ERROR - "cannot implicitly convert expression (s) of type int[3u] to int*"

[Ellery Newcomer]

On 06/18/2010 12:25 AM, Chick Corea wrote:
> [NOTE - sent twice as I was unsure that first attempt,
> pre-subscription, was received.]
>
> Working through the basics of D and running into simple problems that I
> cannot solve, such as:
>
>      Error: cannot implicitly convert expression (s) of type int[3u] to int*
>      Error: cannot implicitly convert expression (a) of type int[] to int*
>
> Those are the result of code that I pulled directly from the D v1 docs from
>
>      http://www.digitalmars.com/d/1.0/arrays.html
>
> Specifically, the code is this.
>
>          int* p;
>          int[3] s;
>          int[] a;
>          p = s;
>          p = a;
>
> I initially encountered this problem with the mark/release example code from
> the D v2 docs - here:
>
>     http://www.digitalmars.com/d/2.0/memory.html
>
> When I entered that code, it failed to compile.  After debugging a few errors,
> such as std/outofmemory.d being replaced by core.memory, I was left
> w/ the same error as above but w/ void*/void[].
>
> What is wrong w/ that ?  How is it different from the docs that it does not
> work ?  More importantly, what rule is being violated so that we won't
> encounter similar problems.
>

Rather simple. The docs are wrong (although I don't doubt that at some 
point in D's history the above was valid). Use

p = s.ptr;

instead of

p = s;

because arrays are not not not not not not not pointers. They're more of a

struct{
   size_t length;
   type* ptr;
}

>
> Any help would be appreciated.  D looks very promising for a real
> application that I need to write, as if it could provide the performance
> of C/C++ with the programmer-productivity of Perl/Python/etc.

Yup. That's the jingle.

> But if the time that we save writing the app in D will be lost to debugging
> simple problems like this then I won't have much of a choice.

Hang in there. In my experience, picking up a new language is always a 
frustrating experience. I think you'll find that D is worth it, though.

>
> Thanks in advance.
>
> CHICKZ