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

Dave Abrahams dabrahams at apple.com
Sun Feb 14 10:39:31 CST 2016

on Sun Feb 14 2016, David Hart <swift-evolution at swift.org> wrote:

> I don’t really agree with Dave’s comments about removing ‘with',

When one road merges with another, both are changed.

> 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:

I don't see any overrides around here.  Care to clarify?

> 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.
>>
>>> Ricardo Parada
>>>
>>>> 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)
>>>>>
>>>>> Comments:
>>>>>
>>>>> 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
>>>>
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>>
>> --
>> -Dave
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--
-Dave

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