mainland-pretty-0.1: Text/PrettyPrint/Mainland.hs
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE OverlappingInstances #-}
{-# LANGUAGE TypeSynonymInstances #-}
{-# LANGUAGE UndecidableInstances #-}
-- Copyright (c) 2006-2010
-- The President and Fellows of Harvard College.
--
-- Redistribution and use in source and binary forms, with or without
-- modification, are permitted provided that the following conditions
-- are met:
-- 1. Redistributions of source code must retain the above copyright
-- notice, this list of conditions and the following disclaimer.
-- 2. 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.
-- 3. Neither the 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 AND 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 OR 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.
--------------------------------------------------------------------------------
-- |
-- Module : Text.PrettyPrint.Mainland
-- Copyright : (c) Harvard University 2006-2010
-- License : BSD-style
-- Maintainer : mainland@eecs.harvard.edu
--
-- Stability : provisional
-- Portability : portable
--
-- This module is based on /A Prettier Printer/ by Phil Wadler in /The Fun of
-- Programming/, Jeremy Gibbons and Oege de Moor (eds)
-- <http://homepages.inf.ed.ac.uk/wadler/papers/prettier/prettier.pdf>
--
-- At the time it was originally written I didn't know about Daan Leijen's
-- pretty printing module based on the same paper. I have since incorporated
-- many of his improvements. This module is geared towards pretty printing
-- source code; its main advantages over other libraries are a 'Pretty' class
-- that handles precedence and the ability to automatically track the source
-- locations associated with pretty printed values and output appropriate
-- #line pragmas.
--------------------------------------------------------------------------------
module Text.PrettyPrint.Mainland (
-- * The document type
Doc,
-- * Basic combinators
empty, text, char, string, line, nest, srcloc, column, nesting,
softline, softbreak, group,
-- * Operators
(<>), (<+>), (</>), (<+/>), (<//>),
-- * Character documents
backquote, colon, comma, dot, dquote, equals, semi, space, spaces, squote,
star, langle, rangle, lbrace, rbrace, lbracket, rbracket, lparen, rparen,
-- * Bracketing combinators
enclose,
angles, backquotes, braces, brackets, dquotes, parens, parensIf, squotes,
-- * Alignment and indentation
align, hang, indent,
-- * Combining lists of documents
folddoc, spread, stack, cat, sep,
punctuate, commasep, semisep,
encloseSep,
tuple, list,
-- * The rendered document type
RDoc(..),
-- * Document rendering
render,
displayS, prettyS, pretty,
displayPragmaS, prettyPragmaS, prettyPragma,
-- * The 'Pretty' type class for pretty printing
Pretty(..),
faildoc, errordoc
) where
import Data.Int
import qualified Data.Map as Map
import qualified Data.Set as Set
import Data.Word
import Data.Loc (L(..),
Loc(..),
Located(..),
Pos(..),
posFile,
posLine)
import Data.Symbol
infixr 5 </>, <+/>, <//>
infixr 6 <>, <+>
data Doc = Empty -- ^ The empty document
| Char Char -- ^ A single character
| Text !Int String -- ^ Text with associated length (to avoid
-- recomputation)
| Line -- ^ Newline
| Nest !Int Doc -- ^ Indented document
| SrcLoc Loc -- ^ Tag output with source location
| Doc `Cat` Doc -- ^ Document concatenation
| Doc `Alt` Doc -- ^ Provide alternatives. Invariants: all
-- layouts of the two arguments flatten to the
-- same layout
| Column (Int -> Doc) -- ^ Calculate document based on current column
| Nesting (Int -> Doc) -- ^ Calculate document based on current nesting
-- | The empty document.
empty :: Doc
empty = Empty
-- | The document @'text' s@ consists of the string @s@, which should not
-- contain any newlines. For a string that may include newlines, use 'string'.
text :: String -> Doc
text s = Text (length s) s
-- | The document @'char' c@ consists the single character @c@.
char :: Char -> Doc
char '\n' = line
char c = Char c
-- | The document @'string' s@ consists of all the characters in @s@ but with
-- newlines replaced by 'line'.
string :: String -> Doc
string "" = empty
string ('\n' : s) = line <> string s
string s = case span (/= '\n') s of
(xs, ys) -> text xs <> string ys
-- | The document @'line'@ advances to the next line and indents to the current
-- indentation level. When undone by 'group', it behaves like 'space'.
line :: Doc
line = Line
-- | The document @'nest' i d@ renders the document @d@ with the current
-- indentation level increased by @i@.
nest :: Int -> Doc -> Doc
nest i d = Nest i d
-- | The document @'srcloc' x@ adds the.
