[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.

I am using dmd v1.062 for v1 code, and dmd v2.047, downloaded and installed today onto a  WinXP system.

    $ dmd -v
    Digital Mars D Compiler v1.062
    Copyright (c) 1999-2010 by Digital Mars written by Walter Bright
    Documentation: http://www.digitalmars.com/d/1.0/index.html
    Usage:
      dmd files.d ... { -switch }

   $ dmd -v                   # different path from above
   Digital Mars D Compiler v2.047
   Copyright (c) 1999-2010 by Digital Mars written by Walter Bright
   Documentation: http://www.digitalmars.com/d/2.0/index.html
   Usage:
     dmd files.d ... { -switch }

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.
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.

Thanks in advance.

CHICKZ

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

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
<snip>

This was deprecated in 0.177, but the example code is out of date.

http://d.puremagic.com/issues/show_bug.cgi?id=996

Stewart.

On Fri, 18 Jun 2010 01:25:32 -0400, Chick Corea <chick.zcorea@gmail.com> wrote:
> 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 can't speak as to why the D2 code doesn't work, but this example in the documentation is flat out wrong. To assign a D array to a pointer, you must use the .ptr property, so that the correct code is actually:

 int* p;
 int[3] s;
 int[] a;
 p = s.ptr;
 p = a.ptr;

Hope this clears things up.

Stewart Gordon wrote:
> 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
> <snip>
> 
> This was deprecated in 0.177, but the example code is out of date.
> 
> http://d.puremagic.com/issues/show_bug.cgi?id=996
> 
> Stewart.

I've just checked in a fix.

On Fri, 18 Jun 2010 08:41:17 -0700, Justin Spahr-Summers <Justin.SpahrSummers@gmail.com> wrote:
> 
> On Fri, 18 Jun 2010 01:25:32 -0400, Chick Corea <chick.zcorea@gmail.com> wrote:
> > 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 can't speak as to why the D2 code doesn't work, but this example in the documentation is flat out wrong. To assign a D array to a pointer, you must use the .ptr property, so that the correct code is actually:
> 
>  int* p;
>  int[3] s;
>  int[] a;
>  p = s.ptr;
>  p = a.ptr;
> 
> Hope this clears things up.

I followed up last night, but my post didn't show up until this morning. Sorry for the redundant answer! :X

Thanks for the help, folks.

CHICKZ