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deque-blog/evalMoneyIn2.hs

Created August 14, 2017 16:07
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evalMoneyIn2.hs
evalMoneyIn :: (Conversion -> Maybe Rate) -> MoneyBag -> Currency -> Maybe Money
evalMoneyIn findRate (MoneyBag m) refCurrency = do
let convert (curr, amount) = (* amount) <$> findRate (curr, refCurrency)
amounts <- mapM convert (M.toList m)
pure $ Money { amount = sum amounts, currency = refCurrency }
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