Church-encoded Writer carrier #369
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robrix
commented
Mar 15, 2020
| newtype StateC s m a = StateC { runStateC :: s -> m (s, a) } | ||
| newtype StateC s m a = StateC (s -> m (s, a)) |
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| Tell w' -> do | ||
| let !w'' = mappend w w' | ||
| pure (w'', ctx) |
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mappending strictly here made for a ~2.5x improvement to the performance of this carrier in the benchmarks.
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| (w', a) <- runWriter (hdl (m <$ ctx)) | ||
| let !w'' = mappend w w' | ||
| pure (w'', (,) w' <$> a) |
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I strongly prefer BangPatterns to seq for these; plus, it turns out that we were inadvertently making listen and censor too strict.
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This PR introduces and benchmarks a high-performance Church-encoded
Writercarrier. In benchmarks where it wrapsIO, it outperforms every other carrier by quite a decent margin.