recursive equal, and firstDifference functions

[Dan]

On Wednesday, 20 March 2013 at 02:54:23 UTC, Jonathan M Davis 
wrote:
> On Wednesday, March 20, 2013 03:48:38 Dan wrote:
>> On Wednesday, 20 March 2013 at 02:03:31 UTC, Jonathan M Davis
>> 
>> wrote:
>> > We already get this. That's what == does by default. It's 
>> > just
>> > that it uses ==
>> > on each member, so if == doesn't work for a particular member
>> > variable and the
>> > semantics you want for == on the type it's in, you need to
>> > override opEquals.
>> 
>> Really?
>> 
>> string is one most people would like == to just work for. This
>> writes true then false. This certainly takes getting used to. 
>> It
>> alone is a good reason for the mixins and potentially a
>> non-member instancesDeepEqual.
>> 
>> import std.stdio;
>> struct S {
>>    string s;
>> }
>> void main() {
>>    writeln("foo" == "foo".idup);
>>    writeln(S("foo") == S("foo".idup));
>> }
>
> That's a bug:
>
> http://d.puremagic.com/issues/show_bug.cgi?id=3789
>

 From Feb 2010. Maybe by now it is so understood how it works that 
at some point fixing it could be a problem. For some the language 
is better defined by how the compiler treats your code than what 
is listed in bugzilla. Even in looking through the history of 
that bug I could not find any definitive - some say its a bug, 
others say its not. You refer to TDPL which is a good source but 
if it is not viewed as a bug by Walter...