Ruby Programming Language

Ruby Programming Language

Jonathan Gertig

CSC 415: Programming Languages

Dr. Lyle

November 20, 2012

Ruby Programming Language

The History of Ruby and The Creation of Rails

“I hope to see Ruby help every programmer in the world to be productive, and to enjoy programming, and to be happy. That is the primary purpose of Ruby language.”

- Yukihiro Matsumoto 2008 Google Tech Talk on Ruby 1.9

The Metasomatism (process by which rubies are formed)

February 24, 1993 is the day that Ruby began forming. The creator Yukihiro Matsumoto stated in 2001, during an interview with Bruce Stewart, that at the time he had just become very interested in scripting languages and wanted to find one that had object oriented aspects. He explained that he began his search by looking into the still beta Perl 5 which was to showcase new object oriented features, but sadly he was nun too impressed. He moved onto Python and was impressed with its objected oriented nature and interpretive design, but it had too many notes of procedural programming and just did not feel like it was a scripting language. Matsumoto related that he had decided on wanting “a scripting language more powerful than Perl, and more object-oriented than Python.” This is how Ruby was born. The name Ruby itself was just an idea one of Matsumoto's friend's had based on the fact that Ruby itself is based in large part off of Pearl which is another type of precious stone.

The Cutting and Forming

Ruby was first publicly released December 21st, 1995 in its beta 0.95 form. Ruby 1.0 was released Christmas day 1996. September 22nd, 1997 Matsumoto is hired to work full time on his once pet project. Ruby 1.9 was released December 2007 with the latest stable build at version 1.9.3. As of October 25th of this year the Ruby core team have announced a 'feature freeze' meaning that all features under-development for 2.0.0 that have not already been approved by Matz will not make it in.

The Age of Rails

Rails came about from the work that David Heinemeier Hansson did on Basecamp. Hansson first released this full-stack web application framework for Ruby, open source in July of 2004. Rails is a Model-View-Controller frame work built on the Active record pattern as well. Since the release of Rails, Ruby which in and of it self is a general purpose programing language, has gained a resurgence in popularity as a great option for agile and scalable web applications.

Data Types

“I believe people want to express themselves when they program. They don't want to fight with the language. Programming languages must feel natural to programmers.”

- Yukihiro Matsumoto

Standard Types

Ruby does not work in the standard coding format of naming the variable type first, if it is of the standard data types it does not need to be named at all and therefore has a format of variable name = data, for example Name = “Jon” or a = 0;

Numbers

The standard types in ruby are numbers, strings, ranges, arrays, and hashes. All programing languages deal with numbers that is how computers work. Ruby works in such a way that numbers can be up to any length as long as there is memory space. With in the ranges of -2*pow(30) to 2*pow(30)-1 or -2*pow(62) to 2*pow(62)-1 they are held as binary internally and are of object type Fixnum but outside of these ranges they are of object type Bignum. Ruby is one of few languages to have native support for big numbers. Ruby also has native support for octal, hex, and binary formats the only change required is a leading sign for octal a 0 will precede the number for instance the number 0377 would be understood to be 225 in octal. 0D is used for decimal but is default so is not necessary, 0x is for hex and 0b is for binary. Any numeric literal with a decimal point is assigned to object type Float

Strings

Ruby strings are just basically a sequence of 8-bit bytes. The escape literals for a single quoted string, which you can use %q// to denote, are “\” and “\'”. Double quoted strings, which you can use %Q!! to denote, have a huge amount of escape literals, most notably would be “#{}” because it allows you to place any ruby code with in the string. This is in my opinion so much better then having to concatenate the string to add in a word dynamically. Even if the speed may be the same the syntax is better. You can also construct a string with what is known as a here document which would look like varName <End_of_String

anything here

and here

End_of_String

Ranges

A range in ruby is a range object with two references to Fixnum objects this is different to how Pearl stores ranges as lists. Ranges can be used as sequences, conditions, or intervals. A range being used as a sequence is the most basic use of ranges and allows you even to have a sequence of custom objects. You can test if an object, number, string, or whatever else is within the range by using “===”.

Arrays & Hashes

I combined arrays and hashes sections because in Ruby and most languages they are the same thing but only differ in the key access type. Arrays use integers as the index location but hashes are built to allow any object as a key.

Abstract Types

Ruby's abstract data types unlike Ada or many other languages have gone like the tide of object-oriented languages. That is there are no direct abstract data types in Ruby what you will need to do is create an object to describe your new data type.

Control Structures

There are all the basic control structures in Ruby as there are in other languages. Ruby has if, while, for, try-catch. All Ruby structures require “end” to end the block of code. This in my sight is a down fall for Ruby it is syntactically easier to learn because of it but it does not feel like it is a proper closing method.

Classes and Working with Objects

Classes

Classes in Ruby are similar to those of Java and C# in that Ruby classes can only have one superclass. This method is strong and simple but having only one superclass is a problem because real world objects may inherit attributes from many sources. Ruby has dealt with this issue by what are called mix-ins or modules. Ruby classes allow for global variables with in classes, these variables are not instance variables and are indicated by @@ before the name of the variable. Ruby classes like all object-oriented languages have class methods, or methods that are available out side of an object from that class such as a File.delete() method.

