• Alain De Vos (3/3) May 06 2021 Is a fixed length array created on the heap and a dynamic array
• Paul Backus (11/14) May 06 2021 Static arrays (`T[N]`) are value types, like structs. If you
• Alain De Vos (15/15) May 07 2021 Following code compiles without errors, only errors during runtime
• Paul Backus (16/32) May 07 2021 The result of a `~` expression is always a newly-allocated

Alain De Vos <devosalain ymail.com> writes:

Is a fixed length array created on the heap and a dynamic array 
on the stack ? And is this important with relation to the garbage 
collector ?

Paul Backus <snarwin gmail.com> writes:

On Thursday, 6 May 2021 at 22:35:38 UTC, Alain De Vos wrote:
 Is a fixed length array created on the heap and a dynamic array 
 on the stack ? And is this important with relation to the 
 garbage collector ?

Static arrays (`T[N]`) are value types, like structs. If you 
declare them as local variables, they're allocated on the stack.

Dynamic arrays (`T[]`), also known as slices, are reference 
types, consisting of a pointer and a length. If you declare them 
as local variables, the pointer and length will be stored on the 
stack. The data they point to, however, may be stored on either 
the stack or the heap.

For more information about slices in D, I highly recommend this 
excellent article by Steven Schveighoffer:

https://dlang.org/articles/d-array-article.html

Alain De Vos <devosalain ymail.com> writes:

Following code compiles without errors, only errors during runtime
```
int main(){
	int[2]  a=new int[2];
	int[]   b=new int[0];
	int[2]  c=[1,2];
	a=a~3;
	b=b~3;
	c=c~3;
	c=b;
	b=a;
	a=c;
return 0;
}
```

Paul Backus <snarwin gmail.com> writes:

On Friday, 7 May 2021 at 22:21:09 UTC, Alain De Vos wrote:
 Following code compiles without errors, only errors during 
 runtime
 ```
 int main(){
 	int[2]  a=new int[2];
 	int[]   b=new int[0];
 	int[2]  c=[1,2];
 	a=a~3;
 	b=b~3;
 	c=c~3;
 	c=b;
 	b=a;
 	a=c;
 return 0;
 }
 ```

The result of a `~` expression is always a newly-allocated 
dynamic array on the GC heap. [1]

When you assign a dynamic array to a static array, the elements 
from the dynamic array on the right-hand side are copied into the 
static array on the left-hand side. [2] So the statement

     a = a ~ 3;

...is essentially shorthand for

     auto _tmp = a ~ 3;
     foreach (i; 0 .. _tmp.length)
         a[i] = _tmp[i];

Because `a` has length `2` and `a ~ 3` has length `3`, this 
results in a `RangeViolation` at runtime when attempting to copy 
`_tmp[2]` into `a[2]`.

[1] https://dlang.org/spec/expression.html#cat_expressions
[2] https://dlang.org/spec/arrays.html#array-copying