view package:microlens-mtl

view is a synonym for (^.), generalised for MonadReader (we are able to use it instead of (^.) since functions are instances of the MonadReader class):

>>> view _1 (1, 2)
1

When you're using Reader for config and your config type has lenses generated for it, most of the time you'll be using view instead of asks:

doSomething :: (MonadReader Config m) => m Int
doSomething = do
thingy        <- view setting1  -- same as “asks (^. setting1)”
anotherThingy <- view setting2
...

preview is a synonym for (^?), generalised for MonadReader (just like view, which is a synonym for (^.)).

>>> preview each [1..5]
Just 1