Pros of JRuby

• Runs on the Java Virtual Machine (JVM), allowing integration with Java libraries and frameworks
• Often provides better performance for long-running processes and multi-threaded applications
• Offers true parallelism through JVM threads, unlike MRI Ruby's Global Interpreter Lock (GIL)

Cons of JRuby

• Slower startup time compared to MRI Ruby due to JVM initialization
• Some Ruby gems may not be compatible or require special handling
• Occasional differences in behavior or feature implementation compared to MRI Ruby

Code Comparison

Ruby (MRI):

# Concurrency example
threads = 5.times.map do
  Thread.new { puts "Hello from thread #{Thread.current.object_id}" }
end
threads.each(&:join)

JRuby:

# Concurrency example with true parallelism
threads = 5.times.map do
  java.lang.Thread.new { puts "Hello from thread #{java.lang.Thread.currentThread.getId}" }
end
threads.each(&:join)

In this example, JRuby can leverage true parallelism through Java threads, potentially offering better performance for concurrent operations compared to MRI Ruby's GIL-limited threads.

Pros of mruby

• Lightweight and embeddable, ideal for resource-constrained environments
• Designed for easy integration into C programs
• Faster startup time and lower memory footprint

Cons of mruby

• Limited standard library compared to Ruby
• Not all Ruby gems are compatible with mruby
• Fewer language features and optimizations

Code Comparison

Ruby:

# Ruby example
class Greeter
  def initialize(name)
    @name = name
  end

  def greet
    puts "Hello, #{@name}!"
  end
end

Greeter.new("World").greet

mruby:

# mruby example
class Greeter
  def initialize(name)
    @name = name
  end

  def greet
    puts "Hello, #{@name}!"
  end
end

Greeter.new("World").greet

The basic syntax and structure are identical in this simple example. However, mruby may have limitations with more complex Ruby features or certain standard library methods.

Summary

Ruby is a full-featured, general-purpose programming language, while mruby is a lightweight implementation designed for embedding. mruby sacrifices some features and compatibility for a smaller footprint and easier integration with C programs. The choice between the two depends on the specific requirements of your project, such as resource constraints, embedding needs, and required language features.

Pros of Opal

• Allows running Ruby code in web browsers
• Enables Ruby developers to write front-end code without learning JavaScript
• Smaller community size may lead to faster decision-making and implementation of new features

Cons of Opal

• Limited compatibility with Ruby's standard library and some gems
• Performance may be slower than native JavaScript for complex operations
• Smaller ecosystem and community support compared to Ruby

Code Comparison

Ruby:

def greet(name)
  puts "Hello, #{name}!"
end

greet("World")

Opal:

def greet(name)
  `console.log("Hello, " + #{name} + "!")`
end

greet("World")

The main difference in this example is that Opal uses backticks to directly interact with JavaScript's console.log function, while Ruby uses the native puts method for output. This demonstrates how Opal bridges Ruby syntax with JavaScript functionality for browser-based execution.

Both Ruby and Opal aim to provide a developer-friendly language experience, but they serve different purposes. Ruby is a general-purpose language with a wide range of applications, while Opal focuses on bringing Ruby-like syntax to web development, allowing developers to write Ruby code that compiles to JavaScript for browser execution.

Pros of Crystal

• Significantly faster execution speed due to compilation to native code
• Static typing for improved type safety and earlier error detection
• Syntax very similar to Ruby, making it easy for Ruby developers to transition

Cons of Crystal

• Smaller ecosystem with fewer libraries and tools compared to Ruby
• Less mature and stable, with potential for breaking changes
• Limited platform support, primarily focused on Unix-like systems

Code Comparison

Ruby:

def fibonacci(n)
  return n if n <= 1
  fibonacci(n - 1) + fibonacci(n - 2)
end

puts fibonacci(10)

Crystal:

def fibonacci(n : Int32) : Int32
  return n if n <= 1
  fibonacci(n - 1) + fibonacci(n - 2)
end

puts fibonacci(10)

The Crystal version includes type annotations for improved performance and safety, while maintaining a nearly identical syntax to Ruby. This demonstrates Crystal's goal of being a statically-typed language with Ruby-like syntax, offering potential performance benefits while remaining familiar to Ruby developers.