division of objects into classes and structures is bad

[Andrei Alexandrescu]

Don wrote:
> Andrei Alexandrescu wrote:
>> Don wrote:
>>> Christopher Wright wrote:
>>>> Don wrote:
>>>>> The creation of temporaries during expressions is something I'm 
>>>>> currently working on solving. The case you mentioned is addressed 
>>>>> by a proposal I made long ago:
>>>>
>>>> The easiest way is to add an intermediate struct. This takes a fair 
>>>> bit of manual effort, though, and prevents you from using auto.
>>>
>>> That particular case is the easiest possible one. The case x = y - x, 
>>> for example, is much more difficult to recognize.
>>>
>>>>
>>>> Essentially, you need a struct MyClassAddition that just records 
>>>> operands. Then give it an implicit cast to MyClass that does the 
>>>> work. This is an ugly solution because you need to duplicate the 
>>>> operator overloads on MyClassXXX as well as MyClass.
>>>>
>>>> I believe I got this solution from an article by Andrei. It should 
>>>> work pretty well for classes that define few overloads.
>>>
>>> I'm talking about a language solution. I want to solve this for the 
>>> general case.
>>
>> Don't forget that the case you are solving is not general enough 
>> because  you are focusing on eliminating temporaries, which is only 
>> part of the story. I suggest you make place in your thoughts for loop 
>> fusion.
> 
> Yes. That's the classic problem for matrices, but I'm still trying to 
> work out if it is really a general problem. I was hoping to see some new 
> use cases, but none so far.

I think the matrices case is important enough to make it its own class 
of problems. For example, bitmap processing is another instance of 
matrix usefulness, just one that doesn't usually jump to mind when 
thinking of matrices.

Then how about BigInt and arbitrary precision numbers? Wouldn't fusing 
some operations together be useful?


Andrei