Add example of incremental, name based parsing #209
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There is already an example for indexed-based decoding, but not for name-based. This also adds a salaries.csv file, which is used by the new code, but incidentally closes haskell-hvr#208
MaxGabriel
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Fwiw, I've never used the incremental CSV parsing stuff, so I'm mostly cargo-culting from the indexed based version and puzzling things out/playing type tetris. But, this compiles/runs, so that's a good sign |
| main :: IO () | ||
| main = withFile "salaries.csv" ReadMode $ \ csvFile -> do | ||
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| let headerLoop (FailH _ errMsg) = putStrLn errMsg >> exitFailure |
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Use die errMsg instead? (Also below.)
| headerLoop (PartialH fn) = headerLoop =<< feedHeader fn | ||
| headerLoop (DoneH header parser) = loop 0 parser | ||
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| loop !_ (Fail _ errMsg) = putStrLn errMsg >> exitFailure |
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Why !_ and not just _?
One possible explanation: There are errors inside acc that should be brought to surface before crashing. Is that true?
| isEof <- hIsEOF csvFile | ||
| if isEof | ||
| then return $ k B.empty | ||
| else k `fmap` B.hGetSome csvFile 4096 |
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Use k <$> ... instead of k ``fmap`` ....
| then return $ k B.empty | ||
| else k `fmap` B.hGetSome csvFile 4096 | ||
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| feed k = do |
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feed looks like an identical clone of feedHeader. Please get rid of one of them.
| where | ||
| sumSalaries :: [Either String SalaryInfo] -> Int | ||
| sumSalaries rs = | ||
| let good = rights rs |
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What happens to the lefts? Is Left s an error message?
Usually, swallowing errors is not a good idea. These errors should be raised. (If these are errors.)
| sumSalaries :: [Either String SalaryInfo] -> Int | ||
| sumSalaries rs = | ||
| let good = rights rs | ||
| in sum $ map (\sinfo -> salary sinfo) good |
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Unnecessary lambda? Does sum $ map salary good also work?
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@MaxGabriel Why did you close the PR now? |
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ping @MaxGabriel |
There is already an example for indexed-based decoding, but not for name-based.
This also adds a salaries.csv file, which is used by the new code, but incidentally closes #208