anchor.diff:  (defmacro with-input-file ((streamvar path element-type if-does-not-exist external-format) &body body)
     `(call-with-input-file ,path ,element-type ,if-does-not-exist ,external-format (lambda (,streamvar) ,@body)))
   
  +(defun output-file-if-does-not-exist (if-does-not-exist)
  +  (case if-does-not-exist
  +    ((:error :create nil) if-does-not-exist)
  +    (otherwise :create)))
  +(declaim (inline output-file-if-does-not-exist))
   
   (defmacro with-io-syntax (&body body)
     ;; Leave the current package as-is.
  
positive.code: DO:             Store the NEW-CONTENTS, into the file at PATH, each string on a line.
                  By default, that file is created or superseded; this can be changed with
                  the keyword IF-DOES-NOT-EXIST or IF-EXISTS.
  NEW-CONTENT:    A sequence of strings, none of them should contain #\newline,
                  otherwise the mapping between strings and file lines won't be
                  conserved.
  RETURN:         The NEW-CONTENTS or if-exists or if-does-not-exist in case of error.
  "
    (with-open-file (out path :direction :output
                         :if-does-not-exist if-does-not-exist
                         :if-exists if-exists
                         :external-format external-format)
      (if (and (streamp out) (not (or (eq out if-exists)  (eq out if-does-not-exist))))
  
negative.code:                                     (external-format :default))
    "
  RETURN: The NEW-CONTENTS, or if-exists or if-does-not-exist in case of error.
  
  DO:     Store the NEW-CONTENTS into the file at PATH.  By default,
          that file is created or superseded; this can be changed with
          the keyword IF-DOES-NOT-EXIST or IF-EXISTS.
  
  NEW-CONTENT:  A sequence of ELEMENT-TYPE.
  
  IF-DOES-NOT-EXIST:  Can be :error, :create, nil,
                      or another value, equivalent to :CREATE for setf.
  "
    (with-open-file (out path :direction :output
                         :if-does-not-exist (output-file-if-does-not-exist if-does-not-exist)
                         :if-exists if-exists
                         :element-type element-type
                         :external-format external-format)
  