Re: What is the proper way to outline static-if-conditions ?

[Elmar via Digitalmars-d-learn]

On Sunday, 10 October 2021 at 14:36:50 UTC, Elmar wrote:
On Sunday, 10 October 2021 at 14:08:13 UTC, drug wrote:
You just need to check if T is a pointer:
```D
import std;
alias DA = int[];
alias SA = int[3];

alias PSA = SA*;
alias PDA = DA*;

version(all)
	enum isPointedStaticArray(T) = isPointer!T && 
isStaticArray!(PointerTarget!T);
else
	enum isPointedStaticArray(T) = isPointer!T && 
is(PointerTarget!T : P[N], P, size_t N);  // this way you can 
get array length

static assert(!isPointedStaticArray!DA);
static assert(!isPointedStaticArray!SA);
static assert(!isPointedStaticArray!PDA);
static assert( isPointedStaticArray!PSA);

void main()
{
}
```
https://run.dlang.io/is/qKdx1D

Also you can use another way to detect static array - it can 
be useful if you need to get its length

Wow, this is a fine solution. I gonna use it, thank you :-) .

Well, I just wondered why your code would compile and mine 
wouldn't. The `version(all)` variant will not compile on my 
computer with `rdmd` because `PointerTarget` only allows pointers.

But the 2nd one will compile. The `is()` expression catches the 
compilation error which is nice. This is sufficient:

```d
enum isPointedStaticArray(T) = is(PointerTarget!T : P[N], P, 
size_t N);
```

It would be nice if one could use pattern-matching for it in D. 
Is this possible?

```d
	enum isPointedStaticArray(X : P*, P) = 
.isStaticArray!(PointerTarget!X);
        enum isPointedStaticArray(X : else) = false;
```