ghc-mod/core/Language/Haskell/GhcMod/Read.hs
2017-01-12 17:05:47 +01:00

107 lines
4.6 KiB
Haskell

module Language.Haskell.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