Re: chars

Keith Thompson wrote:
user923005 <dcorbit@xxxxxxxxx> writes:
On Jan 7, 12:20 pm, "Bill Cunningham" <nos...@xxxxxxxxx> wrote:
[...]
Do I sound like I'm getting it right now?
Not sure. A string (in C) is a pointer to an array {or an array} of
zero or more characters with a terminating zero.

No, a pointer is not a string, and an array is not a string.

A string is, by definition, "a contiguous sequence of characters
terminated by and including the first null character", and a "pointer
to a string" is "a pointer to its initial (lowest addressed)
character".

Yes. I would add "in memory" for the string.

So a pointer may *point* to a string, but it cannot *be* a string.
And an array may *contain* a string, but it cannot *be* a string.

The term "string" refers to a data layout, not a data type.

Indeed.

So this is a string:

char *foo = "I am a string";

No, foo is a pointer to a string.

No, foo is a pointer to char, the first element in the anonymous array.

and this is a string:

char bar[4] = "123";

bar, an array object, contains a string. I suppose you could say that
the value of bar is a string.

No. An array in C has no defined value. The value of bar[0] is '1' and the value of bar is '&bar[0]', the address (of type char*) of the first element of the array (the '1').

but this is not a string, it's just an array because it does not have
a terminating zero:

char barbad[4] = "1234";

and neither is this:

char badbar[3] = {'a', 'b', 'c'};

Correct, neither barbad nor badbar contains a string.

Indeed.

I think we overload 'array' a little. Correctly..

char arr[80] = "Hello";
char *arp = malloc(80);
strcpy(arp, arr);

...barring error, it is arr which is the array and arp a pointer to contiguous memory. And 'strcmp(arr, arp) == 0'. Both are strings.

--
Joe Wright
"If you think Health Care is expensive now, wait until it's free."
.

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