Re: [PIC] Learning C

Things got a lot clearer when I finally realized that there is absolutely
no difference to the compiler between:

x=array[i]

And:

x=*(array+i)

The same is true for a pointer... you can use ptr[i] interchangeably with
*(ptr+i) .

Once they're defined, the only difference between an array and a pointer is
that you can't change the address of an array (its determined by the
compiler), but the address a pointer points at can be changed at will.

On Tue, Nov 19, 2024, 12:57 PM smplx <[email protected]> wrote:

>
> I guess the most confusing thing about "C" pointers is the way "C" treats
> array names / pointers and struct names / pointers.
>
> e.g.
> char buff[256];
> char *str;
>
> int x, j;
>
> x = buff[j];
>
> x = str[j];
>
> // buff above is the name of an array
> // str above is a pointer to an array
>
> char func(char *xstr, int k)
> {
>         return xstr[k];
> }
>
> x = func(buff, 23);  // convert buff to a pointer and pass it
> x = func(str, 23);   // pass str as a pointer
>
> Then you see something like:
>
> struct  FRED
> {
>         ....
>         int     blah;
>         ...
> };
>
> int func2(struct FRED arg)
> {
>         return arg.blah;
> }
>
> int func3(struct FRED *arg)
> {
>         return arg->blah;
> }
>
> x = func2(something); // pass struct by value
>
> x = func3( & something); // pass struxt by reference
>
> x = func(buff); // pass array by reference
>
> // pass by value makes copy of 'something' on stack and passes address of
> copy to func2
>
> // pass by reference passes address of 'something' directly to func2
> // ALSO: pass by reference passes address of 'buff' directly to func
>
> yes array / struct passing is inconsistant and confusing
>
> just remember:
>
> something->blah
>
> is equivalent to:
>
> (*something).blah
>
>
> Best regards
> Sergio Masci
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