Thinking about the difference between fixed and 'dynamic' arrays.

[Siarhei Siamashka]

On Tuesday, 29 November 2022 at 23:25:46 UTC, DLearner wrote:
> Many languages also have variable length arrays, I suggest D's 
> 'dynamic array' _does not_ operate as expected.
> I'm not suggesting that the result contradicts D's definition 
> of 'dynamic array', nor it's implementation, just that 'dynamic 
> array' is not a reasonable description for a construct that 
> behaves like VarArr2[3] becoming 40.

Which programming languages set your expectations this way? Many 
programming languages have the concept of "deep" vs. "shallow" 
copy. D is a part of a big crowd:

D:
```D
import std;

void main()
{
   auto a = [1, 2, 3, 4, 5];
   auto b = a;
   auto c = a.dup;

   a[1] = 99;

   writeln(a); // [1, 99, 3, 4, 5]
   writeln(b); // [1, 99, 3, 4, 5]
   writeln(c); // [1, 2, 3, 4, 5]
}
```

Python:
```Python
a = [1, 2, 3, 4, 5]
b = a
c = a.copy()

a[1] = 99

print(a) # [1, 99, 3, 4, 5]
print(b) # [1, 99, 3, 4, 5]
print(c) # [1, 2, 3, 4, 5]
```

Ruby/Crystal:
```Ruby
a = [1, 2, 3, 4, 5]
b = a
c = a.dup

a[1] = 99

pp a # [1, 99, 3, 4, 5]
pp b # [1, 99, 3, 4, 5]
pp c # [1, 2, 3, 4, 5]
```

Kotlin:
```Kotlin
fun main() {
   var a = intArrayOf(1, 2, 3, 4, 5)
   var b = a
   var c = a.copyOf()

   a[1] = 99

   println(a.contentToString()) // [1, 99, 3, 4, 5]
   println(b.contentToString()) // [1, 99, 3, 4, 5]
   println(c.contentToString()) // [1, 2, 3, 4, 5]
}
```

I could list even more languages.