;;; -*- Log: code.log; Package: Lisp -*-
;;;
;;; **********************************************************************
;;; This code was written as part of the CMU Common Lisp project at
;;; Carnegie Mellon University, and has been placed in the public domain.
;;;
(ext:file-comment
  "$Header: /project/cmucl/cvsroot/src/code/print.lisp,v 1.122 2008/03/13 12:25:49 rtoy Exp $")
;;;
;;; **********************************************************************
;;;
;;; CMU Common Lisp printer.
;;;
;;; Written by Neal Feinberg, Bill Maddox, Steven Handerson, and Skef Wholey.
;;; Modified by various CMU Common Lisp maintainers.
;;;

(in-package "LISP")

(export '(*print-readably* *print-escape* *print-pretty* *print-circle*
	  *print-base* *print-radix* *print-case* *print-gensym* *print-level*
	  *print-length* *print-array* *print-lines* *print-right-margin*
	  *print-miser-width* *print-pprint-dispatch* with-standard-io-syntax
	  write prin1 print princ pprint
	  write-to-string prin1-to-string princ-to-string
	  print-unreadable-object print-not-readable
	  print-not-readable-object))

(in-package "KERNEL")
(export '(*current-level* *pretty-printer* output-object output-ugly-object
	  check-for-circularity handle-circularity descend-into
	  punt-if-too-long output-symbol-name))

(in-package "LISP")



;;;; Exported printer control variables.

(defvar *print-readably* nil
  "If true, all objects will printed readably.  If readably printing is
  impossible, an error will be signalled.  This overrides the value of
  *PRINT-ESCAPE*.")
(defvar *print-escape* T
  "Flag which indicates that slashification is on.  See the manual")
(defvar *print-pretty* nil
  "Flag which indicates that pretty printing is to be used")
(defvar *print-base* 10.
  "The output base for integers and rationals.")
(defvar *print-radix* nil
  "This flag requests to verify base when printing rationals.")
(defvar *print-level* nil
  "How many levels deep to print.  Unlimited if null.")
(defvar *print-length* nil
  "How many elements to print on each level.  Unlimited if null.")
(defvar *print-circle* nil
  "Whether to worry about circular list structures. See the manual.")
(defvar *print-case* :upcase
  "What kind of case the printer should use by default")
(defvar *print-array* t
  "Whether the array should print it's guts out")
(defvar *print-gensym* t
  "If true, symbols with no home package are printed with a #: prefix.
  If false, no prefix is printed.")
(defvar *print-lines* nil
  "The maximum number of lines to print.  If NIL, unlimited.")
(defvar *print-right-margin* nil
  "The position of the right margin in ems.  If NIL, try to determine this
   from the stream in use.")
(defvar *print-miser-width* nil
  "If the remaining space between the current column and the right margin
   is less than this, then print using ``miser-style'' output.  Miser
   style conditional newlines are turned on, and all indentations are
   turned off.  If NIL, never use miser mode.")
(defvar *print-pprint-dispatch* nil
  "The pprint-dispatch-table that controls how to pretty print objects.  See
   COPY-PPRINT-DISPATH, PPRINT-DISPATCH, and SET-PPRINT-DISPATCH.")

(defmacro with-standard-io-syntax (&body body)
  "Bind the reader and printer control variables to values that enable READ
   to reliably read the results of PRINT.  These values are:
       *PACKAGE*			The COMMON-LISP-USER package
       *PRINT-ARRAY*			T
       *PRINT-BASE*			10
       *PRINT-CASE*			:UPCASE
       *PRINT-CIRCLE*			NIL
       *PRINT-ESCAPE*			T
       *PRINT-GENSYM*			T
       *PRINT-LENGTH*			NIL
       *PRINT-LEVEL*			NIL
       *PRINT-LINES*			NIL
       *PRINT-MISER-WIDTH*		NIL
       *PRINT-PRETTY*			NIL
       *PRINT-RADIX*			NIL
       *PRINT-READABLY*			T
       *PRINT-RIGHT-MARGIN*		NIL
       *READ-BASE*			10
       *READ-DEFAULT-FLOAT-FORMAT* 	SINGLE-FLOAT
       *READ-EVAL*			T
       *READ-SUPPRESS*			NIL
       *READTABLE*			the standard readtable."
  `(%with-standard-io-syntax #'(lambda () ,@body)))

(defun %with-standard-io-syntax (function)
  (let ((*package* (find-package "CL-USER"))
	(*print-array* t)
	(*print-base* 10)
	(*print-case* :upcase)
	(*print-circle* nil)
	(*print-escape* t)
	(*print-gensym* t)
	(*print-length* nil)
	(*print-level* nil)
	(*print-lines* nil)
	(*print-miser-width* nil)
	(*print-pretty* nil)
	(*print-radix* nil)
	(*print-readably* t)
	(*print-right-margin* nil)
	(*read-base* 10)
	(*read-default-float-format* 'single-float)
	(*read-eval* t)
	(*read-suppress* nil)
	(*readtable* std-lisp-readtable))
    (funcall function)))


;;;; Routines to print objects.

(defun write (object &key
		     ((:stream stream) *standard-output*)
		     ((:escape *print-escape*) *print-escape*)
		     ((:radix *print-radix*) *print-radix*)
		     ((:base *print-base*) *print-base*)
		     ((:circle *print-circle*) *print-circle*)
		     ((:pretty *print-pretty*) *print-pretty*)
		     ((:level *print-level*) *print-level*)
		     ((:length *print-length*) *print-length*)
		     ((:case *print-case*) *print-case*)
		     ((:array *print-array*) *print-array*)
		     ((:gensym *print-gensym*) *print-gensym*)
		     ((:readably *print-readably*) *print-readably*)
		     ((:right-margin *print-right-margin*) 
		      *print-right-margin*)
		     ((:miser-width *print-miser-width*) 
		      *print-miser-width*)
		     ((:lines *print-lines*) *print-lines*)
		     ((:pprint-dispatch *print-pprint-dispatch*)
		      *print-pprint-dispatch*))
  "Outputs OBJECT to the specified stream, defaulting to *standard-output*"
  (output-object object (out-synonym-of stream))
  object)

(defun prin1 (object &optional stream)
  "Outputs a mostly READable printed representation of OBJECT on the specified
  stream."
  (let ((*print-escape* T))
    (output-object object (out-synonym-of stream)))
  object)

(defun princ (object &optional stream)
  "Outputs an asthetic but not READable printed representation of OBJECT on the
  specified stream."
  (let ((*print-escape* NIL)
	(*print-readably* NIL))
    (output-object object (out-synonym-of stream)))
  object)

(defun print (object &optional stream)
  "Outputs a terpri, the mostly READable printed represenation of OBJECT, and 
  space to the stream."
  (let ((stream (out-synonym-of stream)))
    (terpri stream)
    (prin1 object stream)
    (write-char #\space stream)
    object))

(defun pprint (object &optional stream)
  "Prettily outputs the Object preceded by a newline."
  (let ((*print-pretty* t)
	(*print-escape* t)
	(stream (out-synonym-of stream)))
    (terpri stream)
    (output-object object stream))
  (values))


(defun write-to-string
       (object &key
	       ((:escape *print-escape*) *print-escape*)
	       ((:radix *print-radix*) *print-radix*)
	       ((:base *print-base*) *print-base*)
	       ((:circle *print-circle*) *print-circle*)
	       ((:pretty *print-pretty*) *print-pretty*)
	       ((:level *print-level*) *print-level*)
	       ((:length *print-length*) *print-length*)
	       ((:case *print-case*) *print-case*)
	       ((:array *print-array*) *print-array*)
	       ((:gensym *print-gensym*) *print-gensym*)
	       ((:readably *print-readably*) *print-readably*)
	       ((:right-margin *print-right-margin*) *print-right-margin*)
	       ((:miser-width *print-miser-width*) *print-miser-width*)
	       ((:lines *print-lines*) *print-lines*)
	       ((:pprint-dispatch *print-pprint-dispatch*)
		*print-pprint-dispatch*))
  "Returns the printed representation of OBJECT as a string."
  (stringify-object object))

(defun prin1-to-string (object)
  "Returns the printed representation of OBJECT as a string with 
   slashification on."
  (stringify-object object t))

(defun princ-to-string (object)
  "Returns the printed representation of OBJECT as a string with
  slashification off."
  (stringify-object object nil))

;;; STRINGIFY-OBJECT -- Internal.
;;;
;;; This produces the printed representation of an object as a string.  The
;;; few ...-TO-STRING functions above call this.
;;;
(defvar *string-output-streams* ())
;;;
(defun stringify-object (object &optional (*print-escape* *print-escape*))
  (let ((stream (if *string-output-streams*
		    (pop *string-output-streams*)
		    (make-string-output-stream))))
    (setup-printer-state)
    (output-object object stream)
    (prog1
	(get-output-stream-string stream)
      (push stream *string-output-streams*))))



;;;; PRINT-UNREADABLE-OBJECT macro

(defmacro print-unreadable-object ((object stream &key type identity)
				   &body body)
  `(%print-unreadable-object ,object ,stream ,type ,identity
			     ,(if body
				  `#'(lambda () ,@body)
				  nil)))

(define-condition print-not-readable (error)
  ((object :reader print-not-readable-object :initarg :object))
  (:report
   (lambda (condition stream)
     (let ((obj (print-not-readable-object condition))
	   (*print-array* nil))
       (format stream "~S cannot be printed readably." obj)))))

;;; Guts of print-unreadable-object.
;;;
;;; When *print-pretty* and the stream is a pretty-stream, format the object
;;; within a logical block - pprint-logical-block does not rebind the stream
;;; when it is already a pretty stream so output from the body will go to the
;;; same stream.
;;;
(defun %print-unreadable-object (object stream type identity body)
  (when *print-readably*
    (error 'print-not-readable :object object))
  (flet ((print-description ()
	   (when type
	     (write (type-of object) :stream stream :circle nil
		    :level nil :length nil)
	     (when (or body identity)
	       (write-char #\space stream)
	       (pprint-newline :fill stream)))
	   (when body
	     (funcall body))
	   (when identity
	     (when body
	       (write-char #\space stream)
	       (pprint-newline :fill stream))
	     (write-char #\{ stream)
	     (write (get-lisp-obj-address object) :stream stream
		    :radix nil :base 16)
	     (write-char #\} stream))))
    (cond ((and (pp:pretty-stream-p stream) *print-pretty*)
	   (pprint-logical-block (stream nil :prefix "#<" :suffix ">")
	     (print-description)))
	  ((and *print-level* (>= *current-level* *print-level*))
	   (write-char #\# stream))
	  (t
	   (write-string "#<" stream)
	   (print-description)
	   (write-char #\> stream))))
  nil)


;;;; WHITESPACE-CHAR-P

;;; This is used in other files, but is defined in this one for some reason.

