[musl] [PATCH] complex: fix comment in cacosh

[musl] [PATCH] complex: fix comment in cacosh

[Szabolcs Nagy]

The principal experssions defining acosh and acos are such that

  acosh(z) = +-i acos(z)

where the + is only true on the Im(z)>0 half of the complex plane
(and partly on Im(z)==0 depending on number representation).

fix the comment without expanding on the details.
---
 src/complex/cacosh.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/complex/cacosh.c b/src/complex/cacosh.c
index 76127f75..586328ce 100644
--- a/src/complex/cacosh.c
+++ b/src/complex/cacosh.c
@@ -1,6 +1,6 @@
 #include "complex_impl.h"
 
-/* acosh(z) = i acos(z) */
+/* acosh(z) = +-i acos(z) */
 
 double complex cacosh(double complex z)
 {
-- 
2.43.0

Re: [musl] [PATCH] complex: fix comment in cacosh

[Rich Felker]

On Sun, Mar 10, 2024 at 09:00:40PM +0100, Szabolcs Nagy wrote:
> The principal experssions defining acosh and acos are such that
> 
>   acosh(z) = +-i acos(z)
> 
> where the + is only true on the Im(z)>0 half of the complex plane
> (and partly on Im(z)==0 depending on number representation).
> 
> fix the comment without expanding on the details.
> ---
>  src/complex/cacosh.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/src/complex/cacosh.c b/src/complex/cacosh.c
> index 76127f75..586328ce 100644
> --- a/src/complex/cacosh.c
> +++ b/src/complex/cacosh.c
> @@ -1,6 +1,6 @@
>  #include "complex_impl.h"
>  
> -/* acosh(z) = i acos(z) */
> +/* acosh(z) = +-i acos(z) */
>  
>  double complex cacosh(double complex z)
>  {

I'm fine with taking this patch as-is, but it naturally raises a
question: should it instead be:

-/* acosh(z) = i acos(z) */
+/* acosh(z) = ±i acos(z) */

IOW, should we use non-ascii characters in comments like this? My
leaning would be yes, especially since it may be needed to properly
attribute an algorithm or something where the only alternative is
misspelling someone's name or leaving it out entirely.

Really the only consideration for not doing this would be if it
actively breaks compiling in some environments, but I don't think
that's the case.

Rich

Re: [musl] [PATCH] complex: fix comment in cacosh

[Thorsten Glaser]

Rich Felker dixit:

>I'm fine with taking this patch as-is, but it naturally raises a
>question: should it instead be:
>
>-/* acosh(z) = i acos(z) */
>+/* acosh(z) = ±i acos(z) */

Yes, please.

>Really the only consideration for not doing this would be if it
>actively breaks compiling in some environments, but I don't think
>that's the case.

I’ve been using UTF-8 in comments in mksh for a while, and it
hasn’t broken on Minix, Plan 9, DEC ULTRIX, 4.4BSD on Windows,
Dell UNIX (bare SVR4), Haiku, Syllable OS, and a plethora of
other old, weird, and other systems. Even Xenix works… and an
EBCDIC system as well.

They just interpret it as pertaining to whatever the local
codepage is, and the EBCDIC system converted it as-if-it-were
“extended ASCII”, but it hasn’t broken anything.

IOW, I haven’t seen a nōn-8bit-clean C compiler yet. Nor sh.

bye,
//mirabilos
-- 
„Cool, /usr/share/doc/mksh/examples/uhr.gz ist ja ein Grund,
mksh auf jedem System zu installieren.“
	-- XTaran auf der OpenRheinRuhr, ganz begeistert
(EN: “[…]uhr.gz is a reason to install mksh on every system.”)

Re: [musl] [PATCH] complex: fix comment in cacosh

[Szabolcs Nagy]

* Rich Felker <dalias@libc.org> [2024-03-10 17:19:06 -0400]:

> On Sun, Mar 10, 2024 at 09:00:40PM +0100, Szabolcs Nagy wrote:
> > The principal experssions defining acosh and acos are such that
> > 
> >   acosh(z) = +-i acos(z)
> > 
> > where the + is only true on the Im(z)>0 half of the complex plane
> > (and partly on Im(z)==0 depending on number representation).
> > 
> > fix the comment without expanding on the details.
> > ---
> >  src/complex/cacosh.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/src/complex/cacosh.c b/src/complex/cacosh.c
> > index 76127f75..586328ce 100644
> > --- a/src/complex/cacosh.c
> > +++ b/src/complex/cacosh.c
> > @@ -1,6 +1,6 @@
> >  #include "complex_impl.h"
> >  
> > -/* acosh(z) = i acos(z) */
> > +/* acosh(z) = +-i acos(z) */
> >  
> >  double complex cacosh(double complex z)
> >  {
> 
> I'm fine with taking this patch as-is, but it naturally raises a
> question: should it instead be:
> 
> -/* acosh(z) = i acos(z) */
> +/* acosh(z) = ±i acos(z) */
> 
> IOW, should we use non-ascii characters in comments like this? My

fine with me,

for me it's easier to type +- on the keyboard though.

> leaning would be yes, especially since it may be needed to properly
> attribute an algorithm or something where the only alternative is
> misspelling someone's name or leaving it out entirely.
> 
> Really the only consideration for not doing this would be if it
> actively breaks compiling in some environments, but I don't think
> that's the case.
> 
> Rich

Re: [musl] [PATCH] complex: fix comment in cacosh

[Damian McGuckin]

On Mon, 11 Mar 2024, Szabolcs Nagy wrote:

>> +/* acosh(z) = ?i acos(z) */
>>
>> IOW, should we use non-ascii characters in comments like this? My

What is the non-asci character you are typing.

All I see is a question mark visually in my mailer and when I od the 
content, I also see a question mark.

Thanks - Damian

Re: [musl] [PATCH] complex: fix comment in cacosh

[Gabriel Ravier]

On 3/11/24 08:43, Damian McGuckin wrote:
> On Mon, 11 Mar 2024, Szabolcs Nagy wrote:
>
>>> +/* acosh(z) = ?i acos(z) */
>>>
>>> IOW, should we use non-ascii characters in comments like this? My
>
> What is the non-asci character you are typing.
>
> All I see is a question mark visually in my mailer and when I od the 
> content, I also see a question mark.
>
> Thanks - Damian

U+00B1, the Plus-Minus sign (i.e. a + on top of a -)

Re: [musl] [PATCH] complex: fix comment in cacosh

[Damian McGuckin]

On Mon, 11 Mar 2024, Gabriel Ravier wrote:

>>  What is the non-ascii character you are typing.
>>
>>  All I see is a question mark visually in my mailer and when I od the
>>  content, I also see a question mark.
>>
>>  Thanks - Damian
>
> U+00B1, the Plus-Minus sign (i.e. a + on top of a -)

I will wait until the release. I am sure it will be in the file. Looks 
like I will have to tweak the setting for 'vi'.

Thanks - Damian