New to this language

ruby-talk
1

Hi,

I am completely new to this language. I am trying to learn it on my own
by reading the book available online. I wanted to type some code and
test it while I was learning.

I was wondering if someone could answer the following questions that
would help me get started on writing some small amount of code testing
it myself.

1) Just like in C++ you have a .h and a .cpp file , In this language how
would you store your file. In other words if I open emacs and want to
write a very simple small class in what format would I save this file ?

2) How do you compile your code? What is the syntax?

3) Do you need a main and a makefile ? I am sure you would need a main
to test it . If yes how do you save the main? In what format?

These questions may seem really stupid, but I have no idea about this
language. I have a little knowledge of C and Java, but not ruby.

Any help is appreciated,

Thanks in advance,

Vidhi.

2

Vidhi,

Welcome to Ruby.

1) Just like in C++ you have a .h and a .cpp file , In this language how
would you store your file. In other words if I open emacs and want to
write a very simple small class in what format would I save this file ?

You store all your code in .rb files. There is no separate header file. You declare and define a class in one place, just like in Java. (That's not strictly true; in Ruby you can "re-open" a class and add more methods later. Don't worry about that yet.)

superclass.rb:

  class Superclass
    attr_accessor :super_instance_var
    def initialize
      @super_instance_var = 42
    end
  end

myclass.rb

  require 'superclass'

  class MyClass < Superclass
    attr_accessor :my_instance_var
    def initialize
      @my_instance_var = 'hello'
    end
  end

another.rb

  require 'myclass'

  mc = MyClass.new
  puts mc.my_instance_var
  puts mc.super_instance_var

2) How do you compile your code? What is the syntax?

Ruby is an interpreted language, which means that it doesn't need to be compiled before you run it. To run "another.rb" above, type

  ruby another.rb

3) Do you need a main and a makefile ? I am sure you would need a main
to test it . If yes how do you save the main? In what format?

You don't need a main method. All Ruby code is executed as it is seen by the interpreter. Some of the code above (superclass.rb and myclass.rb) define classes and some of the code (another.rb) creates an instance of a class and prints some output.

I hope this helps.

Jim

···

--
Jim Menard, jimm@io.com, http://www.io.com/~jimm

3

Hi,

Ghelani, Vidhi, 11/2/2005 14:01:

1) Just like in C++ you have a .h and a .cpp file , In this language how
would you store your file. In other words if I open emacs and want to
write a very simple small class in what format would I save this file ?

.rb

2) How do you compile your code? What is the syntax?

Ruby is not compiled, it's interpreted. To run a file you can use 'ruby foo.rb', when 'foo' is the name of your file.

3) Do you need a main and a makefile ? I am sure you would need a main
to test it . If yes how do you save the main? In what format?

You don't need a main either a makefile.

4

Hi,

Hello.

I am completely new to this language. I am trying to learn it on my own
by reading the book available online. I wanted to type some code and
test it while I was learning.

Welcome to Ruby.

I was wondering if someone could answer the following questions that
would help me get started on writing some small amount of code testing
it myself.

I'll sure try...

1) Just like in C++ you have a .h and a .cpp file , In this language how
would you store your file. In other words if I open emacs and want to
write a very simple small class in what format would I save this file ?

Ruby reads plain text files. It you make a test file that's full of Ruby code, you're good to go.

The traditional extension for these files is .rb, but I don't think Ruby really cares. Extensions are mainly used to support Windows and give hints to various editors/IDEs.

Unix (and Mac OS X) cares more about the "shebang" line. The first line of a Unix script is often a "sharp" (#), followed by a "bang" (!), followed by the path to Ruby. Unix uses this when the file is executed to determine what to run it with. Here's the shebang line for my Mac OS X install:

#!/usr/local/bin/ruby

A lot of people prefer:

#!/usr/bin/env ruby

That shebang can often find the right Ruby to run on differing systems.

