of a class from outside of it. Rather one passes a message to the class and receives a response.
See the examples section for samples of code demonstrating Ruby syntax.
Some features which differ notably from languages such as C or Perl:
$ and @ do not indicate variable data type as in Perl, but rather function as scope resolution operators.
99.0) or an explicit conversion (99.to_f). It is insufficient to append a dot (99.), because numbers are susceptible to method syntax.
"" and [] are all evaluated to true. In C, the expression 0 ? 1 : 0 evaluates to 0 (i.e. false). In Ruby, however, it yields 1, as all numbers evaluate to true; only nil and false evaluate to false. A corollary to this rule is that Ruby methods by convention — for example, regular-expression searches — return numbers, strings, lists, or other non-false values on success, but nil on failure (e.g., mismatch). This convention is also used in Smalltalk, where only the special objects true and false can be used in a boolean expression.
char for characters). This may cause surprises when slicing strings: "abc"[0] yields 97 (an integer, representing the ASCII code of the first character in the string); to obtain "a" use "abc"[0,1] (a substring of length 1) or "abc"[0].chr.
Some features which differ notably from other languages:
and and or, do not follow the normal rules of precedence: and does not bind tighter than or. Ruby also has expression operators || and && which work as expected.
(), to avoid ambiguous meaning of code. Not using () is still common practise, and can be especially nice to use Ruby as a human readable domain-specific programming language itself, along with the method called method_missing().
A list of "gotchas" may be found in Hal Fulton\'s book The Ruby Way, 2nd ed (ISBN 0-672-32884-4), Section 1.5. A similar list in the 1st edition pertained to an older version of Ruby (version 1.6), some problems of which have been fixed in the meantime. retry, for example, now works with while, until, and for, as well as iterators.
The following examples can be run in a Ruby shell such as Interactive Ruby Shell or saved in a file and run from the command line by typing ruby
Classic Hello world example:
Some basic Ruby code:
-199.abs # 199 "ruby is cool".length # 12 "Rick".index("c") # 2 "Nice Day Isn\'t It?".downcase.split(//).sort.uniq.join # " \'?acdeinsty"
Conversions:
There are a variety of methods of defining strings in Ruby
The below conventions are equivalent for double quoted strings:
The below conventions are equivalent for single quoted strings:
Constructing and using an array:
a[2] # 3.14 a.reverse # [[4, 5], 2, 1, 3.14, \'hi\', 1] a.flatten.uniq # [1, \'hi\', 3.14, 2, 4, 5]
Constructing and using a hash:
hash.each_pair do |key, value| # Or: hash.each do |key, value| puts "#{key} is #{value}" end
hash.delete_if {|key, value| key == :water} # Deletes :water => \'wet\'
The two syntaxes for creating a code block:
do puts "Hello, World!" end
Parameter-passing a block to be a closure:
def remember(&a_block) @block = a_block end
remember {|name| puts "Hello, #{name}!"}
@block.call("Jon")
Returning closures from a method:
setter, getter = create_set_and_get # ie. returns two values setter.call(21) getter.call # => 21
Yielding the flow of program control to a block which was provided at calling time:
use_hello {|string| puts string} # => \'hello\'
Iterating over enumerations and arrays using blocks:
array.each_index { |index| puts index.to_s + ": " + array[index] }
(3..6).each { |num| puts num }
A method such as inject() can accept both a parameter and a block. Inject iterates over each member of a list, performing some function on while retaining an aggregate. This is analogous to the foldl function in functional programming languages. For example:
On the first pass, the block receives 10 (the argument to inject) as sum, and 1 (the first element of the array) as element; this returns 11. 11 then becomes sum on the next pass, which is added to 3 to get 14. 14 is then added to 5, to finally return 19.
