Haskell Lens @HaskellLens

Learn lens one tweet at a time. Send tips and suggestions to @HaskellLens lens.github.io Joined January 2014

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Haskell Lens @HaskellLens

12 years ago

The _Empty Prisms gives you a general check to see if a container is empty: > isn't _Empty (Map.singleton "Hello" "World") True

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Haskell Lens @HaskellLens

12 years ago

To check if a lens/prism/traversal/etc accesses any data you can use `has` (or `hasn't` for the opposite). Can be useful with Prelude filter

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Edward Kmett @kmett

12 years ago

Lens 4.0 has been released. hackage.haskell.org/package/lens

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Haskell Lens @HaskellLens

12 years ago

If you only want to use operators lens provides, you can import 'Control.Lens.Operators'

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Haskell Lens @HaskellLens

12 years ago

Control.Lens.TH contains Template Haskell to avoid boilerplate. Supports lens, prism, isos and wrapped: hackage.haskell.org/package/lens-3…

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Haskell Lens @HaskellLens

12 years ago

You can use lengthOf to count the amount of targets any Getting would reach: lengthOf (traversed . _Just) [ Just (), Nothing, Just () ] ≡ 2

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Haskell Lens @HaskellLens

12 years ago

The 'Strict' type class gives a unified isomorphism between strict and lazy data types such as Text, ByteString, etc hackage.haskell.org/package/lens-3…

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Haskell Lens @HaskellLens

12 years ago

Control.Lens.Cons gives a unified interface to manipulating list-like types with cons, uncons, head, tail and so on. hackage.haskell.org/package/lens-3…