michaelt/lens-simple
1
1
Fork 0
mirror of https://github.com/michaelt/lens-simple.git synced 2024-09-11 13:45:53 +03:00
Code Issues Projects Releases Wiki Activity

readme

Browse Source
This commit is contained in:
michaelt 2015-05-05 20:19:11 -04:00
parent e6a1eca545
commit 97d8bfc61e
1 changed files with 9 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
README.md
View File

@ -1,28 +1,19 @@
lens-simple
===========
lens-family-simple
==================
This just re-exports the combinators and elementary 'van Laarhoven' lenses from Russell O'Connor's sublime [`lens-family`](http://hackage.haskell.org/package/lens-family) package, including "Lens.Family2.State.Strict". `lens-family` has a complex structure and distinctly unpleasant module names, so I made this for my own use, but maybe with experience it will prove to be a sensible idea -- or not. It is mostly just intended to simplify imports for use with [`pipes`](http://hackage.haskell.org/package/pipes) and associated `pipes` libraries. The special quasi-lenses that pervade these libraries frequently require, at a minimum, that some version of `view/(^.)` and `zoom` should be in scope. (The effect of `import Lens.Simple` is at the moment a bit like that of `import Control.Lens`; presumably much more should be hidden!)
This just re-exports the combinators and elementary 'van Laarhoven' lenses from Russell O'Connor's sublime [`lens-family-core`](http://hackage.haskell.org/package/lens-family-core) package, including "Lens.Family.State.Strict", and the corresponding TH module from [`lens-family-th`](http://hackage.haskell.org/package/lens-family-th).
`lens-family` has a complex structure and distinctly unpleasant module names, so I made this for my own use, but maybe with experience it will prove to be a sensible idea -- or not. It is mostly just intended to simplify imports for use with [`pipes`](http://hackage.haskell.org/package/pipes) and associated `pipes` libraries. The special quasi-lenses that pervade these libraries frequently require, at a minimum, that some version of `view/(^.)` and `zoom` should be in scope. (The effect of `import Lens.Simple` is at the moment a bit like that of `import Control.Lens`; presumably much more should be hidden!)
The only non-ghc-boot library `lens-family-core` and `lens-family-core` require is `mtl`.
Because we are using the `Rank2Types` version, this requires `ghc` of course; the only non-boot library `lens-family` and `lens-family-core` require is `mtl`.
The naming in `lens-family` is more or less uniform with the more powerful and elaborate [`lens`](http://hackage.haskell.org/package/lens) library, so it can be dropped in favor of `lens` should this become necessary.
Note the separate [`lens-family-th`](http://hackage.haskell.org/package/lens-family-th) package.
-----
The pong example from `lens/examples` is included here as an illustration of the strenth of `lens-families` + `lens-families-th`. Apart from the change of imports we are missing only the `(<~)` operator (just as well if we are planning on using pipes), so the only substantive change is to replace
reset = do
ballPos .= (0, 0)
ballSpeed <~ nextSpeed
with
reset = do
ballPos .= (0, 0)
s <- nextSpeed
ballSpeed .= s
The pong example from `lens/examples` is included here as an illustration of the strenth of `lens-families` + `lens-families-th`. Nothing is needed but the change of imports.