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Should prism and lens be defined as #57

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phadej opened this issue Apr 2, 2017 · 1 comment

phadej commented Apr 2, 2017 •

edited

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prism :: (b -> t) -> (s -> Either t a) -> Prism s t a b
prism setter getter pab = dimap getter (either id setter) (right pab)

Then there won't be unnecessary rmap preprocessing.

lens :: (s -> a) -> (s -> b -> t) -> Lens s t a b
lens getter setter pab = dimap (\s -> (getter s, s)) (\(b, s) -> setter s b) (first' pab)

and here we won't apply setter to s before actually needed (making of pair is unavoidable)

The text was updated successfully, but these errors were encountered:

phadej changed the title ~~Should prism be defined as~~ Should prism and lens be defined as

Contributor

paf31 commented Apr 2, 2017

That sounds like an improvement to me.

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