diff --git a/Data/DString.hs b/Data/DString.hs new file mode 100644 --- /dev/null +++ b/Data/DString.hs @@ -0,0 +1,120 @@ +----------------------------------------------------------------------------- +-- | +-- Module : Data.DString +-- Copyright : (c) 2009 Bas van Dijk +-- License : BSD-style (see the file LICENSE) +-- +-- Maintainer : Bas van Dijk +-- Stability : experimental +-- Portability : portable (Haskell 98) +-- +-- Difference strings: a data structure for O(1) append on +-- strings. Note that a DString is just a newtype wrapper around a +-- 'DList Char'. The reason we need a new type instead of just a type +-- synonym is that we can have an 'instance IsString DString' so we +-- can write overloaded string literals of type DString. +-- +----------------------------------------------------------------------------- + +module Data.DString + ( DString + + -- * Conversion + , fromDList + , toDList + , toString + , fromShowS + , toShowS + + -- * Basic functions + , empty + , singleton + , cons + , snoc + , append + , concat + , list + , head + , tail + , unfoldr + , foldr + ) + where + +import Prelude hiding (concat, foldr, head, tail) +import qualified Data.DList as D +import Data.Monoid +import Data.String + +newtype DString = DS { toDList :: D.DList Char -- ^ Convert a difference string to a difference list + } + +-- | Convert a difference list of Chars to a difference string +fromDList :: D.DList Char -> DString +fromDList = DS + +instance Monoid DString where + mempty = empty + mappend = append + +instance IsString DString where + fromString = fromDList . D.fromList + +-- | Convert a difference string back to a normal String +toString :: DString -> String +toString = D.toList . toDList + +-- | Convert a ShowS to a difference string +fromShowS :: ShowS -> DString +fromShowS = fromDList . D.DL + +-- | Convert a difference string to a ShowS +toShowS :: DString -> ShowS +toShowS = D.unDL . toDList + +-- | Create a difference string containing no characters +empty :: DString +empty = fromDList D.empty + +-- | Build a difference string from a single Char +singleton :: Char -> DString +singleton = fromDList . D.singleton + +-- | /O(1)/, Prepend a Char to a difference string +cons :: Char -> DString -> DString +cons c ds = fromDList $ D.cons c (toDList ds) + +-- | /O(1)/, Append a Char to a difference string +snoc :: DString -> Char -> DString +snoc ds c = fromDList $ D.snoc (toDList ds) c + +-- | /O(1)/, Appending difference strings +append :: DString -> DString -> DString +x `append` y = fromDList (toDList x `D.append` toDList y) + +-- | /O(spine)/, Concatenate difference strings +concat :: [DString] -> DString +concat = fromDList . D.concat . map toDList + +-- | /O(length ds)/, difference list elimination, head, tail. +list :: b -> (Char -> DString -> b) -> DString -> b +list nill consit ds = + case toString ds of + [] -> nill + x : xs -> consit x $ fromString xs + +-- | Return the head of the difference string +head :: DString -> Char +head = list (error "Data.DString.head: empty list") const + +-- | Return the tail of the difference string +tail :: DString -> DString +tail = list (error "Data.DString.tail: empty list") (flip const) + +-- | Unfoldr for difference strings +unfoldr :: (b -> Maybe (Char, b)) -> b -> DString +unfoldr pf b = fromDList $ D.unfoldr pf b + +-- | Foldr over difference strings +foldr :: (Char -> b -> b) -> b -> DString -> b +foldr f b = D.foldr f b . toDList diff --git a/LICENSE b/LICENSE new file mode 100644 --- /dev/null +++ b/LICENSE @@ -0,0 +1,30 @@ +Copyright (c) 2009, Bas van Dijk +All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions are +met: + + * Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + + * Redistributions in binary form must reproduce the above + copyright notice, this list of conditions and the following + disclaimer in the documentation and/or other materials provided + with the distribution. + + * Neither the name of Bas van Dijk nor the names of its + contributors may be used to endorse or promote products derived + from this software without specific prior written permission. + +THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. diff --git a/Setup.lhs b/Setup.lhs new file mode 100644 --- /dev/null +++ b/Setup.lhs @@ -0,0 +1,4 @@ +#! /usr/bin/env runhaskell + +> import Distribution.Simple +> main = defaultMain diff --git a/dstring.cabal b/dstring.cabal new file mode 100644 --- /dev/null +++ b/dstring.cabal @@ -0,0 +1,24 @@ +Name: dstring +Version: 0.1 +Synopsis: Difference strings. +Description: + Difference strings: a data structure for O(1) append on + strings. Note that a DString is just a newtype wrapper around a + 'DList Char'. The reason we need a new type instead of just a type + synonym is that we can have an 'instance IsString DString' so we can + write overloaded string literals of type DString. + +Category: Data +License: BSD3 +License-file: LICENSE +Author: Bas van Dijk +Maintainer: Bas van Dijk +Copyright: 2009 Bas van Dijk +Cabal-version: >= 1.2 +Build-Type: Simple +Stability: experimental + +Library + Build-Depends: base, dlist + Exposed-modules: Data.DString + Ghc-options: -O2 -Wall