Handle exponents correctly.

lib/alchemist/measurement.rb

@@ -18,7 +18,7 @@ def per
 
     def to type = nil
       if type
-        convertor.send(type)
+        convertor.send(type, exponent)
       else
         convertor
       end
@@ -52,7 +52,7 @@ def * multiplicand
 
     def base unit_type
       conversion_base = conversion_base_for(unit_type)
-      convert_to_base conversion_base
+      convert_to_base(conversion_base) * exponent
     end
 
     def to_s
@@ -68,7 +68,7 @@ def to_f
     end
 
     def <=>(other)
-      (self.to_f * exponent).to_f <=> other.to(unit_name).to_f
+      self.to_f <=> other.to(unit_name).to_f
     end
 
     def types

lib/alchemist/measurement_convertor.rb

@@ -9,7 +9,7 @@ def initialize from
 
     def method_missing method, *args, &block
       exponent, unit_name = PrefixParser.new.parse(method)
-      convert(from.shared_types(unit_name), unit_name, exponent)
+      convert(from.shared_types(unit_name), unit_name, args.first || exponent)
     end
 
     private
@@ -32,7 +32,7 @@ def convert_from_type(type, unit_name, exponent)
       conversion_factor = library.conversion_base_for(type, unit_name)
 
       value = value_from(conversion_base, conversion_factor)
-      Measurement.new(value, unit_name, exponent)
+      Measurement.new(value / from.exponent, unit_name, exponent)
     end
 
     def value_from(base, factor)

spec/measurement_spec.rb

@@ -67,6 +67,11 @@ module Alchemist
       expect(1.6.meters.floor).to eq(1.meter)
     end
 
+    it "handles exponents correctly" do
+      expect(1.kg.to.kg).to eq(1.kg)
+      expect(1.kg.to(:kg)).to eq(1.kg)
+    end
+
     describe '#geospatial' do
 
       it 'should convert angles to meters' do