David T. Lewis uploaded a new version of Collections to project The Trunk: http://source.squeak.org/trunk/Collections-dtl.931.mcz
==================== Summary ====================
Name: Collections-dtl.931 Author: dtl Time: 11 March 2021, 5:44:43.577146 pm UUID: 1ed239e3-d108-43c3-8b6e-de8c43d842d1 Ancestors: Collections-nice.930
Set logic methods should be discoverable, so give them a method category. Add an implementation of Collection>>symmetricDifference: so that the basic set operations of union, intersection, difference, and symmetric difference are available.
=============== Diff against Collections-nice.930 ===============
Item was changed: + ----- Method: Collection>>difference: (in category 'set logic') ----- - ----- Method: Collection>>difference: (in category 'enumerating') ----- difference: aCollection "Answer the set theoretic difference of two collections."
^ self reject: [:each | aCollection includes: each]!
Item was changed: + ----- Method: Collection>>intersection: (in category 'set logic') ----- - ----- Method: Collection>>intersection: (in category 'enumerating') ----- intersection: aCollection "Answer the set theoretic intersection of two collections."
^ self select: [:each | aCollection includes: each]!
Item was added: + ----- Method: Collection>>symmetricDifference: (in category 'set logic') ----- + symmetricDifference: aCollection + "Answer the set theoretic symmetric difference of two collections." + + ^ (self difference: aCollection) union: (aCollection difference: self) + !
Item was changed: + ----- Method: Collection>>union: (in category 'set logic') ----- - ----- Method: Collection>>union: (in category 'enumerating') ----- union: aCollection "Answer the set theoretic union of two collections."
^ self asSet addAll: aCollection; yourself!
Item was changed: + ----- Method: HashedCollection>>union: (in category 'set logic') ----- - ----- Method: HashedCollection>>union: (in category 'enumerating') ----- union: aCollection "Answer the set theoretic union of the receiver and aCollection, using the receiver's notion of equality and not side effecting the receiver at all."
^ self copy addAll: aCollection; yourself
!