microlens-0.4.13.1: A tiny lens library with no dependencies
Copyright (C) 2013-2016 Edward Kmett 2015-2016 Artyom Kazak 2018 Monadfix
License BSD-style (see the file LICENSE)
Safe Haskell Trustworthy
Language Haskell2010

Lens.Micro.Extras

Description

Synopsis

Documentation

view :: Getting a s a -> s -> a Source #

view is a synonym for ( ^. ):

>>> view _1 (1, 2)
1

The reason it's not in Lens.Micro is that view in lens has a more general signature:

view :: MonadReader s m => Getting a s a -> m a

So, you would be able to use this view with functions, but not in various reader monads. For most people this shouldn't be an issue; if it is for you, use view from microlens-mtl .

preview :: Getting ( First a) s a -> s -> Maybe a Source #

preview is a synonym for ( ^? ):

>>> preview _head [1,2,3]
Just 1

The reason it's not in Lens.Micro is that preview in lens has a more general signature:

preview :: MonadReader s m => Getting (First a) s a -> m (Maybe a)

Just like with view , you would be able to use this preview with functions, but not in reader monads; if this is an issue for you, use preview from microlens-mtl .