Halipeto/Utilities.lhs

% % Halipeto -- Haskell static web page generator % Copyright 2004 Andrew Cooke (andrew@acooke.org) % Copyright 2007-2010 Peter Simons (simons@cryp.to) % % This program is free software; you can redistribute it and/or modify % it under the terms of the GNU General Public License as published by % the Free Software Foundation; either version 2 of the License, or % (at your option) any later version. % % This program is distributed in the hope that it will be useful, % but WITHOUT ANY WARRANTY; without even the implied warranty of % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the % GNU General Public License for more details. % % You should have received a copy of the GNU General Public License % along with this program; if not, write to the Free Software % Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA % % EXCEPT % % Files in FromHaxml are from HaXml - http://www.cs.york.ac.uk/HaXml - % see the COPYRIGHT and LICENSE in that directory. The files included % are a subset of the full HaXml distribution and have been modified to % originate from the FromHaxml module (so that install on Win32 is % easy). % \section{Utilities} Various general routines. \begin{code}

module Halipeto.Utilities (
  slash, toSlash, fromSlash, toSep, fromSep, dropSpace,
  mapT2, mapT3,
  thenMaybe
) where

import Data.Char

\end{code} Concatenation of paths and files. \begin{code}

slash' :: Char
slash' = '/'

\end{code} %%Haddock: Concatenate two directories \begin{code}

slash :: String -> String -> String
slash p f = if null f || head f == slash' || null p || last p == slash'
              then p ++ f
              else p ++ [slash'] ++ f

\end{code} %%Haddock: Convert a list of directories to a file path \begin{code}

toSlash :: [String] -> FilePath
toSlash = foldl slash ""

\end{code} %%Haddock: Convert a file path to a list of directories \begin{code}

fromSlash :: FilePath -> [String]
fromSlash = fromSep slash'

\end{code} Separation and expansion of strings. %%Haddock: Join a list with a given separator character \begin{code}

toSep :: Char -> [String] -> String
toSep  _  []     = undefined
toSep  _  [s]    = s
toSep sep (s:ss) = s ++ [sep] ++ toSep sep ss

\end{code} %%Haddock: Split a list on a given separator character \begin{code}

fromSep :: Char -> String -> [String]
fromSep sep s' = uncurry (:) $ foldr f ("", []) s'
  where
    f c (s, l) | c == sep && l == [] && s == "" = ("", l)
               | c == sep                       = ("", s:l)
               | otherwise                      = (c:s, l)

\end{code} Remove space from the start of a string. %%Haddock: Drop leading spaces \begin{code}

dropSpace :: String -> String
dropSpace ""                = ""
dropSpace (c:s) | isSpace c = dropSpace s
                | otherwise = (c:s)

\end{code} Maps over uniform tuples. %%Haddock: Map over a uniform tuple \begin{code}

mapT2 :: (a -> b) -> (a, a) -> (b, b)
mapT2 f (x1, x2) = (f x1, f x2)

\end{code} %%Haddock: Map over a uniform triple \begin{code}

mapT3 :: (a -> b) -> (a, a, a) -> (b, b, b)
mapT3 f (x1, x2, x3) = (f x1, f x2, f x3)

\end{code} Chain functions that return Maybe. %%Haddock: Chain Maybe functions \begin{code}

thenMaybe :: (a -> Maybe b) -> (b -> Maybe c) -> (a -> Maybe c)
thenMaybe f1 f2 a = case f1 a of
                     Nothing -> Nothing
                     Just a' -> f2 a'

\end{code}