# [swift-evolution] ed/ing, InPlace, Set/SetAlgebra naming resolution

David Hart david at hartbit.com
Sun Feb 14 10:33:15 CST 2016

```I don’t really agree with Dave’s comments about removing ‘with', but here’s one of mine – making the non-mutating difference an override of intersection because it sounds clearer to me and is consistent with the mutable versions being overrides:

Non-mutable

let union = a.merged(with: b)
let intersection = a.members(in: b)
let difference = a.members(notIn: b)
let symmetricDifference = a.merged(with: b, removingMembersInCommon: true)

Mutable (In-Place)

a.merge(with: b) // union in-place
a.removeMembers(notIn: b) // intersect in-place
a.removeMembers(in: b)	// difference in-place
a.merge(with: b, removingMembersInCommon: true) // symmetric difference in-place

> On 14 Feb 2016, at 17:10, Dave Abrahams via swift-evolution <swift-evolution at swift.org> wrote:
>
>
> on Sat Feb 13 2016, Ricardo Parada <rparada-AT-mac.com> wrote:
>
>> Hi Dave,
>>
>> I would be okay with staying away from the mathematical terms similar
>> to what you are suggesting except that the union can still be made
>> more concise if you use merged / merge for the base name and shorten
>> the labels to a bare minimum without loosing clarity.  In addition,
>> the merge can have a second parameter with a default to false in order
>> to implement the symmetric difference (a.k.a. exclusive or).  Recall
>> that symmetric difference is the union of two sets and then removing
>> the intersection (or members in common).  I think it looks perfect
>> (concise and clear).  What does everybody else think?
>>
>> Non-mutable
>>
>> let union = 			a.merged(with: b)
>> let intersection = 		a.members(in: b)
>> let difference = 		a.removingMembers(in: b)
>> let symmetricDifference = 	a.merged(with: b, removingMembersInCommon: true)
>>
>> Mutable (In-Place)
>>
>> a.merge(with: b)		// union in-place
>> a.removeMembers(notIn: b)	// intersect in-place
>> a.removeMembers(in: b)		// difference in-place
>> a.merge(with: b, removeMembersInCommon: true)	// symmetric difference in-place
>
> I love your changes to my suggestion, Ricardo!  The minor alterations I
> would make are:
>
> 1. In both cases the Bool parameter ought to be called
>   “removingMembersInCommon”
>
> 2. I would remove “with” from the in-place merge operation.  We're
>   really asking the receiver to merge b into itself.  “With” gives it
>   the sense that it might almost be mutating b.
>
>>
>>> On Feb 13, 2016, at 1:16 PM, Dave Abrahams via swift-evolution <swift-evolution at swift.org> wrote:
>>>
>>>
>>> on Fri Feb 12 2016, Ricardo Parada <swift-evolution at swift.org
>>> <mailto:swift-evolution at swift.org>> wrote:
>>>
>>>> Hi all,
>>>>
>>>> I can’t make up my mind.  Let me propose two different alternatives
>>>> that I’m not sure if they have been considered:
>>>>
>>>> ALTERNATIVE 1
>>>>
>>>> Non-mutable (noun-based)
>>>>
>>>> -  func union(other: Self) -> Self
>>>> +  func union(other: Self) -> Self		Assumes union is a noun, i.e. not a verb
>>>>
>>>> -  func intersect(other: Self) -> Self
>>>> +  func intersection(other: Self) -> Self
>>>>
>>>> -  func subtract(other: Self) -> Self
>>>> +  func subtraction(other: Self) -> Self
>>>>
>>>> -  func exclusiveOr(other: Self) -> Self
>>>> +  func symmetricSubtraction(other: Self) -> Self
>>>>
>>>> Mutable (verb-based)
>>>>
>>>> -  mutating func unionInPlace(other: Self)
>>>> +  mutating func unite(other: Self)
>>>>
>>>> -  mutating func intersectInPlace(other: Self)
>>>> +  mutating func intersect(other: Self)
>>>>
>>>> -  mutating func subtractInPlace(other: Self)
>>>> +  mutating func subtract(other: Self)
>>>>
>>>> -  mutating func exclusiveOrInPlace(other: Self)
>>>> +  mutating func symmetricSubtract(other: Self)
>>>>
>>>>
>>>> With this alternative we keep the union name which I assume is
>>>> popular.  However, one has to accept unite as a verb (for the mutable
>>>> version) as I wanted all the mutable methods use verbs for
>>>> consistency.  I think unite is acceptable because it can be found in
>>>> the dictionary and it is a verb.
>>>>
>>>> Notice that all the non-mutable methods use nouns: union,
>>>> intersection, subtraction and symmetricSubtraction.
>>>>
>>>> I understand some may oppose to symmetricSubtraction saying that
>>>> symmetricSubraction is not as common as "exclusive or".  However,
>>>> using symmetricSubtraction is consistent with subtraction and it hints
>>>> to a variation of the “subtraction" operation.  We will get used to it
>>>> quickly / easily.
>>>>
>>>> The mutable methods all use verbs:  unite, intersect, subtract and symmetricSubtract.
>>>>
>>>> ALTERNATIVE 2
>>>>
>>>> Non-mutable
>>>>
>>>> -  func union(other: Self) -> Self
>>>> +  func adding(other: Self) -> Self
>>>>
>>>> -  func intersect(other: Self) -> Self
>>>> +  func intersecting(other: Self) -> Self
>>>>
>>>> -  func exclusiveOr(other: Self) -> Self
>>>> +  func exclusiveOring(other: Self) -> Self
>>>>
>>>> -  func subtract(other: Self) -> Self
>>>> +  func removing(other: Self) -> Self
>>>>
>>>> Mutable
>>>>
>>>> -  mutating func unionInPlace(other: Self)
>>>> +  mutating func add(other: Self)
>>>>
>>>> -  mutating func intersectInPlace(other: Self)
>>>> +  mutating func intersect(other: Self)
>>>>
>>>> -  mutating func exclusiveOrInPlace(other: Self)
>>>> +  mutating func exclusiveOr(other: Self)
>>>>
>>>> -  mutating func subtractInPlace(other: Self)
>>>> +  mutating func remove(other: Self)
>>>>
>>>> Comments: This alternative gives up on union in favor or add.  Many
>>>> may not like this, that is why I have it as the second alternative.
>>>> It brings back exclusiveOr and treats it as a verb.  Some may argue
>>>> that exclusiveOr is a noun for the "exclusive or" operation.
>>>
>>> If we are going to force Set fit the naming guidelines, I would prefer
>>> to stay away from the mathematical terms altogether.
>>>
>>>  func insertingContentsOf(other: Self) -> Self                 // union
>>>  mutating func insertContentsOf(other)
>>>
>>>  func members(in other: Self) -> Self                           // intersection
>>>  mutating func removeMembers(notIn: other)
>>>
>>>  func removingMembersAndAddingNonMembers(in other: Self) -> Self // symmetric difference
>>>  mutating func removeMembersAndAddingNonMembers(in other: Self)
>>>
>>>  func removingMembers(in other: Self) -> Self                    // subtract
>>>  mutating func removeMembers(in other: Self)
>>>
>>> If it would help with clarity, we could replace "in" with "foundIn"
>>> above.
>>>
>>> --
>>> -Dave
>>>
>>> _______________________________________________
>>> swift-evolution mailing list
>>> swift-evolution at swift.org <mailto:swift-evolution at swift.org>
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>> <https://lists.swift.org/mailman/listinfo/swift-evolution>
>
> --
> -Dave
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution

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