[swift-evolution] Proposal: Remove % operator for floating-point types

[Joe Groff]

> On Dec 18, 2015, at 3:40 PM, August Joki via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 
> 
> -August
> 
>> On 18 Dec, 2015, at 15:31, Kevin Ballard via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> On Fri, Dec 18, 2015, at 03:04 PM, Chris Lattner via swift-evolution wrote:
>>>  
>>>> On Dec 18, 2015, at 3:03 PM, Stephen Canon <scanon at apple.com <mailto:scanon at apple.com>> wrote:
>>>>  
>>>>  
>>>>> On Dec 18, 2015, at 5:57 PM, Chris Lattner <clattner at apple.com <mailto:clattner at apple.com>> wrote:
>>>>>  
>>>>> On Dec 18, 2015, at 1:12 PM, Stephen Canon via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>>>>>> Hi everybody —
>>>>>>  
>>>>>> I’d like to propose removing the “%” operator for floating-point types.
>>>>>  
>>>>> I support removing this - it is actively harmful for a surprising operation like this to have such short and inviting syntax.  As asked downthread, have you given any thought into whether a Decimal type would support this operation?
>>>>  
>>>> The same concerns apply to decimal.  It makes sense to have the operation (for both binary and decimal floating-point) as “Type.remainder(a,b)” or a free function like "remainder(a, b)”, but I would prefer not to use the operator “%” for it because it behaves very differently from integer %, and in ways that are not at all obvious to most users.
>>>  
>>> Great, I’d prefer decimal and the float types to have a consistent interface where possible.  +1 from me on the proposal.
>>  
>> Agreed. +1 from me too. The `10.0 % 0.1` behavior is sufficiently surprising that I think that justifies removal by itself.
>>  
>> I'm also in favor of adding mod and remainder as instance methods of the floating point types, e.g. `10.0.mod(0.1)` (as opposed to static methods or free functions).
> Shouldn’t that be added to any Arithmetic type?

We don't offer protocols that abstract over both integer and float arithmetic. They behave differently, and require different algorithms and interfaces. Floating-point types gaining a `mod` member does not necessarily mean integer types should get the same.

-Joe
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20151218/8fec0191/attachment.html>