This module, Lens.Simple, just re-exports the main modules from Russell O'Connor's lens-family package, the original van Laarhoven lens library. Lens.Simple also re-exports makeLenses and other TH incantations from Dan Burton's associated lens-family-th. The idea is just to make a sort of low-powered, minimal-dependency lens-family equivalent of the 800 lb gorilla of lens library imports:

import Control.Lens

to wit, the elegant and spritely:

import Lens.Simple

Check it out, it's even one character shorter!

If you are unfamiliar with the use of what O'Connor calls van Laarhoven lenses, you might take a look at the excellent tutorial for the wreq library. All of the tutorial material will compile if you replace import Control.Lens with the suave import Lens.Simple. The error messages you get might be a little less opaque. But the point is basically academic, of course: you have already weighed down your sandbox with the lens library by installing wreq and if you get any deeper into wreq you will need it.

As another illustration of the simplicity of the fundamental van Laarhoven lens combinators, note that the gloss pong example from the lens library examples directory requires only this abbreviating change of imports. If you care to make that program more complicated, you might at some point need the unfathomably more sophisticated material in Control.Lens. Within its more limited sphere, lens-family accords as far as possible with lens, so this switch will often be all that is necessary to begin using them.

This module was originally intended to simplify the use of packages that follow the original promise of the van Laarhoven lenses. Correct practice is to export lenses without depending on a lens-library, where possible; in basic cases these use just familiar Prelude types. Examples of best practices in this respect are pipes-bytestring and pipes-group. Because of the heavily monadic character of those libraries, the extra material in Control.Lens is rarely of use anyway; one sticks largely to view/(^.), set/(.~), over/(%~) and zoom.

Note that many of the other lenses and combinators are a bit more specialized than their Control.Lens equivalents: for example, _1 and _2 are here familiarly specialized to act just on real Haskell pairs. With the loss of abstraction we also of course lose the concomitant opaque error messages about Field1 s t a b etc.

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