nice how D's pieces fit together

[anonymous]

Just a little newbie aha moment I'd like to share.

I was about to post this:

>int[] f() {return [1, 2, 3];}
>
>As far as I understand, f returns a fresh array on each call, 
>and therefore, it should be safe to store the result in an 
>immutable variable.
>
>Unfortunately, this fails: immutable v = f();
>"Error: cannot implicitly convert expression (f()) of type int[] 
>to immutable(int[])"
>
>I could cast explicitly, of course: auto v = cast(immutable) f();
>But can the cast be avoided?

Then it struck me:
The compiler doesn't know that f's return value is unknown to the 
rest of the world, because f isn't marked pure.
And, indeed, make f pure and it just works: int[] f() pure 
{return [1, 2, 3];} immutable v = f();

Awesome!