(defun whitespace-char-p (char)
  "Determines whether or not the character is considered whitespace."
  (or (char= char #\space)
      (char= char #\tab)
      (char= char #\return)
      (char= char #\linefeed)))



;;;; Circularity detection stuff.

;;; *CIRCULARITY-HASH-TABLE* -- internal.
;;;
;;; When *print-circle* is T, this gets bound to a hash table that (eventually)
;;; ends up with entries for every object printed.  When we are initially
;;; looking for circularities, we enter a T when we find an object for the
;;; first time, and a 0 when we encounter an object a second time around.
;;; When we are actually printing, the 0 entries get changed to the actual
;;; marker value when they are first printed.
;;; 
(defvar *circularity-hash-table* nil)

;;; *CIRCULARITY-COUNTER* -- internal.
;;;
;;; When NIL, we are just looking for circularities.  After we have found them
;;; all, this gets bound to 0.  Then whenever we need a new marker, it is
;;; incremented.
;;;
(defvar *circularity-counter* nil)

;;; CHECK-FOR-CIRCULARITY -- interface.
;;;
(defun check-for-circularity (object &optional assign (mode t))
  "Check to see if OBJECT is a circular reference, and return something non-NIL
   if it is.  If ASSIGN is T, then the number to use in the #n= and #n# noise
   is assigned at this time.  Note: CHECK-FOR-CIRCULARITY must be called
   *EXACTLY* once with ASSIGN T, or the circularity detection noise will get
   confused about when to use #n= and when to use #n#.  If this returns
   non-NIL when ASSIGN is T, then you must call HANDLE-CIRCULARITY on it."
  (cond ((null *print-circle*)
	 ;; Don't bother, nobody cares.
	 nil)
	((null *circularity-hash-table*)
	 (values nil :initiate))
	((null *circularity-counter*)
	 (ecase (gethash object *circularity-hash-table*)
	   ((nil)
	    ;; First encounter.
	    (setf (gethash object *circularity-hash-table*) mode)
	    ;; We need to keep looking.
	    nil)
	   ((:logical-block)
            (setf (gethash object *circularity-hash-table*)
                  :logical-block-circular)
	    t)
	   ((t)
	    (cond ((eq mode :logical-block)
                   ;; We've seen the object before in output-object, and now
                   ;; a second time in a PPRINT-LOGICAL-BLOCK (for example
                   ;; via pprint-dispatch). Don't mark it as circular yet.
                   (setf (gethash object *circularity-hash-table*)
                         :logical-block)
                   nil)
		  (t
		   ;; Second encounter.
		   (setf (gethash object *circularity-hash-table*) 0)
		   ;; It's a circular reference.
		   t)))
	   ((0 :logical-block-circular)
	    ;; It's a circular reference.
	    t)))
	(t
	 (let ((value (gethash object *circularity-hash-table*)))
	   (case value
	     ((nil t :logical-block)
	      ;; If NIL, we found an object that wasn't there the
	      ;; first time around.  If T or :LOGICAL-BLOCK, exactly
	      ;; one occurance of this object appears.  Either way,
	      ;; just print the thing without any special processing.
	      ;; Note: you might argue that finding a new object means
	      ;; that something is broken, but this can happen.  If
	      ;; someone uses the ~@<...~:> format directive, it
	      ;; conses a new list each time though format (i.e. the
	      ;; &REST list), so we will have different cdrs.
	      nil)
             (:logical-block-circular
	      ;; A circular reference to something that will be printed
	      ;; as a logical block. Wait until we're called from
	      ;; PPRINT-LOGICAL-BLOCK with ASSIGN true before assigning the
	      ;; number.
	      ;;
	      ;; If mode is :LOGICAL-BLOCK and assign is false, return true
	      ;; to indicate that this object is circular, but don't assign
	      ;; it a number yet. This is neccessary for cases like
	      ;; #1=(#2=(#2# . #3=(#1# . #3#))))).
              (cond ((and (not assign)
                          (eq mode :logical-block))
                     t)
                    ((and assign
                          (eq mode :logical-block))
                     (let ((value (incf *circularity-counter*)))
                       ;; first occurrence of this object: Set the counter.
                       (setf (gethash object *circularity-hash-table*) value)
                       value))
                    (t
                     nil)))
	     (0
	      (if assign
		  (let ((value (incf *circularity-counter*)))
		    ;; First occurance of this object.  Set the counter.
		    (setf (gethash object *circularity-hash-table*) value)
		    value)
		  t))
	     (t
	      ;; Second or later occurance.
	      (- value)))))))

;;; HANDLE-CIRCULARITY -- interface.
;;; 
(defun handle-circularity (marker stream)
  "Handle the results of CHECK-FOR-CIRCULARITY.  If this returns T then
   you should go ahead and print the object.  If it returns NIL, then
   you should blow it off."
  (case marker
    (:initiate
     ;; Someone forgot to initiate circularity detection.
     (let ((*print-circle* nil))
       (error "Attempt to use CHECK-FOR-CIRCULARITY when circularity ~
	       checking has not been initiated.")))
    ((t :logical-block)
     ;; It's a second (or later) reference to the object while we are
     ;; just looking.  So don't bother groveling it again.
     nil)
    (t
     (write-char #\# stream)
     (let ((*print-base* 10) (*print-radix* nil))
       (cond ((minusp marker)
	      (output-integer (- marker) stream)
	      (write-char #\# stream)
	      nil)
	     (t
	      (output-integer marker stream)
	      (write-char #\= stream)
	      t))))))

(defmacro with-circularity-detection ((object stream) &body body)
  (let ((marker (gensym "WITH-CIRCULARITY-DETECTION-"))
        (body-name (gensym "WITH-CIRCULARITY-DETECTION-BODY-")))
    `(labels ((,body-name ()
               ,@body))
      (cond ((not *print-circle*)
            (,body-name))
            (*circularity-hash-table*
             (let ((,marker (check-for-circularity ,object t :logical-block)))
               (if ,marker
                   (when (handle-circularity ,marker ,stream)
                    (,body-name))
                  (,body-name))))
            (t
             (let ((*circularity-hash-table* (make-hash-table :test 'eq)))
               (output-object ,object (make-broadcast-stream))
               (let ((*circularity-counter* 0))
                 (let ((,marker (check-for-circularity ,object t
                                                       :logical-block)))
                   (when ,marker
                     (handle-circularity ,marker ,stream)))
                (,body-name))))))))

;;;; Level and Length abbreviations.

;;; *CURRENT-LEVEL* -- interface.
;;; 
(defvar *current-level* 0
  "The current level we are printing at, to be compared against *PRINT-LEVEL*.
   See the macro DESCEND-INTO for a handy interface to depth abbreviation.")

;;; DESCEND-INTO -- interface.
;;; 
(defmacro descend-into ((stream) &body body)
  "Automatically handle *print-level* abbreviation.  If we are too deep, then
   a # is printed to STREAM and BODY is ignored."
  (let ((flet-name (gensym)))
    `(flet ((,flet-name ()
	      ,@body))
       (cond ((and (null *print-readably*)
		   *print-level*
		   (>= *current-level* *print-level*))
	      (write-char #\# ,stream))
	     (t
	      (let ((*current-level* (1+ *current-level*)))
		(,flet-name)))))))

;;; PUNT-IF-TOO-LONG -- interface.
;;; 
(defmacro punt-if-too-long (index stream)
  "Punt if INDEX is equal or larger then *PRINT-LENGTH* (and *PRINT-READABLY*
   is NIL) by outputting \"...\" and returning from the block named NIL."
  `(when (and (not *print-readably*)
	      *print-length*
	      (>= ,index *print-length*))
     (write-string "..." ,stream)
     (return)))


;;;; OUTPUT-OBJECT -- the main entry point.

;;; *PRETTY-PRINTER* -- public.
;;; 
(defvar *pretty-printer* nil
  "The current pretty printer.  Should be either a function that takes two
   arguments (the object and the stream) or NIL to indicate that there is
   no pretty printer installed.")

;;; OUTPUT-OBJECT -- interface.
;;; 
(defun output-object (object stream)
  "Output OBJECT to STREAM observing all printer control variables."
  (labels ((print-it (stream)
	     (if *print-pretty*
		 (if *pretty-printer*
		     (funcall *pretty-printer* object stream)
		     (let ((*print-pretty* nil))
		       (output-ugly-object object stream)))
		 (output-ugly-object object stream)))
	   (check-it (stream)
	     (multiple-value-bind (marker initiate)
		 (check-for-circularity object t)
	       (if (eq initiate :initiate)
		   (let ((*circularity-hash-table*
                          (make-hash-table :test 'eq)))
                     (check-it (make-broadcast-stream))
                     (let ((*circularity-counter* 0))
                       (check-it stream)))
		   (if marker
                       (when (handle-circularity marker stream)
                         (print-it stream))
                       (print-it stream))))))
    (cond ((or (not *print-circle*)
	       (numberp object)
	       (characterp object)
	       (and (symbolp object) (symbol-package object) t))
	   ;; If it a number, character, or interned symbol, we do not want
	   ;; to check for circularity/sharing.
	   (print-it stream))
	  ((or *circularity-hash-table*
	       (consp object)
	       (%instancep object)
	       (typep object '(array t *))
	       (typep object 'weak-pointer))
	   ;; If we have already started circularity detection, this
	   ;; object might be a shared reference.  If we have not,
	   ;; then if it is a cons, a instance, an array of element
	   ;; type t, or a weak-pointer it might contain a circular
	   ;; reference to itself or multiple shared references.
	   (check-it stream))
	  (t
	   (print-it stream)))))

;;; OUTPUT-UGLY-OBJECT -- interface.
;;; 
(defun output-ugly-object (object stream)
  "Output OBJECT to STREAM observing all printer control variables except
   for *PRINT-PRETTY*.  Note: if *PRINT-PRETTY* is non-NIL, then the pretty
   printer will be used for any components of OBJECT, just not for OBJECT
   itself."
  (typecase object
    (fixnum
     (output-integer object stream))
    (list
     (if (null object)
	 (output-symbol object stream)
	 (output-list object stream)))
    (instance
     (output-instance object stream))
    (function
     (if (funcallable-instance-p object)
	 (output-instance object stream)
	 (output-function object stream)))
    (symbol
     (output-symbol object stream))
    (number
     (etypecase object
       (integer
	(output-integer object stream))
       (float
	(output-float object stream))
       (ratio
	(output-ratio object stream))
       (complex
	(output-complex object stream))))
    (character
     (output-character object stream))
    (vector
     (output-vector object stream))
    (array
     (output-array object stream))
    (system-area-pointer
     (output-sap object stream))
    (weak-pointer
     (output-weak-pointer object stream))
    (lra
     (output-lra object stream))
    (code-component
     (output-code-component object stream))
    (fdefn
     (output-fdefn object stream))
    #+gencgc
    (scavenger-hook
     (output-scavhook object stream))
    (t
     (output-random object stream))))


;;;; Symbols.

