recursive equal, and firstDifference functions

[monarch_dodra]

On Tuesday, 19 March 2013 at 10:08:43 UTC, Jonathan M Davis wrote:
> On Tuesday, March 19, 2013 09:25:43 timotheecour wrote:
>> we need a std.algorithm.equalRecurse(T1,T2)(T1 a, T2 b) that
>> compares recursively a and b;
>> 
>> its behavior should be:
>> 
>> if opEqual is defined, call it
>> else, if its a range, call std.algorithm.equal (ie compare nb
>> elements, then each element for equality)
>> else, if it's a class/struct, make sure types are same and call
>> it recursively on each field.
>> else if it's a numerical type, call "=="
>> else (is there an else?)
>> 
>> just as std.algorithm.equal, we should have
>> equalRecurse([1],[1.0]);
>
> If you want recursive equal, then do equal!equal. Granted, 
> that's only one
> level of recursion, but how many levels deep are you really 
> going to have your
> ranges? And you have to get to == eventually anyway in order to 
> compare the
> deepest elements. Going beyond a range of ranges is likely to 
> be quite rare,
> and when it does happen, you can simply nest equal as many 
> times as you need.
>
> - Jonathan M Davis

"equal!equal(RoR1, RoR2)"

That looks cute, but I think it says something about how powerful 
and expressive D can be, while being compile-time optimized. It's 
those little things that still amaze me about D.