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Optimize TH toEncoding #596

merged 2 commits into from Oct 18, 2017


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Lysxia commented Oct 8, 2017


AesonCompareAutoInstances is the one that is in benchmarks/, just to check that I didn't introduce any performance regression. The SmallRecord file compares results with a record having 5 fields.

The speedup is in the BigRecord/encode/th case.

The reason for the slowdown was that we were using a recursive function to convert lists of pairs (whose size is known statically) to a comma-separated encoding.


Cool, thanks!

instance ToJSON v => GKeyValue v (DList Pair) where
gPair k v = DList.singleton (pack k .= v)
instance (v ~ Value) => KeyValuePair v (DList Pair) where

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bergmark Oct 8, 2017


Is there a reason this isn't KeyValuePair Value (DList Pair) ?

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Lysxia Oct 8, 2017


It improves type inference. Otherwise the TH deriving results in ambiguous type variables and we would need more type annotations.

@bergmark bergmark added this to the milestone Oct 8, 2017

@bergmark bergmark merged commit 07564d8 into bos:master Oct 18, 2017

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@Lysxia Lysxia deleted the Lysxia:opti-th-encode branch Nov 13, 2017

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