Further cleanings.

```Smalltalk
coll1 := OrderedCollection new.
coll2 := OrderedCollection new.

1000 timesRepeat: [ coll1 add: 3000 atRandom.coll2 add: 3000 atRandom ].

"Before"
[ coll1 intersection: coll2 ] bench.  "'3468.413 per second'"

"After"
[ coll1 intersection: coll2 ] bench.  "'4011.395 per second'"

coll3 := #(1 2 3 4 5) asOrderedCollection.
coll4 :=#(4 5 6 7 8) asOrderedCollection.

"Before"
[ coll3 intersection: coll4 ] bench. "'731581.767 per second'"

"After"
[ coll3 intersection: coll4 ] bench. "'772582.850 per second'"
```

src/Collections-Abstract/Collection.class.st

@@ -907,11 +907,7 @@ Collection >> intersection: aCollection [
 
 	"(#() intersection: #(1 2 3 4)) >>> #()"
 
-	| set outputSet |
-	set := self asSet.
-	outputSet := Set new.
-	aCollection do: [ :each | (set includes: each) ifTrue: [ outputSet add: each ] ].
-	^ self species withAll: outputSet asArray
+	^ self species withAll: (self asSet intersection: aCollection) asArray
 ]
 
 { #category : #testing }

src/Collections-Unordered/Set.class.st

@@ -152,15 +152,16 @@ Set >> includes: anObject [
 Set >> intersection: aCollection [
 	"Answer the set theoretic intersection of two collections.
 	Optimized version for Sets where no intermediate Set is necessary"
+
 	"(#(1 2 3 4) asSet intersection: #(3 4 5) asSet) >>> #(3 4) asSet"
+
 	"(#(1 2 3 4) asSet intersection: #() asSet) >>> Set new"
+
 	"( #() asSet intersection: #(1 2 3 4) asSet) >>> Set new"
-	
+
 	| outputSet |
 	outputSet := self class new.
-	aCollection do: [ :each|
-		((self includes: each) and: [(outputSet includes: each) not])
-				ifTrue: [ outputSet add: each]].
+	aCollection do: [ :each | (self includes: each) ifTrue: [ outputSet add: each ] ].
 	^ outputSet
 ]