Theresa's Calculator

calculator.rb

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+# Welcome to my calculator program
+# Created: 2.9.17
+# The user can choose to add, subtract, multiply, or divide, the program
+# will print an error message if they try to divide by 0 or write a letter for
+# where a number should go. The user will be reprompted if they type anything
+# other than what I have asked them to type when deciding what math in my
+# calculator.
+
+# Welcome message to the user
+puts "Welcome to my calculator!"
+puts "What kind of math would you like to do?"
+puts "(add, '+', subtract, '-', multiply, '*', or divide, '/')"
+
+# Get operation type the user wants to use
+operation_wanted = gets.chomp
+operation = ["add", "+", "subtract", "-", "multiply", "*", "divide", "/"]
+
+# Reprompts user if the operation type is not one allowed
+until operation.include?(operation_wanted)
+  puts "Please type an operation type listed above: "
+  operation_wanted = gets.chomp
+end
+
+puts "\nGreat! Moving on."
+
+# Getting numbers from the user that they want to calculate
+# I found this method of reprompting the user from stackoverflow
+# I do not understand it completely but I am working on understanding better
+# (hence why I have added extra comments..)
+first_number = nil # variable is initialized so it can be called on my method
+until first_number.is_a?(Integer) do # checking method to see if input is an integer
+  print "Please enter a number: "
+  begin
+    first_number = Integer(gets) # geting input from the user
+  rescue ArgumentError # rescue only works if you know exactly what kind of error could occure in ones code (from what I understand...)
+    first_number = nil # this sets the input so that loop can restart fresh
+  end
+end
+
+# This is redundant, a method could likely be used here
+second_number = nil
+until second_number.is_a?(Integer) do
+  print "Please enter another number: "
+  begin
+    second_number = Integer(gets)
+  rescue ArgumentError
+    second_number = nil
+  end
+end
+
+# Math calculations are created to be called upon later
+addition = first_number + second_number
+subtraction = first_number - second_number
+multiply = first_number * second_number
+
+# Here is another place a method could likely be used.
+# Case statment created so the correct opperations are performed depending on
+# what the user chooses.
+case operation_wanted
+  when "add", "+"
+    puts "#{first_number} + #{second_number} = #{addition}"
+  when "subtract", "-"
+    puts "#{first_number} - #{second_number} = #{subtraction}"
+  when "multiply", "*"
+    puts "#{first_number} * #{second_number} = #{multiply}"
+  when "divide", "/"
+    if second_number == 0 # catch for if the user tries to devide by zero
+      puts "Sorry... you can't divide by 0"
+    else
+      divide = first_number / second_number
+      puts "#{first_number} / #{second_number} = #{divide}"
+    end
+  else
+    puts "Sorry, you've done something wrong"
+end