Formula#calculate is using QuantityInput

Updated FormulaBuilder to properly index parts[]

app/models/formula.rb

@@ -20,7 +20,7 @@ class Formula < ActiveRecord::Base
   def calculate(inputs)
     raise(InvalidInputs, 'No inputs') if inputs.empty?
 
-    deps = inputs.map { |q, v| [q.name, v.transpose.first] }.to_h
+    deps = inputs.map { |q, v| [q.name, QuantityInput.new(q, v.transpose.first)] }.to_h
     length = deps.values.first.length
 
     raise(InvalidFormula, 'Invalid formula') unless self.valid?
@@ -47,6 +47,10 @@ class Formula < ActiveRecord::Base
       super(*args)
       @quantity = q
     end
+
+    def lastBefore(timepoints)
+      self.map{ BigDecimal(2000) }
+    end
   end
 
   def parse
@@ -77,7 +81,7 @@ class Formula < ActiveRecord::Base
     errors
   end
 
-  def get_binding(quantities, args, length)
+  def get_binding(quantities, parts, length)
     binding
   end
 end