pez 0.0.1 → 0.0.2

raw patch · 1 files changed

+52/−51 lines, 1 files

Files

• pez.cabal +52/−51

@@ -1,57 +1,58 @@ Name:                pez-Version:             0.0.1+Version:             0.0.2 Synopsis:            A Potentially-Excellent Zipper library Homepage:            http://coder.bsimmons.name/blog/2011/04/pez-zipper-library-released/-Description:- PEZ is a generic zipper library. It uses lenses from the 'fclabels' package to- reference a "location" to move to in the zipper. The zipper is restricted to- types in the Typeable class, allowing the user to "move up" through complex data- structures such as mutually-recursive types.- .- Both the Typeable class and fclabels lenses can be derived in GHC, making it- easy for the programmer to use a zipper with a minimum of boilerplate.- .- First import the library, which brings in the Typeable and fclabels modules.- You will also want to enable a few extensions:- .- > {-# LANGUAGE TemplateHaskell, DeriveDataTypeable, TypeOperators #-}- > module Main where- >- > import Data.Typeable.Zipper- .- Create a datatype, deriving an instance of the Typeable class, and generate a- lens using functions from fclabels:- .- > data Tree a = Node { _leftNode :: Tree a, - >                      _val      :: a, - >                      _rightNode :: Tree a }- >             | Nil  - >             deriving (Typeable,Show)- >- > $(mkLabelsNoTypes [''Tree])- .- Now we can go crazy using Tree in a Zipper:- .- > treeBCD = Node (Node Nil 'b' Nil) 'c' (Node Nil 'd' Nil)- > - > descendLeft :: Zipper1 (Tree a) -> Zipper1 (Tree a)- > descendLeft z = case (viewf z) of- >                      Nil -> z- >                      _   -> descendLeft $ moveTo leftNode z- >- > insertLeftmost :: a -> Tree a -> Tree a- > insertLeftmost x = close . setL focus x . descendLeft . zipper- >- > treeABCD = insertLeftmost 'a' treeBCD- .- Because of the flexibility of fclabels, this zipper library can be used to- express moving about in reversible computations simply by defining such a lens,- for instance:- .- > stringRep :: (Show b, Read b) => b :-> String- > stringRep = lens show (const . read)- .- Please send any feature requests or bug reports along.++Description:         PEZ is a generic zipper library. It uses lenses from the 'fclabels' package to+                     reference a "location" to move to in the zipper. The zipper is restricted to+                     types in the Typeable class, allowing the user to "move up" through complex data+                     structures such as mutually-recursive types.+                     .+                     Both the Typeable class and fclabels lenses can be derived in GHC, making it+                     easy for the programmer to use a zipper with a minimum of boilerplate.+                     .+                     First import the library, which brings in the Typeable and fclabels modules.+                     You will also want to enable a few extensions:+                     .+                     > {-# LANGUAGE TemplateHaskell, DeriveDataTypeable, TypeOperators #-}+                     > module Main where+                     >+                     > import Data.Typeable.Zipper+                     .+                     Create a datatype, deriving an instance of the Typeable class, and generate a+                     lens using functions from fclabels:+                     .+                     > data Tree a = Node { _leftNode :: Tree a, +                     >                      _val      :: a, +                     >                      _rightNode :: Tree a }+                     >             | Nil  +                     >             deriving (Typeable,Show)+                     >+                     > $(mkLabelsNoTypes [''Tree])+                     .+                     Now we can go crazy using Tree in a Zipper:+                     .+                     > treeBCD = Node (Node Nil 'b' Nil) 'c' (Node Nil 'd' Nil)+                     > +                     > descendLeft :: Zipper1 (Tree a) -> Zipper1 (Tree a)+                     > descendLeft z = case (viewf z) of+                     >                      Nil -> z+                     >                      _   -> descendLeft $ moveTo leftNode z+                     >+                     > insertLeftmost :: a -> Tree a -> Tree a+                     > insertLeftmost x = close . setL focus x . descendLeft . zipper+                     >+                     > treeABCD = insertLeftmost 'a' treeBCD+                     .+                     Because of the flexibility of fclabels, this zipper library can be used to+                     express moving about in reversible computations simply by defining such a lens,+                     for instance:+                     .+                     > stringRep :: (Show b, Read b) => b :-> String+                     > stringRep = lens show (const . read)+                     .+                     Please send any feature requests or bug reports along.+   License:             BSD3 License-file:        LICENSE