ShowM.hs

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--  See end of this file for licence information.
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-- |
--  Module      :  ShowM
--  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011 Douglas Burke
--  License     :  GPL V2
--
--  Maintainer  :  Douglas Burke
--  Stability   :  experimental
--  Portability :  H98
--
--  This module defines an extension of the Show class for displaying
--  multi-line values.  It serves the following purposes:
--
--  (1) provides a method with greater layout control of multiline values,
--
--  (2) provides a possibility to override the default Show behaviour
--      for programs that use the extended ShowM interface, and
--
--  (3) uses a ShowS intermediate value to avoid unnecessary
--      concatenation of long strings.
--
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module Swish.Utils.ShowM (ShowM(..)) where

------------------------------------------------------------
--  ShowM framework
------------------------------------------------------------

-- |ShowM is a type class for values that may be formatted in
--  multi-line displays.
class (Show sh) => ShowM sh where
    -- |Multi-line value display method
    --  Create a multiline displayable form of a value, returned
    --  as a 'ShowS' value.  The default implementation behaves just
    --  like a normal instance of 'Show'.
    --
    --  This function is intended to allow the calling function some control
    --  of multiline displays by providing:
    --
    --  (1) the first line of the value is not preceded by any text, so
    --      it may be appended to some preceding text on the same line,
    --
    --  (2) the supplied line break string is used to separate lines of the
    --      formatted text, and may include any desired indentation, and
    --
    --  (3) no newline is output following the final line of text.
    showms :: String -> sh -> ShowS
    showms _ = shows

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--
--  Copyright (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011 Douglas Burke
--  All rights reserved.
--
--  This file is part of Swish.
--
--  Swish 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.
--
--  Swish 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 Swish; if not, write to:
--    The Free Software Foundation, Inc.,
--    59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
--
--------------------------------------------------------------------------------