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float-raw.lisp
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float-raw.lisp
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; ACL2 Version 8.5 -- A Computational Logic for Applicative Common Lisp
; Copyright (C) 2024, Regents of the University of Texas
; This version of ACL2 is a descendent of ACL2 Version 1.9, Copyright
; (C) 1997 Computational Logic, Inc. See the documentation topic NOTE-2-0.
; This program is free software; you can redistribute it and/or modify
; it under the terms of the LICENSE file distributed with ACL2.
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; LICENSE for more details.
; Written by: Matt Kaufmann and J Strother Moore
; email: Kaufmann@cs.utexas.edu and Moore@cs.utexas.edu
; Department of Computer Science
; University of Texas at Austin
; Austin, TX 78712 U.S.A.
(in-package "ACL2")
; The Common Lisp HyperSpec
; (http://www.lispworks.com/documentation/HyperSpec/Body/12_aaaa.htm), Section
; 12.1.1.1.1 "Examples of Associativity and Commutativity in Numeric
; Operations", makes it clear that nothing can be deduced about the order of
; operations. So we convert all operations with more than two arguments to
; right-associated binary operations; for example, (df+ x y z) is treated
; identically to (df+ x (df+ y z)).
; For ACL2, transcendental functions traffic completely in double-floatas. For
; example, if x is of double-float type, (sqrt x) is also of double-float type
; even if x and its square root both have rational mathemmatical values. See
; also the CL HyperSpec Section 12.1.4.4. Of course, we need guards checked in
; some cases before calling such functions. For example, if x is negative then
; we can (or must?) get a complex float for (expt x y) when y is not an
; integer; but ACL2 doesn't recognize complex floats.
(defmacro df-signal? (form op)
; Form should return a single numeric value in ACL2. We ensure that if there
; is no error then the result is truly a floating-point number that represents
; a rational number -- not an infinity or NaN. Actually we don't need to worry
; about NaN in guard-verified code; it's simple to include that test in Allegro
; CL with a documented function (rather than just testing against
; #.*infinity-double* and #.*negative-infinity-double*), so we do so, but we
; don't bother testing for Nan in LispWorks.
; We return form unchanged in other than Allegro CL and LispWorks, because we
; already know that an error is signalled on overflow for other Lisps that host
; ACL2; see break-on-overflow-and-nan.
#-(or allegro lispworks)
(declare (ignore op))
#-(or allegro lispworks)
form
#+allegro
`(let ((result ,form))
(when (excl:exceptional-floating-point-number-p result)
(error "Floating-point exception for a call of ~s"
',op))
result)
#+lispworks
`(let ((result ,form))
(when (or (= result +1D++0) (= result -1D++0))
(error "Floating-point overflow for a call of ~s"
',op))
result))
(defmacro defun-df-binary (name op)
; We can perhaps avoid calling df-signal? in cases where overflow is
; impossible, but we don't; see defun-df-unary.
`(progn
(defun ,name (x y)
(declare (type double-float x y))
(the double-float
(df-signal? (,op (the double-float x)
(the double-float y))
,op)))))
(defmacro defun-df-unary (name op)
; We can perhaps avoid calling df-signal? in cases where overflow is
; impossible, e.g., if op is sin. But since df-signal? is needed on most df
; operations, so we already likely have slowdown from df-signal? in LispWorks
; and Allegro CL, we keep things simple and apply df-signal? unconditionally.
; That could change if there are complaints.
`(progn
(defun ,name (x)
(declare (type double-float x))
(the double-float
(df-signal? (,op (the double-float x))
,op)))))
(defun-df-binary binary-df+ +)
(defun-df-binary binary-df* *)
(defun-df-binary binary-df/ /)
(defun-df-binary binary-df-log log)
(defun-df-binary df-expt-fn expt)
(defun-df-unary unary-df- -)
(defun-df-unary unary-df/ /)
(defun-df-unary df-exp-fn exp)
(defun-df-unary df-sqrt-fn sqrt)
(defun-df-unary unary-df-log log)
(defun-df-unary df-abs-fn abs)
(defun-df-unary df-sin-fn sin)
(defun-df-unary df-cos-fn cos)
(defun-df-unary df-tan-fn tan)
(defun-df-unary df-asin-fn asin)
(defun-df-unary df-acos-fn acos)
(defun-df-unary df-atan-fn atan)
(defun-df-unary df-sinh-fn sinh)
(defun-df-unary df-cosh-fn cosh)
(defun-df-unary df-tanh-fn tanh)
(defun-df-unary df-asinh-fn asinh)
(defun-df-unary df-acosh-fn acosh)
(defun-df-unary df-atanh-fn atanh)
(defun df-pi ()
pi)
(defun df-string (x)
(the string (cond ((typep x 'double-float)
; We make some effort to make the result independent of what is printed by the
; host Lisp. Some lisps use "e" for the exponent while others use "E", and
; some use the "+" sign in the exponent but others do not. We choose "E+"
; (like CCL) but it would be fine to use "e" and/or to omit the "+".