;;; Values of *PRINT-CASE* and (READTABLE-CASE *READTABLE*) the last time the
;;; printer was called.
;;;
(defvar *previous-case* nil)
(defvar *previous-readtable-case* nil)

;;; This variable contains the current definition of one of three symbol
;;; printers.  SETUP-PRINTER-STATE sets this variable.
;;;
(defvar *internal-symbol-output-function* nil)

;;; SETUP-PRINTER-STATE -- Internal.
;;;
;;; This function sets the internal global symbol
;;; *internal-symbol-output-function* to the right function depending on the
;;; value of *print-case*.  See the manual for details.  The print buffer
;;; stream is also reset.
;;;
(defun setup-printer-state ()
  (unless (and (eq *print-case* *previous-case*)
	       (eq (readtable-case *readtable*) *previous-readtable-case*))
    (setq *previous-case* *print-case*)
    (setq *previous-readtable-case* (readtable-case *readtable*))
    (unless (member *print-case* '(:upcase :downcase :capitalize))
      (setq *print-case* :upcase)
      (error "Invalid *PRINT-CASE* value: ~S" *previous-case*))
    (unless (member *previous-readtable-case*
		    '(:upcase :downcase :invert :preserve))
      (setf (readtable-case *readtable*) :upcase)
      (error "Invalid READTABLE-CASE value: ~S" *previous-readtable-case*))

    (setq *internal-symbol-output-function*
	  (case *previous-readtable-case*
	    (:upcase
	     (case *print-case*
	       (:upcase #'output-preserve-symbol)
	       (:downcase #'output-lowercase-symbol)
	       (:capitalize #'output-capitalize-symbol)))
	    (:downcase
	     (case *print-case*
	       (:upcase #'output-uppercase-symbol)
	       (:downcase #'output-preserve-symbol)
	       (:capitalize #'output-capitalize-symbol)))
	    (:preserve #'output-preserve-symbol)
	    (:invert #'output-invert-symbol)))))

;;; OUTPUT-QUOTED-SYMBOL-NAME  --  Internal
;;;
;;;    Out Pname (a symbol-name or package-name) surrounded with |'s, and with
;;; any embedded |'s or \'s escaped.
;;;
(defun output-quoted-symbol-name (pname stream)
  (write-char #\| stream)
  (dotimes (index (length pname))
    (let ((char (schar pname index)))
      (when (or (char= char #\\) (char= char #\|))
	(write-char #\\ stream))
      (write-char char stream)))
  (write-char #\| stream))

(defun output-symbol (object stream)
  (if (or *print-escape* *print-readably*)
      (let ((package (symbol-package object))
	    (name (symbol-name object)))
	(cond
	 ;; If the symbol is in the keyword package, output a colon.
	 ((eq package *keyword-package*)
	  (write-char #\: stream))
	 ;; If the symbol's home package is the current one, then a
	 ;; prefix is never necessary.
	 ((eq package *package*))
	 ;; Uninterned symbols print with a leading #:.
	 ((null package)
	  (when (or *print-gensym* *print-readably*)
	    (write-string "#:" stream)))
	 (t
	  (multiple-value-bind (symbol accessible)
			       (find-symbol name *package*)
	    ;; If we can find the symbol by looking it up, it need not be
	    ;; qualified.  This can happen if the symbol has been inherited
	    ;; from a package other than its home package.
	    (unless (and accessible (eq symbol object))
	      (output-symbol-name (package-name package) stream)
	      (multiple-value-bind (symbol externalp)
				   (find-external-symbol name package)
		(declare (ignore symbol))
		(if externalp
		    (write-char #\: stream)
		    (write-string "::" stream)))))))
	(output-symbol-name name stream))
      (output-symbol-name (symbol-name object) stream nil)))
	    
;;; OUTPUT-SYMBOL-NAME -- internal interface.
;;;
;;; Output the string NAME as if it were a symbol name.  In other words,
;;; diddle it's case according to *print-case* and readtable-case.
;;; 
(defun output-symbol-name (name stream &optional (maybe-quote t))
  (declare (type simple-base-string name))
  (let ((*readtable* (if *print-readably*
			 std-lisp-readtable
			 *readtable*)))
    (setup-printer-state)
    (if (and maybe-quote (symbol-quotep name))
	(output-quoted-symbol-name name stream)
	(funcall *internal-symbol-output-function* name stream))))


;;;; Escaping symbols:

;;;    When we print symbols we have to figure out if they need to be
;;; printed with escape characters.  This isn't a whole lot easier than
;;; reading symbols in the first place.
;;;
;;; For each character, the value of the corresponding element is a fixnum with
;;; bits set corresponding to attributes that the character has.  At characters
;;; have at least one bit set, so we can search for any character with a
;;; positive test.
;;;
(defvar character-attributes
  (make-array char-code-limit :element-type '(unsigned-byte 16)
	      :initial-element 0))
;;;
(declaim (type (simple-array (unsigned-byte 16) (#.char-code-limit))
	       character-attributes))

(eval-when (compile load eval)

;;; Constants which are a bit-mask for each interesting character attribute.
;;;
(defconstant other-attribute		(ash 1 0)) ; Anything else legal.
(defconstant number-attribute		(ash 1 1)) ; A numeric digit.
(defconstant uppercase-attribute 	(ash 1 2)) ; An uppercase letter.
(defconstant lowercase-attribute 	(ash 1 3)) ; A lowercase letter.
(defconstant sign-attribute		(ash 1 4)) ; +-
(defconstant extension-attribute 	(ash 1 5)) ; ^_
(defconstant dot-attribute 		(ash 1 6)) ; .
(defconstant slash-attribute		(ash 1 7)) ; /
(defconstant funny-attribute		(ash 1 8)) ; Anything illegal.

;;; LETTER-ATTRIBUTE is a local of SYMBOL-QUOTEP.  It matches letters that
;;; don't need to be escaped (according to READTABLE-CASE.)
;;;
(defconstant attribute-names
  `((number . number-attribute) (lowercase . lowercase-attribute)
    (uppercase . uppercase-attribute) (letter . letter-attribute)
    (sign . sign-attribute) (extension . extension-attribute)
    (dot . dot-attribute) (slash . slash-attribute)
    (other . other-attribute) (funny . funny-attribute)))

); Eval-When (compile load eval)

(flet ((set-bit (char bit)
	 (let ((code (char-code char)))
	   (setf (aref character-attributes code)
		 (logior bit (aref character-attributes code))))))

  (dolist (char '(#\! #\@ #\$ #\% #\& #\* #\= #\~ #\[ #\] #\{ #\}
		  #\? #\< #\>))
    (set-bit char other-attribute))

  (dotimes (i 10)
    (set-bit (digit-char i) number-attribute))

  (do ((code (char-code #\A) (1+ code))
       (end (char-code #\Z)))
      ((> code end))
    (declare (fixnum code end))
    (set-bit (code-char code) uppercase-attribute)
    (set-bit (char-downcase (code-char code)) lowercase-attribute))

  (set-bit #\- sign-attribute)
  (set-bit #\+ sign-attribute)
  (set-bit #\^ extension-attribute)
  (set-bit #\_ extension-attribute)
  (set-bit #\. dot-attribute)
  (set-bit #\/ slash-attribute)

  ;; Make anything not explicitly allowed funny...
  (dotimes (i char-code-limit)
    (when (zerop (aref character-attributes i))
      (setf (aref character-attributes i) funny-attribute))))

;;; For each character, the value of the corresponding element is the lowest
;;; base in which that character is a digit.
;;;
(defvar digit-bases
  (make-array char-code-limit :element-type '(unsigned-byte 8)
	      :initial-element 36))
;;;
(declaim (type (simple-array (unsigned-byte 8) (#.char-code-limit))
	       digit-bases))

(dotimes (i 36)
  (let ((char (digit-char i 36)))
    (setf (aref digit-bases (char-code char)) i)))


;;; SYMBOL-QUOTEP  --  Internal
;;;
;;;    A FSM-like thingie that determines whether a symbol is a potential
;;; number or has evil characters in it.
;;;
(defun symbol-quotep (name)
  (declare (simple-string name))
  (macrolet ((advance (tag &optional (at-end t))
	       `(progn
		 (when (= index len)
		   ,(if at-end '(go TEST-SIGN) '(return nil)))
		 (setq current (schar name index)
		       code (char-code current)
		       bits (aref attributes code))
		 (incf index)
		 (go ,tag)))
	     (test (&rest attributes)
		`(not (zerop
		       (the fixnum
			    (logand
			     (logior ,@(mapcar
					#'(lambda (x)
					    (or (cdr (assoc x attribute-names))
						(error "Blast!")))
					attributes))
			     bits)))))
	     (digitp ()
	       `(< (the fixnum (aref bases code)) base)))

    (prog ((len (length name))
	   (attributes character-attributes)
	   (bases digit-bases)
	   (base *print-base*)
	   (letter-attribute
	    (case (readtable-case *readtable*)
	      (:upcase uppercase-attribute)
	      (:downcase lowercase-attribute)
	      (t (logior lowercase-attribute uppercase-attribute))))
	   (index 0)
	   (bits 0)
	   (code 0)
	   current)
      (declare (fixnum len base index bits code))
      (advance START t)

