[swift-evolution] [Proposal] Add floor() and ceiling() functions to FloatingPoint

[Erica Sadun]

I'm with those recommending round, rounded, roundUp, roundedUp, roundDown, 
roundedDown, with Remy's precision factored in as needed.

This is usually the point where Dave A wanders in and explains how this can all be 
implemented by a single FloatingPoint protocol, with built-in properties
and methods across all FP types in order to limit the API surface area that would be
otherwise affected by creating a whole bunch of native stdlib freestanding functions,
even generic ones.

-- E, starting the "Tailor Swift Simply" party


> On Jun 27, 2016, at 12:53 AM, Xiaodi Wu via swift-evolution <swift-evolution at swift.org> wrote:
> 
> I disagree: in English, the nouns are floor and ceiling. That's what they should be called.
> On Mon, Jun 27, 2016 at 02:41 David Hart <david at hartbit.com <mailto:david at hartbit.com>> wrote:
> Whatever the naming scheme, I would be hesitant to have the non-mutating versions of floor and ceil have different endings, seeing how connected they are. So:
> 
> floor, ceil 
> floored, ceiled 
> flooring, ceiling
> 
> But not a mix.
> 
> On 27 Jun 2016, at 07:13, Xiaodi Wu via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> 
>> On Mon, Jun 27, 2016 at 12:45 AM, Charlie Monroe via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> Given the API guidelines, it should be
>> 
>> rounded, ceiled, floored 
>> 
>> for returning the rounded/ceiled/floored value and
>> 
>> round(), ceil(), floor()
>> 
>> would be the mutating variants. Question is where it's not too confusing for anyone knowing these from another language.
>> 
>> Although colloquially they can be "verbed," ceil[ing] and floor are formally nouns, just like sine, union, etc. So the API guidelines would recommend: `rounded`, `ceiling`, `floor` for the non-mutating version and `round`, `formCeiling`, and `formFloor` for the mutating version.
>> 
>> 
>>> On Jun 25, 2016, at 9:02 PM, Remy Demarest via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>> 
>>> We don't seem to have a rounded() function either as part of FloatingPoint, we should probably have these methods in the end:
>>> 
>>> func rounded() -> Self
>>> func rounded(withPrecision: Int) -> Self
>>> 
>>> Along with the 4 other methods proposed below.
>>> 
>>>> Le 25 juin 2016 à 11:55, Haravikk via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> a écrit :
>>>> 
>>>> 
>>>>> On 25 Jun 2016, at 11:06, Karl via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>>> 
>>>>> floor() and ceil(), exactly like C. ceiling() is more descriptive and is a mathematical term of art <http://mathworld.wolfram.com/CeilingFunction.html>.
>>>>> nextIntegralUp() and nextIntegralDown() are more descriptive still, but possibly misleading as (4.0).nextIntegralUp() == 4.0
>>>> I'm in favour of these capabilities being there, but in terms of naming I've often wondered why it can't just be part of a rounding group of methods like so:
>>>> 
>>>> 	func roundedUp() -> Self { … }
>>>> 	func roundedUp(withPrecision:Int) -> Self { … }
>>>> 	func roundedDown() -> Self { … }
>>>> 	func roundedDown(withPrecision:Int) -> Self { … }
>>>> 
>>>> Since the methods with implied precision of zero are equivalent to floor and ceiling surely? I know floor and ceiling are pretty common terms, but they're just a form rounding when it comes down to it.

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