Hi all I published to the inbox some cool collection extension methods that we use all the time in Moose. flatCollect:, collectAsSet:, and groupedBy: http://code.google.com/p/pharo/issues/detail?id=432&colspec=ID%20Type%20Stat... I would like to have your feedback because we found them really useful in practice. Here are some examples: testFlatCollectArray "self debug: #testFlatCollectArray" self assert: ((#((1 2) (3 4) (5 3)) flatCollect: [ :each ]) = #(1 2 3 4 5 3)). self assert: ((#((1 2) (2 3) (1 3 4)) flatCollect: [:each]) = #(1 2 2 3 1 3 4)). self assert: ((#((1 2) (2 3) (1 3 4)) flatCollect: [:each| Set with: each]) = #(#(1 2) #(2 3) #(1 3 4))). testFlatCollectSet "self debug: #testFlatCollectSet" self assert: ((#((1 2) (1 2) (1 3 4)) asSet flatCollect: [:each]) = #(1 1 2 3 4) asSet). self assert: ((#() asSet flatCollect: [:each]) = #() asSet). self assert: ((#((1 2) () (1 3 4)) asSet flatCollect: [:each]) = #(1 1 2 3 4) asSet). self assert: ((#((1 2) #((99)) (1 3 4)) asSet flatCollect: [:each]) = #(1 1 2 3 4 (99)) asSet). self assert: ((#((1 2) #(()) (1 3 4)) asSet flatCollect: [:each]) = #(1 1 2 3 4 ()) asSet). testGroupedByArray "self debug: #testGroupedByArray" | res | res := #(1 2 3 4 5) groupedBy: [:each | each odd]. self assert: (res at: true) = #(1 3 5). self assert: (res at: false) = #(2 4) testGroupedBy "self debug: #testGroupedBy" | res | res := #(1 2 3 4 5) asOrderedCollection groupedBy: [:each | each odd]. self assert: (res at: true) = #(1 3 5) asOrderedCollection. self assert: (res at: false) = #(2 4) asOrderedCollection