1 ;;;; This file contains the definitions of float specific number
2 ;;;; support (other than irrational stuff, which is in irrat.) There is
3 ;;;; code in here that assumes there are only two float formats: IEEE
4 ;;;; single and double. (Long-float support has been added, but bugs
5 ;;;; may still remain due to old code which assumes this dichotomy.)
7 ;;;; This software is part of the SBCL system. See the README file for
10 ;;;; This software is derived from the CMU CL system, which was
11 ;;;; written at Carnegie Mellon University and released into the
12 ;;;; public domain. The software is in the public domain and is
13 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
14 ;;;; files for more information.
16 (in-package "SB!KERNEL")
20 (eval-when (:compile-toplevel :load-toplevel :execute)
22 ;;; These functions let us create floats from bits with the
23 ;;; significand uniformly represented as an integer. This is less
24 ;;; efficient for double floats, but is more convenient when making
25 ;;; special values, etc.
26 (defun single-from-bits (sign exp sig)
27 (declare (type bit sign) (type (unsigned-byte 24) sig)
28 (type (unsigned-byte 8) exp))
30 (dpb exp sb!vm:single-float-exponent-byte
31 (dpb sig sb!vm:single-float-significand-byte
32 (if (zerop sign) 0 -1)))))
33 (defun double-from-bits (sign exp sig)
34 (declare (type bit sign) (type (unsigned-byte 53) sig)
35 (type (unsigned-byte 11) exp))
36 (make-double-float (dpb exp sb!vm:double-float-exponent-byte
37 (dpb (ash sig -32) sb!vm:double-float-significand-byte
38 (if (zerop sign) 0 -1)))
39 (ldb (byte 32 0) sig)))
40 #!+(and long-float x86)
41 (defun long-from-bits (sign exp sig)
42 (declare (type bit sign) (type (unsigned-byte 64) sig)
43 (type (unsigned-byte 15) exp))
44 (make-long-float (logior (ash sign 15) exp)
45 (ldb (byte 32 32) sig)
46 (ldb (byte 32 0) sig)))
52 (defconstant least-positive-single-float (single-from-bits 0 0 1))
53 (defconstant least-positive-short-float least-positive-single-float)
54 (defconstant least-negative-single-float (single-from-bits 1 0 1))
55 (defconstant least-negative-short-float least-negative-single-float)
56 (defconstant least-positive-double-float (double-from-bits 0 0 1))
58 (defconstant least-positive-long-float least-positive-double-float)
59 #!+(and long-float x86)
60 (defconstant least-positive-long-float (long-from-bits 0 0 1))
61 (defconstant least-negative-double-float (double-from-bits 1 0 1))
63 (defconstant least-negative-long-float least-negative-double-float)
64 #!+(and long-float x86)
65 (defconstant least-negative-long-float (long-from-bits 1 0 1))
67 (defconstant least-positive-normalized-single-float
68 (single-from-bits 0 sb!vm:single-float-normal-exponent-min 0))
69 (defconstant least-positive-normalized-short-float
70 least-positive-normalized-single-float)
71 (defconstant least-negative-normalized-single-float
72 (single-from-bits 1 sb!vm:single-float-normal-exponent-min 0))
73 (defconstant least-negative-normalized-short-float
74 least-negative-normalized-single-float)
75 (defconstant least-positive-normalized-double-float
76 (double-from-bits 0 sb!vm:double-float-normal-exponent-min 0))
78 (defconstant least-positive-normalized-long-float
79 least-positive-normalized-double-float)
80 #!+(and long-float x86)
81 (defconstant least-positive-normalized-long-float
82 (long-from-bits 0 sb!vm:long-float-normal-exponent-min
83 (ash sb!vm:long-float-hidden-bit 32)))
84 (defconstant least-negative-normalized-double-float
85 (double-from-bits 1 sb!vm:double-float-normal-exponent-min 0))
87 (defconstant least-negative-normalized-long-float
88 least-negative-normalized-double-float)
89 #!+(and long-float x86)
90 (defconstant least-negative-normalized-long-float
91 (long-from-bits 1 sb!vm:long-float-normal-exponent-min
92 (ash sb!vm:long-float-hidden-bit 32)))
94 (defconstant most-positive-single-float
95 (single-from-bits 0 sb!vm:single-float-normal-exponent-max
96 (ldb sb!vm:single-float-significand-byte -1)))
97 (defconstant most-positive-short-float most-positive-single-float)
98 (defconstant most-negative-single-float
99 (single-from-bits 1 sb!vm:single-float-normal-exponent-max
100 (ldb sb!vm:single-float-significand-byte -1)))
101 (defconstant most-negative-short-float most-negative-single-float)
102 (defconstant most-positive-double-float
103 (double-from-bits 0 sb!vm:double-float-normal-exponent-max
104 (ldb (byte sb!vm:double-float-digits 0) -1)))
106 (defconstant most-positive-long-float most-positive-double-float)
107 #!+(and long-float x86)
108 (defconstant most-positive-long-float
109 (long-from-bits 0 sb!vm:long-float-normal-exponent-max
110 (ldb (byte sb!vm:long-float-digits 0) -1)))
111 (defconstant most-negative-double-float
112 (double-from-bits 1 sb!vm:double-float-normal-exponent-max
113 (ldb (byte sb!vm:double-float-digits 0) -1)))
115 (defconstant most-negative-long-float most-negative-double-float)
116 #!+(and long-float x86)
117 (defconstant most-negative-long-float
118 (long-from-bits 1 sb!vm:long-float-normal-exponent-max
119 (ldb (byte sb!vm:long-float-digits 0) -1)))
121 ;;; We don't want to do these DEFCONSTANTs at cross-compilation time,
122 ;;; because the cross-compilation host might not support floating
123 ;;; point infinities.
