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Fix parsing of exact numbers with negative exponents

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* libguile/numbers.c (mem2decimal_from_point): Use scm_divide instead of
  scm_divide2real when applying a negative exponent, to preserve
  exactness in case the "#e" forced exactness specifier is present.
  This fixes a bug where numeric literals such as "#e1e-5" yielded
  incorrect fractions.
This commit is contained in:
Mark H Weaver 2011-04-06 18:24:40 -04:00
parent ce6066065d
commit 6ebecdeb7d
2 changed files with 6 additions and 1 deletions
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2
libguile/numbers.c
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@ -5668,7 +5668,7 @@ mem2decimal_from_point (SCM result, SCM mem,
if (sign == 1)
result = scm_product (result, e);
else
result = scm_divide2real (result, e);
result = scm_divide (result, e);
/* We've seen an exponent, thus the value is implicitly inexact. */
x = INEXACT;

5
test-suite/tests/numbers.test
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@ -1456,6 +1456,11 @@
(pass-if (string=? (number->string 35 36) "z"))
(pass-if (= (num->str->num 35 36) 35))
;; Before Guile 2.0.1, even in the presence of a #e forced exactness
;; specifier, negative exponents were applied inexactly and then
;; later coerced to exact, yielding an incorrect fraction.
(pass-if (eqv? (string->number "#e1e-10") 1/10000000000))
;; Numeric conversion from decimal is not precise, in its current
;; implementation, so 11.333... and 1.324... can't be expected to
;; reliably come out to precise values. These tests did actually work