Regex character and collation class documentation

[Polytropon]

On Mon, 13 Nov 2017 09:09:52 -0500, James B. Byrne via freebsd-questions wrote:
> A file named cname.h does not even exist on my system.  At least if it
> does then find does not report it. 

Check the following ocation:

/usr/src/lib/libc/regex/cname.h



> On the other hand, this file:
> 
> /usr/local/include/nstring.h

Due to the path, this file seems to be installed by a port.
You could check which one it was.



> contains this:
> 
> /* The standard C library routines isdigit(), for some weird
>    historical reason, does not take a character (type 'char') as its
>    argument.  Instead it takes an integer.  When the integer is a whole
>    number, it represents a character in the obvious way using the local
>    character set encoding.  When the integer is negative, the results
>    are undefined.
> 
>    Passing a character to isdigit(), which expects an integer,
>    results in isdigit() sometimes getting a negative number.
> 
>    On some systems, when the integer is negative, it represents exactly
>    the character you want it to anyway (e.g. -1 is the character that
>    is encoded 0xFF).  But on others, it does not.
> 
>    (The same is true of other routines like isdigit()).
> 
>    Therefore, we have the substitutes for isdigit() etc. that take an
>    actual character (type 'char') as an argument.
> */
> 
> #define ISALNUM(C) (isalnum((unsigned char)(C)))
> #define ISALPHA(C) (isalpha((unsigned char)(C)))
> #define ISCNTRL(C) (iscntrl((unsigned char)(C)))
> #define ISDIGIT(C) (isdigit((unsigned char)(C)))
> #define ISGRAPH(C) (isgraph((unsigned char)(C)))
> #define ISLOWER(C) (islower((unsigned char)(C)))
> #define ISPRINT(C) (isprint((unsigned char)(C)))
> #define ISPUNCT(C) (ispunct((unsigned char)(C)))
> #define ISSPACE(C) (isspace((unsigned char)(C)))
> #define ISUPPER(C) (isupper((unsigned char)(C)))
> #define ISXDIGIT(C) (isxdigit((unsigned char)(C)))
> #define TOUPPER(C) ((char)toupper((unsigned char)(C)))
> 
> But nowhere can I find 'isnul' or ISNUL'.

Yes, nothing in that file.



The only occurances of NUL I find are in the character-name table
in /usr/src/lib/libc/regex/cname.h:

/* character-name table */
static struct cname {
	char *name;
	char code;
} cnames[] = {
	{"NUL",			'\0'},

	/* ... lots of lines omitted ... */

	{NULL,  0}
};



-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...