Ruby Simplified Part 3: Ruby conditional statements

Let’s look at some conditional statements in Ruby, if-else, case, and unless.

=begin
A simple program to test user input,
notice that this comment is multiline
=end

# If-Else statement
puts "Please input number..."
x = gets        # Get user input
x = x.chomp     # Chop off the '\n' at the end
x = x.to_i      # convert the string into an integer

if (x < 0) 
    puts "user input " + x.to_s + " is negative"    # convert integer into string with .to_s
elsif (x == 0)
    puts "user input " + x.to_s + " is zero"
else
    puts "user input " + x.to_s + " is positive"
end

# The 'if' modifier
puts "Writes this line only if x is 1" if x == 1

# Case statement
puts "Please input another number..."
x = gets.chomp.to_i     # Notice how we shorten the operations

case
    when x < 0 
        puts "user input " + x.to_s + " is negative" 
    when x == 0
        puts "user input " + x.to_s + " is zero"
    when x > 0
        puts "user input " + x.to_s + " is positive"
end

# Unless statement
puts "Please input another number..."
x = gets.chomp.to_i

unless x > 0        # The equivalent of 'unless' is the if(!...) in C#
    unless x == 0
        puts "user input " + x.to_s + " is negative"
    else
        puts "user input " + x.to_s + " is zero"
    end
else
    puts "user input " + x.to_s + " is positive"
end

# Unless conditional
puts "Write this line unless x is 0, meaning, if x is 0 then don’t write this line" unless x == 0

# Anything inside 'BEGIN' is called before the program is run
BEGIN { puts "Simple program to test user input." }

# Anything inside 'END' is called after the program is run
END { puts "All done!" }

Ruby Simplified Part 2: Major language features

Some features of the Ruby programming language, comparing them with C#,

1. Ruby is a dynamically typed programming language.
    C# got dynamic extensions to the language in C# 4.0

2. Ruby is open source. Not only is it free of charge, but also free to use, copy, modify, and distribute.
    C# is not open source, for an open source implementation of the ECMA standards for C#, see the Mono Project.

3. Ruby was designed as an interpreted language. The first Ruby interpreter (MRI) was written in C and was a single pass interpreter. The current official interpreter (YARV), however, compiles Ruby into something called ‘YARV Instruction Sequence’, which is then compiled just-in-time (JIT) to assembly language. There are several other implementations of Ruby (ex., JRuby, IronRuby, and MacRuby) which also compile the Ruby code in a two step process to machine language.
    C# also has a two-step process, it’s first compiled into an intermediate language (IL) by the C# compiler and then JIT compiled to machine language by the CLR.

4. Ruby is a pure object oriented language. In Ruby everything is an object. You can append .class to anything to get the class name. Type puts 1.class (you’ll get ‘Fixnum’).
    In C#, not everything is a object (numbers, structs, etc.)

5. Ruby has automatic memory management.
    C# also has a full fledged garbage collector.

6. Ruby supports single inheritance only. Although we’ll see how to implement multiple inheritance using modules/mixins.
    C# also supports single inheritance only. Multiple inheritance in C# is implemented using interfaces.

7. Ruby has modern exception handling features (using begin-rescue-ensure).
    C# equivalent of this is the try-catch-finally blocks.

Ruby Simplified Part 1: Installing Ruby on Windows

Install the current version of Ruby (2.0.0-p247) using the Ruby Installer. During installing choose the options below, and finish the installation process.

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Now if you go to the C:\Ruby folder, you’ll see,

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Open up a command prompt, and type ruby –v,

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We’ve successfully installed the current version! To get help with more Ruby commands use ruby –h.

Now let’s try out “Hello World” in Ruby. Type ‘irb’ at the command prompt to get the Interactive Ruby Shell – it’s a command line for Ruby. Then use puts to output a string.

image

To run a ruby file, create a file ‘hello.rb’,

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Now execute the file with ruby hello.rb,

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Ruby Simplified Series

Ruby has become a very popular programming language because of it’s simplicity and productivity. In this series we’ll explore some of the syntax and features of the Ruby programming language.

Ruby Simplified Part 1: Installing Ruby on Windows

Ruby Simplified Part 2: Major language features