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How to create lenses for Algebraic Data Types with fclabels
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| {-# LANGUAGE | |
| TemplateHaskell | |
| #-} | |
| module Label where | |
| import Data.Label.Partial | |
| import Data.Label.Base | |
| import Data.Label.Derive | |
| data Foo a b c = A a | |
| | B b | |
| | C c | |
| (a,b,c) = $(getLabel ''Foo) | |
| test1 = get right (Right "test") -- Just "test" | |
| test2 = get a (A "a") -- Just "a" | |
| {- References: | |
| Problem I ran into: | |
| http://stackoverflow.com/questions/26370141/type-failure-when-using-left-lens-from-fclabels | |
| Overview Blog post from fclabels author: | |
| http://fvisser.nl/post/2013/okt/1/fclabels-2.0.html | |
| -} |
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