124 (eval-when (:load-toplevel :execute)
125 (defconstant single-float-positive-infinity
126 (single-from-bits 0 (1+ sb!vm:single-float-normal-exponent-max) 0))
127 (defconstant short-float-positive-infinity single-float-positive-infinity)
128 (defconstant single-float-negative-infinity
129 (single-from-bits 1 (1+ sb!vm:single-float-normal-exponent-max) 0))
130 (defconstant short-float-negative-infinity single-float-negative-infinity)
131 (defconstant double-float-positive-infinity
132 (double-from-bits 0 (1+ sb!vm:double-float-normal-exponent-max) 0))
134 (defconstant long-float-positive-infinity double-float-positive-infinity)
135 #!+(and long-float x86)
136 (defconstant long-float-positive-infinity
137 (long-from-bits 0 (1+ sb!vm:long-float-normal-exponent-max)
138 (ash sb!vm:long-float-hidden-bit 32)))
139 (defconstant double-float-negative-infinity
140 (double-from-bits 1 (1+ sb!vm:double-float-normal-exponent-max) 0))
142 (defconstant long-float-negative-infinity double-float-negative-infinity)
143 #!+(and long-float x86)
144 (defconstant long-float-negative-infinity
145 (long-from-bits 1 (1+ sb!vm:long-float-normal-exponent-max)
146 (ash sb!vm:long-float-hidden-bit 32)))
149 (defconstant single-float-epsilon
150 (single-from-bits 0 (- sb!vm:single-float-bias
151 (1- sb!vm:single-float-digits)) 1))
152 (defconstant short-float-epsilon single-float-epsilon)
153 (defconstant single-float-negative-epsilon
154 (single-from-bits 0 (- sb!vm:single-float-bias sb!vm:single-float-digits) 1))
155 (defconstant short-float-negative-epsilon single-float-negative-epsilon)
156 (defconstant double-float-epsilon
157 (double-from-bits 0 (- sb!vm:double-float-bias
158 (1- sb!vm:double-float-digits)) 1))
160 (defconstant long-float-epsilon double-float-epsilon)
161 #!+(and long-float x86)
162 (defconstant long-float-epsilon
163 (long-from-bits 0 (- sb!vm:long-float-bias (1- sb!vm:long-float-digits))
164 (+ 1 (ash sb!vm:long-float-hidden-bit 32))))
165 (defconstant double-float-negative-epsilon
166 (double-from-bits 0 (- sb!vm:double-float-bias sb!vm:double-float-digits) 1))
168 (defconstant long-float-negative-epsilon double-float-negative-epsilon)
169 #!+(and long-float x86)
170 (defconstant long-float-negative-epsilon
171 (long-from-bits 0 (- sb!vm:long-float-bias sb!vm:long-float-digits)
172 (+ 1 (ash sb!vm:long-float-hidden-bit 32))))
174 ;;;; float predicates and environment query
177 (declaim (maybe-inline float-denormalized-p float-infinity-p float-nan-p
178 float-trapping-nan-p))
180 (defun float-denormalized-p (x)
182 "Return true if the float X is denormalized."
183 (number-dispatch ((x float))
185 (and (zerop (ldb sb!vm:single-float-exponent-byte (single-float-bits x)))
188 (and (zerop (ldb sb!vm:double-float-exponent-byte
189 (double-float-high-bits x)))
191 #!+(and long-float x86)
193 (and (zerop (ldb sb!vm:long-float-exponent-byte (long-float-exp-bits x)))
196 (macrolet ((def-frob (name doc single double #!+(and long-float x86) long)
199 (number-dispatch ((x float))
201 (let ((bits (single-float-bits x)))
202 (and (> (ldb sb!vm:single-float-exponent-byte bits)
203 sb!vm:single-float-normal-exponent-max)
206 (let ((hi (double-float-high-bits x))
207 (lo (double-float-low-bits x)))
208 (declare (ignorable lo))
209 (and (> (ldb sb!vm:double-float-exponent-byte hi)
210 sb!vm:double-float-normal-exponent-max)
212 #!+(and long-float x86)
214 (let ((exp (long-float-exp-bits x))
215 (hi (long-float-high-bits x))
216 (lo (long-float-low-bits x)))
217 (declare (ignorable lo))
218 (and (> (ldb sb!vm:long-float-exponent-byte exp)
219 sb!vm:long-float-normal-exponent-max)
222 (def-frob float-infinity-p
223 "Return true if the float X is an infinity (+ or -)."
