anchor.diff:  
   header source
   : source
  -    sourceA @ sourceC @
  +    sourceC 2@
  +;
  +
  +: source! ( addr u -- ) \ set the source
  +    sourceC 2!
   ;
   
   header source-id
  
positive.code: :noname
      source >r >r >in @ >r
      source-id >r d# -1 sourceid !
      sourceC ! sourceA ! d# 0 >in !
      interpret
      r> sourceid !
      r> >in ! r> sourceA ! r> sourceC !
  ;
  
  header quit
  
negative.code:     negate and throw
  ;
  
  header-imm 2literal
  : 2literal
      swap DOUBLE
  header-imm literal
  : tliteral
      dup 0< if
  