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Change tanh to produce inexact values when approximating near 0.

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Since the approximation is that (tanh x) = x for small x, previously
(tanh 1/10000000000000000000) produced an `exact?` answer, even though
this is an approximation.

Found by Typed Racket random testing:
http://drdr.racket-lang.org/54493/racket/share/pkgs/typed-racket-test/tr-random-testing.rkt
This commit is contained in:
Sam Tobin-Hochstadt 2020-05-13 15:14:30 -04:00
parent 8859d6596a
commit e8202b7fa3
2 changed files with 2 additions and 1 deletions
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1
pkgs/racket-test-core/tests/racket/math.rktl
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@ -329,6 +329,7 @@
(test 0 tanh 0) (test 0 tanh 0)
(test #t double=? tanh+1 (tanh 1)) (test #t double=? tanh+1 (tanh 1))
(test 1.0 tanh 20) (test 1.0 tanh 20)
(test #t flonum? (tanh (inexact->exact 1/100000000000)))
#reader "maybe-single.rkt" #reader "maybe-single.rkt"
(begin (begin

2
racket/collects/racket/math.rkt
View File

@ -73,7 +73,7 @@
[(real? z) [(real? z)
(let loop ([z z]) (let loop ([z z])
(cond [(z . < . 0) (- (loop (- z)))] (cond [(z . < . 0) (- (loop (- z)))]
[(z . < . 1.29047841397589243466D-08) z] [(z . < . 1.29047841397589243466D-08) (exact->inexact z)]
[(z . < . 0.54930614433405484570D+00) [(z . < . 0.54930614433405484570D+00)
(define p0 -0.16134119023996228053D+04) (define p0 -0.16134119023996228053D+04)
(define p1 -0.99225929672236083313D+02) (define p1 -0.99225929672236083313D+02)