this post was submitted on 10 Aug 2023
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Lenses are not always better: (kbin.social)
submitted 2 years ago* (last edited 2 years ago) by jaror@kbin.social to c/haskell@kbin.social
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Lenses are not always better:

fresh :: FDState s c -> (Int, FDState s c)
fresh = id &&& id
  >>> first (^. nextId)
  >>> (\(i, s) -> (i, s & alive %~ Set.insert i))
  >>> second (nextId %~ (+ 1))


fresh :: FDState s c -> (Int, FDState s c)
fresh s@FDState {_nextId = i, _alive = as} =
  (i, s {_nextId = i + 1, _alive = Set.insert i as})

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