     TEST-SIGN ; At end, see if it is a sign...
      (return (not (test sign)))

     OTHER ; Not potential number, see if funny chars...
      (let ((mask (logxor (logior lowercase-attribute uppercase-attribute
				  funny-attribute)
			  letter-attribute)))
	(do ((i (1- index) (1+ i)))
	    ((= i len) (return-from symbol-quotep nil))
	  (unless (zerop (logand (aref attributes (char-code (schar name i)))
				 mask))
	    (return-from symbol-quotep t))))

     START
      (when (digitp)
	(if (test letter)
	    (advance LAST-DIGIT-ALPHA)
	    (advance DIGIT)))
      (when (test letter number other slash) (advance OTHER nil))
      (when (char= current #\.) (advance DOT-FOUND))
      (when (test sign extension) (advance START-STUFF nil))
      (return t)
		  
     DOT-FOUND ; Leading dots...
      (when (test letter) (advance START-DOT-MARKER nil))
      (when (digitp) (advance DOT-DIGIT))
      (when (test number other) (advance OTHER nil))
      (when (test extension slash sign) (advance START-DOT-STUFF nil))
      (when (char= current #\.) (advance DOT-FOUND))
      (return t)

     START-STUFF ; Leading stuff before any dot or digit.
      (when (digitp)
	(if (test letter)
	    (advance LAST-DIGIT-ALPHA)
	    (advance DIGIT)))
      (when (test number other) (advance OTHER nil))
      (when (test letter) (advance START-MARKER nil))
      (when (char= current #\.) (advance START-DOT-STUFF nil))
      (when (test sign extension slash) (advance START-STUFF nil))
      (return t)

     START-MARKER ; Number marker in leading stuff...
      (when (test letter) (advance OTHER nil))
      (go START-STUFF)

     START-DOT-STUFF ; Leading stuff containing dot w/o digit...
      (when (test letter) (advance START-DOT-STUFF nil))
      (when (digitp) (advance DOT-DIGIT))
      (when (test sign extension dot slash) (advance START-DOT-STUFF nil))
      (when (test number other) (advance OTHER nil))
      (return t)

     START-DOT-MARKER ; Number marker in leading stuff w/ dot..
      ;; Leading stuff containing dot w/o digit followed by letter...
      (when (test letter) (advance OTHER nil))
      (go START-DOT-STUFF)

     DOT-DIGIT ; In a thing with dots...
      (when (test letter) (advance DOT-MARKER))
      (when (digitp) (advance DOT-DIGIT))
      (when (test number other) (advance OTHER nil))
      (when (test sign extension dot slash) (advance DOT-DIGIT))
      (return t)

     DOT-MARKER ; Number maker in number with dot...
      (when (test letter) (advance OTHER nil))
      (go DOT-DIGIT)

     LAST-DIGIT-ALPHA ; Previous char is a letter digit...
      (when (or (digitp) (test sign slash))
	(advance ALPHA-DIGIT))
      (when (test letter number other dot) (advance OTHER nil))
      (return t)
      
     ALPHA-DIGIT ; Seen a digit which is a letter...
      (when (or (digitp) (test sign slash))
	(if (test letter)
	    (advance LAST-DIGIT-ALPHA)
	    (advance ALPHA-DIGIT)))
      (when (test letter) (advance ALPHA-MARKER))
      (when (test number other dot) (advance OTHER nil))
      (return t)

     ALPHA-MARKER ; Number marker in number with alpha digit...
      (when (test letter) (advance OTHER nil))
      (go ALPHA-DIGIT)

     DIGIT ; Seen only real numeric digits...
      (when (digitp)
	(if (test letter)
	    (advance ALPHA-DIGIT)
	    (advance DIGIT)))
      (when (test number other) (advance OTHER nil))
      (when (test letter) (advance MARKER)) 
      (when (test extension slash sign) (advance DIGIT))
      (when (char= current #\.) (advance DOT-DIGIT))
      (return t)

     MARKER ; Number marker in a numeric number...
      (when (test letter) (advance OTHER nil))
      (go DIGIT))))


;;;; *INTERNAL-SYMBOL-OUTPUT-FUNCTION*
;;;
;;; Case hackery.  These functions are stored in
;;; *INTERNAL-SYMBOL-OUTPUT-FUNCTION* according to the values of *PRINT-CASE*
;;; and READTABLE-CASE.
;;;

;; Called when:
;; READTABLE-CASE	*PRINT-CASE*
;; :UPCASE		:UPCASE
;; :DOWNCASE		:DOWNCASE
;; :PRESERVE		any
(defun output-preserve-symbol (pname stream)
  (declare (simple-string pname))
  (write-string pname stream))

;; Called when:
;; READTABLE-CASE	*PRINT-CASE*
;; :UPCASE		:DOWNCASE
(defun output-lowercase-symbol (pname stream)
  (declare (simple-string pname))
  (dotimes (index (length pname))
    (let ((char (schar pname index)))
      (write-char (char-downcase char) stream))))

;; Called when:
;; READTABLE-CASE	*PRINT-CASE*
;; :DOWNCASE		:UPCASE
(defun output-uppercase-symbol (pname stream)
  (declare (simple-string pname))
  (dotimes (index (length pname))
    (let ((char (schar pname index)))
      (write-char (char-upcase char) stream))))

;; Called when:
;; READTABLE-CASE	*PRINT-CASE*
;; :UPCASE		:CAPITALIZE
;; :DOWNCASE		:CAPITALIZE
;;
(defun output-capitalize-symbol (pname stream)
  (declare (simple-string pname))
  (let ((prev-not-alpha t)
	(up (eq (readtable-case *readtable*) :upcase)))
    (dotimes (i (length pname))
      (let ((char (char pname i)))
	(write-char (if up
			(if (or prev-not-alpha (lower-case-p char))
			    char
			    (char-downcase char))
			(if prev-not-alpha
			    (char-upcase char)
			    char))
		    stream)
	(setq prev-not-alpha (not (alphanumericp char)))))))

;; Called when:
;; READTABLE-CASE	*PRINT-CASE*
;; :INVERT		any
(defun output-invert-symbol (pname stream)
  (declare (simple-string pname))
  (let ((all-upper t)
	(all-lower t))
    (dotimes (i (length pname))
      (let ((ch (schar pname i)))
	(when (both-case-p ch)
	  (if (upper-case-p ch)
	      (setq all-lower nil)
	      (setq all-upper nil)))))
    (cond (all-upper (output-lowercase-symbol pname stream))
	  (all-lower (output-uppercase-symbol pname stream))
	  (t
	   (write-string pname stream)))))


#|
(defun test1 ()
  (let ((*readtable* (copy-readtable nil)))
    (format t "READTABLE-CASE  Input   Symbol-name~@
	       ----------------------------------~%")
    (dolist (readtable-case '(:upcase :downcase :preserve :invert))
      (setf (readtable-case *readtable*) readtable-case)
      (dolist (input '("ZEBRA" "Zebra" "zebra"))
	(format t "~&:~A~16T~A~24T~A"
		(string-upcase readtable-case)
		input
		(symbol-name (read-from-string input)))))))

(defun test2 ()
  (let ((*readtable* (copy-readtable nil)))
    (format t "READTABLE-CASE  *PRINT-CASE*  Symbol-name  Output  Princ~@
	       --------------------------------------------------------~%")
    (dolist (readtable-case '(:upcase :downcase :preserve :invert))
      (setf (readtable-case *readtable*) readtable-case)
      (dolist (*print-case* '(:upcase :downcase :capitalize))
	(dolist (symbol '(|ZEBRA| |Zebra| |zebra|))
	  (format t "~&:~A~15T:~A~29T~A~42T~A~50T~A"
		  (string-upcase readtable-case)
		  (string-upcase *print-case*)
		  (symbol-name symbol)
		  (prin1-to-string symbol)
		  (princ-to-string symbol)))))))

|#


(defun array-readably-printable-p (array)
  (and (eq (array-element-type array) t)
       (let ((zero (position 0 (array-dimensions array)))
             (number (position 0 (array-dimensions array)
                               :test (complement #'eql)
                               :from-end t)))
         (or (null zero) (null number) (> zero number)))))


;;;; Recursive objects.

(defun output-list (list stream)
  (descend-into (stream)
    (write-char #\( stream)
    (let ((length 0)
	  (list list))
      (loop
	(punt-if-too-long length stream)
	(output-object (pop list) stream)
	(unless list
	  (return))
	(when (or (atom list) (check-for-circularity list))
	  (write-string " . " stream)
	  (output-object list stream)
	  (return))
	(write-char #\space stream)
	(incf length)))
    (write-char #\) stream)))


(defun output-vector (vector stream)
  (declare (vector vector))
  (cond ((stringp vector)
	 (cond ((or *print-escape* *print-readably*)
		(write-char #\" stream)
		(quote-string vector stream)
		(write-char #\" stream))
	       (t
		(write-string vector stream))))
	((not (or *print-array* *print-readably*))
	 (output-terse-array vector stream))
	((bit-vector-p vector)
	 (write-string "#*" stream)
	 (dotimes (i (length vector))
	   (ecase (aref vector i)
	     (0 (write-char #\0 stream))
	     (1 (write-char #\1 stream)))))
	((and *print-readably*
	      (not (array-readably-printable-p vector)))
	 (output-array vector stream))
	(t
	 (descend-into (stream)
	   (write-string "#(" stream)
	   (dotimes (i (length vector))
	     (unless (zerop i)
	       (write-char #\space stream))
	     (punt-if-too-long i stream)
	     (output-object (aref vector i) stream))
	   (write-string ")" stream)))))

;;; QUOTE-STRING -- Internal.
;;;
;;; This function outputs a string quoting characters sufficiently, so someone
;;; can read it in again.  Basically, put a slash in front of an character
;;; satisfying FROB.
;;;
(defun quote-string (string stream)
  (macrolet ((frob (char)
	       ;; Probably should look at readtable, but just do this for now.
	       `(or (char= ,char #\\)
		    (char= ,char #\"))))
    (with-array-data ((data string) (start) (end (length string)))
      (do ((index start (1+ index)))
	  ((>= index end))
	(let ((char (schar data index)))
	  (when (frob char) (write-char #\\ stream))
	  (write-char char stream))))))

