class Calculator
    def initialize
        @history = []
    end

    def add(a, b)
        result = a + b
        @history << "#{a} + #{b} = #{result}"
        result
    end

    def multiply(a, b)
        result = a * b
        @history << "#{a} * #{b} = #{result}"
        result
    end

    def history
        @history.each_with_index do |operation, index|
        puts "#{index + 1}. #{operation}"
        end
    end
end

# Array operations with blocks
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

even_numbers = numbers.select { |n| n.even? }
squares = numbers.map { |n| n ** 2 }
sum = numbers.reduce(0) { |acc, n| acc + n }

puts "Even numbers: #{even_numbers}"
puts "Squares: #{squares}"
puts "Sum: #{sum}"

# Calculator usage
calc = Calculator.new
calc.add(5, 3)
calc.multiply(4, 6)
calc.history

Demonstrates Ruby's elegant syntax with blocks, classes, and enumerable methods.

class Animal
    def speak
        "Generic animal sound"
    end
end

class Dog < Animal
    def speak
        "Woof!"
    end
end

class Cat < Animal
    def speak
        "Meow!"
    end
end

animals = [Dog.new, Cat.new, Animal.new]

animals.each do |animal|
    puts animal.speak
end

Shows how Ruby supports inheritance and method overriding in object-oriented programming.

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

class Person
    include Greetable
end

class Robot
    include Greetable
end

p1 = Person.new
r1 = Robot.new

puts p1.greet("Alice")
puts r1.greet("R2D2")

Demonstrates Ruby's use of modules for reusable functionality and multiple inheritance.

File.open("example.txt", "w") do |file|
    file.puts "This is a sample text file."
    file.puts "Written with Ruby!"
end

puts "File written successfully."

puts "Reading file contents:"
File.readlines("example.txt").each_with_index do |line, index|
    puts "#{index + 1}: #{line.strip}"
end

Shows how to read and write files in Ruby safely using blocks.

def divide(a, b)
    begin
        result = a / b
        puts "Result: #{result}"
    rescue ZeroDivisionError => e
        puts "Error: Division by zero!"
    ensure
        puts "Division attempt finished."
    end
end

divide(10, 2)
divide(5, 0)

Demonstrates the use of begin-rescue-ensure for robust error handling in Ruby.

person = {
    name: "Alice",
    age: 25,
    city: "Kathmandu"
}

person.each do |key, value|
    puts "#{key.capitalize}: #{value}"
end

puts "Name in uppercase: #{person[:name].upcase}"

Shows how to create and iterate through hashes using Ruby's symbol keys.

text = "Contact us at support@example.com or visit our website."

email_pattern = /\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z]{2,}\b/i

if text.match?(email_pattern)
    puts "Email found!"
    puts text.scan(email_pattern)
else
    puts "No email found."
end

Explores Ruby's powerful regex features for pattern matching and text parsing.

numbers = (1..10).to_a

evens = numbers.select { |n| n.even? }
squares = numbers.map { |n| n ** 2 }
sum = numbers.reduce(:+)

puts "Even numbers: #{evens}"
puts "Squares: #{squares}"
puts "Sum: #{sum}"

Demonstrates functional programming style using map, select, and reduce on Ruby collections.

require 'json'

data = {
    name: "Saurav",
    age: 22,
    skills: ["Ruby", "JavaScript", "Flutter"]
}

json_str = JSON.pretty_generate(data)
puts "JSON Output:"
puts json_str

parsed = JSON.parse(json_str)
puts "Parsed Name: #{parsed['name']}"

Shows how to work with JSON data using Ruby's built-in JSON module.

require 'date'

now = Time.now
puts "Current time: #{now}"
puts "Formatted: #{now.strftime("%A, %d %B %Y %I:%M %p")}"

birthday = Date.new(2000, 5, 12)
age = ((Date.today - birthday).to_i / 365.25).floor
puts "Age based on DOB #{birthday}: #{age} years"

Illustrates Ruby's Time and Date manipulation for formatting and calculation.