Re: Decimal: Formal review begins

From: Peter Dimov (pdimov_at_[hidden])
Date: 2025-01-21 19:15:39

> Assuming normalized numbers (which should be the case) of the same sign,
> operator< is equivalent (NaN notwithstanding) to comparing the two integers
> 
> eeeeeeee... mmmmmmmmmm...
> 
> I'm not quite sure whether zero needs to be a special case here. There's special
> case logic in operator< for it, but I'm not positive it's needed.

The current operator< is this:

https://godbolt.org/z/Tj7Me5aW3

This is a sketch of what I was thinking about:

https://godbolt.org/z/9M1cevYef

I haven't run this against the test suite, so it might not be quite correct,
but it looks correct to me. :-)

It assumes that zeroes are normalized. The current implementation seems
to not assume that; it handles 0e+7, but since the _fast types are supposed
to be normalized, this should never happen, should it?

> This makes me wonder whether { uintNN_t exp_and_mant; bool sign; }
> wouldn't be a better representation for _fast, although that would depend on
> how important comparisons are, performance-wise.

Should look somewhat like this:

https://godbolt.org/z/bqWKxbdjd