224 (zerop (ldb sb!vm:single-float-significand-byte bits))
225 (and (zerop (ldb sb!vm:double-float-significand-byte hi))
227 #!+(and long-float x86)
228 (and (zerop (ldb sb!vm:long-float-significand-byte hi))
231 (def-frob float-nan-p
232 "Return true if the float X is a NaN (Not a Number)."
233 (not (zerop (ldb sb!vm:single-float-significand-byte bits)))
234 (or (not (zerop (ldb sb!vm:double-float-significand-byte hi)))
236 #!+(and long-float x86)
237 (or (not (zerop (ldb sb!vm:long-float-significand-byte hi)))
240 (def-frob float-trapping-nan-p
241 "Return true if the float X is a trapping NaN (Not a Number)."
242 (zerop (logand (ldb sb!vm:single-float-significand-byte bits)
243 sb!vm:single-float-trapping-nan-bit))
244 (zerop (logand (ldb sb!vm:double-float-significand-byte hi)
245 sb!vm:double-float-trapping-nan-bit))
246 #!+(and long-float x86)
247 (zerop (logand (ldb sb!vm:long-float-significand-byte hi)
248 sb!vm:long-float-trapping-nan-bit))))
250 ;;; If denormalized, use a subfunction from INTEGER-DECODE-FLOAT to find the
251 ;;; actual exponent (and hence how denormalized it is), otherwise we just
252 ;;; return the number of digits or 0.
253 #!-sb-fluid (declaim (maybe-inline float-precision))
254 (defun float-precision (f)
256 "Returns a non-negative number of significant digits in its float argument.
257 Will be less than FLOAT-DIGITS if denormalized or zero."
258 (macrolet ((frob (digits bias decode)
260 ((float-denormalized-p f)
261 (multiple-value-bind (ignore exp) (,decode f)
262 (declare (ignore ignore))
264 (+ ,digits (1- ,digits) ,bias exp))))
267 (number-dispatch ((f float))
269 (frob sb!vm:single-float-digits sb!vm:single-float-bias
270 integer-decode-single-denorm))
272 (frob sb!vm:double-float-digits sb!vm:double-float-bias
273 integer-decode-double-denorm))
276 (frob sb!vm:long-float-digits sb!vm:long-float-bias
277 integer-decode-long-denorm)))))
279 (defun float-sign (float1 &optional (float2 (float 1 float1)))
281 "Returns a floating-point number that has the same sign as
282 float1 and, if float2 is given, has the same absolute value
284 (declare (float float1 float2))
285 (* (if (etypecase float1
286 (single-float (minusp (single-float-bits float1)))
287 (double-float (minusp (double-float-high-bits float1)))
289 (long-float (minusp (long-float-exp-bits float1))))
294 (defun float-format-digits (format)
296 ((short-float single-float) sb!vm:single-float-digits)
297 ((double-float #!-long-float long-float) sb!vm:double-float-digits)
299 (long-float sb!vm:long-float-digits)))
301 #!-sb-fluid (declaim (inline float-digits float-radix))
303 (defun float-digits (f)
304 (number-dispatch ((f float))
305 ((single-float) sb!vm:single-float-digits)
306 ((double-float) sb!vm:double-float-digits)
308 ((long-float) sb!vm:long-float-digits)))
310 (defun float-radix (x)
312 "Return (as an integer) the radix b of its floating-point argument."
313 (declare (type float x))
314 ;; ANSI says this function "should signal an error if [..] argument
315 ;; is not a float". Since X is otherwise ignored, Python doesn't
316 ;; check the type by default, so we have to do it ourself:
318 (error 'type-error :datum x :expected-type 'float))
321 ;;;; INTEGER-DECODE-FLOAT and DECODE-FLOAT
324 (declaim (maybe-inline integer-decode-single-float
325 integer-decode-double-float))
327 ;;; Handle the denormalized case of INTEGER-DECODE-FLOAT for SINGLE-FLOAT.
328 (defun integer-decode-single-denorm (x)
329 (declare (type single-float x))
330 (let* ((bits (single-float-bits (abs x)))
331 (sig (ash (ldb sb!vm:single-float-significand-byte bits) 1))
333 (declare (type (unsigned-byte 24) sig)
334 (type (integer 0 23) extra-bias))
336 (unless (zerop (logand sig sb!vm:single-float-hidden-bit))
338 (setq sig (ash sig 1))
341 (- (- sb!vm:single-float-bias)
342 sb!vm:single-float-digits
344 (if (minusp (float-sign x)) -1 1))))
346 ;;; Handle the single-float case of INTEGER-DECODE-FLOAT. If an infinity or
347 ;;; NaN, error. If a denorm, call i-d-s-DENORM to handle it.
