Null revisited (briefly)

[Chris Torek]

>In article <10138 at socslgw.csl.sony.JUNET> diamond at diamond.
>(Norman Diamond) writes:
>>When you assign 'x' to a character, you are assigning an int to a
>>character.  The reader knows that the type mismatch was intentional.

This is correct.

In article <1783 at dlvax2.datlog.co.uk> scm at datlog.co.uk ( Steve Mawer ) writes:
>Not if he knows the C language.  A single character written within
>single quotes is a *character constant*.  This isn't an int.

False.  A character constant is an int (not a char) whose value is the
representation of that character in the machine's character set
(typically ASCII; EBCDIC is confused about where the []s go, and
sometimes does not have {} \ and ~, depending on which EBCDIC you
are using---there are at least three major variants).

>'\0' is a special case to permit the representation of non-graphical
>characters (also newline, tab, backslash, return, etc.) and is not
>the same as 0, which is an integer constant.

Aside from the backslash interpretation, '\0' is *not* a special case.
The type of '\0' is int and its value is zero, no matter what the
character set; this is guaranteed by the C language.  (The <type,value>
pair for an unadorned 0 is also <int,0>, although the <type,value>
pair of something like 65432 is sometimes <long,65432>.)

>It should, however, be noted that some compilers will allow the use
>of multiple characters, as in 'abcd' (which *may* work on 32 bit
>machines).  I wouldn't recommend this usage in portable software.

This is correct.  It is hard to predict whether (char)'abcd' will
be the same as (char)'a' or (char)'d' (or even b or c), so it is
best to avoid these.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris at mimsy.umd.edu	Path:	uunet!mimsy!chris