Beautiful functional programming

28

Golfed version using Dynamic and with a newtype for Object over HashMap Text Dynamic:

{-# LANGUAGE OverloadedStrings #-}

import qualified Data.HashMap.Strict as HM
import Data.HashMap.Strict ((!))
import Data.Text (Text)
import Data.Dynamic
import Data.Bifunctor (second)
import Data.Maybe (fromJust)

import Data.Vector (Vector)

import Data.Traversable (mapAccumL)

newtype Object = MkObject {unObj :: HM.HashMap Text Dynamic}

hiJose :: V.Vector Object -> V.Vector Object
hiJose = snd . mapAccumL go (1 :: Int)
  where
    go count (MkObject obj) =
        second (\lessons -> MkObject $ HM.insert "lessons" (toDyn lessons) obj)
      . mapAccumL numberLessons
      (if flip fromDyn False $ obj ! "reset_lesson_position"
        then 1 else count) . fromJust . fromDynamic $ obj ! "lessons"
      where
        numberLessons subCount vecObj =
            ( subCount + 1, toDyn . MkObject
            . HM.insert "position" (toDyn count) . unObj . fromJust $ fromDynamic vecObj )

Yes, Map.(!) and fromJust is partial, but it sort of highlights in how the original implementations a malformed data input can blow you up.

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