348 (defun integer-decode-single-float (x)
349 (declare (single-float x))
350 (let* ((bits (single-float-bits (abs x)))
351 (exp (ldb sb!vm:single-float-exponent-byte bits))
352 (sig (ldb sb!vm:single-float-significand-byte bits))
353 (sign (if (minusp (float-sign x)) -1 1))
354 (biased (- exp sb!vm:single-float-bias sb!vm:single-float-digits)))
355 (declare (fixnum biased))
356 (unless (<= exp sb!vm:single-float-normal-exponent-max)
357 (error "can't decode NaN or infinity: ~S" x))
358 (cond ((and (zerop exp) (zerop sig))
359 (values 0 biased sign))
360 ((< exp sb!vm:single-float-normal-exponent-min)
361 (integer-decode-single-denorm x))
363 (values (logior sig sb!vm:single-float-hidden-bit) biased sign)))))
365 ;;; Like INTEGER-DECODE-SINGLE-DENORM, only doubly so.
366 (defun integer-decode-double-denorm (x)
367 (declare (type double-float x))
368 (let* ((high-bits (double-float-high-bits (abs x)))
369 (sig-high (ldb sb!vm:double-float-significand-byte high-bits))
370 (low-bits (double-float-low-bits x))
371 (sign (if (minusp (float-sign x)) -1 1))
372 (biased (- (- sb!vm:double-float-bias) sb!vm:double-float-digits)))
375 (extra-bias (- sb!vm:double-float-digits 33))
377 (declare (type (unsigned-byte 32) sig) (fixnum extra-bias))
379 (unless (zerop (logand sig bit)) (return))
380 (setq sig (ash sig 1))
382 (values (ash sig (- sb!vm:double-float-digits 32))
383 (truly-the fixnum (- biased extra-bias))
385 (let ((sig (ash sig-high 1))
387 (declare (type (unsigned-byte 32) sig) (fixnum extra-bias))
389 (unless (zerop (logand sig sb!vm:double-float-hidden-bit))
391 (setq sig (ash sig 1))
393 (values (logior (ash sig 32) (ash low-bits (1- extra-bias)))
394 (truly-the fixnum (- biased extra-bias))
397 ;;; Like INTEGER-DECODE-SINGLE-FLOAT, only doubly so.
398 (defun integer-decode-double-float (x)
399 (declare (double-float x))
401 (hi (double-float-high-bits abs))
402 (lo (double-float-low-bits abs))
403 (exp (ldb sb!vm:double-float-exponent-byte hi))
404 (sig (ldb sb!vm:double-float-significand-byte hi))
405 (sign (if (minusp (float-sign x)) -1 1))
406 (biased (- exp sb!vm:double-float-bias sb!vm:double-float-digits)))
407 (declare (fixnum biased))
408 (unless (<= exp sb!vm:double-float-normal-exponent-max)
409 (error "Can't decode NaN or infinity: ~S." x))
410 (cond ((and (zerop exp) (zerop sig) (zerop lo))
411 (values 0 biased sign))
412 ((< exp sb!vm:double-float-normal-exponent-min)
413 (integer-decode-double-denorm x))
416 (logior (ash (logior (ldb sb!vm:double-float-significand-byte hi)
417 sb!vm:double-float-hidden-bit)
422 #!+(and long-float x86)
423 (defun integer-decode-long-denorm (x)
424 (declare (type long-float x))
425 (let* ((high-bits (long-float-high-bits (abs x)))
426 (sig-high (ldb sb!vm:long-float-significand-byte high-bits))
427 (low-bits (long-float-low-bits x))
428 (sign (if (minusp (float-sign x)) -1 1))
429 (biased (- (- sb!vm:long-float-bias) sb!vm:long-float-digits)))
432 (extra-bias (- sb!vm:long-float-digits 33))
434 (declare (type (unsigned-byte 32) sig) (fixnum extra-bias))
436 (unless (zerop (logand sig bit)) (return))
437 (setq sig (ash sig 1))
439 (values (ash sig (- sb!vm:long-float-digits 32))
440 (truly-the fixnum (- biased extra-bias))
442 (let ((sig (ash sig-high 1))
444 (declare (type (unsigned-byte 32) sig) (fixnum extra-bias))
446 (unless (zerop (logand sig sb!vm:long-float-hidden-bit))
448 (setq sig (ash sig 1))
450 (values (logior (ash sig 32) (ash low-bits (1- extra-bias)))
451 (truly-the fixnum (- biased extra-bias))
454 #!+(and long-float x86)
455 (defun integer-decode-long-float (x)
456 (declare (long-float x))
457 (let* ((hi (long-float-high-bits x))
458 (lo (long-float-low-bits x))
459 (exp-bits (long-float-exp-bits x))
460 (exp (ldb sb!vm:long-float-exponent-byte exp-bits))
461 (sign (if (minusp exp-bits) -1 1))
462 (biased (- exp sb!vm:long-float-bias sb!vm:long-float-digits)))
463 (declare (fixnum biased))
464 (unless (<= exp sb!vm:long-float-normal-exponent-max)
465 (error "can't decode NaN or infinity: ~S" x))
466 (cond ((and (zerop exp) (zerop hi) (zerop lo))
467 (values 0 biased sign))
468 ((< exp sb!vm:long-float-normal-exponent-min)
469 (integer-decode-long-denorm x))
471 (values (logior (ash hi 32) lo) biased sign)))))
473 ;;; Dispatch to the correct type-specific i-d-f function.