Blocks work with many built-in methods:
File.readlines(\'file.txt\').each do |line| puts line end
Using an enumeration and a block to square the numbers 1 to 10:
The following code defines a class named Person. In addition to \'initialize\', the usual constructor to create new objects, it has two methods: one to override the <=> comparison operator (so Array#sort can sort by age) and the other to override the to_s method (so Kernel#puts can format its output). Here, "attr_reader" is an example of metaprogramming in Ruby: "attr_accessor" defines getter and setter methods of instance variables, "attr_reader" only getter methods. Also, the last evaluated statement in a method is its return value, allowing the omission of an explicit \'return\'.
group = [ Person.new("Jon", 20), Person.new("Marcus", 63), Person.new("Ash", 16) ]
puts group.sort.reverse
The above prints three names in reverse age order:
An exception is raised with a raise call:
An optional message can be added to the exception:
You can also specify which type of exception you want to raise:
Alternatively, you can pass an exception instance to the raise method:
This last constuct is useful when you need to raise a custom exception class featuring a constructor which takes more than one argument:
def initialize input, line, pos
super "Could not parse \'#{input}\' at line #{line}, position #{pos}"
end
end
raise ParseError.new( "Foo", 3, 9 )
Exceptions are handled by the rescue clause. Such a clause can catch exceptions which inherit from StandardError:
rescue
end
It is a common mistake to attempt to catch all exceptions with a simple rescue clause. To catch all exceptions one must write:
rescue Exception # don\'t write just rescue -- this only catches StandardError, a subclass of Exception
end
Or catch particular exceptions:
rescue RuntimeError
end
It is also possible to specify that the exception object be made available to the handler clause:
rescue RuntimeError => e
end
Alternatively, the most recent exception is stored in the magic global $!.
You can also catch several exceptions:
rescue RuntimeError, Timeout::Error => e
end
Or catch an array of exceptions:
rescue *array_of_exceptions => e
end
More sample Ruby code is available as algorithms in the following articles:
Ruby has two main implementations: The official Ruby interpreter often referred to as the Matz\'s Ruby Interpreter (MRI), which is the most widely used, and JRuby, a Java-based implementation.
There are other less known implementations such as IronRuby (pre-alpha sources available on August 31st, 2007John Lam. IronRuby on Rubyforge!. Retrieved on 2007-08-31.), Rubinius, Ruby.NET, XRuby and YARV. YARV is Ruby 1.9\'s official new virtual machine and is no longer a separate project.
Ruby is available for the following operating systems:
Other ports may also exist.
The Ruby interpreter and libraries are distributed disjointedly (dual licensed) under the free and open source licenses GPL and Ruby License Ruby License (ruby-lang.org).
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This section needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (February 2008) |
class Car
attr_reader :car_brand
attr_reader :car_hps
def initialize(driver)
@car_brand = "Fiat"
@car_hps = 70
if driver == "Schumi" then
@carbrand="Ferrari"
@car_hps = 600
end
end
end c = Car.new("Schumi")
class Car
attr_reader :car_brand attr_reader :car_hps
def initialize(driver)
@car_brand, @car_hps = case driver
when "Schumi"
[ "Ferrari", 600 ]
else
[ "Fiat", 70 ]
end
end
end c = Car.new("Schumi")
Version 1.8, the current stable version of the interpreter, has some limitations, which include:
Ruby 2.0 aims to address all of the aforementioned problems:
Version 1.9, the codebase which is considered the development version of 2.0, which was released on 26 December 2007 added unicode support and significantly improved performance over 1.8.
Some problems which may not be solved in version 2.0 include:
The Ruby Application Archive (RAA), as well as RubyForge, serve as repositories for a wide range of Ruby applications and libraries, containing more than two thousand items. Although the number of applications available does not match the volume of material available in the Perl or Python community, there are a wide range of tools and utilities which serve to foster further development in the language.
RubyGems has become the standard package manager for Ruby libraries. It is very similar in purpose to Perl\'s CPAN, although its usage is more like apt-get.
| | Free software Portal |
Wikibooks has a book on the topic of
At Wikiversity, you can learn about:
| Ruby programming language | |
|---|---|
| Interpreters | ERuby · Hackety Hack · Interactive Ruby Shell · IronRuby · JRuby · XRuby · Rubinius · Mod ruby · Mongrel · Rinda · SketchUp Ruby · YARV |
| Libraries | Camping · Cerise · IOWA · Merb · Nitro · Ramaze · RubyGems · Ruby on Rails · WEBrick |
| Development-related | RadRails · Rake · Capistrano · Ruby Application Archive · Ruby Central · Ruby Document format · RubyForge · Why\'s (poignant) Guide to Ruby |
This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia
