[swift-evolution] implementing real (floating point) number comparison tolerance as a compiler directive.

[davesweeris at mac.com]

K… Does replacing my cute == function with one that accounts for everything in that link (or at least a sufficiently large subset of it) solve the problem?
> On Mar 2, 2016, at 2:56 PM, Joe Groff <jgroff at apple.com> wrote:
> 
> 
>> On Mar 2, 2016, at 12:45 PM, David Sweeris <davesweeris at mac.com <mailto:davesweeris at mac.com>> wrote:
>> 
>> func == (lhs: Double, rhs: (value: Double, tolerance: Double)) -> Bool {
>>     return ((rhs.value - rhs.tolerance)...(rhs.value + rhs.tolerance)) ~= lhs
>> }
>> 3.0 == 3.01 ≈ 0.001 // false
>> 3.0 == 3.01 ≈ 0.01 // true
>> 
>> I tried using "ε", which is the standard symbol for "error", but that doesn't seem to be a valid operator character. "≈" (⌥-x, at least on a mac) is the only other one that seemed to make sense, with the possible exception of "∂", but I don't think that's as well-known.
> 
> That's cute. In a real implementation of tolerant comparison, you'd want to scale the tolerance to the magnitude of the larger operand, though. (See http://code.jsoftware.com/wiki/Essays/Tolerant_Comparison <http://code.jsoftware.com/wiki/Essays/Tolerant_Comparison> .)
> 
> -Joe

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