anchor.diff:  --------------------------------------------------
   *Input*:
   
  -<1> string expression
  +<1> string expression. If `null`, the function returns `null`.
   
   *Output*: integer
   
  
positive.code: --------------------------------------------------
  *Input*:
  
  <1> string expression
  <2> string expression
  
  *Output*: boolean value
  
  
negative.code: --------------------------------------------------
  *Input*:
  
  <1> string expression. If `null`, the function returns `null`.
  <2> string expression. If `null`, the function returns `null`.
  <3> string expression. If `null`, the function returns `null`.
  
  *Output*: string
  
  