finding composed structs

[Dan]

On Tuesday, 30 October 2012 at 16:44:02 UTC, Ali Çehreli wrote:
>
> There is the following discussion currently on the main D forum:
>   
> http://forum.dlang.org/thread/iphhuttpkogmfwpuvfla@forum.dlang.org
>
> That behavior will be changed:
>
> http://forum.dlang.org/thread/iphhuttpkogmfwpuvfla@forum.dlang.org?page=4#post-k6a30m:24140h:241:40digitalmars.com
>

Interesting, thanks! In reading this and (per Tobias' comment) 
revisiting TDPL I think my original statement was incomplete and 
the situation is not as bad as I thought.

> For any struct S, '==' means either bitwise comparison or a 
> call to
> opEquals of S if it exists.

 From TDPL: Objects of struct type can be compared for equality 
out of the box with == and ! =. Comparison is carried out member 
by member and yields false if at least two corresponding members 
in the compared objects are not equal, and true otherwise.

So the issue in my example is not a problem with structs in 
general, but just a bug related to dynamic arrays only. My fear 
of having to provide opEquals at each level is unwarranted - the 
compiler will generate good ones for me (except for dynamic 
arrays until the bug is fixed).

I've convinced myself of this in the following example.
http://dpaste.dzfl.pl/14649c64

So until this bug is fixed any time I have any dynamic array, 
including string in struct S, implement opEquals. When the bug is 
fixed I can remove them. What I didn't realize is that including 
an opEquals in A will cause generation of opEquals in B,C,D for 
free (maybe only if called).

If this is still off base please let me know.

Thanks
Dan