Just a friendly reminder about using arrays in boolean conditions

[kdevel]

On Wednesday, 27 November 2024 at 06:46:18 UTC, Jonathan M Davis 
wrote:

> [...] Either way, I would consider it good practice to be 
> explicit about testing for null vs empty instead of if(arr), 
> because if(arr) is misunderstood so frequently that the odds 
> are very high that the programmer who wrote the code 
> misunderstood what they were actually testing. And even if they 
> didn't, you have no way of knowing that when reading their 
> code. On the other hand, code like
> [line breaks inserted]
>
> if(arr !is null)

That translates into broken English "if array not is null". More 
idiomatic and more readable is

    if (arr.ptr)

But wait, that's not the same!

    import std;

    void main ()
    {
       auto arr = typeid (int).initializer;
       writeln (arr ! is null); // true
       writeln (arr.ptr);       // null
       writeln (arr.length);    // 4
       writeln (arr.empty);     // false
       writeln (arr ? true : false); // true
       writeln (arr);           // segfault
    }

It appears to me that if (arr !is null) and if (arr) are 
equivalent.