107 lines
4.6 KiB
Haskell
107 lines
4.6 KiB
Haskell
module GhcMod.Read where
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import Text.Read (readPrec_to_S, readPrec, minPrec)
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import qualified Text.ParserCombinators.ReadP as P
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import Text.ParserCombinators.ReadPrec (lift)
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-- This library (libraries/base) is derived from code from several
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-- sources:
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-- * Code from the GHC project which is largely (c) The University of
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-- Glasgow, and distributable under a BSD-style license (see below),
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-- * Code from the Haskell 98 Report which is (c) Simon Peyton Jones
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-- and freely redistributable (but see the full license for
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-- restrictions).
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-- * Code from the Haskell Foreign Function Interface specification,
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-- which is (c) Manuel M. T. Chakravarty and freely redistributable
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-- (but see the full license for restrictions).
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-- The full text of these licenses is reproduced below. All of the
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-- licenses are BSD-style or compatible.
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-- -----------------------------------------------------------------------------
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-- The Glasgow Haskell Compiler License
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-- Copyright 2004, The University Court of the University of Glasgow.
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-- All rights reserved.
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-- Redistribution and use in source and binary forms, with or without
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-- modification, are permitted provided that the following conditions are met:
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-- - Redistributions of source code must retain the above copyright notice,
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-- this list of conditions and the following disclaimer.
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-- - Redistributions in binary form must reproduce the above copyright notice,
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-- this list of conditions and the following disclaimer in the documentation
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-- and/or other materials provided with the distribution.
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-- - Neither name of the University nor the names of its contributors may be
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-- used to endorse or promote products derived from this software without
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-- specific prior written permission.
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-- THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY COURT OF THE UNIVERSITY OF
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-- GLASGOW AND THE CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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-- INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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-- FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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-- UNIVERSITY COURT OF THE UNIVERSITY OF GLASGOW OR THE CONTRIBUTORS BE LIABLE
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-- FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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-- DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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-- SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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-- CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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-- LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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-- OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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-- DAMAGE.
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-- -----------------------------------------------------------------------------
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-- Code derived from the document "Report on the Programming Language
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-- Haskell 98", is distributed under the following license:
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-- Copyright (c) 2002 Simon Peyton Jones
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-- The authors intend this Report to belong to the entire Haskell
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-- community, and so we grant permission to copy and distribute it for
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-- any purpose, provided that it is reproduced in its entirety,
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-- including this Notice. Modified versions of this Report may also be
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-- copied and distributed for any purpose, provided that the modified
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-- version is clearly presented as such, and that it does not claim to
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-- be a definition of the Haskell 98 Language.
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-- -----------------------------------------------------------------------------
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-- Code derived from the document "The Haskell 98 Foreign Function
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-- Interface, An Addendum to the Haskell 98 Report" is distributed under
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-- the following license:
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-- Copyright (c) 2002 Manuel M. T. Chakravarty
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-- The authors intend this Report to belong to the entire Haskell
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-- community, and so we grant permission to copy and distribute it for
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-- any purpose, provided that it is reproduced in its entirety,
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-- including this Notice. Modified versions of this Report may also be
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-- copied and distributed for any purpose, provided that the modified
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-- version is clearly presented as such, and that it does not claim to
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-- be a definition of the Haskell 98 Foreign Function Interface.
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-- -----------------------------------------------------------------------------
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readEither :: Read a => String -> Either String a
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readEither s =
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case [ x | (x,"") <- readPrec_to_S read' minPrec s ] of
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[x] -> Right x
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[] -> Left "Prelude.read: no parse"
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_ -> Left "Prelude.read: ambiguous parse"
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where
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read' =
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do x <- readPrec
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lift P.skipSpaces
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return x
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readMaybe :: Read a => String -> Maybe a
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readMaybe s = case readEither s of
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Left _ -> Nothing
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Right a -> Just a
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