(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)))
+ (write-char #\space stream))
(when body
(funcall body))
(when identity
- (when body
- (write-char #\space stream)
- (pprint-newline :fill stream))
+ (when (or body (not type))
+ (write-char #\space stream))
(write-char #\{ stream)
(write (get-lisp-obj-address object) :stream stream
:radix nil :base 16)
(not (array-readably-printable-p array)))
(error 'print-not-readable :object array))
(write-char #\# stream)
- (let ((*print-base* 10))
+ (let ((*print-base* 10)
+ (*print-radix* nil))
(output-integer (array-rank array) stream))
(write-char #\A stream)
(with-array-data ((data array) (start) (end))
;;; [CMUC]<steele>tradix.press. DO NOT EVEN THINK OF ATTEMPTING TO
;;; UNDERSTAND THIS CODE WITHOUT READING THE PAPER!
+(declaim (type (simple-array character (10)) *digits*))
(defvar *digits* "0123456789")
(defun flonum-to-string (x &optional width fdigits scale fmin)
;; all done
(values digit-string (1+ digits) (= decpnt 0) (= decpnt digits) decpnt)))
+;;; implementation of figure 1 from Burger and Dybvig, 1996. As the
+;;; implementation of the Dragon from Classic CMUCL (and above,
+;;; FLONUM-TO-STRING) says: "DO NOT EVEN THINK OF ATTEMPTING TO
+;;; UNDERSTAND THIS CODE WITHOUT READING THE PAPER!", and in this case
+;;; we have to add that even reading the paper might not bring
+;;; immediate illumination as CSR has attempted to turn idiomatic
+;;; Scheme into idiomatic Lisp.
+;;;
+;;; FIXME: figure 1 from Burger and Dybvig is the unoptimized
+;;; algorithm, noticeably slow at finding the exponent. Figure 2 has
+;;; an improved algorithm, but CSR ran out of energy
+;;;
+;;; FIXME: Burger and Dybvig also provide an algorithm for
+;;; fixed-format floating point printing. If it were implemented,
+;;; then we could delete the Dragon altogether (see FLONUM-TO-STRING).
+;;;
+;;; possible extension for the enthusiastic: printing floats in bases
+;;; other than base 10.
+(defconstant single-float-min-e
+ (nth-value 1 (decode-float least-positive-single-float)))
+(defconstant double-float-min-e
+ (nth-value 1 (decode-float least-positive-double-float)))
+#!+long-float
+(defconstant long-float-min-e
+ (nth-value 1 (decode-float least-positive-long-float)))
+
+(defun flonum-to-digits (v)
+ (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)
+ #!+long-float
+ (long-float long-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 ((scale (r s m+ m-)
+ (do ((k 0 (1+ k))
+ (s s (* s print-base)))
+ ((not (or (> (+ r m+) s)
+ (and high-ok (= (+ r m+) s))))
+ (do ((k k (1- k))
+ (r r (* r print-base))
+ (m+ m+ (* m+ print-base))
+ (m- m- (* m- print-base)))
+ ((not (or (< (* (+ r m+) print-base) s)
+ (and high-ok (= (* (+ r m+) print-base) s))))
+ (values k (generate r s m+ m-)))))))
+ (generate (r s m+ m-)
+ (let (d tc1 tc2)
+ (tagbody
+ loop
+ (setf (values d r) (truncate (* r print-base) s))
+ (setf m+ (* m+ print-base))
+ (setf m- (* m- print-base))
+ (setf tc1 (or (< r m-) (and low-ok (= r m-))))
+ (setf tc2 (or (> (+ r m+) s)
+ (and high-ok (= (+ r m+) s))))
+ (when (or tc1 tc2)
+ (go end))
+ (vector-push-extend (char *digits* d) result)
+ (go loop)
+ end
+ (let ((d (cond
+ ((and (not tc1) tc2) (1+ d))
+ ((and tc1 (not tc2)) d)
+ (t ; (and tc1 tc2)
+ (if (< (* r 2) s) d (1+ d))))))
+ (vector-push-extend (char *digits* d) result)
+ (return-from generate result))))))
+ (if (>= e 0)
+ (if (/= f (expt float-radix (1- float-digits)))
+ (let ((be (expt float-radix e)))
+ (scale (* f be 2) 2 be be))
+ (let* ((be (expt float-radix e))
+ (be1 (* be float-radix)))
+ (scale (* f be1 2) (* float-radix 2) be1 be)))
+ (if (or (= e min-e) (/= f (expt float-radix (1- float-digits))))
+ (scale (* f 2) (* (expt float-radix (- e)) 2) 1 1)
+ (scale (* f float-radix 2)
+ (* (expt float-radix (- 1 e)) 2) float-radix 1))))))))
+\f
;;; 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
;;; attractive to handle exponential notation with the same accuracy
;;; as non-exponential notation, using the method described in the
;;; Steele and White paper.
+;;;
+;;; NOTE II: this has been bypassed slightly by implementing Burger
+;;; and Dybvig, 1996. When someone has time (KLUDGE) they can
+;;; probably (a) implement the optimizations suggested by Burger and
+;;; Dyvbig, and (b) remove all vestiges of Dragon4, including from
+;;; fixed-format printing.
;;; Print the appropriate exponent marker for X and the specified exponent.
(defun print-float-exponent (x exp stream)
(write-string "0.0" stream)
(print-float-exponent x 0 stream))
(t
- (output-float-aux x stream (float 1/1000 x) (float 10000000 x))))))))
+ (output-float-aux x stream -3 8)))))))
(defun output-float-aux (x stream e-min e-max)
- (if (and (>= x e-min) (< x e-max))
- ;; free format
- (multiple-value-bind (str len lpoint tpoint) (flonum-to-string x)
- (declare (ignore len))
- (when lpoint (write-char #\0 stream))
- (write-string str stream)
- (when tpoint (write-char #\0 stream))
- (print-float-exponent x 0 stream))
- ;; exponential format
- (multiple-value-bind (f ex) (scale-exponent x)
- (multiple-value-bind (str len lpoint tpoint)
- (flonum-to-string f nil nil 1)
- (declare (ignore len))
- (when lpoint (write-char #\0 stream))
- (write-string str stream)
- (when tpoint (write-char #\0 stream))
- ;; Subtract out scale factor of 1 passed to FLONUM-TO-STRING.
- (print-float-exponent x (1- ex) stream)))))
+ (multiple-value-bind (e string)
+ (flonum-to-digits x)
+ (cond
+ ((< e-min e e-max)
+ (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 (<= (length string) e)
+ (write-char #\0 stream))
+ (print-float-exponent x 0 stream))
+ (progn
+ (write-string "0." stream)
+ (dotimes (i (- e))
+ (write-char #\0 stream))
+ (write-string string stream)
+ (print-float-exponent x 0 stream))))
+ (t (write-string string stream :end 1)
+ (write-char #\. stream)
+ (write-string string stream :start 1)
+ (when (= (length string) 1)
+ (write-char #\0 stream))
+ (print-float-exponent x (1- e) stream)))))
\f
;;;; other leaf objects
projects / sbcl.git / blobdiff