Optimizable Freer #8
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robrix
commented
Jul 21, 2017
src/Control/Monad/Free/Freer.hs
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| go (Map f a) = algebra a Nothing f | ||
| go (Seq f a b) = algebra a (Just b) (go . flip fmap b . f) | ||
| go (Then a f) = algebra a Nothing (go . f) | ||
| {-# INLINE iterLookahead #-} |
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I’m not sure just yet whether this will cut it, but iterLookahead provides the algebra with the next step, when it’s available. In theory, this should accommodate algorithms requiring lookahead.
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cc @tclem |
This reverts commit 01d645e.
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This PR defines
MapandSeqconstructors forFreerin an attempt to enable optimization by analyzing subsequent values.A few of the mechanisms operating over
Seqare defined by rewriting theSeqas aThen; this includes theTraversableinstance (because this would require splitting theSequp into separate values, necessarily parameterized by different types), and alsoproject& thereforeiterFreer. Unfortunately, this means thatsequenceA . sequenceA /= id(which in fairness is generally the case, e.g. forMaybe),project . embed /= id, &c.