(let* ((s (princ-to-string x))
(p1 (position #\E s))
(p2 (and (not p1) ; optimization
(position #\e s)))
(p (or p1 p2)))
(cond
((and p
(not (member (char s (1+ p))
'(#\+ #\-))))
(cond (p1
(concatenate 'string
(subseq s 0 (1+ p1))
"+"
(subseq s (1+ p1) (length s))))
(t ; p2
(concatenate 'string
(subseq s 0 p2)
"E+"
(subseq s (1+ p2) (length s))))))
(p2 (concatenate 'string
(subseq s 0 p2)
"E"
(subseq s (1+ p2) (length s))))
(t s))))
(t (error "~s called on non-df value, ~s"
'df-string
x)
""))))
; Now we define *1* functions. They always return ordinary ACL2 objects, never
; floats. The idea is that in *1* evaluation we only encounter floats at the
; top level. Of course, printing in the top-level loop is expected to write
; out floats based on the stobjs-out, just as stobjs are printed using the
; stobjs-out. (Note that binding *read-default-float-format* to 'double-float
; will cause the exponent to be E rather than D, so that the result can be read
; back in.)
(defun make-df (x)
; If there is a double-float corresponding to x, return it; else return nil.
; Note that although we expect that *1* functions are normally not handed
; dfs, an exception is when ec-call is invoked from raw Lisp.
(cond ((typep x 'double-float) x) ; See note above about ec-call.
((rationalp x)
(let ((xf (to-df x)))
(and #-gcl (= xf x)
; As of this writing, GCL 2.6.14 (or at least one sub-version) and probably
; previous versions (including at least one sub-version of 2.6.12) returned t
; when evaluating (= (float 1/3 0.0d0) 1/3). So the test (= xf x) above isn't
; adequate in GCL.
#+gcl (= (rational xf) x)
xf)))
(t nil)))
(defmacro defun-df-*1*-unary (fn &rest more-guard-conjuncts)
`(defun-*1* ,fn (x)
(the rational
(let ((xf (make-df x)))
(cond ((and xf
; If there are more conjuncts, apply each to the double-float corresponding to
; x, for efficiency.
,@(and more-guard-conjuncts
`((let ((x xf))
,@more-guard-conjuncts))))
(rational (,fn xf)))
(t (gv ,fn (x)
,(cond
((eq fn 'unary-df-)
`(df-round (funcall ',(*1*-symbol 'unary--) x)))
((eq fn 'unary-df/)
`(df-round (funcall ',(*1*-symbol 'unary-/) x)))
; If there is a guard violation during a proof or when guard-checking is off,
; the constrained function will be called, which will have the usual effect of
; calling a constrained function, and that's entirely appropriate here.
(t `(,(packn (list 'constrained- fn)) x))))))))))
(defmacro defun-df-*1*-binary (fn &rest more-guard-conjuncts)
`(defun-*1* ,fn (x y)
(the rational
(let ((xf (make-df x))
(yf (make-df y)))
(declare (type (or double-float null) xf yf))
(cond ((and xf yf
,@(and more-guard-conjuncts
; The raw Lisp versions of the conjuncts expect dfs, but x and y are probably
; rational. So we replace x and y by numerically equal values of double-float
; type.
`((let ((x xf)
(y yf))
(declare (ignorable x y))
,@more-guard-conjuncts))))
(rational (,fn xf yf)))
(t (gv ,fn (x y)
,(cond
((eq fn 'binary-df+)
`(df-round (funcall ',(*1*-symbol 'binary-+) x y)))
((eq fn 'binary-df*)
`(df-round (funcall ',(*1*-symbol 'binary-*) x y)))
((eq fn 'binary-df/)
`(df-round
(funcall ',(*1*-symbol 'binary-*)
x
(funcall ',(*1*-symbol 'unary-/)
y))))
(t
; If there is a guard violation during a proof or when guard-checking is off,
; the constrained function will be called, which will have the usual effect of
; calling a constrained function, and that's entirely appropriate here.
`(,(packn (list 'constrained- fn)) x y))))))))))
(defun-*1* from-df (x)
(cond ((typep x 'double-float) ; impossible?
(rational x))
((dfp x) x)
(t (gv from-df (x)
; Logically, (from-df x) = x. We don't want (from-df x) here because that
; would probably cause a raw Lisp error if x is not a number.
x))))
(defun-*1* dfp (x)
(dfp x))
(defconstant rational-pi
(rational pi))
(defun-*1* df-pi ()
rational-pi)
(defun-*1* to-df (x)
(rational (cond ((typep x 'double-float)
(rational x))
((rationalp x)
(rational (to-df x)))
(t (gv to-df (x)
(constrained-to-df x))))))
(defun-*1* df-string (x)
(cond ((typep x 'double-float)
(df-string x))
((rationalp x)
(df-string (to-df x)))
(t (gv df-string (x)
(constrained-df-string x)))))
(defmacro defun-df-*1*-from-function-sigs ()
(cons
'progn
(loop with tmp
for tuple in *df-function-sigs-exec*
as fn = (car tuple)
as args = (cadr tuple)
when (setq tmp (cond ((null args) ; df-pi
nil)
((null (cdr args))
`(defun-df-*1*-unary ,fn
,@(cddr tuple)))
((null (cddr args))
`(defun-df-*1*-binary ,fn
,@(cddr tuple)))
(t (error "Unexpected: ~s has ~s arguments, ~
which is more than 2."
fn (length args)))))
collect tmp)))
(defun-df-*1*-from-function-sigs)
(defun-df-*1*-unary unary-df-)
(defun-df-*1*-unary unary-df/)
(defun-df-*1*-unary df-rationalize)
(defun-df-*1*-binary binary-df+)
(defun-df-*1*-binary binary-df*)
(defun-df-*1*-binary binary-df/ (not (= y 0)))