On Mon, 19 Aug 2024, 22:27 FX Coudert via Gcc, <gcc@gcc.gnu.org> wrote:
> Hi Peter,
>
> You are right, thanks for reporting these issues in the libquadmath
> documentation. I am CC’ing the GCC mailing-list. Does the following patch
> seem right?
>
> diff --git a/libquadmath/libquadmath.texi b/libquadmath/libquadmath.texi
> index dc2a9ff374b..ce4accf6421 100644
> --- a/libquadmath/libquadmath.texi
> +++ b/libquadmath/libquadmath.texi
> @@ -118,15 +118,15 @@ The following mathematical constants of type
> @code{__float128} are defined.
> @table @asis
> @item @code{M_Eq}: the constant e (Euler's number)
> -@item @code{M_LOG2Eq}: binary logarithm of 2
> -@item @code{M_LOG10Eq}: common, decimal logarithm of 2
> +@item @code{M_LOG2Eq}: base 2 logarithm of e
> +@item @code{M_LOG10Eq}: decimal (base 10) logarithm of e
> @item @code{M_LN2q}: natural logarithm of 2
> @item @code{M_LN10q}: natural logarithm of 10
> @item @code{M_PIq}: pi
> @item @code{M_PI_2q}: pi divided by two
> @item @code{M_PI_4q}: pi divided by four
> @item @code{M_1_PIq}: one over pi
> -@item @code{M_2_PIq}: one over two pi
> +@item @code{M_2_PIq}: two over pi
> @item @code{M_2_SQRTPIq}: two over square root of pi
> @item @code{M_SQRT2q}: square root of 2
> @item @code{M_SQRT1_2q}: one over square root of 2
>
>
> Regarding the naming of M_SQRT1_2q, it simply follows the traditional
> M_SQRT1_2 macro which, according to glibc doc: "These constants come from
> the Unix98 standard and were also available in 4.4BSD”. I agree with you
> that logic would dictate M_1_SQRT2, but we simply follow the existing
> pattern there.
>
> Best,
> FX
>
>
> > Many thanks for the 'quadmath.h' library, which is where I found this
> email address. I have addressed this email to you as the problem isn't a
> bug in GCC itself, it didn't seem right to try and coerce it into the bug
> report system
The docs are part of libquadmath, which is part of GCC, so it certainly
would have been appropriate in the GCC bug database.
, and I didn't know where else to start, but I appreciate that the problem
> is not yours, especially as the corresponding comments in 'quadmath.h'
> itself are correct. I'd be grateful if you could forward it to whoever is
> maintaining the Quad-Precision Math Library Manuals.
> >
> > Three of the constants are mis-labelled in the current (14.2) version of
> that Library Manual document (and in all the previous versions I've looked
> at) , as follows:
> >
> > M_LOG2Eq: ) both are described as logarithms of 2, whereas they are
> logarithms of 'e'
> > M_LOG10Eq: )
> > ...
> > M_2_PIq: described as "one over two pi", actually two over pi [2/pi]
> >
> > Additionally, whilst I realise that the two are mathematically equal,
> the generic 'M_numerator_denominatorq' naming format convention suggests
> that M_SQRT1_2q, described as "one over square root of 2", should better be
> labelled as "square root of (1/2)"; M_1_SQRT2q would be the name that
> corresponds to the original description. Is this a lacuna in the standard?
> >
> > Regards
> >
> > Peter Randall
>
>
>
