[boost] Re: runtime unit-modifiable physical-quantities using pqs1-00-01

From: Dan W. (danw_at_[hidden])
Date: 2004-01-02 22:05:21

David Abrahams wrote:
> I don't think that's a good excuse for code duplication.  There are
> ways to hide configurability so that it looks like you "can't mess
> with it."

I'm sure there is. I was also looking at it this way, though:  Andy 
Little's solution has a fixed 7 template dimensions, but no resizing 
code overhead. Seems to me like trading compile-time data size for 
compilation complexity.  But data size is not much of an issue if we are 
right in saying that physical quantities might be used much less often 
than custom types.  For the great majority of custom quantity types, I'd 
guesstimate one might use one dimension mostly, sometimes two, very 
rarely three;  so it might really be inefficient to keep 7 (or more) 
template dimensions for these smaller types all over the compiler's 
temporary memory buffers;  and so, perhaps for these types I would 
rather take Matthias Shabel's greater compilation complexity for the 
sake of better compile time memory efficiency.

But I've never written a compiler, so maybe I'm totally off-track...

And I also realize, just some subtle simplification in syntax might 
probably save programmers more time than a 1000-fold improvement in 
compilation speed, so maybe I was totally off track anyhow...

dan