anchor.diff:          
           match implementation with
               | Imperative -> binomialPricing pricing
  -            | Functional -> binomialPricingFunc pricing+            | Functional -> binomialPricingFunc pricing
  +            | FunctionalFast -> binomialPricingFuncFast pricing
positive.code:             Delta = 1.0
          }
  
      let binomial (stock:StockInfo) (option:OptionLeg) (steps:int) implementation = 
  
          //we need to construct the binomial pricing model, using the CRR (Cox, Ross and Rubinstein)
  
negative.code: type Implementation =
      | Functional 
      | Imperative
      | FunctionalFast
  
  //this type holds the configuration for binomial pricing model
  type BinomialPricing = {
  