This is the mail archive of the mailing list for the GCC project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: real.c implementation

> I don't know the answers to these questions.  Steele and White,
> Clinger, and David Gay (his code is at worked out
> provably correct methods to do exact binary<->decimal conversion.
>  All of them rely on extra-precision integer arithmetic for some
> cases.

Gay's program is in the GCC java library subdirectory.  It used
to be in the C++ library also; I remember chasing a bug in it.
Dewar has mentioned that the GCC Ada front end does correctly rounded
conversions.  Glibc, the GNU system library, has been through
several decimal converters; currently it has a correctly rounded
method that uses the GNU multiple precision library (gmp).  I think
that gmp can also be used as a floating point emulator.

The C language standard references IEEE.  Some months ago the IEEE 754
revision committee posted some messages to the effect that they were
going to require a correctly rounded method, but then they seemed to
withdraw that.  As a practical matter, conversion according to IEEE is
already correctly rounded over a wide domain that covers the vast
majority of real programs, and the largest allowable error is less
than twice the error of correct rounding; so the distinction is minor.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]