|  | Simple Array Question | | |
| | | Ray D. |  |
|  Posted: Tue Aug 26, 2008 9:44 pm Post subject: Simple Array Question |  |
This is probably very simple but I'm blanking and I haven't found a
tutorial that mentions this so I figure I'll ask here - I want to
access multiple array elements at once, as shown below. This syntax
gives me an error, so what is the correct method? Thanks for the
help!!
char Message[16]
....
Message[i:i+3] |
| |
| | | Bartc | |
| | Posted: Tue Aug 26, 2008 9:44 pm Post subject: Re: Simple Array Question | |
"Ray D." <ray.delvecchio@gmail.com> wrote in message
news:112e2694-2fa9-4716-bdb6-f23a0c8d08d0@79g2000hsk.googlegroups.com...
| Quote: | This is probably very simple but I'm blanking and I haven't found a
tutorial that mentions this so I figure I'll ask here - I want to
access multiple array elements at once, as shown below. This syntax
gives me an error, so what is the correct method? Thanks for the
help!!
char Message[16]
...
Message[i:i+3]
|
C doesn't support array slicing like this.
You have to program your way around it. And if your intention is to obtain a
string of 4 characters, usually you'd want a nul character at the end of
that, a further difficulty if you want to avoid copying those 4 characters.
--
Bartc |
| |
| | | Jens Thoms Toerring | |
| | Posted: Tue Aug 26, 2008 9:44 pm Post subject: Re: Simple Array Question | |
Sergio Perticone <g4ll0ws@gmail.com> wrote:
| Quote: | On 27 Ago, 00:40, Sergio Perticone <g4ll...@gmail.com> wrote:
[snip]
strncpy(buf, Message+i, i+3);
Sorry: strncpy(buf, Message+i, 3);
|
From the original post
I would guess that you need
strncpy( buf, Message + i, 4 );
At least in other languages I am aware of that have such a range
operator both the start and end element are usually included into
the result.
And the OP should make sure that he appends a '\0' character
in case he wants to use the result as a string since that's
not automatically appended by strncpy() if there's not a '\0'
somewhere in 'Message[ i ]' to 'Message[ i + 3 ]'.
Regards, Jens
--
\ Jens Thoms Toerring ___ jt@toerring.de
\__________________________ LINK |
| |
| | | Bartc | |
| | Posted: Tue Aug 26, 2008 9:44 pm Post subject: Re: Simple Array Question | |
"Sergio Perticone" <g4ll0ws@gmail.com> wrote in message
news:bdb169bb-4b74-4eb5-9a38-2a4c30de4afb@d1g2000hsg.googlegroups.com...
| Quote: | On 27 Ago, 00:40, Sergio Perticone <g4ll...@gmail.com> wrote:
[snip]
strncpy(buf, Message+i, i+3);
Sorry: strncpy(buf, Message+i, 3);
|
This might also need: buf[3]=0;
--
Bartc |
| |
| | | pete | |
| | Posted: Tue Aug 26, 2008 9:44 pm Post subject: Re: Simple Array Question | |
Ray D. wrote:
| Quote: | This is probably very simple but I'm blanking and I haven't found a
tutorial that mentions this so I figure I'll ask here - I want to
access multiple array elements at once, as shown below. This syntax
gives me an error, so what is the correct method? Thanks for the
help!!
char Message[16]
...
Message[i:i+3]
|
Are you trying to read an int from an array of char?
--
pete |
| |
| | | ssylee | |
| | Posted: Tue Aug 26, 2008 9:52 pm Post subject: Re: Simple Array Question | |
On Aug 26, 2:44 pm, "Ray D." <ray.delvecc...@gmail.com> wrote:
| Quote: | This is probably very simple but I'm blanking and I haven't found a
tutorial that mentions this so I figure I'll ask here - I want to
access multiple array elements at once, as shown below. This syntax
gives me an error, so what is the correct method? Thanks for the
help!!
char Message[16]
...
Message[i:i+3]
|
I'm not so sure if you can access multiple elements of an array at
once. I normally would access the array elements one by one inside a
for loop (which is really fast unless you have a specific delay on the
loop), although I'm not sure if this is what you're looking for. |
| |
| | | Sergio Perticone | |
| | Posted: Tue Aug 26, 2008 10:40 pm Post subject: Re: Simple Array Question | |
On 26 Ago, 23:44, "Ray D." <ray.delvecc...@gmail.com> wrote:
| Quote: | This is probably very simple but I'm blanking and I haven't found a
tutorial that mentions this so I figure I'll ask here - I want to
access multiple array elements at once, as shown below. This syntax
gives me an error, so what is the correct method? Thanks for the
help!!
char Message[16]
...
Message[i:i+3]
|
Wrong. But you could copy the "slice" in a temporary buffer:
char buf[ENOUGH_SPACE];
/* ... */
strncpy(buf, Message+i, i+3); |
| |
| | | Sergio Perticone | |
| | Posted: Tue Aug 26, 2008 10:43 pm Post subject: Re: Simple Array Question | |
On 27 Ago, 00:40, Sergio Perticone <g4ll...@gmail.com> wrote:
| Quote: | [snip]
strncpy(buf, Message+i, i+3);
|
Sorry: strncpy(buf, Message+i, 3);
s. |
| |
| | | Gene | |
| | Posted: Tue Aug 26, 2008 11:20 pm Post subject: Re: Simple Array Question | |
| |  | |
On Aug 26, 5:44 pm, "Ray D." <ray.delvecc...@gmail.com> wrote:
| Quote: | This is probably very simple but I'm blanking and I haven't found a
tutorial that mentions this so I figure I'll ask here - I want to
access multiple array elements at once, as shown below. This syntax
gives me an error, so what is the correct method? Thanks for the
help!!
char Message[16]
...
Message[i:i+3]
|
I ran into this kind of thing so often that I wrote a little function
for it:
// slice a string using Perl/Python position indexing conventions
// use end == dst_size to slice to the end of src (or ourput buffer
full)
char *str_slice (char *dst, int dst_size, char *src, int beg, int end)
{
int len;
if (dst_size > 0)
{
len = strlen (src);
if (beg < 0)
beg = len + beg;
else if (beg > len)
beg = len;
if (end < 0)
end = len + end;
else if (end > len)
end = len;
len = end - beg;
if (len <= 0)
{
dst[0] = '\0';
}
else
{
if (len >= dst_size)
len = dst_size - 1;
memcpy (dst, &src[beg], len);
dst[len] = '\0';
}
}
return dst;
} |
| |
| | | Richard Bos | |
| | Posted: Wed Aug 27, 2008 7:44 am Post subject: Re: Simple Array Question | |
"Bartc" <bc@freeuk.com> wrote:
| Quote: | "Sergio Perticone" <g4ll0ws@gmail.com> wrote in message
On 27 Ago, 00:40, Sergio Perticone <g4ll...@gmail.com> wrote:
strncpy(buf, Message+i, i+3);
Sorry: strncpy(buf, Message+i, 3);
This might also need: buf[3]=0;
|
Or you could start out using the right function, instead of the unwieldy
and un-C-string-like strncpy(), and write
char buf[SLICE_LENGTH+1];
buf[0]='\0';
strncat(buf, Message+i, SLICE_LENGTH);
That way at least you know both that you'll get a properly terminated
string, _and_ that you won't spend time filling buffers with null
characters, no matter how large SLICE_LENGTH is and how few characters
really are in buf.
Alternatively, if what you really want is to copy a number of bytes, not
a string, use memcpy().
Richard |
| |
| Page 1 of 2 .:. Goto page 1, 2 Next | |
|
|
