Calculator I had to create for the WDI homework first week. The instructions are at the top.

Calculator.rb

# Create a command line calculator. It should have a basic and advanced mode.
# 
# * basic calculator (+, -, *, /)
# * advanced calculator (exponents, square root)
# 
# * For a basic calculator, press 1.  
# * For an advanced calculator, press 2. To quit, press Q.  
# * For calculators, first enter type of calculation, then enter 2 numbers.  
# 
# Create methods for each operation, and each one to show and interact with a text menu.
# ----------------------------------------------------------------------------
# Add a trip calculator to your program. Ask the user (politely) for four inputs:
# 
# **Distance** – how far will you drive?  
# **MPG** – what is the fuel efficiency of the car?  
# **$PG** – how much does gas cost per gallon?  
# **Speed** – how fast will you drive?  
# 
# Your output is a string: “Your trip will take 3.5 hours and cost $255.33.”
# 
# Add this as a menu choice.

def add(num1, num2)
  num1 = num1.to_f
  num2 = num2.to_f
  
  if (num1 && num2).is_a? Float
    answer = num1 + num2
    puts "#{num1} + #{num2} = #{answer}"
  else
    puts 'You did not enter valid numbers. Please try again.'
  end
end

def subtract(num1, num2)
  num1 = num1.to_f
  num2 = num2.to_f
  
  if (num1 && num2).is_a? Float
    answer = num1 - num2
    puts "#{num1} - #{num2} = #{answer}"
  else
    puts 'You did not enter valid numbers. Please try again.'
  end
end

def multiply(num1, num2)
  num1 = num1.to_f
  num2 = num2.to_f
  
  if (num1 && num2).is_a? Float
    answer = num1 * num2
    puts "#{num1} * #{num2} = #{answer}"
  else
    puts 'You did not enter valid numbers. Please try again.'
  end
end

def divide(num1, num2)
  num1 = num1.to_f
  num2 = num2.to_f
  
  if (num1 && num2).is_a? Float
    answer = num1 / num2
    puts "#{num1} / #{num2} = #{answer}"
  else
    puts 'You did not enter valid numbers. Please try again.'
  end
end

def exponent(num, exp)
  num = num.to_i
  exp = num.to_i
  
  if (num && exp).is_a? Fixnum
    answer = num ** exp
    puts "#{num} to the power of #{exp} is #{answer}"
  else
    puts 'You did not enter valid numbers. Please try again.'
  end
end

def square_root(num)
  num = num.to_i
  
  if num.is_a? Fixnum
    answer = Math.sqrt(num.to_i)
    puts "The square root of #{num} is #{answer}"
  else
    puts 'You did not enter valid numbers. Please try again.'
  end
end

def trip_time(distance, speed)
  distance = distance.to_f
  speed = speed.to_i
  
  unless (distance || speed).zero?
    time = distance / speed
    time = time.round(2)
    return time
  else
    puts 'You did not enter valid numbers. Please try again.'
  end 
end

def trip_cost(distance, mpg, gas_cost)
  distance = distance.to_f
  mpg = mpg.to_f
  gas_cost = gas_cost.to_f
  
  if ((distance && mpg && gas_cost).is_a? Float) && ((distance && mpg && gas_cost).zero? == false)
    gas_for_trip = distance / mpg
    trip_cost = gas_cost * gas_for_trip
    trip_cost = trip_cost.round(2)
    return trip_cost
  else
    puts 'You did not enter valid numbers. Please try again.'
  end  
end

def bmi(height, weight)
  height = height.to_i
  weight = weight.to_f
  
  unless (height || weight).zero?
    bmi = (weight / (height * height)) * 703
    bmi = bmi.round(2)
    puts "Your BMI is #{bmi}."
  else
    puts 'You did not enter valid numbers. Please try again.'
  end
end

def basic
  puts 'What type of calculation would you like to perform:'
  puts 'add, subtract, multiply, or divide?'
  calc_type = gets.chomp.downcase
  puts "Please enter 2 numbers that you would like to #{calc_type} separated by comma."
  nums = gets.chomp
  nums = nums.split(',')
    
  case calc_type
  
  when 'add'
    add(nums[0], nums[1])
  
  when 'subtract'
    subtract(nums[0], nums[1])
  
  when 'multiply'
    multiply(nums[0], nums[1])
  
  when 'divide'
    divide(nums[0], nums[1])
  
  else
    puts 'I didn\'t understand your command.'
    basic
  end
  
  puts ''
  start

end

def advanced
  puts 'What type of calculation would you like to perform:'
  puts 'square root, or exponent?'
  calc_type = gets.chomp.downcase
  
  if calc_type == 'exponent'
    puts 'Enter 2 numbers separated by a comma:'
    nums = gets.chomp.split(',')
  
  elsif calc_type == 'square root'
    puts 'What is the number you\'d like the square root of?'
    num = gets.chomp
    
  else
    puts 'I didn\'t understand your command.'
    advanced
  end
  
  case calc_type
  
  when 'square root'
    square_root(num)
  
  when 'exponent'
    exponent(nums[0], nums[1])
  
  else
    puts 'I didn\'t understand your command.'
    advanced
  end
  
  puts ''
  start
  
end

def trip_calc
  puts 'How many miles are you going to drive?'
  distance = gets.chomp
  puts 'What is the fuel efficiency of the car?'
  mpg = gets.chomp
  puts 'How much does gas cost per gallon?'
  gas_cost = gets.chomp
  puts 'What is the speed you will you drive? (Please enter number only)'
  speed = gets.chomp
  
  time = trip_time(distance, speed)
  cost = trip_cost(distance, mpg, gas_cost)
  
  if (time && cost).is_a? Float
    puts "Your trip will take #{time} hours and cost $#{cost}."
  end
  
  puts ''
  start

end

def bmi_calc
  puts 'Please enter your height in inches:'
  height = gets.chomp
  puts 'Please enter your weight in lbs:'
  weight = gets.chomp
  
  bmi(height, weight)
  
  puts ''
  start
end

def start
  puts '---------------------------------------------------'
  puts 'For a basic calculator, press 1.'
  puts 'For an advanced calculator, press 2.'
  puts 'For a trip calculator, press 3.'
  puts 'For a BMI calculator, press 4. To quit, press Q.'
  puts '---------------------------------------------------'
  choice = gets.chomp.downcase
  
  if choice == '1'
    basic
  
  elsif choice == '2'
    advanced
    
  elsif choice == '3'
    trip_calc
    
  elsif choice == '4'
    bmi_calc
  
  elsif choice == 'q'
    Process.exit(0)
  
  else
    puts 'I didn\'t understand your command.'
    start
  end

end

start

Holy smokeys' looks very eleganté