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The math library is missing the signum function.

//Returns 1 if x > 0, 0 if x == 0, or -1 if x < 0
template <typename T> constexpr T sign(T x);

Here are a whole bunch of people arguing about ways to implement it. Be
nice if there was a standard version with optimal efficiency on each
platform.
http://stackoverflow.com/questions/1903954/is-there-a-standard-sign-function-signum-sgn-in-c-c

It is possible to add new functions to the <cmath> header without getting
them in the C standard first?

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<div dir=3D"ltr">The math library is missing the signum function.<br><br>//=
Returns 1 if x &gt; 0, 0 if x =3D=3D 0, or -1 if x &lt; 0<br>template &lt;t=
ypename T&gt; constexpr T sign(T x);<br><br>Here are a whole bunch of peopl=
e arguing about ways to implement it. Be nice if there was a standard versi=
on with optimal efficiency on each platform.<br>http://stackoverflow.com/qu=
estions/1903954/is-there-a-standard-sign-function-signum-sgn-in-c-c<br><br>=
It is possible to add new functions to the &lt;cmath&gt; header without get=
ting them in the C standard first?<br></div>

<p></p>

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.

On Aug 21, 2014, at 1:50 PM, Matthew Fioravante <fmatthew5876@gmail.com> wr=
ote:

> The math library is missing the signum function.
>=20
> //Returns 1 if x > 0, 0 if x =3D=3D 0, or -1 if x < 0
> template <typename T> constexpr T sign(T x);
>=20
> Here are a whole bunch of people arguing about ways to implement it. Be n=
ice if there was a standard version with optimal efficiency on each platfor=
m.
> http://stackoverflow.com/questions/1903954/is-there-a-standard-sign-funct=
ion-signum-sgn-in-c-c
>=20
> It is possible to add new functions to the <cmath> header without getting=
 them in the C standard first?

Yes, as long as the spec clearly states that the signature is not guarantee=
d to be available from <math.h>.  Unofficially, but from a practical standp=
oint, we own <cmath>, and the C committee owns <math.h>.  Whenever either o=
f the two committees tries to specify the other's header (and both committe=
es have attempt to do so in the past), a little bit more chaos escapes into=
 the universe, and is nearly impossible to recapture.  To this day we suffe=
r from such attempts in the past.

Howard

--=20

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Howard Hinnant <howard.hinnant@gmail.com> writes:

| guaranteed to be available from <math.h>.  Unofficially, but from a
| practical standpoint, we own <cmath>, and the C committee owns
| <math.h>.  Whenever either of the two committees tries to specify the
| other's header (and both committees have attempt to do so in the
| past), a little bit more chaos escapes into the universe, and is
| nearly impossible to recapture.  To this day we suffer from such
| attempts in the past.

Amen to that.

Furthermore, LWG should stop Pavlovian reflexive adoption of everything
WG14 invents as <cxxx>.  Case in point: <cstdalign>.

-- Gaby

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Maybe it would make sense to have a C++ <math> header which includes
<cmath> and also has C++ specific math functions? Similarly for other
headers. The header <cmath> sounds like a C compatibility header, not the
primary header for the C++ math library.

On Saturday, August 23, 2014 4:59:58 PM UTC-4, Gabriel Dos Reis wrote:
>
> Howard Hinnant <howard....@gmail.com <javascript:>> writes:
>
> | guaranteed to be available from <math.h>.  Unofficially, but from a
> | practical standpoint, we own <cmath>, and the C committee owns
> | <math.h>.  Whenever either of the two committees tries to specify the
> | other's header (and both committees have attempt to do so in the
> | past), a little bit more chaos escapes into the universe, and is
> | nearly impossible to recapture.  To this day we suffer from such
> | attempts in the past.
>
> Amen to that.
>
> Furthermore, LWG should stop Pavlovian reflexive adoption of everything
> WG14 invents as <cxxx>.  Case in point: <cstdalign>.
>
> -- Gaby
>

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<div dir=3D"ltr">Maybe it would make sense to have a C++ &lt;math&gt; heade=
r which includes &lt;cmath&gt; and also has C++ specific math functions? Si=
milarly for other headers. The header &lt;cmath&gt; sounds like a C compati=
bility header, not the primary header for the C++ math library.<br><br>On S=
aturday, August 23, 2014 4:59:58 PM UTC-4, Gabriel Dos Reis wrote:<blockquo=
te class=3D"gmail_quote" style=3D"margin: 0;margin-left: 0.8ex;border-left:=
 1px #ccc solid;padding-left: 1ex;">Howard Hinnant &lt;<a href=3D"javascrip=
t:" target=3D"_blank" gdf-obfuscated-mailto=3D"G-V-DPRqRUcJ" onmousedown=3D=
"this.href=3D'javascript:';return true;" onclick=3D"this.href=3D'javascript=
:';return true;">howard....@gmail.com</a>&gt; writes:
<br>
<br>| guaranteed to be available from &lt;math.h&gt;. &nbsp;Unofficially, b=
ut from a
<br>| practical standpoint, we own &lt;cmath&gt;, and the C committee owns
<br>| &lt;math.h&gt;. &nbsp;Whenever either of the two committees tries to =
specify the
<br>| other's header (and both committees have attempt to do so in the
<br>| past), a little bit more chaos escapes into the universe, and is
<br>| nearly impossible to recapture. &nbsp;To this day we suffer from such
<br>| attempts in the past.
<br>
<br>Amen to that.
<br>
<br>Furthermore, LWG should stop Pavlovian reflexive adoption of everything
<br>WG14 invents as &lt;cxxx&gt;. &nbsp;Case in point: &lt;cstdalign&gt;.
<br>
<br>-- Gaby
<br></blockquote></div>

<p></p>

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------=_Part_5487_1573500003.1409184808351--

.

On Aug 27, 2014, at 8:13 PM, Matthew Fioravante <fmatthew5876@gmail.com> wr=
ote:

> Maybe it would make sense to have a C++ <math> header which includes <cma=
th> and also has C++ specific math functions? Similarly for other headers. =
The header <cmath> sounds like a C compatibility header, not the primary he=
ader for the C++ math library.

No, just put the C++ specific math functions in <cmath>, and then explicitl=
y state that they do not appear in <math.h> (unless the C committee says ot=
herwise).

We don't need more headers.  And there is no problem in the C++ committee a=
dding functionality to <cmath>.  We only get in trouble when the C++ commit=
tee adds (or subtracts) functionality to <math.h>, or when the C committee =
adds (or subtracts) functionality to <cmath>.

Howard

--=20

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Howard Hinnant <howard.hinnant@gmail.com> writes:

| On Aug 27, 2014, at 8:13 PM, Matthew Fioravante <fmatthew5876@gmail.com> =
wrote:
|=20
| > Maybe it would make sense to have a C++ <math> header which includes
| > <cmath> and also has C++ specific math functions? Similarly for
| > other headers. The header <cmath> sounds like a C compatibility
| > header, not the primary header for the C++ math library.
|=20
| No, just put the C++ specific math functions in <cmath>, and then
| explicitly state that they do not appear in <math.h> (unless the C
| committee says otherwise).

Agreed.  We already have too many C++ headers that do "math" stuff and I
always forget which one to include -- <cmath>, <cstdlib>, <numerics>,
<algorithm>, <complex>, <valarray>, etc.

| We don=E2=80=99t need more headers.  And there is no problem in the C++
| committee adding functionality to <cmath>.  We only get in trouble
| when the C++ committee adds (or subtracts) functionality to <math.h>,
| or when the C committee adds (or subtracts) functionality to <cmath>.
|=20
| Howard

-- Gaby

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