Again, Ruby itself doesn't much care, but this is support Unix.

So, we can combine those practices to create pretty standard Ruby source that should work in most places. Here's the famous "Hello World" example, which you could save in something like "hello.rb":

#!/usr/bin/env ruby

puts "Hello world!"

__END__

2) How do you compile your code? What is the syntax?

Ruby does away with that icky "compile" step. Just run your code:

% ruby hello.rb

Better, run your code with warnings turned on, so Ruby can help you find bugs:

% ruby -w hello.rb

3) Do you need a main and a makefile ? I am sure you would need a main
to test it . If yes how do you save the main? In what format?

In Ruby, "main" is the code that appears outside methods. Just put it in your file and it will be run.

These questions may seem really stupid, but I have no idea about this
language. I have a little knowledge of C and Java, but not ruby.

Again, welcome and just shout if we can be of more help.

James Edward Gray II

···

On Feb 11, 2005, at 11:01 AM, Ghelani, Vidhi wrote:

5

If you've not seen these yet, you may want to check them out:

http://ruby-forum.org/bb/index.php

more here:

···

On Sat, 12 Feb 2005 02:01:31 +0900, Ghelani, Vidhi <vidhi.ghelani@intel.com> wrote:

Hi,

I am completely new to this language. I am trying to learn it on my own
by reading the book available online.

--
Bill Guindon (aka aGorilla)

6

Hi,

> 3) Do you need a main and a makefile ? I am sure you would need a main
> to test it . If yes how do you save the main? In what format?

You don't need a main method. All Ruby code is executed as it is seen by the
interpreter. Some of the code above (superclass.rb and myclass.rb) define
classes and some of the code (another.rb) creates an instance of a class and
prints some output.

Else, you can use

if __FILE__ == $0
  p 'Hello World!'
end

In any file so the code in the if-block will be executed only if the
file is being run directly by the interpreter (e.g.: ruby
hello_world.rb). It's useful so you can have a file that behaves like
a library and a program, depending on how it's loaded. You load a
library with the require (or load) command (e.g.: require 'open-uri').

I like to use such capability to test one or another thing in a file
while I'm working on it.

Welcome to Ruby.

Cheers,
Joao

7

one thing I want to add, is that you need not create a seperate file per class. You can as well group classes by functionality and put multiple classes in one file. (I think using one file per class is a java idiom).

first.rb
class Greet
  def initialize(name)
    @name = name
  end
end

class GreetEnglish < Greet
  def greetme
    puts "Hello #{name}"
  end
end

class GreetGerman < Greet
  def greetme
    puts "Hallo #{name}"
  end
end

class GreetSpanish < Greet
  def greetme
    puts "Hola #{name}"
  end
end

greeters = [GreetEnglish, GreetGerman, GreetSpanish]
greeter = greeters[rand(greeters.length)].new
greeter.greet

is perfectly reasonable and allowed. (Though maybe not two good design, and you can shorten this alot when you have learned about dynamic programming).

And additionally, if you want to play with the language use irb, the ruby interactive shell.

good luck and enjoy ruby,

Brian

···

On Sat, 12 Feb 2005 02:15:18 +0900 Jim Menard <jimm@io.com> wrote:

Vidhi,

Welcome to Ruby.

> 1) Just like in C++ you have a .h and a .cpp file , In this language how
> would you store your file. In other words if I open emacs and want to
> write a very simple small class in what format would I save this file ?

You store all your code in .rb files. There is no separate header file. You
declare and define a class in one place, just like in Java. (That's not
strictly true; in Ruby you can "re-open" a class and add more methods later.
Don't worry about that yet.)

superclass.rb:

  class Superclass
    attr_accessor :super_instance_var
    def initialize
      @super_instance_var = 42
    end
  end

myclass.rb

  require 'superclass'

  class MyClass < Superclass
    attr_accessor :my_instance_var
    def initialize
      @my_instance_var = 'hello'
    end
  end

another.rb

  require 'myclass'

  mc = MyClass.new
  puts mc.my_instance_var
  puts mc.super_instance_var

> 2) How do you compile your code? What is the syntax?