(defun output-array (array stream)
  "Outputs the printed representation of any array in either the #< or #A
   form."
  (if (or *print-array* *print-readably*)
      (output-array-guts array stream)
      (output-terse-array array stream)))

;;; Master function for outputing the #A form of an array
;;;
(defun output-array-guts (array stream)
  (with-array-data ((data array) (start) (end))
    (declare (ignore end))
    (cond (*print-readably*
	   (write-string "#A(" stream)
	   (output-object (array-element-type array) stream)
	   (write-char #\Space stream)
	   (output-object (array-dimensions array) stream)
	   (write-char #\Space stream)
	   (sub-output-array-guts data (array-dimensions array) stream start)
	   (write-char #\) stream))
	  (t
	   (write-char #\# stream)
	   (let ((*print-base* 10))
	     (output-integer (array-rank array) stream))
	   (write-char #\A stream)
	   (sub-output-array-guts data (array-dimensions array) stream
				  start)))))

(defun sub-output-array-guts (array dimensions stream index)
  (declare (type (simple-array * (*)) array) (fixnum index))
  (cond ((null dimensions)
	 (output-object (aref array index) stream))
	(t
	 (descend-into (stream)
	   (write-char #\( stream)
	   (let* ((dimension (car dimensions))
		  (dimensions (cdr dimensions))
		  (count (reduce #'* dimensions)))
	     (dotimes (i dimension)
	       (unless (zerop i)
		 (write-char #\space stream))
	       (punt-if-too-long i stream)
	       (sub-output-array-guts array dimensions stream index)
	       (incf index count)))
	   (write-char #\) stream)))))

;;; Used to output the #< form of any array.
;;;
(defun output-terse-array (array stream)
  (let ((*print-level* nil)
	(*print-length* nil))
    (print-unreadable-object (array stream :type t :identity t))))

;;; Instance Printing.  If it's a structure, call the structure printer.
;;; Otherwise, call PCL if it's loaded.  If not, print unreadably.

(defun output-instance (instance stream)
  (let ((layout (typecase instance
		  (instance (%instance-ref instance 0))
		  (funcallable-instance
		   (%funcallable-instance-layout instance)))))

    (if (typep layout 'layout)
	(let ((class (layout-class layout)))
	  (cond
	   ((typep class 'slot-class) ; has slot print-function
	    (if (layout-invalid layout)
		(print-unreadable-object
		    (instance stream :identity t :type t)
		  (write-string "Obsolete Instance" stream))
		(cond (;; non-CLOS :print-function option
		       (slot-class-print-function class)
		       (funcall (slot-class-print-function class)
				instance stream *current-level*))
		      ;; When CLOS loaded, use PRINT-OBJECT.
		      ((fboundp 'print-object)
		       (print-object instance stream))
		      (t
		       (default-structure-print
			   instance stream *current-level*)))))
	   ((fboundp 'print-object)
	    (print-object instance stream))
	   (t
	    (print-unreadable-object (instance stream :identity t)
	      (write-string "Unprintable Instance" stream)))))
	(print-unreadable-object (instance stream :identity t)
	  (write-string "Unprintable Instance" stream)))))

#+ORIGINAL
(defun output-instance (instance stream)
  (let ((layout (typecase instance
		  (instance (%instance-ref instance 0))
		  (funcallable-instance
		   (%funcallable-instance-layout instance)))))

    (if (typep layout 'layout)
	(let ((class (layout-class layout)))
	  (cond ((typep class 'slot-class)
		 (if (layout-invalid layout)
		     (print-unreadable-object (instance stream :identity t
							:type t)
		       (write-string "Obsolete Instance" stream))
		     (funcall (or (slot-class-print-function class)
				  #'default-structure-print)
			      instance stream *current-level*)))
		((fboundp 'print-object)
		 (print-object instance stream))
		(t
		 (print-unreadable-object (instance stream :identity t)
		   (write-string "Unprintable Instance" stream)))))
	(print-unreadable-object (instance stream :identity t)
	  (write-string "Unprintable Instance" stream)))))


;;;; Integer, ratio, and complex printing.  (i.e. everything but floats)

(defun output-integer (integer stream)
  (unless (and (fixnump *print-base*)
	       (< 1 *print-base* 37))
    (let ((obase *print-base*))
      (setq *print-base* 10.)
      (error "~A is not a reasonable value for *Print-Base*." obase)))
  (when (and (not (= *print-base* 10.))
	     *print-radix*)
    ;; First print leading base information, if any.
    (write-char #\# stream)
    (write-char (case *print-base*
		  (2.  #\b)
		  (8.  #\o)
		  (16. #\x)
		  (T (let ((fixbase *print-base*)
			   (*print-base* 10.)
			   (*print-radix* ()))
		       (sub-output-integer fixbase stream))
		     #\r))
		stream))
  ;; Then output a minus sign if the number is negative, then output
  ;; the absolute value of the number.
  (cond ((bignump integer) (print-bignum integer stream))
	((< integer 0)
	 (write-char #\- stream)
	 (sub-output-integer (- integer) stream))
	(t
	 (sub-output-integer integer stream)))
  ;; Print any trailing base information, if any.
  (if (and (= *print-base* 10.) *print-radix*)
      (write-char #\. stream)))

(defun sub-output-integer (integer stream)
  (let ((quotient ())
	(remainder ()))
    ;; Recurse until you have all the digits pushed on the stack.
    (if (not (zerop (multiple-value-setq (quotient remainder)
		      (truncate integer *print-base*))))
	(sub-output-integer quotient stream))
    ;; Then as each recursive call unwinds, turn the digit (in remainder) 
    ;; into a character and output the character.
    (write-char (code-char (if (and (> remainder 9.)
				    (> *print-base* 10.))
			       (+ (char-code #\A) (- remainder 10.))
			       (+ (char-code #\0) remainder)))
		stream)))

;;;; Bignum printing

;;; Contributed by Mark Wooding, based on the algorithm in Emacs calc
;;; by David I. Bell and Landon Curt Noll.  Slightly modified to be
;;; less scheme-like by rtoy.  Caching by rtoy.

;;; A cache of the power lists we need for the algorithm.  A power
;;; list is an alist of (2^k . r^(2^k)), where r is the desired
;;; *print-base*.  The last entry in the alist should be (1 . r).
(defparameter *power-lists*
  (make-array 37 :initial-contents (let ((r '()))
				     (dotimes (k 37)
				       (push (list (cons 1 k)) r))
				     (nreverse r))))

;;; PRINT-BIGNUM -- internal.
;;;
(defun print-bignum (big stream)
  (print-bignum-fast big stream)
  big)

(defun power-list (n r)
  "Compute a list of pairs (2^i . r^{2^i}), stopping with the largest r^{2^i}
greater than n."
  (declare (integer n) (fixnum r))
  (do ((l nil (acons i r l))
       (i 1 (* 2 i))
       (r r (* r r)))
      ((> r n) l)))

(declaim (inline digit-to-char))
(defun digit-to-char (d)
  "Convert digit into a character representation.  We use 0..9, a..z for
10..35, and A..Z for 36..52."
  (declare (fixnum d))
  (labels ((offset (d b) (code-char (+ d (char-code b)))))
    (cond ((< d 10) (offset d #\0))
	  ((< d 36) (offset (- d 10) #\A))
	  (t (error "overflow in digit-to-char")))))

(defun print-fixnum-sub (n r z s)
  "Print a fixnum N to stream S, maybe with leading zeros.  This isn't
ever-so efficient, but we probably don't need to care."
  (declare (fixnum n r z)
	   (stream s))
  (labels ((gen-digits (n l z)
	     (declare (fixnum n z)
		      (list l))
	     (cond ((zerop n)
		    (dotimes (i z)
		      (write-char #\0 s))
		    (dolist (d l)
		      (write-char d s)))
		   (t
		    (multiple-value-bind (n d)
			(truncate n r)
		      (gen-digits n (cons (digit-to-char d) l) (1- z)))))))
    (gen-digits n nil z)))

(defun print-bignum-fast-sub (n r z s pl)
  "Use the power list (see power-list) PL to split N roughly in half; then
print the left and right halves using (cdr PL).  Make sure we count the
leading zeroes correctly."
  (declare (integer n)
	   (type (integer 2 36) r)
	   (stream s)
	   (list pl)
	   (fixnum z))
  (if (fixnump n)
      (print-fixnum-sub n r z s)
      (do ((nz (caar pl) (caar rest))
	   (split (cdar pl) (cdar rest))
	   (rest pl (rest rest)))
	  ((<= split n)
	   (multiple-value-bind (u v)
	       (truncate n split)
	     (print-bignum-fast-sub u r (if (> z nz) (- z nz) 0) s rest)
	     (print-bignum-fast-sub v r nz s rest))))))

(defun maybe-update-power-list (n base)
  ;; Look up entry and see if we need to add entries to it
  (let ((pl (aref *power-lists* base)))
    (do ((index (caar pl) (caar pl))
	 (max (cdar pl) (cdar pl)))
	((>= max n))
      (setf pl (acons (* index 2) (* max max)  pl)))
    (setf (aref *power-lists* base) pl)
    pl))

(defun print-bignum-fast (n s)
  "Primary fast bignum-printing interface.  Prints integer N to stream S in
radix-R.  If you have a power-list then pass it in as PL."
  (when (minusp n)
    (write-char #\- s)
    (setf n (- n)))
  (print-bignum-fast-sub n *print-base* 0 s (maybe-update-power-list n *print-base*)))


(defun output-ratio (ratio stream)
  (when *print-radix*
    (write-char #\# stream)
    (case *print-base*
      (2 (write-char #\b stream))
      (8 (write-char #\o stream))
      (16 (write-char #\x stream))
      (t (write *print-base* :stream stream :radix nil :base 10)
	 (write-char #\r stream))))
  (let ((*print-radix* nil))
    (output-integer (numerator ratio) stream)
    (write-char #\/ stream)
    (output-integer (denominator ratio) stream)))

(defun output-complex (complex stream)
  (write-string "#C(" stream)
  (output-object (realpart complex) stream)
  (write-char #\space stream)
  (output-object (imagpart complex) stream)
  (write-char #\) stream))


;;;; Float printing.

