anchor.diff:               (opt-tailcall-fun l .body front-tag))))))
   
   (metacode-walker opt-tailcall (x)
  -  :if-named-function
  -    (with-compiler-tag front-tag
  -      `(,front-tag
  -        ,@(opt-tailcall-fun x. (lambda-body x.) front-tag))))
  +  :if-named-function (with-compiler-tag front-tag
  +                       `(,front-tag
  +                         ,@(opt-tailcall-fun x. (lambda-body x.) front-tag))))
  
positive.code: ; tré – Copyright (c) 2010–2014,2016 Sven Michael Klose <pixel@copei.de>
  
  (defun atom&integer== (a b)
    (& (number? a)
       (number? b)
       (integer== a b)))
  
  (defun function-exits? (x)
    (alet x.
      (?
  	  (not x)          t
  	  (%%go? !)        (!? (member .!. .x :test #'atom&integer==)
  		                   (function-exits? .!))
  	  (| (vm-jump? !)
  	     (%=? !))      nil
  
negative.code: 
  (defun opt-tailcall-fun (l body front-tag)
    (with-lambda name args dummy-body l 
      (& body
         (? (& (%=-funcall-of? body. name)
               (function-exits? .body))
  