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

Sat Feb 13 23:09:21 CST 2016

```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

> 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
>
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