Ruby is an interpreted language, which means that it doesn't need to be
compiled before you run it. To run "another.rb" above, type

  ruby another.rb

> 3) Do you need a main and a makefile ? I am sure you would need a main
> to test it . If yes how do you save the main? In what format?

You don't need a main method. All Ruby code is executed as it is seen by the
interpreter. Some of the code above (superclass.rb and myclass.rb) define
classes and some of the code (another.rb) creates an instance of a class and
prints some output.

8

Bill Guindon wrote:

···

On Sat, 12 Feb 2005 02:01:31 +0900, Ghelani, Vidhi > <vidhi.ghelani@intel.com> wrote:

Hi,

I am completely new to this language. I am trying to learn it on my own
by reading the book available online.

If you've not seen these yet, you may want to check them out:

Ruby | zenspider.com | by ryan davis
http://www.rubygarden.org/ruby?HomePage
http://ruby-forum.org/bb/index.php

more here:
http://www.rubygarden.org/ruby?RubyOnTheNet

Thanks for those links. I'm also new to the language, so they were very
helpful. Especially the Zen Spider one.

-Chris

9

Hi Vidhi:

  You mentioned being only somewhat familiar with
C++/Java, but what Joao mentioned, is basically the
functional equivalent of a main() in a Java class.
This allows you to run the file by itself, i.e. ruby
file.rb, and allow you to easily reuse the contents in
another file, i.e.

(hello.rb)
def hello
  puts "hello"
end

if $0 == __FILE__
  hello
end

so you run it and you get

ruby hello.rb

hello

Compilation finished at Fri Feb 11 09:58:52

so now you want to reuse the contents of hello.rb
(beatles.rb)
require "hello"

def song_chorus
  hello
  puts "goodbye"
end
if $0 == __FILE__
  song_chorus
end

you run this file and get a

hello
goodbye

  Hope this helps.

Forrest

···

--- Joao Pedrosa <joaopedrosa@gmail.com> wrote:

Hi,

> > 3) Do you need a main and a makefile ? I am sure
you would need a main
> > to test it . If yes how do you save the main? In
what format?
>
> You don't need a main method. All Ruby code is
executed as it is seen by the
> interpreter. Some of the code above (superclass.rb
and myclass.rb) define
> classes and some of the code (another.rb) creates
an instance of a class and
> prints some output.

Else, you can use

if __FILE__ == $0
  p 'Hello World!'
end

In any file so the code in the if-block will be
executed only if the
file is being run directly by the interpreter (e.g.:
ruby
hello_world.rb). It's useful so you can have a file
that behaves like
a library and a program, depending on how it's
loaded. You load a
library with the require (or load) command (e.g.:
require 'open-uri').

I like to use such capability to test one or another
thing in a file
while I'm working on it.

Welcome to Ruby.

Cheers,
Joao

10

Here's a great link that is not published much but has a ton of code examples that I found very useful:
  PLEAC-Ruby
-Ezra

···

On Feb 11, 2005, at 2:55 PM, Chris Ruzin wrote:

Bill Guindon wrote:

On Sat, 12 Feb 2005 02:01:31 +0900, Ghelani, Vidhi >> <vidhi.ghelani@intel.com> wrote:

Hi,

I am completely new to this language. I am trying to learn it on my own
by reading the book available online.

If you've not seen these yet, you may want to check them out:

Ruby | zenspider.com | by ryan davis
Captcha
http://ruby-forum.org/bb/index.php

more here:
Captcha

Thanks for those links. I'm also new to the language, so they were very
helpful. Especially the Zen Spider one.

-Chris

-Ezra Zygmuntowicz
Yakima Herald-Republic
WebMaster
509-577-7732
ezra@yakima-herald.com