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Calc: allow infinite binary word size (bug#43764)

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Setting the word size ("b w") to 0 removes the word size clipping for
all bit operations (effectively as if a word size of -∞ had been set).
Rotation is disallowed; logical and arithmetic shifts behave
identically.

After a suggestion by Vincent Belaïche.

* lisp/calc/calc-bin.el (calc-word-size, math-binary-arg)
(math-binary-modulo-args, calcFunc-lsh, calcFunc-ash, calcFunc-rot)
(math-clip, math-format-twos-complement): Allow a word size of 0,
meaning -∞.
* test/lisp/calc/calc-tests.el
(calc-tests--not, calc-tests--and, calc-tests--or, calc-tests--xor)
(calc-tests--diff): New functions.
(calc-tests--clip, calc-tests--rot, calc-shift-binary): Extend to
cover word size 0.
(calc-bit-ops): New test.
* doc/misc/calc.texi (Binary Functions): Update manual.
* etc/NEWS: Announce the change.
This commit is contained in:
Mattias Engdegård 2020-10-10 18:02:49 +02:00
parent add1314195
commit cf40795888
4 changed files with 99 additions and 21 deletions
Download patch file Download diff file Expand all files Collapse all files

32
lisp/calc/calc-bin.el
View file

@ -145,9 +145,10 @@
(setq math-half-2-word-size (math-power-of-2 (1- (math-abs n))))
(calc-do-refresh)
(calc-refresh-evaltos)
(if (< n 0)
(message "Binary word size is %d bits (two's complement)" (- n))
(message "Binary word size is %d bits" n))))
(cond
((< n 0) (message "Binary word size is %d bits (two's complement)" (- n)))
((> n 0) (message "Binary word size is %d bits" n))
(t (message "No fixed binary word size")))))
@ -262,9 +263,10 @@
(defun math-binary-arg (a w)
(if (not (Math-integerp a))
(setq a (math-trunc a)))
(if (< a 0)
(logand a (1- (ash 1 (if w (math-trunc w) calc-word-size))))
a))
(let ((w (if w (math-trunc w) calc-word-size)))
(if (and (< a 0) (not (zerop w)))
(logand a (1- (ash 1 w)))
a)))
(defun math-binary-modulo-args (f a b w)
(let (mod)
@ -285,7 +287,7 @@
(let ((bits (math-integer-log2 mod)))
(if bits
(if w
(if (/= w bits)
(if (and (/= w bits) (not (zerop w)))
(calc-record-why
"*Warning: Modulus inconsistent with word size"))
(setq w bits))
@ -371,11 +373,12 @@
(math-clip (calcFunc-lsh a n (- w)) w)
(if (Math-integer-negp a)
(setq a (math-clip a w)))
(cond ((or (Math-lessp n (- w))
(Math-lessp w n))
(cond ((and (or (Math-lessp n (- w))
(Math-lessp w n))
(not (zerop w)))
0)
((< n 0)
(math-quotient (math-clip a w) (math-power-of-2 (- n))))
(ash (math-clip a w) n))
(t
(math-clip (math-mul a (math-power-of-2 n)) w))))))
@ -403,7 +406,8 @@
(setq a (math-clip a w)))
(let ((two-to-sizem1 (math-power-of-2 (1- w)))
(sh (calcFunc-lsh a n w)))
(cond ((zerop (logand a two-to-sizem1))
(cond ((or (zerop w)
(zerop (logand a two-to-sizem1)))
sh)
((Math-lessp n (- 1 w))
(math-add (math-mul two-to-sizem1 2) -1))
@ -421,6 +425,8 @@
(if (eq (car-safe a) 'mod)
(math-binary-modulo-args 'calcFunc-rot a n w)
(setq w (if w (math-trunc w) calc-word-size))
(when (zerop w)
(error "Rotation requires a nonzero word size"))
(or (integerp w)
(math-reject-arg w 'fixnump))
(or (Math-integerp a)
@ -452,6 +458,8 @@
(if (Math-natnum-lessp a (math-power-of-2 (- -1 w)))
a
(math-sub a (math-power-of-2 (- w)))))
((math-zerop w)
a)
((Math-negp a)
(math-binary-arg a w))
((integerp a)
@ -682,6 +690,8 @@
(defun math-format-twos-complement (a)
"Format an integer in two's complement mode."
(when (zerop calc-word-size)
(error "Nonzero word size required"))
(let* (;(calc-leading-zeros t)
(num
(cond