Re: Null-terminated strings: the final analysis.

Mark McIntyre <markmcintyre@xxxxxxxxxxxxxxxxxxx> writes:
On 12/04/09 20:16, Mark Wooding wrote:
Joe Wright<joewwright@xxxxxxxxxxx> writes:

I believe strings can contain tabs, and other things that don't print but I
agree strings cannot contain the NUL character.

... by a trivial consequence of C's definition of a string, no less.

Exactly - definitionally.

Further, a text file is corrupted by the NUL character in a line.

Only because C strings can't represent lines of text containing a zero
byte.

Again we're into definitions: my definition of a text file is one that
doesn't contain non-alphanumeric characters. So if you send a null into
such a file, its corrupted.

I presume you meant non-printable, not non-alphanumeric; surely a text
file can contain spaces and punctuation characters.

Tab and newline characters are non-printable; can a text file contain
those?

I'm sure you can construct a rigorous definition of "text file" that
excludes null characters. But I don't think there's any universal
definition.

On the systems I use, if I write a '\a' character (ASCII BEL) to a
text file, I can reasonably expect to see a '\a' character when I read
it back. The same is not true of '\0' if I use fgets() to read it
(though I think can see the '\0' if I use fgetc()).

Using this to justify C's representative inadequacy is circular.

But then so is the counter-argument that is being made. C defines a
string as a null-terminated array of characters, therefore its circular
to complain that a string can't contain a null.

And anyway, if you want char arrays containing nulls, C can do those, no
problem.

Yes, but you can't store a null character in the middle of a string,
which makes char arrays containing nulls more difficult to deal with.
I'm not saying it's a fatal flaw in the language, but it is a slight
inconvenience.

And there are languages whose native strings *can* contain embedded
null characters. In C, strlen("foo\0bar") returns 3; in Perl,
length("foo\0bar") returns 7, and there's nothing particularly special
about the 4th character.

--
Keith Thompson (The_Other_Keith) kst-u@xxxxxxx <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
.

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