std.rational?

[H. S. Teoh]

On Tue, Oct 01, 2013 at 08:26:49AM +0200, ilya-stromberg wrote:
> On Monday, 30 September 2013 at 18:01:29 UTC, Joseph Rushton
> Wakeling wrote:
> >On 30/09/13 19:39, Joseph Rushton Wakeling wrote:
> >>... although the new gcf will fail if passed immutable/const
> >>BigInts.
> >
> >On this note: http://d.puremagic.com/issues/show_bug.cgi?id=11148
> >
> >I had to tweak CommonInteger to handle immutable/const BigInts,
> >and I'm not sure whether this was done correctly, although it
> >seems to be largely in line with how CommonType works.
> 
> Note that denumerator must be allways positive (> 0).
> But numerator can be positive, zero or negative, and can be bigger
> than denumerator.
> It means that we can use different types for numerator and
> denumerator:
[...]

This is needlessly complex. We should just use signed types for both
numerator and denominator, and handle sign by a canonicalization
operation (canonicalization is already needed for reducing the fraction
to its lowest terms anyway, and if gcd is implemented appropriately, it
will return a number of appropriate sign to cancel out the negative sign
in the denominator (or numerator), so this doesn't even need to be a
separate check).


T

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