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Fix exponentiation of negative single-floats and moderately large bignums.

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This commit is contained in:
Vincent St-Amour 2015-11-29 15:07:32 -06:00
parent a389678556
commit e7e75c2292
2 changed files with 12 additions and 0 deletions
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3
pkgs/racket-test-core/tests/racket/number.rktl
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@ -572,6 +572,9 @@
(test -inf.0 expt -4.0 (add1 (expt 2 5000)))
(test +inf.f expt -4.0f0 (expt 2 5000))
(test -inf.f expt -4.0f0 (add1 (expt 2 5000)))
;; exponent large enough to overflow singles, but not doubles
(test +inf.f expt -4.0f0 (lcm (exact-round -1.7976931348623151e+308)))
(test -inf.f expt -4.0f0 (add1 (lcm (exact-round -1.7976931348623151e+308))))
(define (inf-non-real? x)
(and (not (real? x))

9
racket/src/racket/src/number.c
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@ -3634,7 +3634,16 @@ scheme_expt(int argc, Scheme_Object *argv[])
be converted to infinity, this would return a complex NaN.
Instead, we want to return (positive of negative) infinity.
See discussion in Github issue 1148. */
#ifdef MZ_USE_SINGLE_FLOATS
if (sgl) {
/* Need to go through singles to get right overflow behavior. */
e_dbl = (double)(scheme_bignum_to_float(e));
} else {
e_dbl = scheme_bignum_to_double(e);
}
#else
e_dbl = scheme_bignum_to_double(e);
#endif
if ((d < 0.0) && MZ_IS_POS_INFINITY(e_dbl)) {
if (SCHEME_TRUEP(scheme_odd_p(1, &e))) {
return SELECT_EXPT_PRECISION(scheme_single_minus_inf_object,