Mail Archives: djgpp-workers/2003/08/29/17:42:51
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In a message dated 8/29/2003 5:10:01 PM Eastern Standard Time,
ams AT ludd DOT luth DOT se writes:
> >In this case, the affected math function sets errno to ERANGE and
> (possibly)
> >raises an appropriate exception. In no case should a math function issue
> >SIGFPE.
>
> What signal should it generate if not SIGFPE?
>
> For me raise an exception == generate a signal. Both Eli and you
> seems to say that raising an exception is something else than
> generating a signal.
>
> Can somebody explain this to me?
>
You mentioned acos(2) somewhere in this thread. Appended to this email as a
postscript is acosl.c. In the first few steps, if the absolute value of the
argument exceeds 1, the function takes actions prescribed in C99, pages 229
(7.12.4.1) and 446 (F.9.11). The actions include raising the invalid floating
point exception.
KB Williams
PS
/* ------- */
/* acosl.c */
/* ------- */
#include <errno.h>
#include <math.h>
#include <fdlibml.h>
#include <fenv.h>
/*
Written for DJGPP/GCC by KB Williams, kbwms AT aol DOT com,
December 2001
*/
# ifdef __STDC__
long double
acosl(long double Arg)
# else
long double
acosl(Arg)
long double Arg;
# endif
// 1. If |Arg| > 1
// Set errno to EDOM, set Retval to NaN,
// raise invalid exception
// 2. If |Arg| == 1
// Retval = (Arg > 0) ? 0 : Pi
// 3. If Arg == 0
// Set Retval to Pi/2
// 4. Calculate acos(Arg) for
// x in (-1, -.5), or (+.5, +1) or [-.5, +.5]
{
long double AbsArg, Retval;
AbsArg = fabsl(Arg);
if (AbsArg >= 1) // Steps 1 & 2
{
if (AbsArg > 1)
{
errno = EDOM;
Retval = NANL; // Return NaN
feraiseexcept(FE_INVALID); // Raise invalid exception
}
else // Arg == +- 1
{
if (Arg > 0) // acosl(1) = 0
Retval = 0;
else // acosl(-1) = pi
Retval = PIL;
}
}
else if (Arg == 0) // Step 3
{
Retval = PIO2L;
}
else if (Arg < -0.5L) // Step 4
{
Retval = (PIL - 2.0L * asinl(sqrtl(0.5L * (1.0L + Arg))));
}
else if (Arg > 0.5L)
{
Retval = (2.0L * asinl(sqrtl(0.5L * (1.0L - Arg))));
}
else
{
Retval = (PIO2L - asinl(Arg));
}
return Retval;
}
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<HTML><FONT FACE=3Darial,helvetica><FONT SIZE=3D3 FAMILY=3D"SERIF" FACE=3D"=
Georgia" LANG=3D"0">In a message dated 8/29/2003 5:10:01 PM Eastern Standard=
Time, ams AT ludd DOT luth DOT se writes:<BR>
<BR>
<BLOCKQUOTE TYPE=3DCITE style=3D"BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT=
: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px"></FONT><FONT COLOR=3D"#000000"=
style=3D"BACKGROUND-COLOR: #ffffff" SIZE=3D2 FAMILY=3D"SANSSERIF" FACE=3D"A=
rial" LANG=3D"0">>In this case, the affected math function sets errno to=20=
ERANGE and (possibly) <BR>
>raises an appropriate exception. In no case should a math function=
issue <BR>
>SIGFPE.<BR>
<BR>
What signal should it generate if not SIGFPE?<BR>
<BR>
For me raise an exception =3D=3D generate a signal. Both Eli and you<BR>
seems to say that raising an exception is something else than<BR>
generating a signal.<BR>
<BR>
Can somebody explain this to me?<BR>
</BLOCKQUOTE><BR>
</FONT><FONT COLOR=3D"#000000" style=3D"BACKGROUND-COLOR: #ffffff" SIZE=3D3=
FAMILY=3D"SERIF" FACE=3D"Georgia" LANG=3D"0"><BR>
You mentioned acos(2) somewhere in this thread. Appended to this email=
as a postscript is acosl.c. In the first few steps, if the absolute v=
alue of the argument exceeds 1, the function takes actions prescribed in C99=
, pages 229 (7.12.4.1) and 446 (F.9.11). The actions include raising t=
he invalid floating point exception.<BR>
<BR>
<BR>
KB Williams<BR>
<BR>
PS<BR>
<BR>
/* ------- */<BR>
/* acosl.c */<BR>
/* ------- */<BR>
#include <errno.h><BR>
#include <math.h><BR>
#include <fdlibml.h><BR>
#include <fenv.h><BR>
/*<BR>
Written for DJGPP/GCC by KB Williams, kbwms AT aol DOT com,<BR>
December 2001<BR>
*/<BR>
# ifdef __STDC__<BR>
long double<BR>
acosl(long double Arg)<BR>
# else<BR>
long double<BR>
acosl(Arg)<BR>
long double Arg;<BR>
# endif<BR>
// 1. If |Arg| > 1<BR>
// Set errno to EDOM, set Re=
tval to NaN,<BR>
// raise invalid exception<B=
R>
// 2. If |Arg| =3D=3D 1<BR>
// Retval =3D (Arg > 0) ?=
0 : Pi<BR>
// 3. If Arg =3D=3D 0<BR>
// Set Retval to Pi/2<BR>
// 4. Calculate acos(Arg) for<BR>
// x in (-1, -.5), or (+.5,=20=
+1) or [-.5, +.5]<BR>
{<BR>
long double AbsArg, Retval;<BR>
<BR>
AbsArg =3D fabsl(Arg);<BR>
<BR>
if (AbsArg >=3D 1) =
&nbs=
p; // Steps 1 & 2<BR>
{<BR>
if (AbsArg > 1)<BR>
{<BR>
errno=20=
=3D EDOM;<BR>
Retval=20=
=3D NANL; &=
nbsp; // Return NaN<BR>
feraiseex=
cept(FE_INVALID); // Raise invalid exception<BR>
}<BR>
else  =
; &nb=
sp; // Arg =3D=3D +- 1=
<BR>
{<BR>
if (Arg &=
gt; 0) &nbs=
p; // acosl(1) =3D 0<BR>
&nbs=
p; Retval =3D 0;<BR>
else =
; &nb=
sp; // acosl(-1) =3D p=
i<BR>
&nbs=
p; Retval =3D PIL;<BR>
}<BR>
}<BR>
else if (Arg =3D=3D 0)  =
; // Step=20=
3<BR>
{<BR>
Retval =3D PIO2L;<BR>
}<BR>
else if (Arg < -0.5L) &nb=
sp; // Step 4<BR>
{<BR>
Retval =3D (PIL - 2.0L * asinl(sq=
rtl(0.5L * (1.0L + Arg))));<BR>
}<BR>
else if (Arg > 0.5L)<BR>
{<BR>
Retval =3D (2.0L * asinl(sqrtl(0.=
5L * (1.0L - Arg))));<BR>
}<BR>
else<BR>
{<BR>
Retval =3D (PIO2L - asinl(Arg));<=
BR>
}<BR>
return Retval;<BR>
}<BR>
</FONT></HTML>
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