474 (defun integer-decode-float (x)
476 "Returns three values:
477 1) an integer representation of the significand.
478 2) the exponent for the power of 2 that the significand must be multiplied
479 by to get the actual value. This differs from the DECODE-FLOAT exponent
480 by FLOAT-DIGITS, since the significand has been scaled to have all its
481 digits before the radix point.
482 3) -1 or 1 (i.e. the sign of the argument.)"
483 (number-dispatch ((x float))
485 (integer-decode-single-float x))
487 (integer-decode-double-float x))
490 (integer-decode-long-float x))))
492 #!-sb-fluid (declaim (maybe-inline decode-single-float decode-double-float))
494 ;;; Handle the denormalized case of DECODE-SINGLE-FLOAT. We call
495 ;;; INTEGER-DECODE-SINGLE-DENORM and then make the result into a float.
496 (defun decode-single-denorm (x)
497 (declare (type single-float x))
498 (multiple-value-bind (sig exp sign) (integer-decode-single-denorm x)
499 (values (make-single-float
500 (dpb sig sb!vm:single-float-significand-byte
501 (dpb sb!vm:single-float-bias
502 sb!vm:single-float-exponent-byte
504 (truly-the fixnum (+ exp sb!vm:single-float-digits))
507 ;;; Handle the single-float case of DECODE-FLOAT. If an infinity or NaN,
508 ;;; error. If a denorm, call d-s-DENORM to handle it.
509 (defun decode-single-float (x)
510 (declare (single-float x))
511 (let* ((bits (single-float-bits (abs x)))
512 (exp (ldb sb!vm:single-float-exponent-byte bits))
513 (sign (float-sign x))
514 (biased (truly-the single-float-exponent
515 (- exp sb!vm:single-float-bias))))
516 (unless (<= exp sb!vm:single-float-normal-exponent-max)
517 (error "can't decode NaN or infinity: ~S" x))
519 (values 0.0f0 biased sign))
520 ((< exp sb!vm:single-float-normal-exponent-min)
521 (decode-single-denorm x))
523 (values (make-single-float
524 (dpb sb!vm:single-float-bias
525 sb!vm:single-float-exponent-byte
529 ;;; Like DECODE-SINGLE-DENORM, only doubly so.
530 (defun decode-double-denorm (x)
531 (declare (double-float x))
532 (multiple-value-bind (sig exp sign) (integer-decode-double-denorm x)
533 (values (make-double-float
534 (dpb (logand (ash sig -32) (lognot sb!vm:double-float-hidden-bit))
535 sb!vm:double-float-significand-byte
536 (dpb sb!vm:double-float-bias
537 sb!vm:double-float-exponent-byte 0))
538 (ldb (byte 32 0) sig))
539 (truly-the fixnum (+ exp sb!vm:double-float-digits))
542 ;;; Like DECODE-SINGLE-FLOAT, only doubly so.
543 (defun decode-double-float (x)
544 (declare (double-float x))
546 (hi (double-float-high-bits abs))
547 (lo (double-float-low-bits abs))
548 (exp (ldb sb!vm:double-float-exponent-byte hi))
549 (sign (float-sign x))
550 (biased (truly-the double-float-exponent
551 (- exp sb!vm:double-float-bias))))
552 (unless (<= exp sb!vm:double-float-normal-exponent-max)
553 (error "can't decode NaN or infinity: ~S" x))
555 (values 0.0d0 biased sign))
556 ((< exp sb!vm:double-float-normal-exponent-min)
557 (decode-double-denorm x))
559 (values (make-double-float
560 (dpb sb!vm:double-float-bias
561 sb!vm:double-float-exponent-byte hi)
565 #!+(and long-float x86)
566 (defun decode-long-denorm (x)
567 (declare (long-float x))
568 (multiple-value-bind (sig exp sign) (integer-decode-long-denorm x)
569 (values (make-long-float sb!vm:long-float-bias (ash sig -32)
570 (ldb (byte 32 0) sig))
571 (truly-the fixnum (+ exp sb!vm:long-float-digits))
574 #!+(and long-float x86)
575 (defun decode-long-float (x)
576 (declare (long-float x))
577 (let* ((hi (long-float-high-bits x))
578 (lo (long-float-low-bits x))
579 (exp-bits (long-float-exp-bits x))
580 (exp (ldb sb!vm:long-float-exponent-byte exp-bits))
581 (sign (if (minusp exp-bits) -1l0 1l0))
582 (biased (truly-the long-float-exponent
583 (- exp sb!vm:long-float-bias))))
584 (unless (<= exp sb!vm:long-float-normal-exponent-max)
585 (error "can't decode NaN or infinity: ~S" x))
587 (values 0.0l0 biased sign))
588 ((< exp sb!vm:long-float-normal-exponent-min)
589 (decode-long-denorm x))
591 (values (make-long-float
592 (dpb sb!vm:long-float-bias sb!vm:long-float-exponent-byte
598 ;;; Dispatch to the appropriate type-specific function.
