{- |

Module : $Header$

Description : simple pretty printing combinators

Copyright : (c) Klaus Luettich, C. Maeder Uni Bremen 2002-2005

License : GPLv2 or higher, see LICENSE.txt

Maintainer : Christian.Maeder@dfki.de

Stability : provisional

Portability : portable

Rather than using (slow, sequential) strings create (fast, tree-like)

documents and render them later as text for IO.

A very simplified version of John Hughes's

and Simon Peyton Jones's Pretty Printer Combinators. Only catenable

string sequences are left over.

-}

module ATerm.SimpPretty (

-- * The document type

SDoc, -- Abstract

-- * Primitive documents

empty, comma,

-- * Converting values into documents

text,

-- * Wrapping documents in delimiters

parens, brackets, braces,

-- * Combining documents

(<>),

-- * Rendering documents

render, fullRender, writeFileSDoc

) where

import System.IO

infixl 6 <>

{- ---------------------------------------------------------------------------

The interface -}

-- The primitive SDoc values

text :: String -> SDoc

text = Text

empty :: SDoc -- ^ An empty document

empty = text ""

comma :: SDoc -- ^ A ',' character

comma = text ","

parens :: SDoc -> SDoc -- ^ Wrap document in @(...)@

parens p = text "(" <> p <> text ")"

braces :: SDoc -> SDoc -- ^ Wrap document in @{...}@

braces p = text "{" <> p <> text "}"

brackets :: SDoc -> SDoc -- ^ Wrap document in @[...]@

brackets p = text "[" <> p <> text "]"

-- Horizontal composition @<>@

(<>) :: SDoc -> SDoc -> SDoc -- ^Beside

(<>) = Beside

-- Displaying @SDoc@ values.

instance Show SDoc where

showsPrec = const showSDoc

-- | Renders the document as a string using the default style

render :: SDoc -> String

render doc = showSDoc doc ""

{- ---------------------------------------------------------------------------

The SDoc data type -}

-- | The abstract type of documents

data SDoc

= Text String

| Beside SDoc SDoc

{- ---------------------------------------------------------------------------

simple layout -}

writeFileSDoc :: FilePath -> SDoc -> IO ()

writeFileSDoc fp sd =

do h <- openFile fp WriteMode

fullRender (hPutStr h) (>>) sd

hClose h

showSDoc :: SDoc -> String -> String

showSDoc = fullRender showString (.)

fullRender :: (String -> a) -> (a -> a -> a) -> SDoc -> a

fullRender txt comp

= lay

where

lay (Text s) = txt s

lay (Beside p q) = lay p `comp` lay q