Added divide and multiple, added specs for addition, subtraction, mul…

.gitignore

@@ -48,3 +48,6 @@ build-iPhoneSimulator/
 
 # unless supporting rvm < 1.11.0 or doing something fancy, ignore this:
 .rvmrc
+
+*.sublime-project
+*.sublime-workspace

lib/roman_numeral.rb

@@ -32,8 +32,12 @@ def initialize( numeral_string )
   end
 
   def self.romanize(decimal)
-    reverse_hashroman = HASHROMAN.invert
-
+    roman=""
+    HASHROMAN.sort_by {|num, val| val }.reverse.each{|num, val|
+      roman+=num.to_s*(decimal/val).floor # It's a symbol at this point,
+      decimal-=(decimal/val).floor*val
+    }
+    roman
   end
 
   def self.decimal_value(numerical_string)
@@ -53,7 +57,17 @@ def +( other_roman )
   end
 
   def -( numeral_string )
-    "MCMXCVI"
+    dec_num = decimal_val - numeral_string.decimal_val
+    dec_num >0 ? RomanNumeral.romanize(dec_num) : "-" + RomanNumeral.romanize(dec_num.abs)
   end
-end
 
+  def *( other_roman )
+    dec_num = other_roman.decimal_val * decimal_val
+    RomanNumeral.romanize(dec_num)
+  end
+
+  def /( numeral_string )
+    dec_num = (decimal_val / numeral_string.decimal_val).floor
+    dec_num >0 ? RomanNumeral.romanize(dec_num) : "-" + RomanNumeral.romanize(dec_num.abs)
+  end
+end

spec/roman_numeral_spec.rb

@@ -1,14 +1,24 @@
 require 'spec_helper'
 require 'roman_numeral'
 
-
 describe RomanNumeral do
-
   it 'should compute simple arithmatic' do
-    @reports << Benchmark.measure do
+  	# 1996 plus 14 equals 2010
       expect( RomanNumeral.new( 'MCMXCVI' ) + RomanNumeral.new( 'XIV' ) ).to eq('MMX')
-      expect( RomanNumeral.new( 'MMX' ) + RomanNumeral.new( 'XIV' ) ).to eq('MCMXCVI')
-    end
-  end
 
-end
+  	# 2010 minus 14 equals 1996
+      expect( RomanNumeral.new( 'MMX' ) - RomanNumeral.new( 'XIV' ) ).to eq('MCMXCVI')
+
+      # 1996 minus 1996 equals -14
+      expect( RomanNumeral.new( 'MCMXCVI' ) - RomanNumeral.new( 'MMX' ) ).to eq('-XIV')
+
+      # 23 times 11 equals 253
+      expect( RomanNumeral.new( 'XXIII' ) * RomanNumeral.new( 'XI' ) ).to eq('CCLIII')
+
+      # 253 divided by 11 equals 23
+      expect( RomanNumeral.new( 'CCLIII' ) / RomanNumeral.new( 'XI' ) ).to eq('XXIII')
+
+      # 100 divided by 33 equals 3.  The romans had a complicated fraction system, we're not going there.
+      expect( RomanNumeral.new( 'C' ) / RomanNumeral.new( 'XXXIII' ) ).to eq('III')
+  end
+end