Hi Rowan,
> Yes, I agree there's a dilemma there.
>
> The extra point in favour of TOWARD_ZERO is that it's more efficient, because
> we don't have to over-calculate and round, just pass scale directly to the
> implementation. Any other option makes for unnecessary extra calculation in
> code like this:
>
> $total = new Number('20');
> $raw_frac = $total / 7;
> $rounded_frac = $raw_frac->round(2, Round::HALF_UP);
>
> If HALF_UP rounding is the implied default, we have to calculate with scale
> 11 giving 1.42857142857, round to 1.4285714286, then round again to 1.43.
>
> If truncation / TOWARD_ZERO is the implied default, we only calculate with
> scale 10 giving 1.4285714285 and then round once to 1.43.
>
> (Of course, in this example, the most efficient would be for the user to
> write $rounded_frac = $total->div(7, 2, Round::HALF_UP) but they might have
> reasons to keep the division and rounding separate.)
Thanks, when I expand on this issue, I'll also mention the pros and cons of
both, including the points you mentioned.
Regards,
Saki