;;;
;;;  Written by Bill Maddox
;;;
;;;
;;;
;;; FLONUM-TO-STRING (and its subsidiary function FLOAT-STRING) does most of 
;;; the work for all printing of floating point numbers in the printer and in
;;; FORMAT.  It converts a floating point number to a string in a free or 
;;; fixed format with no exponent.  The interpretation of the arguments is as 
;;; follows:
;;;
;;;     X        - The floating point number to convert, which must not be
;;;                negative.
;;;     WIDTH    - The preferred field width, used to determine the number
;;;                of fraction digits to produce if the FDIGITS parameter
;;;                is unspecified or NIL.  If the non-fraction digits and the
;;;                decimal point alone exceed this width, no fraction digits
;;;                will be produced unless a non-NIL value of FDIGITS has been
;;;                specified.  Field overflow is not considerd an error at this
;;;                level.
;;;     FDIGITS  - The number of fractional digits to produce. Insignificant
;;;                trailing zeroes may be introduced as needed.  May be
;;;                unspecified or NIL, in which case as many digits as possible
;;;                are generated, subject to the constraint that there are no
;;;                trailing zeroes.
;;;     SCALE    - If this parameter is specified or non-NIL, then the number
;;;                printed is (* x (expt 10 scale)).  This scaling is exact,
;;;                and cannot lose precision.
;;;     FMIN     - This parameter, if specified or non-NIL, is the minimum
;;;                number of fraction digits which will be produced, regardless
;;;                of the value of WIDTH or FDIGITS.  This feature is used by
;;;                the ~E format directive to prevent complete loss of
;;;                significance in the printed value due to a bogus choice of
;;;                scale factor.
;;;     ALLOW-OVERFLOW-P -
;;;                This parameter, defaulting to non-NIL, allows us to
;;;                overflow any width constraint if necessary to
;;;                produce a reasonable output.  If NIL, then we will
;;;                not exceed the width constraint, even if that means
;;;                we only print out leading zeroes.  Generally
;;;                intended to be set by FIXED-FORMAT-AUX so we don't
;;;                exceed the specified width when printing small
;;;                numbers.
;;;
;;; Returns:
;;; (VALUES DIGIT-STRING DIGIT-LENGTH LEADING-POINT TRAILING-POINT DECPNT)
;;; where the results have the following interpretation:
;;;
;;;     DIGIT-STRING    - The decimal representation of X, with decimal point.
;;;     DIGIT-LENGTH    - The length of the string DIGIT-STRING.
;;;     LEADING-POINT   - True if the first character of DIGIT-STRING is the
;;;                       decimal point.
;;;     TRAILING-POINT  - True if the last character of DIGIT-STRING is the
;;;                       decimal point.
;;;     POINT-POS       - The position of the digit preceding the decimal
;;;                       point.  Zero indicates point before first digit.
;;;     ROUNDOFF        - True If, due to rounding, the exponent for the
;;;                       printed result differs from the real
;;;                       exponent of the number.  For example, .9999
;;;                       has an exponent of -1, but the printed
;;;                       result could be 1.000 with an exponent of 0.
;;;
;;; NOTE:  FLONUM-TO-STRING goes to a lot of trouble to guarantee accuracy.
;;; Specifically, the decimal number printed is the closest possible 
;;; approximation to the true value of the binary number to be printed from 
;;; among all decimal representations  with the same number of digits.  In
;;; free-format output, i.e. with the number of digits unconstrained, it is 
;;; guaranteed that all the information is preserved, so that a properly-
;;; rounding reader can reconstruct the original binary number, bit-for-bit, 
;;; from its printed decimal representation. Furthermore, only as many digits
;;; as necessary to satisfy this condition will be printed.
;;;
;;;
;;; FLONUM-TO-DIGITS actually generates the digits for positive
;;; numbers.  See below for comments.

(defvar *digits* "0123456789")

(defun flonum-to-string (x &key width fdigits scale fmin (num-expt 0 num-expt-p)
			        (allow-overflow-p t))
  (setf x (abs x))
  (cond ((zerop x)
	 ;;zero is a special case which float-string cannot handle
	 (if fdigits
	     (let ((s (make-string (1+ fdigits) :initial-element #\0)))
	       (setf (schar s 0) #\.)
	       (values s (length s) t (zerop fdigits) 0))
	     (values "." 1 t t 0)))
	(t
	 (flet ((fixup-flonum-to-digits (x &optional (expt 0) position relativep)
		  (multiple-value-bind (e s)
		      (flonum-to-digits x position relativep)
		    (values (- e expt) s e))))
	   (multiple-value-bind (e string printed-e)
	       (if fdigits
		   (fixup-flonum-to-digits x
					   num-expt
					   (+ (min (- (+ fdigits (or scale 0)))
						   (- (or fmin 0)))
					      num-expt))
		   (if (and width (> width 1))
		       (let ((ndigits (1- width)))
			 #+(or)
			 (progn
			   (format t "ndigits = ~A~%" ndigits)
			   (format t "scale   = ~A~%" scale))
			 (when (and scale (< scale 0))
			   (setf ndigits (+ ndigits scale)))
			 (when (minusp num-expt)
			   (incf ndigits (- num-expt)))
			 (fixup-flonum-to-digits x num-expt
						 ndigits
						 t))
		       (fixup-flonum-to-digits x num-expt)))
	     (let ((stream (make-string-output-stream))
		   (printed-roundoff-p (and num-expt-p (/= num-expt printed-e))))
	       (when (and num-expt-p (/= num-expt printed-e))
		 ;; The actual exponent of the number differs from the
		 ;; printed exponent.  This happens for something like
		 ;; (format nil "~11,3,2,0,'*,,'EE" .9999).  With only
		 ;; 3 fraction digits, .9999 gets rounded to 1.000 But
		 ;; the exponent for .9999 is -1, and the exponent for
		 ;; the printed result is actually 1.  We need to
		 ;; decrement e by 1 to account for this.
		 (decf e))
	       #+(or)
	       (progn
		 (format t "e = ~S~%" e)
		 (format t "roundoff = ~S~%" printed-roundoff-p))
	       
	       (incf e (or scale 0))
	       (if (plusp e)
		   (progn
		     (write-string string stream :end (min (length string)
							   e))
		     (dotimes (i (- e (length string)))
		       (write-char #\0 stream))
		     (write-char #\. stream)
		     (write-string string stream :start (min (length string)
							     e))
		     (when fdigits
		       (dotimes (i (- fdigits
				      (- (length string) 
					 (min (length string) e))))
			 (write-char #\0 stream))))
		   (progn
		     (write-string "." stream)
		     ;; Write out the leading zeroes.  If fmin is set,
		     ;; we need all of them.  But if fdigits is given
		     ;; and is smaller than -e, we only want fdigits
		     ;; to be output.  That way we don't print too
		     ;; many leading zeroes if the number is too
		     ;; small.
		     ;;
		     ;; Also print them all out if :allow-overflow-p
		     ;; is set or there's no width constraint.
		     #+(or)
		     (progn
		       (format t "fmin = ~S~%" fmin)
		       (format t "fdigits = ~S~%" fdigits)
		       (format t "width = ~S~%" width)
		       (when width
			 (format t "min = ~S~%" (min (- e) width))))

		     (let ((leading-zeros
			    (if (or fmin (null fdigits))
				(if (or allow-overflow-p (null width))
				    (- e)
				    (min (- e) (1- width)))
				(min (- e) fdigits))))
		       (dotimes (i leading-zeros)
			 (write-char #\0 stream))
		       ;; If we're out of room (because fdigits is too
		       ;; small), don't print out our string.  This
		       ;; fixes things like (format nil "~,2f" 0.001).
		       ;; We should print ".00", not ".001".  But if
		       ;; fmin is set, we want to print out something.
		       (when (or (null fdigits)
				 (plusp (+ e fdigits))
				 fmin)
			 ;; But only print the whole string if there's
			 ;; no width constraint or if we're allowed to
			 ;; exceed the width.
			 (if (or allow-overflow-p (null width))
			     (write-string string stream)
			     (write-string string stream
					   :end (min (- width leading-zeros 1)
						     (length string)))))
		       (when fdigits
			 (dotimes (i (+ fdigits e (- (length string))))
			   (write-char #\0 stream))))))
	       (let ((string (get-output-stream-string stream)))
		 (values string (length string)
			 (char= (char string 0) #\.)
			 (char= (char string (1- (length string))) #\.)
			 (position #\. string)
			 printed-roundoff-p))))))))


;;; SCALE-EXPONENT  --  Internal
;;;
;;;    Given a non-negative floating point number, SCALE-EXPONENT returns a new
;;; floating point number Z in the range (0.1, 1.0] and an exponent E such
;;; that Z * 10^E is (approximately) equal to the original number.  There may
;;; be some loss of precision due the floating point representation.  The
;;; scaling is always done with long float arithmetic, which helps printing of
;;; lesser precisions as well as avoiding generic arithmetic.
;;;
;;;    When computing our initial scale factor using EXPT, we pull out part of
;;; the computation to avoid over/under flow.  When denormalized, we must pull
;;; out a large factor, since there is more negative exponent range than
;;; positive range.
;;;
(defun scale-exponent-double (original-x)
  (let* ((x (coerce original-x 'long-float)))
    (multiple-value-bind (sig exponent)
			 (decode-float x)
      (declare (ignore sig))
      (if (= x 0.0l0)
	  (values (float 0.0l0 original-x) 1)
	  (let* ((ex (round (* exponent (log 2l0 10))))
		 (x (if (minusp ex)
			(if (float-denormalized-p x)
			    #-long-float
			    (* x 1.0l16 (expt 10.0l0 (- (- ex) 16)))
			    #+long-float
			    (* x 1.0l18 (expt 10.0l0 (- (- ex) 18)))
			    (* x 10.0l0 (expt 10.0l0 (- (- ex) 1))))
			(/ x 10.0l0 (expt 10.0l0 (1- ex))))))
	    (do ((d 10.0l0 (* d 10.0l0))
		 (y x (/ x d))
		 (ex ex (1+ ex)))
		((< y 1.0l0)
		 (do ((m 10.0l0 (* m 10.0l0))
		      (z y (* y m))
		      (ex ex (1- ex)))
		     ((>= z 0.1l0)
		      (values (float z original-x) ex))))))))))

