Re: Interesting Error

True, but char ** is a pointer to a pointer and char [][] is a
multi-dimensional array.  They're completely different animals.  You
can try it out and see that A) the compiler throws a warning and B) it
doesn't work.


On 12/1/05, Yorch <[email protected]> wrote:
> An array is implemented as a pointer, the name of the array is a
> pointer, so it's the same thing.
>
> On 12/1/05, Michael Barton <[email protected]> wrote:
> > No, that would be the equivalent of
> >   char *token[]  // array of pointers
> > not
> >   char token[][]  // array of arrays.
> >
> > You have to know the size of every dimension in the array except the
> > last one to do anything with it.  Usually that's all done by the
> > compiler.  If you know the size of the array at run time, it's
> > possible to fudge it by doing the array indexing math yourself, but
> > you'd have to stretch quite a bit to come up with an example where
> > it's useful:
> >
> > void blah(char *token, int width)
> > {
> >   printf("token: %c\n", token[width * 2 + 1]);
> >   // token[2][1] -- that's the math the compiler would normally do
> > }
> >
> > int main()
> > {
> >   char token[4][3];
> >   token[2][1] = 'c';
> >   blah((char *)token, 3); // send it the width of the array
> >   return 0;
> > }
> >
> >
> > On 12/1/05, Yorch <[email protected]> wrote:
> > > You can define it this way:
> > >
> > > void blah(char **token);
> > >
> > > this way you won't need to use the size and you can use that pointer
> > > like a 2D array.
> > >
> > > On 11/30/05, [email protected] <[email protected]> wrote:
> > > > Gah, I am not surprised I figured out the problem 5 minutes I send it to the
> > > > list.
> > > >
> > > > Though, to create some discussion on the list, I will ask this:
> > > >
> > > > Why cannot we define like so:
> > > > void blah(char token[][])
> > > > but:
> > > > void blah(char token[][size])?
> > > >
> > > > Enlighten me! :D
> > > >
> > > >
> > > >
> > > > Quoting [email protected]:
> > > >
> > > > >
> > > > >
> > > > > So, I am trying to pass a 2D char variable to a function and then do some
> > > > > stuff
> > > > > with it. However, I am receiving this error and I am not quite sure why:
> > > > >
> > > > > "arithmetic on pointer to an incomplete type"
> > > > >
> > > > > Poking around the internet hasn't lead me to anywhere interesting. I thought
> > > > > it
> > > > > was just my compiler on the linux box so I wrote a test program in dev-c++ so
> > > > > we can see if that was so. This is written and is compiled in C:
> > > > >
> > > > > void blah(char token[][]);
> > > > >
> > > > > int main()
> > > > > {
> > > > >         char token[1][1];
> > > > >
> > > > >         token[0][0] = 'c';
> > > > >
> > > > >         blah(token);
> > > > >
> > > > >         return 0;
> > > > > }
> > > > >
> > > > > void blah(char token[][])
> > > > > {
> > > > >                     printf("token: %c\n", token[0][0]);
> > > > > }
> > > > >
> > > > > It generates the same error.
> > > > >
> > > > > I am assuming, as usual, that it is something obvious and after spending
> > > > > hours
> > > > > (a good 4 hours straight) smashing my keyboard my eyes have gone out of
> > > > > control!
> > > > >
> > > > > Thank you!
> > > > >
> > > > >
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