CODEWITHSUNDEEP
scalafiltering
William Wong
William Wong

Reputation: 319

What's wrong with the following Scala code?

val x = "pizseagtsgevlvwpbshxfwbjijtmslkufgofretehjgpcdedstydokejsnrccnkbruawgjmemfqhwmhjsykrejmmexgrsdlwtaybtnhfcapsylopkthboqkvicgwrvycphqnulnjgfgjlqnhdyfwweyifpxyxrvpnshjrrkmkwrvjjssublanosljhqhppmewuidyqblfcjzkwbhqlljvvcjqthbkpcoquepqzcvbkdlhufbkpiyaqbfblexry"
val y = "pizseagtsgevlvwpbshxfwbjijtmslkufgofretehjgpcdedstydokejsnrccnkbruawgjmemfqhwmhjsykrejmmexgrsdlwtaybtnhfcapsylopkthboqkvicgcjkyxxubpbqcycioryppydvmwubupxrjlwrwujsiimvpbgkdugjbpqtodgbzzpsduewwovwlfrarfiuaztmmohagkjzzdcnjytamlzpwpfmhlgsdlwfbluxqllcjxbltbrlhgngvtxyksllhfhhzknesqggfazixcotpwwbjenbglhcbnhgjgyimfvfbcezatumthzrqtvdyirxulfhwylbdhkibmiagdgeerriszbnfxmoxgabaxkgkydrnrrbatjbavwdxjqirqivqweqdxeiiotbfidiemakmzbwszgrgekrlalsmbplumxeqmfrulddmbactyuhdljlhhjvxumpkyyzouybtwxtoyiffrderzmztkcdsbhcij"
val xy = (x zip y).filter{ case (a,b) => (a==b) }.map{case (a,b) => a}.mkString

I expect the xy will be

pizseagtsgevlvwpbshxfwbjijtmslkufgofretehjgpcdedstydokejsnrccnkbruawgjmemfqhwmhjsykrejmmexgrsdlwtaybtnhfcapsylopkthboqkvicg

but it is

pizseagtsgevlvwpbshxfwbjijtmslkufgofretehjgpcdedstydokejsnrccnkbruawgjmemfqhwmhjsykrejmmexgrsdlwtaybtnhfcapsylopkthboqkvicgydwrsjzpdlblr

Somehow, the filtering does not work as expected. Anything I missed?

Upvotes: 1

Views: 74

Answers (1)

knutwalker
knutwalker

Reputation: 5974

filter does not stop after the first false but continues to traverse the remaining collection. Those additional characters appear later in both string at the same position. What you want instead of filter is takeWhile:

val xy = (x zip y).takeWhile{ case (a,b) => (a==b) }.map{case (a,b) => a}.mkString

Upvotes: 9

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