;; Like scale-exponent-double but for double-double-float.
(defun scale-exponent-double-double (original-x)
  (let* ((x original-x))
    (multiple-value-bind (sig exponent)
	(decode-float x)
      (declare (ignore sig))
      (if (= x 0)
	  (values (float 0 original-x) 1)
	  (let* ((ex (round (* exponent (log 2l0 10))))
		 (x (if (minusp ex)
			(if (float-denormalized-p x)
			    #-long-float
			    (* x (expt 10 16) (expt 10 (- (- ex) 16)))
			    #+long-float
			    (* x 1.0l18 (expt 10.0l0 (- (- ex) 18)))
			    (* x 10 (expt 10 (- (- ex) 1))))
			(/ x 10 (expt 10 (1- ex))))))
	    (do ((d 10 (* d 10))
		 (y x (/ x d))
		 (ex ex (1+ ex)))
		((< y 1)
		 (do ((m 10 (* m 10))
		      (z y (* y m))
		      (ex ex (1- ex)))
		     ((>= (* 10 z) 1)
		      (values (float z original-x) ex))))))))))

#-double-double
(defun scale-exponent (original-x)
  (scale-exponent-double original-x))

#+double-double
(defun scale-exponent (original-x)
  ;; We split this into two types because we don't want
  ;; double-double-float to slow down printing double-floats.
  (if (typep original-x 'double-double-float)
      (scale-exponent-double-double original-x)
      (scale-exponent-double original-x)))

;;;; Entry point for the float printer.

;;; Entry point for the float printer as called by PRINT, PRIN1, PRINC,
;;; etc.  The argument is printed free-format, in either exponential or 
;;; non-exponential notation, depending on its magnitude.
;;;
;;; NOTE: When a number is to be printed in exponential format, it is scaled in
;;; floating point.  Since precision may be lost in this process, the
;;; guaranteed accuracy properties of FLONUM-TO-STRING are lost.  The
;;; difficulty is that FLONUM-TO-STRING performs extensive computations with
;;; integers of similar magnitude to that of the number being printed.  For
;;; large exponents, the bignums really get out of hand.  If bignum arithmetic
;;; becomes reasonably fast and the exponent range is not too large, then it
;;; might become attractive to handle exponential notation with the same
;;; accuracy as non-exponential notation, using the method described in the
;;; Steele and White paper.


;;; PRINT-FLOAT-EXPONENT  --  Internal
;;;
;;;    Print the appropriate exponent marker for X and the specified exponent.
;;;
(defun print-float-exponent (x exp stream)
  (declare (float x) (integer exp) (stream stream))
  (let ((*print-radix* nil))
    ;; CLHS 22.3.3.2 for ~E says (near the bottom) that
    ;;
    ;;    If all of w, d, and e are omitted, then the effect is to
    ;;    print the value using ordinary free-format
    ;;    exponential-notation output; prin1 uses a similar format for
    ;;    any non-zero number whose magnitude is less than 10^-3 or
    ;;    greater than or equal to 10^7. The only difference is that
    ;;    the ~E directive always prints a plus or minus sign in front
    ;;    of the exponent, while prin1 omits the plus sign if the
    ;;    exponent is non-negative.
    ;;
    ;; So we don't want a + sign for the exponent.
    (if (typep x *read-default-float-format*)
	(unless (eql exp 0)
	  (format stream "e~D" exp))
	(format stream "~C~D" 
		(etypecase x
		  (single-float #\f)
		  (double-float #\d)
		  (short-float #\s)
		  (long-float #\L)
		  #+double-double
		  (double-double-float #\w))
		exp))))


;;; FLOAT-FORMAT-NAME  --  Internal
;;;
;;;    Return the string name of X's float format.
;;;
(defun float-format-name (x)
  (declare (float x))
  (etypecase x
    (single-float "SINGLE-FLOAT")
    (double-float "DOUBLE-FLOAT")
    (short-float "SHORT-FLOAT")
    (long-float "LONG-FLOAT")
    #+double-double
    (double-double-float "DOUBLE-DOUBLE-FLOAT")))


;;; OUTPUT-FLOAT-INFINITY  --  Internal
;;;
;;;    Write out an infinity using #. notation, or flame out if
;;; *print-readably* is true and *read-eval* is false.
;;;
(defun output-float-infinity (x stream)
  (declare (float x) (stream stream))
  (cond (*read-eval*
	 (write-string "#." stream))
	(*print-readably*
	 (error 'print-not-readable :object x))
	(t
	 (write-string "#<" stream)))
  (write-string "EXT:" stream)
  (write-string (float-format-name x) stream)
  (write-string (if (plusp x) "-POSITIVE-" "-NEGATIVE-")
		stream)
  (write-string "INFINITY" stream)
  (unless *read-eval*
    (write-string ">" stream)))


;;; OUTPUT-FLOAT-NAN  --  Internal
;;;
;;;    Output a #< NaN or die trying.
;;;
(defun output-float-nan (x stream)
  (print-unreadable-object (x stream)
    (write-string (float-format-name x) stream)
    (write-string (if (float-trapping-nan-p x) " Trapping" " Quiet") stream)
    (write-string " NaN" stream)))


(defconstant output-float-free-format-exponent-min -3
  "Minimum power of 10 that allows the float printer to use free format,
   instead of exponential format.  See section 22.1.3.1.3: Printing Floats
   in the ANSI CL standard.")
(defconstant output-float-free-format-exponent-max 8
  "Maximum power of 10 that allows the float printer to use free format,
   instead of exponential format.  See section 22.1.3.1.3: Printing Floats
   in the ANSI CL standard.")

;;; OUTPUT-FLOAT  --  Internal
;;;
;;;    Functioned called by OUTPUT-OBJECT to handle floats.
;;;

(defun output-float (x stream)
  (cond
   ((float-infinity-p x)
    (output-float-infinity x stream))
   ((float-nan-p x)
    (output-float-nan x stream))
   #+(and nil double-double)
   ((typep x 'double-double-float)
    ;; This is a temporary hack until we get more double-double float
    ;; stuff in place so that we don't need this.  And being able to
    ;; print double-double's now is quite handy while we debug the
    ;; rest of the code.
    (output-double-double-float x stream))
   (t
    (let ((x (cond ((minusp (float-sign x))
		    (write-char #\- stream)
		    (- x))
		   (t
		    x))))
      (cond
       ((zerop x)
	(write-string "0.0" stream)
	(print-float-exponent x 0 stream))
       (t
	(output-float-aux x stream
			  output-float-free-format-exponent-min
			  output-float-free-format-exponent-max)))))))

#+double-double
(defun output-double-double-float (x stream)
  (dd->string (kernel:double-double-hi x)
	      (kernel:double-double-lo x)
	      stream))

;;; The code below for printing double-double's was written by Richard
;;; Fateman.  Used with permission.

#+double-double
(defvar *dd-digits-to-show* 33)

#+double-double
(defun dd->lisp (a0 a1)
  "Convert a DD number to a lisp rational"
  (declare (double-float a0 a1))
  (+ (rational a0) (rational a1)))

#+double-double
;; r rational number >=0
;; n number of digits
(defun decimalize (r n &optional (base 10))
  (let* ((expon (if (= r 0)
		    0
		    (floor (cl::log (cl::abs r) base))))
	 (frac (round (* (cl::abs r)
			 (expt base (- n expon))))))
    (values (signum r)
	    frac
	    (if (= frac 0)
		0
		(cl::1+ expon)))))

#+double-double
(defun dd->string (x0 x1 stream)
  "Print out a double-double to a string"
  (cond ((and (zerop x0) (zerop x1))
	 (format stream "0.dd0"))
	(t
	 (multiple-value-bind (s r e h)
	     (decimalize (dd->lisp x0 x1) *dd-digits-to-show* 10)
	   ;; This is slightly modified from Richard Fateman's version to
	   ;; print numbers in the format x.xxddee instead of 0.xxddee.
	   (let ((out (string-right-trim "0"
					 (subseq (setf h (format nil "~A~%" r))
						 0
						 (min (length h) *dd-digits-to-show*)))))
	     (format stream "~A~A.~Aw~S"
		     (if (< s 0) "-" "")
		     (aref out 0)
		     (subseq out 1)
		     (1- e)))))))


;; Smallest possible (unbiased) exponents
(defconstant double-float-min-e
  (nth-value 1 (decode-float least-positive-double-float)))
(defconstant single-float-min-e
  (nth-value 1 (decode-float least-positive-single-float)))
#+double-double
(defconstant double-double-float-min-e double-float-min-e)

;; Exact powers of ten.  Must be large enough to cover the range from
;; least-positive-double-float to most-positive-double-float
(declaim (type (simple-array integer (326)) *powers-of-ten*))
(defparameter *powers-of-ten*
  (make-array 326
	      :initial-contents
	      (let (p)
		(dotimes (k 326 (nreverse p))
		  (push (expt 10 k) p)))))

