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expt: repair for large power of inexact between 0 and -1

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Closes PR 14824
This commit is contained in:
Matthew Flatt 2014-11-05 09:17:20 -07:00
parent b9d8f65fc9
commit 1e9d7c1d2a
2 changed files with 23 additions and 0 deletions
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11
pkgs/racket-pkgs/racket-test/tests/racket/number.rktl
View File

@ -555,6 +555,17 @@
(test 0.0 expt -10.0 -10000000000000.0)
(test -0.0 expt -10.0 -10000000000001.0)
(test 0.0 expt 0.9999 (expt 2 5000))
(test 0.0 expt 0.9999 (add1 (expt 2 5000)))
(test 0.0 expt 0.9999 (/ (expt 2 5000) 3))
(test 0.0 expt -0.9999 (expt 2 5000))
(test -0.0 expt -0.9999 (add1 (expt 2 5000)))
(test 0.0f0 expt 0.9999f0 (expt 2 5000))
(test 0.0f0 expt 0.9999f0 (add1 (expt 2 5000)))
(test 0.0f0 expt 0.9999f0 (/ (expt 2 5000) 3))
(test 0.0f0 expt -0.9999f0 (expt 2 5000))
(test -0.0f0 expt -0.9999f0 (add1 (expt 2 5000)))
(err/rt-test (max 0 'a))
(err/rt-test (min 0 'a))
(err/rt-test (max 'a 0))

12
racket/src/racket/src/number.c
View File

@ -3605,6 +3605,18 @@ scheme_expt(int argc, Scheme_Object *argv[])
}
}
}
} else if ((d < 0.0) && (d > -1.0)) {
/* If `e` is a positive bignum, then the result should be zero,
but we won't get that result if conversion produces infinity */
if (SCHEME_BIGNUMP(e) && SCHEME_BIGPOS(e)) {
#ifdef MZ_USE_SINGLE_FLOATS
int sgl = !SCHEME_DBLP(n);
#endif
if (SCHEME_FALSEP(scheme_odd_p(1, &e)))
return SELECT_EXPT_PRECISION(scheme_zerof, scheme_zerod);
else
return SELECT_EXPT_PRECISION(scheme_nzerof, scheme_nzerod);
}
}
}