calculator.rb

# Calculator.rb assignment

# array of arrays 
operators = [
  ["add", "+"], 
  ["subtract", "-"], 
  ["multiply", "*"], 
  ["divide", "/"]
]

# added this operator_check long array to ensure user's input is only valid if on this list
operators_check = 
  ["add", "+", 
  "subtract", "-", 
  "multiply", "*", 
  "divide", "/"]

# only accept digits as input
def is_number(string)
  if string.length == 0
    return false
  end
  return string.scan(/\D/).empty?
end

# welcome user to program, provide list of oeprators, looping through list options
puts "Welcome to the Calculator program! I hear you need help..."
puts "Which operator would you like to use from the below list?"
4.times do |i|
  puts "#{i+1}: #{operators[i][0]} (#{operators[i][1]})"
end

# get user's operator pick and reinstate. Throw error if selection is not on offered list
puts "Enter your chosen operator now (name or symbol)."
operator_pick = gets.chomp
# use method.include to throw error if user input is not on the operator list and prompt user to try again
until operators_check.include?(operator_pick)
  puts "ERROR: invalid entry. Please select operator from list."
  puts "Enter your chosen operator now (name or symbol)."
  operator_pick = gets.chomp
  puts "You've selected the #{operator_pick} operator."
end

# get user's first number and reinstate. Error if less than 0
# initially used .to_i on gets.chomp but this converted string to 0
# instead, check if num_one_pick is a number, before calling to_i. If not a number, throw error
# include .to_f to handle float entries as well (but now all outputs are floats? hm)
puts "Next: select a number for this math operation."
num_one_pick = gets.chomp
while is_number(num_one_pick) == false
  puts "ERROR: this entry is not valid."
  puts "Next: select a number for this math operation."
  num_one_pick = gets.chomp
end
num_one_pick = num_one_pick.to_i.to_f

puts "You've selected #{num_one_pick} as your first number."
puts "#{num_one_pick} is a great number."

# get user's second number and reinstate. Error if less than 0
# ensure user input is numerical and reject if non-numerical
# if operator chosen is division, (to prevent division by 0) throw error, prompting the user to enter another number
puts "Finally: select your second number for the Calculator."
num_two_pick = gets.chomp
while is_number(num_two_pick) == false || (num_two_pick == "0" && (operator_pick == "divide" || operator_pick == "/"))
  puts "ERROR: this entry is not valid."
  puts "Please enter a different number for the Calculator."
  num_two_pick = gets.chomp
end

num_two_pick = num_two_pick.to_i.to_f

puts "You've selected #{num_two_pick} as your second number."
puts "#{num_two_pick} is also a great number."

# wrap up and reinstate equation, along with solution
puts "You have created the following problem: #{num_one_pick} #{operator_pick} #{num_two_pick}"
puts "The solution to your problem is: "

# use case command to complete equation
case operator_pick
  when "add", "+"
puts (num_one_pick + num_two_pick)
  when "subtract", "-"
puts (num_one_pick - num_two_pick)
  when "multiply", "*"
puts (num_one_pick * num_two_pick)
  when "divide", "/"
puts (num_one_pick / num_two_pick)
end 
puts "Thank you for using The Calculator. Come back next time you need help!"