anchor.diff:         findSingle (x: x == 3) "none" "multiple" [ 1 9 ]
          => "none"
     */
  -  findSingle = pred: default: multiple: list:
  +  findSingle =
  +    # Predicate
  +    pred:
  +    # Default value to return if element was not found.
  +    default:
  +    # Default value to return if more than one element was found
  +    multiple:
  +    # Input list
  +    list:
       let found = filter pred list; len = length found;
       in if len == 0 then default
         else if len != 1 then multiple
         else head found;
   
     /* Find the first element in the list matching the specified
  -     predicate or returns `default' if no such element exists.
  +     predicate or return `default` if no such element exists.
  +
  +     Type: findFirst :: (a -> bool) -> a -> [a] -> a
   
        Example:
          findFirst (x: x > 3) 7 [ 1 6 4 ]
  
positive.code: 
    /* Return the last element of a list.
  
       Example:
         last [ 1 2 3 ]
         => 3
  
negative.code: 
    /* Return a list or an empty list, depending on a boolean value.
  
       Type: optionals :: bool -> [a] -> [a]
  
       Example:
         optionals true [ 2 3 ]
         => [ 2 3 ]
         optionals false [ 2 3 ]
         => [ ]
    */
    optionals =
      # Condition
      cond:
      # List to return if condition is true
      elems: if cond then elems else [];
  
  
    /* If argument is a list, return it; else, wrap it in a singleton
  