;;; Implementation of Figure 1 from "Printing Floating-Point Numbers
;;; Quickly and Accurately", by Burger and Dybvig, 1996.  As the
;;; implementation of the Dragon algorithm above says: "DO NOT EVEN
;;; THINK OF ATTEMPTING TO UNDERSTAND THIS CODE WITHOUT READING THE
;;; PAPER!"  This is a more idiomatic Lisp translation by CSR of the
;;; scheme implementation in that paper.
;;;
(defun flonum-to-digits (v &optional position relativep)
  ;; V is the number to be printed.  If RELATIVEP is NIL, POSITION is
  ;; the number of digits to the left of the decimal point where we
  ;; want to stop printing.  If RELATIVEP is non-NIL, POSITION is the
  ;; total number of digits we want printed.
  ;;
  ;; Two values are returned: k, and the digit string, without a
  ;; decimal point.  k is the index into the string, before which the
  ;; decimal point would go.
  (let ((print-base 10)			; B
	(float-radix 2)			; b
	(float-digits (float-digits v)) ; p
	(min-e
	 (etypecase v
	   (single-float single-float-min-e)
	   (double-float double-float-min-e)
	   #+double-double
	   (double-double-float double-double-float-min-e))))
    (multiple-value-bind (f e)
	(integer-decode-float v)
      (let ( ;; FIXME: these even tests assume normal IEEE rounding
	    ;; mode.  I wonder if we should cater for non-normal?
	    (high-ok (evenp f))
	    (low-ok (evenp f))
	    (result (make-array 50 :element-type 'base-char
				:fill-pointer 0 :adjustable t)))
	(labels ((flog (x)
		   (declare (type (float (0.0)) x))
		   (let ((xd (etypecase x
			       (single-float
				(float x 1d0))
			       (double-float
				x)
			       #+double-double
			       (double-double-float
				(double-double-hi x)))))
		     (ceiling (- (the (double-float -400d0 400d0) (log xd 10d0))
				 1d-10))))
		 (fixup (r s m+ m- k)
		   (if (if high-ok
			   (>= (+ r m+) s)
			   (> (+ r m+) s))
		       (values (+ k 1) (generate r (* s print-base) m+ m-))
		       (values k (generate r s m+ m-))))
		 (scale (r s m+ m-)
		   (let* ((est (flog v))
			  (scale (the integer (aref lisp::*powers-of-ten* (abs est)))))
		     (if (>= est 0)
			 (fixup r (* s scale) m+ m- est)
			 (fixup (* r scale) s (* m+ scale) (* m- scale) est))))
		 (generate (r s m+ m-)
		   (multiple-value-bind (d r)
		       (truncate (* r print-base) s)
		     (let ((m+ (* m+ print-base))
			   (m- (* m- print-base)))
		       (let ((tc1 (or (< r m-) (and low-ok (= r m-))))
			     (tc2 (let ((test (+ r m+)))
				    (or (> test s)
					(and high-ok (= test s))))))
			 (cond
			   ((and (not tc1) (not tc2))
			    (vector-push-extend (char *digits* d) result)
			    ;; FIXME sucky tail recursion.  This whole
			    ;; kaboodle should be DO*/LOOPified.
			    (generate r s m+ m-))
			   ;; pedantically keeping all the conditions
			   ;; in so that we can move them around.
			   ((and (not tc1) tc2)
			    (vector-push-extend (char *digits* (1+ d)) result)
			    result)
			   ((and tc1 (not tc2))
			    (vector-push-extend (char *digits* d) result)
			    result)
			   ((and tc1 tc2)
			    (vector-push-extend (char *digits*
						      (if (< (* r 2) s) d (1+ d)))
						result)
			    result)))))))
	  (let (r s m+ m-)
	    (if (>= e 0)
		(let* ((be (expt float-radix e))
		       (be1 (* be float-radix)))
		  (if (/= f (expt float-radix (1-
					       float-digits)))
		      (setf r (* f be 2)
			    s 2
			    m+ be
			    m- be)
		      (setf r (* f be1 2)
			    s (* float-radix 2)
			    m+ be1
			    m- be)))
		(if (or (= e min-e) 
			(/= f (expt float-radix (1-
						 float-digits))))
		    (setf r (* f 2)
			  s (* (expt float-radix (- e)) 2)
			  m+ 1
			  m- 1)
		    (setf r (* f float-radix 2)
			  s (* (expt float-radix (- 1 e)) 2)
			  m+ float-radix
			  m- 1)))
	    (when position
	      (flet ((expt-ten (e)
		       (if (minusp e)
			   (/ (aref *powers-of-ten* (- e)))
			   (aref *powers-of-ten* e))))
		(when relativep
		  (let ((r+m (+ r m+)))
		    ;;(format t "r, s = ~A, ~A~%" r s)
		    (do ((k 0 (1+ k))
			 ;; running out of letters here
			 (l 1 (* l print-base)))
			((>= (* s l) r+m)
			 ;; k is now \hat{k}
			 ;;(format t "r>s, k = ~A~%" k)
			 (if (< (+ r (* s (/ (expt-ten (- k position))
					     2)))
				(* s (expt-ten k)))
			     (setf position (- k position))
			     (setf position (- k position 1)))))))
		(let ((low (max m- (/ (* s (expt-ten position)) 2)))
		      (high (max m+ (/ (* s (expt-ten position)) 2))))
		  (when (<= m- low)
		    (setf m- low)
		    (setf low-ok t))
		  (when (<= m+ high)
		    (setf m+ high)
		    (setf high-ok t)))))
	    (scale r s m+ m-)))))))


(defun output-float-aux (x stream e-min e-max)
  (multiple-value-bind (e string)
      (flonum-to-digits x)
    (cond
      ((< e-min e e-max)
       ;; free format
       (cond ((plusp e)
	      (write-string string stream :end (min (length string) e))
	      (dotimes (i (- e (length string)))
		(write-char #\0 stream))
	      (write-char #\. stream)
	      (write-string string stream :start (min (length string) e))
	      (when (<= (length string) e)
		(write-char #\0 stream))
	      (print-float-exponent x 0 stream))
	     (t
	      (write-string "0." stream)
	      (dotimes (i (- e))
		(write-char #\0 stream))
	      (write-string string stream)
	      (print-float-exponent x 0 stream))))
      (t
       ;; Exponential format
       (write-string string stream :end 1)
       (write-char #\. stream)
       (write-string string stream :start 1)
       ;; CLHS 22.1.3.1.3 says at least one digit must be printed
       ;; after the decimal point.
       (when (= (length string) 1)
	 (write-char #\0 stream))
       (print-float-exponent x (1- e) stream)))))


;;;; Other leaf objects.

;;; OUTPUT-CHARACTER  --  Internal
;;;
;;;    If *print-escape* is false, just do a WRITE-CHAR, otherwise output the
;;; character name or the character in the #\char format.
;;;
(defun output-character (char stream)
  (if (or *print-escape* *print-readably*)
      (let ((name (char-name char)))
	(write-string "#\\" stream)
	;; CLHS 22.1.3.2 says graphic characters are not printed using
	;; the character name.
	(if (and name (not (graphic-char-p char)))
	    (quote-string name stream)
	    (write-char char stream)))
      (write-char char stream)))

(defun output-sap (sap stream)
  (declare (type system-area-pointer sap))
  (cond (*read-eval*
	 (format stream "#.(~S #x~8,'0X)"
		 'int-sap (sap-int sap)))
	(t
	 (print-unreadable-object (sap stream)
	   (format stream "System-Area-Pointer: #x~8,'0X"
		   (sap-int sap))))))

(defun output-weak-pointer (weak-pointer stream)
  (declare (type weak-pointer weak-pointer))
  (print-unreadable-object (weak-pointer stream :identity t)
    (multiple-value-bind
	(value validp)
	(weak-pointer-value weak-pointer)
      (cond (validp
	     (write-string "Weak Pointer: " stream)
	     (write value :stream stream))
	    (t
	     (write-string "Broken Weak Pointer" stream))))))

(defun output-code-component (component stream)
  (print-unreadable-object (component stream :identity t)
    (let ((dinfo (%code-debug-info component)))
      (cond ((eq dinfo :bogus-lra)
	     (write-string "Bogus Code Object" stream))
	    (t
	     (write-string "Code Object" stream)
	     (when dinfo
	       (write-char #\space stream)
	       (output-object (c::debug-info-name dinfo) stream)))))))

(defun output-lra (lra stream)
  (print-unreadable-object (lra stream :identity t)
    (write-string "Return PC Object" stream)))

(defun output-fdefn (fdefn stream)
  (print-unreadable-object (fdefn stream)
    (write-string "FDEFINITION object for " stream)
    (output-object (fdefn-name fdefn) stream)))

#+gencgc
(defun output-scavhook (scav stream)
  (print-unreadable-object (scav stream :identity t :type t)))


;;;; Various flavors of function pointers.


;;; OUTPUT-FUNCTION-OBJECT outputs the main part of the printed 
;;; representation of function objects.  It is called from OUTPUT-RANDOM
;;; below.

(defun output-function-object (subr stream)
  (write-string "Function " stream)
  (prin1 (%function-name subr) stream))


;;; OUTPUT-INTERPRETED-FUNCTION  --  Internal
;;;
;;;    Print the name or definition of an interpreted function.
;;;
(defun output-interpreted-function (subr stream)
  (multiple-value-bind
      (def ignore name)
      (eval:interpreted-function-lambda-expression subr)
    (declare (ignore ignore))
    (let ((*print-level* 3))
      (format stream "Interpreted Function ~S" (or name def)))))

(defun output-function (function stream)
  (print-unreadable-object (function stream :identity t)
    (case (function-subtype function)
      ((#.vm:function-header-type #.vm:closure-function-header-type)
       (output-function-object function stream))
      (#.vm:byte-code-function-type
       (write-string "Byte Compiled Function" stream))
      (#.vm:byte-code-closure-type
       (write-string "Byte Compiled Closure" stream))
      (#.vm:closure-header-type
       (cond
	((eval:interpreted-function-p function)
	 (output-interpreted-function function stream))
	(t
	 (write-string "Closure Over " stream)
	 (output-function-object (%closure-function function) stream))))
      (t
       (write-string "Unknown Function" stream)))))


;;;; Catch-all for unknown things.

(defun output-random (object stream)
  (print-unreadable-object (object stream :identity t)
    (let ((lowtag (get-lowtag object)))
      (case lowtag
	(#.vm:other-pointer-type
	  (let ((type (get-type object)))
	    (case type
	      (#.vm:value-cell-header-type
	       (write-string "Value Cell " stream)
	       (output-object (c:value-cell-ref object) stream))
	      (t
	       (write-string "Unknown Pointer Object, type=" stream)
	       (let ((*print-base* 16) (*print-radix* t))
		 (output-integer type stream))))))
	((#.vm:function-pointer-type
	  #.vm:instance-pointer-type
	  #.vm:list-pointer-type)
	 (write-string "Unknown Pointer Object, type=" stream))
	(t
	 (case (get-type object)
	   (#.vm:unbound-marker-type
	    (write-string "Unbound Marker" stream))
	   (t
	    (write-string "Unknown Immediate Object, lowtag=" stream)
	    (let ((*print-base* 2) (*print-radix* t))
	      (output-integer lowtag stream))
	    (write-string ", type=" stream)
	    (let ((*print-base* 16) (*print-radix* t))
	      (output-integer (get-type object) stream)))))))))
