Copyright | (C) 2013-2016 Edward Kmett 2015-2016 Artyom Kazak 2018 Monadfix |
---|---|
License | BSD-style (see the file LICENSE) |
Safe Haskell | Trustworthy |
Language | Haskell2010 |
Documentation
view :: Getting a s a -> s -> a Source #
>>>
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
.