599 (defun decode-float (f)
601 "Returns three values:
602 1) a floating-point number representing the significand. This is always
603 between 0.5 (inclusive) and 1.0 (exclusive).
604 2) an integer representing the exponent.
605 3) -1.0 or 1.0 (i.e. the sign of the argument.)"
606 (number-dispatch ((f float))
608 (decode-single-float f))
610 (decode-double-float f))
613 (decode-long-float f))))
617 #!-sb-fluid (declaim (maybe-inline scale-single-float scale-double-float))
619 ;;; Handle float scaling where the X is denormalized or the result is
620 ;;; denormalized or underflows to 0.
621 (defun scale-float-maybe-underflow (x exp)
622 (multiple-value-bind (sig old-exp) (integer-decode-float x)
623 (let* ((digits (float-digits x))
624 (new-exp (+ exp old-exp digits
626 (single-float sb!vm:single-float-bias)
627 (double-float sb!vm:double-float-bias))))
628 (sign (if (minusp (float-sign x)) 1 0)))
632 (single-float sb!vm:single-float-normal-exponent-min)
633 (double-float sb!vm:double-float-normal-exponent-min)))
634 (when (sb!vm:current-float-trap :inexact)
635 (error 'floating-point-inexact :operation 'scale-float
636 :operands (list x exp)))
637 (when (sb!vm:current-float-trap :underflow)
638 (error 'floating-point-underflow :operation 'scale-float
639 :operands (list x exp)))
640 (let ((shift (1- new-exp)))
641 (if (< shift (- (1- digits)))
644 (single-float (single-from-bits sign 0 (ash sig shift)))
645 (double-float (double-from-bits sign 0 (ash sig shift)))))))
648 (single-float (single-from-bits sign new-exp sig))
649 (double-float (double-from-bits sign new-exp sig))))))))
651 ;;; Called when scaling a float overflows, or the original float was a
652 ;;; NaN or infinity. If overflow errors are trapped, then error,
653 ;;; otherwise return the appropriate infinity. If a NaN, signal or not
655 (defun scale-float-maybe-overflow (x exp)
657 ((float-infinity-p x)
658 ;; Infinity is infinity, no matter how small...
661 (when (and (float-trapping-nan-p x)
662 (sb!vm:current-float-trap :invalid))
663 (error 'floating-point-invalid-operation :operation 'scale-float
664 :operands (list x exp)))
667 (when (sb!vm:current-float-trap :overflow)
668 (error 'floating-point-overflow :operation 'scale-float
669 :operands (list x exp)))
670 (when (sb!vm:current-float-trap :inexact)
671 (error 'floating-point-inexact :operation 'scale-float
672 :operands (list x exp)))
675 (single-float single-float-positive-infinity)
676 (double-float double-float-positive-infinity))))))
678 ;;; Scale a single or double float, calling the correct over/underflow
680 (defun scale-single-float (x exp)
681 (declare (single-float x) (fixnum exp))
682 (let* ((bits (single-float-bits x))
683 (old-exp (ldb sb!vm:single-float-exponent-byte bits))
684 (new-exp (+ old-exp exp)))
687 ((or (< old-exp sb!vm:single-float-normal-exponent-min)
688 (< new-exp sb!vm:single-float-normal-exponent-min))
689 (scale-float-maybe-underflow x exp))
690 ((or (> old-exp sb!vm:single-float-normal-exponent-max)
691 (> new-exp sb!vm:single-float-normal-exponent-max))
692 (scale-float-maybe-overflow x exp))
694 (make-single-float (dpb new-exp
695 sb!vm:single-float-exponent-byte
697 (defun scale-double-float (x exp)
698 (declare (double-float x) (fixnum exp))
699 (let* ((hi (double-float-high-bits x))
700 (lo (double-float-low-bits x))
701 (old-exp (ldb sb!vm:double-float-exponent-byte hi))
702 (new-exp (+ old-exp exp)))
705 ((or (< old-exp sb!vm:double-float-normal-exponent-min)
706 (< new-exp sb!vm:double-float-normal-exponent-min))
707 (scale-float-maybe-underflow x exp))
708 ((or (> old-exp sb!vm:double-float-normal-exponent-max)
709 (> new-exp sb!vm:double-float-normal-exponent-max))
710 (scale-float-maybe-overflow x exp))
712 (make-double-float (dpb new-exp sb!vm:double-float-exponent-byte hi)
715 #!+(and x86 long-float)
716 (defun scale-long-float (x exp)
717 (declare (long-float x) (fixnum exp))
720 ;;; Dispatch to the correct type-specific scale-float function.
