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Calc: GCD(0,x)=GCD(x,0)=|x|, not x (bug#41279)

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Reported by David Ongaro.

* lisp/calc/calc-comb.el (calcFunc-gcd): Fix GCD simplification.
* test/lisp/calc/calc-tests.el (calc-gcd, calc-sum-gcd): New tests.
This commit is contained in:
Mattias Engdegård 2020-05-15 14:52:50 +02:00
parent b76cdd0c1a
commit 60cd6cce55
2 changed files with 30 additions and 2 deletions
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4
lisp/calc/calc-comb.el
View file

@ -241,8 +241,8 @@
(calcFunc-gcd (math-neg a) b))
((Math-looks-negp b)
(calcFunc-gcd a (math-neg b)))
((Math-zerop a) b)
((Math-zerop b) a)
((Math-zerop a) (math-abs b))
((Math-zerop b) (math-abs a))
((and (Math-ratp a)
(Math-ratp b))
(math-make-frac (math-gcd (if (eq (car-safe a) 'frac) (nth 1 a) a)

28
test/lisp/calc/calc-tests.el
View file

@ -368,6 +368,34 @@ An existing calc stack is reused, otherwise a new one is created."
(vec 0 0 (var a var-a) 0)))
'(neg (var a var-a)))))
(ert-deftest calc-gcd ()
(should (equal (calcFunc-gcd 3 4) 1))
(should (equal (calcFunc-gcd 12 15) 3))
(should (equal (calcFunc-gcd -12 15) 3))
(should (equal (calcFunc-gcd 12 -15) 3))
(should (equal (calcFunc-gcd -12 -15) 3))
(should (equal (calcFunc-gcd 0 5) 5))
(should (equal (calcFunc-gcd 5 0) 5))
(should (equal (calcFunc-gcd 0 -5) 5))
(should (equal (calcFunc-gcd -5 0) 5))
(should (equal (calcFunc-gcd 0 0) 0))
(should (equal (calcFunc-gcd 0 '(var x var-x))
'(calcFunc-abs (var x var-x))))
(should (equal (calcFunc-gcd '(var x var-x) 0)
'(calcFunc-abs (var x var-x)))))
(ert-deftest calc-sum-gcd ()
;; sum(gcd(0,n),n,-1,-1)
(should (equal (math-simplify '(calcFunc-sum (calcFunc-gcd 0 (var n var-n))
(var n var-n) -1 -1))
1))
;; sum(sum(gcd(n,k),k,-1,1),n,-1,1)
(should (equal (math-simplify
'(calcFunc-sum
(calcFunc-sum (calcFunc-gcd (var n var-n) (var k var-k))
(var k var-k) -1 1)
(var n var-n) -1 1))
8)))
(provide 'calc-tests)
;;; calc-tests.el ends here