From 06ebc24ffc015fd7f8239a083a4df303ce5b1b47 Mon Sep 17 00:00:00 2001
From: Katrina <katrina.aganon@gmail.com>
Date: Wed, 8 Aug 2018 10:11:26 -0700
Subject: [PATCH] Create calculator.rb

---
 calculator.rb | 142 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 calculator.rb

diff --git a/calculator.rb b/calculator.rb
new file mode 100644
index 0000000..077f6d5
--- /dev/null
+++ b/calculator.rb
@@ -0,0 +1,142 @@
+# The program should use the input operation and two numbers
+# to provide the result of applying the operation to the two numbers
+
+# The program should have support for these four operations: addition,
+# subtraction, multiplication, and division
+
+# The program should accept both the name (add) and the symbol
+# (+) for each possible operation
+
+# The program should handle unexpected user input
+
+# Print operators options method
+def print_operator_options()
+  puts "1. add(+)"
+  puts "2. subtract(-)"
+  puts "3. multiply(*)"
+  puts "4. divide(/)"
+  puts "5. modulo(%)"
+  puts "6. exponential(^)"
+  puts
+end
+
+
+# Addition method
+def add_numbers(num1, num2)
+  return num1 + num2
+end
+
+# Subtraction method
+def subtract_numbers(num1, num2)
+  return num1 - num2
+end
+
+# Multiplication method
+def multiply_numbers(num1, num2)
+  return num1 * num2
+end
+
+# Division method
+def divide_numbers(num1, num2)
+  return num1 / num2
+end
+
+# Modulo method
+def modulo_numbers(num1, num2)
+  integer_division = (num1 / num2) * num2
+  return num1 - integer_division
+end
+
+# Exponential method
+def raise_number_to_power(num1, num2)
+  return num1 ** num2
+end
+
+# Welcome message, ask user for operator (name or symbol)
+puts
+puts "Welcome to the Calculator program! Which operator would you like to use? "
+print_operator_options()
+
+print "Please choose one operator(name or symbol): "
+user_symbol = gets.chomp.strip.downcase
+
+symbols = [
+  "add", "+", "subtract", "-", "multiply", "*",
+  "divide", "/", "modulo", "%", "exponential", "^"
+]
+
+# Check to make sure user input matches the name or symbol operators
+until symbols.include?(user_symbol)
+  puts "Sorry, '#{user_symbol}' is an invalid input"
+  print "Please enter at least one operator(name or symbol): "
+  user_symbol = gets.chomp.strip.downcase
+end
+
+puts
+puts "Thank you! Let's do some math!"
+puts
+
+print "Please enter your first number: "
+first_number = gets.chomp
+
+# Check to get digits entered from user for first number
+until first_number.match?(/^(?=.*[\d])/) ||
+  first_number.match?(/^(?=.*[-])(?=.*[\d])/)
+  # '?=pat' positive lookahead assertion to check if there is at least
+  # one or more digits in the string (starting from beginning of line)
+  # including the symbol '-' to make sure negative numbers work also
+  puts "Hm, something went wrong..."
+  print "Please enter your first number: "
+  first_number = gets.chomp
+end
+
+first_number = first_number.to_i
+
+# Check to get digits entered from user for second number
+print "Please enter your second number: "
+second_number = gets.chomp
+
+until second_number.match?(/^(?=.*[\d])/) ||
+  second_number.match?(/^(?=.*[-])(?=.*[\d])/)
+  puts "Hm, something went wrong..."
+  print "Please enter your second number: "
+  second_number = gets.chomp
+end
+
+second_number = second_number.to_i
+
+puts
+
+# Output message as string, based on the symbols entered by user
+case user_symbol
+  when "add", "+"
+    sum = add_numbers(first_number, second_number)
+    puts "#{first_number} + #{second_number} = #{sum}"
+
+  when "subtract", "-"
+    difference = subtract_numbers(first_number, second_number)
+    puts "#{first_number} - #{second_number} = #{difference}"
+
+  when "multiply", "*"
+    product = multiply_numbers(first_number, second_number)
+    puts "#{first_number} * #{second_number} = #{product}"
+
+  when "divide", "/"
+    if second_number == 0
+      puts "Undefined - cannot divide a number by zero"
+    else
+      quotient = divide_numbers(first_number, second_number)
+      puts "#{first_number} / #{second_number} = #{quotient}"
+    end
+
+  when "modulo", "%"
+    remainder = modulo_numbers(first_number, second_number)
+    puts "#{first_number} % #{second_number} = #{remainder}"
+
+  when "exponential", "^"
+    power = raise_number_to_power(first_number, second_number)
+    puts "#{first_number} ^ #{second_number} = #{power}"
+end
+
+puts
+puts