NPV calculation is now much faster

waissbluth · Aug 8, 2014 · 4eea484 · 4eea484
1 parent 55363f9
commit 4eea484
Showing 1 changed file with 4 additions and 4 deletions.
diff --git a/lib/croovy_finance/npv.rb b/lib/croovy_finance/npv.rb
@@ -10,12 +10,12 @@ def initialize(payments)
   end
 
   def call(rate)
-    exp = 1.0
     factor = 1.0 + rate
+    accum_factor = 1.0
 
-    @payments.map do |pmt|
-      pmt / (factor ** exp).tap {exp += 1.0}
-    end.reduce(:+)
+    @payments.inject(0.0) do |result, pmt|
+      result + pmt / (accum_factor *= factor)
+    end
   end
 
 end