module GhcMod.Read where import Text.Read (readPrec_to_S, readPrec, minPrec) import qualified Text.ParserCombinators.ReadP as P import Text.ParserCombinators.ReadPrec (lift) -- This library (libraries/base) is derived from code from several -- sources: -- * Code from the GHC project which is largely (c) The University of -- Glasgow, and distributable under a BSD-style license (see below), -- * Code from the Haskell 98 Report which is (c) Simon Peyton Jones -- and freely redistributable (but see the full license for -- restrictions). -- * Code from the Haskell Foreign Function Interface specification, -- which is (c) Manuel M. T. Chakravarty and freely redistributable -- (but see the full license for restrictions). -- The full text of these licenses is reproduced below. All of the -- licenses are BSD-style or compatible. -- ----------------------------------------------------------------------------- -- The Glasgow Haskell Compiler License -- Copyright 2004, The University Court of the University of Glasgow. -- 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 name of the University 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 UNIVERSITY COURT OF THE UNIVERSITY OF -- GLASGOW AND THE 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 -- UNIVERSITY COURT OF THE UNIVERSITY OF GLASGOW OR THE 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. -- ----------------------------------------------------------------------------- -- Code derived from the document "Report on the Programming Language -- Haskell 98", is distributed under the following license: -- Copyright (c) 2002 Simon Peyton Jones -- The authors intend this Report to belong to the entire Haskell -- community, and so we grant permission to copy and distribute it for -- any purpose, provided that it is reproduced in its entirety, -- including this Notice. Modified versions of this Report may also be -- copied and distributed for any purpose, provided that the modified -- version is clearly presented as such, and that it does not claim to -- be a definition of the Haskell 98 Language. -- ----------------------------------------------------------------------------- -- Code derived from the document "The Haskell 98 Foreign Function -- Interface, An Addendum to the Haskell 98 Report" is distributed under -- the following license: -- Copyright (c) 2002 Manuel M. T. Chakravarty -- The authors intend this Report to belong to the entire Haskell -- community, and so we grant permission to copy and distribute it for -- any purpose, provided that it is reproduced in its entirety, -- including this Notice. Modified versions of this Report may also be -- copied and distributed for any purpose, provided that the modified -- version is clearly presented as such, and that it does not claim to -- be a definition of the Haskell 98 Foreign Function Interface. -- ----------------------------------------------------------------------------- readEither :: Read a => String -> Either String a readEither s = case [ x | (x,"") <- readPrec_to_S read' minPrec s ] of [x] -> Right x [] -> Left "Prelude.read: no parse" _ -> Left "Prelude.read: ambiguous parse" where read' = do x <- readPrec lift P.skipSpaces return x readMaybe :: Read a => String -> Maybe a readMaybe s = case readEither s of Left _ -> Nothing Right a -> Just a