Modules

Modules in Ruby are versatile and useful entities. One of the major uses is as a package or library of methods that can be used by classes and be completely independent from them. The second use is as a mix-in or as an additional superclass allowing the class to access methods within the module. This allows for pieces of code that are heavily used to be passed around easily. Classes can access a module by using the include tag be for the name of the module.

Concurrency and Multithreading

Multithreading

Threads in Ruby are completely portable this is because they are totally implemented with in the Ruby interpreter. This like Java means that only one core will be used for processing and that there is a likelihood of thread starvation. Threads in ruby work by creating a new tread function and give it a block of code to run such as this example.

threads = []

6.times do |number|

threads < Thread.new(number) do |i|

raise "Boom!" if i == 2

raise "Wam!" if i == 4

print "#{i}\n"

end

end

threads.each do |t|

begin

t.join

rescue RuntimeError => e

puts "Failed: #{e.message}"

end

end

Event Handling

Nativity in Ruby no event handling exists.

Error Handling

Error Catching

When catching errors I ruby you use a begin … end block of code in which you tell Ruby what exceptions you want to deal with by using the rescue tag which is a catch statement for exceptions. After the rescue tag you can place any number of errors then the code to run on the case of that exception happening. You can have as many rescue tags in a begin … end block as you need. If you think that you code has fixed the error you may have have it retry. If you know your code may not fix the error you are having you can raise the error again which passes the exception up a level in the stack.

@esmtp = true

begin

if @esmtp then

@command.ehlo(helodom)

else

@command.helo(helodom)

end

rescue ProtocolError

if @esmtp then

@esmtp = false

retry

else

raise

end

end

In this case the person is attempting to login to a SMTP server with one of two ways, the first being ehlo. This code tries first to connect using the EHLO but if a protocol error is received it switches to the HELO command but if that does not work it re-raises the exception.

Error Raising

The Kernal.raise command is able to do more than reraise an exception because it is able to take parameters to be raise.

raise “matix out of bounds”

Is a command that would raise a run time error with “matrix out of bounds” as the error text. You can all so name the exception or even create a new error class.

class MatrixException < RuntimeError

end

raise MatrixException “matix out of bounds”

Then there is the catch … throw block. Catch … throw works by naming a variable that if thrown all of the commands placed on the control stack after the catch line

are removed from the stack and the block is exited without executing any of the commands.

catch (:done)

while line = gets

throw :done unless fields = line.split(/\t/)

Itemlist.add(Item.new(*fields))

end

Itemlist.run()

end

With this example in the line is not formatted correctly it will trow out all progress it made and exit the block without running Itemlist.run().

Rails

Commands

Rails comes pack loaded with neat and easy commands that you can run to get you off you feet. For example here is how to start a new project with a basic database and getting it running on the local server:

>rails new appName

>cd appName

>Rails generate scaffold User Name:string Birth_Day:Date

>rake db:migrate

>Rails Server

That easy! It generates all the needed files and connections for you and even sets up the routing for you. Many of the commands even have short hand notation such as the server command:

>Rails s

Or the scaffold:

>Rails g s User Name:string Birth_Day:Date

Of course for each generate command there is a destroy command.

Model-View-Controller

There are three main files that need to be edited when working with Ruby on rails the Model the View and the Controller. The Model file is used mostly for the interconnection of database models. The Controller file is the main class file where all the functions and subroutines go. The View is the HTML file that is seen in correlation to the Model it is most likely named after.

Readability

Ruby has great readability the control structures are clearly defined and understandable. Where readability may come into question is anytime when dealing with regular expressions because trying to understand a regular expression with out knowledge is like trying to read an alien language. Ruby is almost like reading a story book.

Writability

Writing Ruby code is very simple to learn there are not very many intricacies in syntax. One of Matsumoto's goals was to make programmers easily productive using Ruby and he did that very well.

Reliability

The Ruby programing language is only as reliable as the system it is running on. Ruby is a bit slow at time when it come to multithreaded or multicored applications. Ruby in an of itself is a very reliable language but Rails is still moving rapidly through the evolution of what it will become.

Cost

If you are learning Ruby as your first language I would say there is a slight learning curve with Ruby which has mainly to do with routing and where to put what in files. I would give learning Ruby as a first language about half a month to be putting out functioning web applications, but if this is not your first language I would say tops a week. In the modern work place you can learn a new language better with practice and google to find the answer to questions. There are elements used by the Ruby language that are not implicitly a part of the language that may take some more time other than what I have suggested.

Citations

Tomas, Dave. Programming Ruby. 2nd. Dallas: The Pragmatic Bookshelf, 2005. eBook

Matsumoto, Yukihiro. Ruby in a Nutshell. Chicago: O'Reilly Media, 2001. eBook.

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