How can you debug code without using a debugger?

Main methods of debugging without a debugger:

• Using puts to output intermediate variable values and program flow.
• Logging to a file using the standard Logger library.
• Applying methods that output information about an object, such as #inspect or #p.
• Using exceptions to check certain conditions or program states.
• Reading stack trace messages when errors occur.

Example of using puts:

# Simple example with puts
def calculate_sum(a, b)
  sum = a + b
  puts "Value of a: #{a}" # Output the value of variable a
  puts "Value of b: #{b}" # Output the value of variable b
  puts "Calculated sum: #{sum}" # Output intermediate result
  sum
end

result = calculate_sum(5, 10)
puts "Final result: #{result}"

Example of logging with Logger:

# Logging example
require 'logger'

# Create a logger for output to a file
log = Logger.new('application.log')

def process_data(data)
  # Write info to log
  log.info("Start processing data: #{data}")
  processed_data = data.upcase
  # Write processing result
  log.debug("Data after processing: #{processed_data}")
  processed_data
rescue => e
  # Log error
  log.error("Error processing data: #{e.message}")
  nil
end

process_data("some input")

Example of using p and inspect:

# Using p and inspect
data = { name: "Alice", age: 30 }

p data # Uses inspect, outputs a more detailed view
puts data.inspect # Explicitly uses inspect

Example of using exceptions:

# Using exceptions to check
def divide(a, b)
  raise ArgumentError, "Division by zero is not allowed" if b == 0
  a / b
end

begin
  result = divide(10, 0)
rescue ArgumentError => e
  puts "An error occurred: #{e.message}" # Catch and handle the exception
end