anchor.diff:  With knn we use a *distance* measure to compare vectors of data to find the k nearest neighbors to
   a specific vector.
   
  -=== Distance
  +=== Euclidean Distance
   
   The Streaming Expression statistical function library has a function called `distance`. The `distance` function
   computes the Euclidean distance between two vectors. This looks promising for comparing vectors of room rates.
  
positive.code: ----
  
  
  == Tuple
  
  The *tuple* is the next data structure we'll explore.
  
  
negative.code: }
  ----
  
  == Lists
  
  Next we have the *list* data structure.
  
  