Access Violation Error & Rectangular Arrays

Derek Parnell derek at
Mon Aug 21 19:10:02 PDT 2006

On Tue, 22 Aug 2006 01:44:26 +0000 (UTC), xycos wrote:

> Hello,
> I apologize for asking such n00bish questions... I come from a C#/Java 
> background, and have never programmed with explicit pointers before.
> Two questions -- First, why won't this work?

Why do you need explicit pointers? This works ...

 class Bar {
     public Foo[5] arr;
     public this() {
         for(int i = 0; i < 5; i++) {
             arr[i] = new Foo(i);

Remember that a class object variable is really a reference to the object
sitting on the heap - a pointer if you will.

> It gives me an "access violation"... The GC shouldn't have killed
> anything; I still have pointers, neh?

Your original code has ...

 class Bar {
     public Foo*[5] arr;
     public this() {
         for(int i = 0; i < 5; i++) {
             Foo z = new Foo(i);
             arr[i] = &z;

The '&z' phrase takes the address of the local variable 'z' and not the
address of the object on the heap.

> Second question: Is there any way to define a rectangular array (one
> of the optimized ones, not the dynamic-arrays-of-arrays things) that
> has its size determined at compile time?

Not yet. This is planned for v2 of D. Until then you need to do some of the
work yourself y using a single-dimension array and calculating the offsets

  int x[5,6] is equivalent to x[30] 

  If you want to reference i,j then you calc the index as x[i*5+j]

(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocrity!"
22/08/2006 11:56:25 AM

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