The online D documentation says

Properties for Integral Data Types
sign    should we do this?

Properties for Floating Point Types
sign    1 if -, 0 if +

This spec is really, really bad.  I use signs in algorithm work.  Most of the time they end up as multiplication factors.  So I want negative signs to yield -1.0, and positive signs to yield +1.0.  The way it should work is

sign    -1.0 if negative, +1.0 if positive or zero or NaN

for both ints and floats.  The zero case should be considered positive.  (I don't want .sign to return zero, otherwise I can't use it as a multiplication factor without special checking.)

Mark

Interesting. The .sign used the C signbit() function as a model. How do you
do your code in C/C++?

"Mark Evans" <Mark_member@pathlink.com> wrote in message news:anng69$1m7f$1@digitaldaemon.com...
> The online D documentation says
>
> Properties for Integral Data Types
> sign    should we do this?
>
> Properties for Floating Point Types
> sign    1 if -, 0 if +
>
> This spec is really, really bad.  I use signs in algorithm work.  Most of
the
> time they end up as multiplication factors.  So I want negative signs to
yield
> -1.0, and positive signs to yield +1.0.  The way it should work is
>
> sign    -1.0 if negative, +1.0 if positive or zero or NaN
>
> for both ints and floats.  The zero case should be considered positive.
(I
> don't want .sign to return zero, otherwise I can't use it as a
multiplication
> factor without special checking.)
>
> Mark
>
>

The closest function is sgn() though some implementations return zero for zero. I've not heard of signbit() and don't consider it a good model.  The problem is that .sign wants to return a bool (saying whether the sign bit is set), but D offers no bool type. The return must then be encoded as an integer.  It is very confusing to get +1 from .sign when the numeric sign is -1.

I don't know any scenarios in which I care whether the sign bit is set; what I always want is the value of the sign, -1 or +1.  The return value should have the same numeric sign as the argument.  In this mode the return value really is an integer or float, not an integer masquerading as a boolean.

M.

In article <ano1r9$27pp$2@digitaldaemon.com>, Walter says...
>
>Interesting. The .sign used the C signbit() function as a model. How do you
>do your code in C/C++?
>

should it be that...

signbit() should return 0 or 1 as a representation of the sign bit,

sign() should return -1 and 1 as a representation of the sign.

i agree with you that the latter is much more usefull and the result should bo of the same type as the argument.

chris


"Mark Evans" <Mark_member@pathlink.com> wrote in message news:ano76a$2cqd$1@digitaldaemon.com...
> The closest function is sgn() though some implementations return zero for
zero.
> I've not heard of signbit() and don't consider it a good model.  The
problem is
> that .sign wants to return a bool (saying whether the sign bit is set),
but D
> offers no bool type. The return must then be encoded as an integer.  It is
very
> confusing to get +1 from .sign when the numeric sign is -1.
>
> I don't know any scenarios in which I care whether the sign bit is set;
what I
> always want is the value of the sign, -1 or +1.  The return value should
have
> the same numeric sign as the argument.  In this mode the return value
really is
> an integer or float, not an integer masquerading as a boolean.
>
> M.
>
> In article <ano1r9$27pp$2@digitaldaemon.com>, Walter says...
> >
> >Interesting. The .sign used the C signbit() function as a model. How do
you
> >do your code in C/C++?
> >
>
>

Yes there could be two properties, .sign and .signbit; .sign is by far the more useful.

Mark