> On Jun 25, 2016, at 05:06, Karl via swift-evolution
> <[email protected] <mailto:[email protected]>> wrote:
>
>> Proposal: https://gist.github.com/karwa/273db66cd8a5fe2c388ccc7de9c4cf31
>> <https://gist.github.com/karwa/273db66cd8a5fe2c388ccc7de9c4cf31>
Karl, thanks for writing this up. It should be extended to include not only
floor( ) and ceiling( ), but also:
/// Returns the integral value closest to `self` whose magnitude is not
greater than that of `self`.
func truncate( ) -> Self
/// Returns the integral value closest to `self`. If two integrers are
equally close, the even one
/// is returned.
// NOTE: The name of this function requires bike-shedding. I’ve
chosen a deliberately poor
// name as a straw-man.
func roundToNearestTiesToEven( ) -> Self
/// Returns the integral value closest to `self`. If two integrers are
equally close, the one with
/// greater magnitude is returned.
// NOTE: The name of this function requires bike-shedding. I’ve
chosen a deliberately poor
// name as a straw-man.
func roundToNearestTiesAway( ) -> Self
and mutating versions of those.
Some collected responses to other comments on this thread:
> David Sweeris wrote:
>
> The only thing I'm worried about is the situation where we have "x = N.M",
> and `x.ceiling` equals maybe "(N+2).0" instead of "(N+1).0" because we ran
> out of precision and can't represent (N+1).0. I'm not sure what the exact
> values are where floats (or doubles) stop having enough precision to
> represent inter-integer values... It might be a moot point.
This never happens. Floor and ceiling are always exact operations.
> Austin Rathe wrote:
>
> func roundedUp(withPrecision:Int) -> Self { … }
While I understand where you’re going with this, you can’t round non-decimal
floating-point numbers to a non-zero number of decimal digits (the result won’t
be representable, in general). This should be available for decimal
floating-point types if/when they are added, but should be handled as part of
conversions to String for binary floating-point types.
– Steve_______________________________________________
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