721 (defun scale-float (f ex)
723 "Returns the value (* f (expt (float 2 f) ex)), but with no unnecessary loss
724 of precision or overflow."
725 (number-dispatch ((f float))
727 (scale-single-float f ex))
729 (scale-double-float f ex))
732 (scale-long-float f ex))))
734 ;;;; converting to/from floats
736 (defun float (number &optional (other () otherp))
738 "Converts any REAL to a float. If OTHER is not provided, it returns a
739 SINGLE-FLOAT if NUMBER is not already a FLOAT. If OTHER is provided, the
740 result is the same float format as OTHER."
742 (number-dispatch ((number real) (other float))
743 (((foreach rational single-float double-float #!+long-float long-float)
744 (foreach single-float double-float #!+long-float long-float))
745 (coerce number '(dispatch-type other))))
748 (coerce number 'single-float))))
750 (macrolet ((frob (name type)
752 (number-dispatch ((x real))
753 (((foreach single-float double-float #!+long-float long-float
757 (bignum-to-float x ',type))
759 (float-ratio x ',type))))))
760 (frob %single-float single-float)
761 (frob %double-float double-float)
763 (frob %long-float long-float))
765 ;;; Convert a ratio to a float. We avoid any rounding error by doing an
766 ;;; integer division. Accuracy is important to preserve read/print
767 ;;; consistency, since this is ultimately how the reader reads a float. We
768 ;;; scale the numerator by a power of two until the division results in the
769 ;;; desired number of fraction bits, then do round-to-nearest.
770 (defun float-ratio (x format)
771 (let* ((signed-num (numerator x))
772 (plusp (plusp signed-num))
773 (num (if plusp signed-num (- signed-num)))
774 (den (denominator x))
775 (digits (float-format-digits format))
777 (declare (fixnum digits scale))
778 ;; Strip any trailing zeros from the denominator and move it into the scale
779 ;; factor (to minimize the size of the operands.)
780 (let ((den-twos (1- (integer-length (logxor den (1- den))))))
781 (declare (fixnum den-twos))
782 (decf scale den-twos)
783 (setq den (ash den (- den-twos))))
784 ;; Guess how much we need to scale by from the magnitudes of the numerator
785 ;; and denominator. We want one extra bit for a guard bit.
786 (let* ((num-len (integer-length num))
787 (den-len (integer-length den))
788 (delta (- den-len num-len))
789 (shift (1+ (the fixnum (+ delta digits))))
790 (shifted-num (ash num shift)))
791 (declare (fixnum delta shift))
793 (labels ((float-and-scale (bits)
794 (let* ((bits (ash bits -1))
795 (len (integer-length bits)))
796 (cond ((> len digits)
797 (aver (= len (the fixnum (1+ digits))))
798 (scale-float (floatit (ash bits -1)) (1+ scale)))
800 (scale-float (floatit bits) scale)))))
802 (let ((sign (if plusp 0 1)))
805 (single-from-bits sign sb!vm:single-float-bias bits))
807 (double-from-bits sign sb!vm:double-float-bias bits))
810 (long-from-bits sign sb!vm:long-float-bias bits))))))
812 (multiple-value-bind (fraction-and-guard rem)
813 (truncate shifted-num den)
814 (let ((extra (- (integer-length fraction-and-guard) digits)))
815 (declare (fixnum extra))
818 ((oddp fraction-and-guard)
822 (if (zerop (logand fraction-and-guard 2))
824 (1+ fraction-and-guard)))
825 (float-and-scale (1+ fraction-and-guard)))))
827 (return (float-and-scale fraction-and-guard)))))
828 (setq shifted-num (ash shifted-num -1))
832 These might be useful if we ever have a machine without float/integer
833 conversion hardware. For now, we'll use special ops that
834 uninterruptibly frob the rounding modes & do ieee round-to-integer.
836 ;;; The compiler compiles a call to this when we are doing %UNARY-TRUNCATE
837 ;;; and the result is known to be a fixnum. We can avoid some generic
838 ;;; arithmetic in this case.
839 (defun %unary-truncate-single-float/fixnum (x)
840 (declare (single-float x) (values fixnum))
841 (locally (declare (optimize (speed 3) (safety 0)))
842 (let* ((bits (single-float-bits x))
843 (exp (ldb sb!vm:single-float-exponent-byte bits))
844 (frac (logior (ldb sb!vm:single-float-significand-byte bits)
845 sb!vm:single-float-hidden-bit))
846 (shift (- exp sb!vm:single-float-digits sb!vm:single-float-bias)))
847 (when (> exp sb!vm:single-float-normal-exponent-max)
848 (error 'floating-point-invalid-operation :operator 'truncate
850 (if (<= shift (- sb!vm:single-float-digits))
852 (let ((res (ash frac shift)))
853 (declare (type (unsigned-byte 31) res))
858 ;;; Double-float version of this operation (see above single op).
