[swift-evolution] Proposal: A standard library Fraction type

[T.J. Usiyan]

The example of time signatures has much less to do with modeling the two
integers presented to the user and more to do with resolving the absolute
duration of a note which is part of why I mentioned both time signature
*and* note duration.

On Mon, Dec 7, 2015 at 8:15 PM, Stephen Canon <scanon at apple.com> wrote:

> Musical time signatures is an odd case, because you really have pairs of
> integers (i.e. if they were rational numbers, then 6/8 would be the same as
> 3/4. They are not the same).
>
> On Dec 7, 2015, at 9:36 AM, T.J. Usiyan <griotspeak at gmail.com> wrote:
>
> Musical time signatures and note duration. Visual code with proportional
> relationships.
>
> On Mon, Dec 7, 2015 at 7:41 PM, Stephen Canon via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>> Can you guys specify some of the use cases that you have in mind for a
>> Rational type?  You mention "alleviating the pain points of floating-point
>> math,” but rationals tend to be used *very* differently from floating-point
>> types in computation.
>>
>> Thanks,
>> – Steve
>>
>> On Dec 7, 2015, at 5:44 AM, Davide De Franceschi via swift-evolution <
>> swift-evolution at swift.org> wrote:
>>
>> While I agree that a Rational type, one that would preserve quotient and
>> denominator info, would be very nice, I think that it's more fit for a Math
>> framework.
>> If we're just talking about a type that holds precise decimal info, I
>> think making NSDecimal (planned to be renamed as Decimal in the future)
>> usable is what we should do.
>>
>> On 7 Dec 2015, at 10:28, T.J. Usiyan via swift-evolution <
>> swift-evolution at swift.org> wrote:
>>
>> I'm all for a stdlib Rational Type. I've written one as well and would be
>> glad not to have to include it as a dependency everywhere.
>> TJ
>>
>> On Mon, Dec 7, 2015 at 1:31 PM, Harlan Haskins via swift-evolution <
>> swift-evolution at swift.org> wrote:
>>
>>> If Swift 3 is going to focus on re-thinking the Numerics in the system,
>>> it might be worth considering adding a Fraction (or Rational) type to the
>>> standard library. This, coupled with an arbitrary-precision integer type,
>>> would be a great way to handle arbitrary-precision decimal arithmetic, and
>>> can alleviate almost all the pain points of floating-point math.
>>>
>>> There exist now some really nice implementations of Fractions, but the
>>> ones I’ve seen haven’t been implemented fully generically.
>>> My favorite is this one:
>>> https://gist.github.com/JadenGeller/5e80ebf32442acc62e8e
>>>
>>> I’d love to see some standard library support with rock-solid, fast
>>> implementations of all the common algorithms (GCD, LCD, LCM, reduction,
>>> etc) and good conformance to the builtin integer protocols. Maybe even
>>> FloatLiteralConvertible, too, with some logic for converting rational
>>> floats.
>>>
>>> Thoughts?
>>>
>>> - Harlan Haskins
>>>
>>
>>
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>>
>
>
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