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Diffstat (limited to 'doc/mpfr.texi')
| -rw-r--r-- | doc/mpfr.texi | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/doc/mpfr.texi b/doc/mpfr.texi index a641b01be..70e834e85 100644 --- a/doc/mpfr.texi +++ b/doc/mpfr.texi @@ -761,14 +761,16 @@ of The Art of Computer Programming (Section 4.2.2). The @code{MPFR_RNDF} mode works as follows: the computed value is either that corresponding to @code{MPFR_RNDD} or that corresponding to -@code{MPFR_RNDU}, except in the case where those values are identical, -in which case the two adjacent floating-point numbers can also be returned. +@code{MPFR_RNDU}. +In particular when those values are identical, +i.e., when the result of the corresponding operation is exactly +representable, that exact result is returned. In summary the error is always at most one unit-in-last-place of the computed -result, which can take two or three possible values. +result, which can take at most two possible values. For @code{MPFR_RNDF} the ternary value makes no sense, the inexact flag is undefined, the divide-by-zero flag is as with other roundings, and the underflow and overflow flags match what would be obtained -in the case the computed value would is @code{MPFR_RNDD} (resp. +in the case the computed value is the same as with @code{MPFR_RNDD} (resp. @code{MPFR_RNDU}). @anchor{ternary value}@cindex Ternary value @@ -1663,7 +1665,7 @@ that the corresponding conversion function (for example @code{mpfr_get_ui} for @code{mpfr_fits_ulong_p}), when called with faithful rounding, will always return a number that is representable in the corresponding type. As a consequence, for @code{MPFR_RNDF}, @code{mpfr_fits_ulong_p} will return -non-zero for a positive number less than @code{ULONG_MAX}. +non-zero for a non-negative number less or equal to @code{ULONG_MAX}. @end deftypefun @node Basic Arithmetic Functions, Comparison Functions, Conversion Functions, MPFR Interface |