bug#12270: 24.1.50; (elisp) Syntax Descriptors: "second character, if present"

bug#12270: 24.1.50; (elisp) Syntax Descriptors: "second character, if present"

[Drew Adams]

This text does not seem correct to me.  At least it seems unclear.
 
 "The first character in a syntax descriptor must be a syntax class
  designator character.  The second character, if present, specifies a
  matching character (e.g. in Lisp, the matching character for `(' is
  `)'); a space specifies that there is no matching character."
 
How can the second char be absent if the third char is present?  It is
wrong to speak of a char being "present" here, AFAICT.  What should be
said instead of "present" is non-space:
 
 "The second character, if not a space, specifies..."
 

In GNU Emacs 24.1.50.1 (i386-mingw-nt5.1.2600)
 of 2012-08-13 on MARVIN
Bzr revision: 109584 monnier@iro.umontreal.ca-20120813141247-76irjqslrfncn30u
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.6) --no-opt --enable-checking --cflags
 -ID:/devel/emacs/libs/libXpm-3.5.8/include
 -ID:/devel/emacs/libs/libXpm-3.5.8/src
 -ID:/devel/emacs/libs/libpng-dev_1.4.3-1/include
 -ID:/devel/emacs/libs/zlib-dev_1.2.5-2/include
 -ID:/devel/emacs/libs/giflib-4.1.4-1/include
 -ID:/devel/emacs/libs/jpeg-6b-4/include
 -ID:/devel/emacs/libs/tiff-3.8.2-1/include
 -ID:/devel/emacs/libs/gnutls-3.0.9/include
 -ID:/devel/emacs/libs/libiconv-1.13.1-1-dev/include
 -ID:/devel/emacs/libs/libxml2-2.7.8/include/libxml2'
 

bug#12270: 24.1.50; (elisp) Syntax Descriptors: "second character, if present"

[Andreas Schwab]

"Drew Adams" <drew.adams@oracle.com> writes:

> This text does not seem correct to me.  At least it seems unclear.
>  
>  "The first character in a syntax descriptor must be a syntax class
>   designator character.  The second character, if present, specifies a
>   matching character (e.g. in Lisp, the matching character for `(' is
>   `)'); a space specifies that there is no matching character."
>  
> How can the second char be absent if the third char is present?

Which third character?

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

bug#12270: 24.1.50; (elisp) Syntax Descriptors: "second character, if present"

[Drew Adams]

> > This text does not seem correct to me.  At least it seems unclear.
> >  
> >  "The first character in a syntax descriptor must be a syntax class
> >   designator character.  The second character, if present, 
> specifies a
> >   matching character (e.g. in Lisp, the matching character 
> for `(' is
> >   `)'); a space specifies that there is no matching character."
> >  
> > How can the second char be absent if the third char is present?
> > It is wrong to speak of a char being "present" here, AFAICT.
> > What should be said instead of "present" is non-space:
> >
> >  "The second character, if not a space, specifies..."
> 
> Which third character?

Which?  Why - do you think there can be more than one third char?  "Which"
implies at a choice from a known group of at least two elements.

Perhaps you meant "What", and you meant to ask about the case where there is no
2nd char.

The point is that IF there is a second char (so that we can in fact speak of
"the second char") and IF it is not a space char, then that non-space char
specifies a matching char.  That is what needs to be conveyed.

In the examples given in the node, ". 23" and ". 14", a second char is PRESENT,
and yet it does NOT specify a matching char, because it is a space char.

The doc does say afterward that a space char specifies that there is no matching
char.  Good.  [It follows (but is not said explicitly) that a space char cannot
_be_ a matching char.]

It would be clearer to say "a non-space 2nd char specifies a matching char".
That's the point.  And that's all that needs to be said.

There is a second bug in this text, BTW: The first example is written `". 23"'
and the second is written `. 14'.  One of them, at least, is written wrong.

bug#12270: 24.1.50; (elisp) Syntax Descriptors: "second character, if present"

[Andreas Schwab]

"Drew Adams" <drew.adams@oracle.com> writes:

> It would be clearer to say "a non-space 2nd char specifies a matching char".

And what if there is no second character?

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

bug#12270: 24.1.50; (elisp) Syntax Descriptors: "second character, if present"

[Drew Adams]

> > "a non-space 2nd char specifies a matching char".
> 
> And what if there is no second character?

A stop sign means stop.

If there is a stop sign, it means stop.

bug#12270: 24.1.50; (elisp) Syntax Descriptors: "second character, if present"

[Andreas Schwab]

Thus nothing to fix here.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

bug#12270: 24.1.50; (elisp) Syntax Descriptors: "second character, if present"

[Drew Adams]

> Thus nothing to fix here.

No, wrong again.

Please add the words "and not a space":

 "The second character, if present and not a space, specifies..."
                                  ^^^^^^^^^^^^^^^^

Otherwise, the text is unclear and arguably incorrect.

Please do not be so stubborn.  It's not about your ego; it's about helping
users.

bug#12270: 24.1.50; (elisp) Syntax Descriptors: "second character, if present"

[Andreas Schwab]

Which is exactly what the docs say.  Just read it.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

bug#12270: 24.1.50; (elisp) Syntax Descriptors: "second character, if present"

[Drew Adams]

>> Please add the words "and not a space":
>> 
>> "The second character, if present and not a space, specifies..."
>>                                   ^^^^^^^^^^^^^^^^
>
> Which is exactly what the docs say.  Just read it.

I know what the doc says.

I also know that the text could be clearer, helping users.

>> Please do not be so stubborn.  It's not about your ego;
>> it's about helping users.