empty arrays and cast(bool): WAT

[Steven Schveighoffer]

On Sat, 18 Feb 2012 21:01:55 -0500, Timon Gehr <timon.gehr at gmx.ch> wrote:

> Why does the following code behave funny?
>
> void main(){
>      string x = " "[1..1];
>      writeln(cast(bool)x); // true
>      char[] y = [' '][1..1];
>      writeln(cast(bool)y); // false
> }
>
> Is there any reason for empty arrays to evaluate to true? This is very  
> bug prone.

Just to weigh in:

1. The most intuitive and useful thing is to check for arr.length.
2. Given that there are valid cases for checking null vs. empty, I think  
there should be a way to find usages of if(arr) for fixing legacy code.

To disallow if(arr) simply because of legacy code is a step in the *wrong*  
direction.  The experience with arrays is going to be a major contributing  
factor to the enjoyment of using D.  I'd rather see the compiler show you  
where cases of if(arr) appear, and allow you to judge whether those should  
be arr.ptr or not.

I agree with Timon, let's make it more intuitive, and break code, and let  
those people be able to fix that code somehow.  If this means deprecating  
it for a time, so be it.

-Steve