859 (defun %unary-truncate-double-float/fixnum (x)
860 (declare (double-float x) (values fixnum))
861 (locally (declare (optimize (speed 3) (safety 0)))
862 (let* ((hi-bits (double-float-high-bits x))
863 (exp (ldb sb!vm:double-float-exponent-byte hi-bits))
864 (frac (logior (ldb sb!vm:double-float-significand-byte hi-bits)
865 sb!vm:double-float-hidden-bit))
866 (shift (- exp (- sb!vm:double-float-digits sb!vm:word-bits)
867 sb!vm:double-float-bias)))
868 (when (> exp sb!vm:double-float-normal-exponent-max)
869 (error 'floating-point-invalid-operation :operator 'truncate
871 (if (<= shift (- sb!vm:word-bits sb!vm:double-float-digits))
873 (let* ((res-hi (ash frac shift))
874 (res (if (plusp shift)
877 (ash (double-float-low-bits x)
878 (- shift sb!vm:word-bits))))
880 (declare (type (unsigned-byte 31) res-hi res))
886 ;;; This function is called when we are doing a truncate without any funky
887 ;;; divisor, i.e. converting a float or ratio to an integer. Note that we do
888 ;;; *not* return the second value of truncate, so it must be computed by the
889 ;;; caller if needed.
891 ;;; In the float case, we pick off small arguments so that compiler can use
892 ;;; special-case operations. We use an exclusive test, since (due to round-off
893 ;;; error), (float most-positive-fixnum) may be greater than
894 ;;; most-positive-fixnum.
895 (defun %unary-truncate (number)
896 (number-dispatch ((number real))
898 ((ratio) (values (truncate (numerator number) (denominator number))))
899 (((foreach single-float double-float #!+long-float long-float))
900 (if (< (float most-negative-fixnum number)
902 (float most-positive-fixnum number))
903 (truly-the fixnum (%unary-truncate number))
904 (multiple-value-bind (bits exp) (integer-decode-float number)
905 (let ((res (ash bits exp)))
910 ;;; Similar to %UNARY-TRUNCATE, but rounds to the nearest integer. If we
911 ;;; can't use the round primitive, then we do our own round-to-nearest on the
912 ;;; result of i-d-f. [Note that this rounding will really only happen with
913 ;;; double floats, since the whole single-float fraction will fit in a fixnum,
914 ;;; so all single-floats larger than most-positive-fixnum can be precisely
915 ;;; represented by an integer.]
916 (defun %unary-round (number)
917 (number-dispatch ((number real))
919 ((ratio) (values (round (numerator number) (denominator number))))
920 (((foreach single-float double-float #!+long-float long-float))
921 (if (< (float most-negative-fixnum number)
923 (float most-positive-fixnum number))
924 (truly-the fixnum (%unary-round number))
925 (multiple-value-bind (bits exp) (integer-decode-float number)
926 (let* ((shifted (ash bits exp))
927 (rounded (if (and (minusp exp)
930 (lognot (ash -1 (- exp))))
940 "RATIONAL produces a rational number for any real numeric argument. This is
941 more efficient than RATIONALIZE, but it assumes that floating-point is
942 completely accurate, giving a result that isn't as pretty."
943 (number-dispatch ((x real))
944 (((foreach single-float double-float #!+long-float long-float))
945 (multiple-value-bind (bits exp) (integer-decode-float x)
948 (let* ((int (if (minusp x) (- bits) bits))
949 (digits (float-digits x))
952 (integer-/-integer int (ash 1 (+ digits (- ex))))
953 (integer-/-integer (ash int ex) (ash 1 digits)))))))
956 (defun rationalize (x)
958 "Converts any REAL to a RATIONAL. Floats are converted to a simple rational
959 representation exploiting the assumption that floats are only accurate to
960 their precision. RATIONALIZE (and also RATIONAL) preserve the invariant:
961 (= x (float (rationalize x) x))"
962 (number-dispatch ((x real))
963 (((foreach single-float double-float #!+long-float long-float))
964 ;; Thanks to Kim Fateman, who stole this function rationalize-float from
965 ;; macsyma's rational. Macsyma'a rationalize was written by the legendary
966 ;; Gosper (rwg). Guy Steele said about Gosper, "He has been called the
967 ;; only living 17th century mathematician and is also the best pdp-10
968 ;; hacker I know." So, if you can understand or debug this code you win
970 (cond ((minusp x) (- (rationalize (- x))))
973 (let ((eps (etypecase x
974 (single-float single-float-epsilon)
975 (double-float double-float-epsilon)
977 (long-float long-float-epsilon)))
980 (do ((xx x (setq y (/ (float 1.0 x) (- xx (float a x)))))
981 (num (setq a (truncate x))
982 (+ (* (setq a (truncate y)) num) onum))
983 (den 1 (+ (* a den) oden))
986 ((and (not (zerop den))
987 (not (> (abs (/ (- x (/ (float num x)
991 (integer-/-integer num den))
992 (declare ((dispatch-type x) xx)))))))