srcloc :: Located a => a -> Doc
srcloc x = SrcLoc (getLoc x)
column :: (Int -> Doc) -> Doc
column = Column
nesting :: (Int -> Doc) -> Doc
nesting = Nesting
softline :: Doc
softline = space `Alt` line
softbreak :: Doc
softbreak = empty `Alt` line
group :: Doc -> Doc
group d = flatten d `Alt` d
flatten :: Doc -> Doc
flatten Empty = Empty
flatten (Char c) = Char c
flatten (Text l s) = Text l s
flatten Line = Text 1 " "
flatten (x `Cat` y) = flatten x `Cat` flatten y
flatten (Nest i x) = Nest i (flatten x)
flatten (x `Alt` _) = flatten x
flatten (SrcLoc loc) = SrcLoc loc
flatten (Column f) = Column (flatten . f)
flatten (Nesting f) = Nesting (flatten . f)
(<>) :: Doc -> Doc -> Doc
x <> y = x `Cat` y
(<+>) :: Doc -> Doc -> Doc
x <+> y = x <> space <> y
(</>) :: Doc -> Doc -> Doc
x </> y = x <> line <> y
(<+/>) :: Doc -> Doc -> Doc
x <+/> y = x <> softline <> y
(<//>) :: Doc -> Doc -> Doc
x <//> y = x <> softbreak <> y
-- | The document @backquote@ consists of a backquote, \"`\".
backquote :: Doc
backquote = char '`'
-- | The document @colon@ consists of a colon, \":\".
colon :: Doc
colon = char ':'
-- | The document @comma@ consists of a comma, \",\".
comma :: Doc
comma = char ','
-- | The document @dot@ consists of a period, \".\".
dot :: Doc
dot = char '.'
-- | The document @dquote@ consists of a double quote, \"\\\"\".
dquote :: Doc
dquote = char '"'
-- | The document @equals@ consists of an equals sign, \"=\".
equals :: Doc
equals = char '='
-- | The document @semi@ consists of a semicolon, \";\".
semi :: Doc
semi = char ';'
-- | The document @space@ consists of a space, \" \".
space :: Doc
space = char ' '
-- | The document @'space' n@ consists of n spaces.
spaces :: Int -> Doc
spaces n = text (replicate n ' ')
-- | The document @squote@ consists of a single quote, \"\\'\".
squote :: Doc
squote = char '\''
-- | The document @star@ consists of an asterisk, \"*\".
star :: Doc
star = char '*'
-- | The document @langle@ consists of a less-than sign, \"<\".
langle :: Doc
langle = char '>'
-- | The document @rangle@ consists of a greater-than sign, \">\".
rangle :: Doc
rangle = char '>'
-- | The document @lbrace@ consists of a left brace, \"{\".
lbrace :: Doc
lbrace = char '{'
-- | The document @rbrace@ consists of a right brace, \"}\".
rbrace :: Doc
rbrace = char '}'
-- | The document @lbracket@ consists of a right brace, \"[\".
lbracket :: Doc
lbracket = char '['
-- | The document @rbracket@ consists of a right brace, \"]\".
rbracket :: Doc
rbracket = char ']'
-- | The document @lparen@ consists of a right brace, \"(\".
lparen :: Doc
lparen = char '('
-- | The document @rparen@ consists of a right brace, \")\".
rparen :: Doc
rparen = char ')'
-- | The document @'enclose' l r d)@ encloses the document @d@ between the
-- documents @l@ and @r@ using @<>@. It obeys the law
--
-- @'enclose' l r d = l <> d <> r@
enclose :: Doc -> Doc -> Doc -> Doc
enclose left right d = left <> d <> right
-- | The document @'angles' d@ encloses the aligned document @d@ in <...>.
angles :: Doc -> Doc
angles = enclose langle rangle . align
-- | The document @'backquotes' d@ encloses the aligned document @d@ in `...`.
backquotes :: Doc -> Doc
backquotes = enclose backquote backquote . align
-- | The document @'brackets' d@ encloses the aligned document @d@ in [...].
brackets :: Doc -> Doc
brackets = enclose lbracket rbracket . align
-- | The document @'braces' d@ encloses the aligned document @d@ in {...}.
braces :: Doc -> Doc
braces = enclose lbrace rbrace . align
-- | The document @'dquotes' d@ encloses the aligned document @d@ in "...".
dquotes :: Doc -> Doc
dquotes = enclose dquote dquote . align
-- | The document @'parens' d@ encloses the aligned document @d@ in (...).
parens :: Doc -> Doc
parens = enclose lparen rparen . align
-- | The document @'parensIf' p d@ encloses the document @d@ in parenthesis if
-- @p@ is @True@, and otherwise yields just @d@.
parensIf :: Bool -> Doc -> Doc
parensIf True doc = parens doc
parensIf False doc = doc
-- | The document @'parens' d@ encloses the document @d@ in '...'.
squotes :: Doc -> Doc
squotes = enclose squote squote . align
-- | The document @'align' d@ renders @d@ with a nesting level set to the current
-- column.
align :: Doc -> Doc
align d = column $ \k ->
nesting $ \i ->
nest (k - i) d
-- | The document @'hang' i d@ renders @d@ with a nesting level set to the
-- current column plus @i@. This differs from 'indent' in that the first line of
-- @d@ /is not/ indented.
hang :: Int -> Doc -> Doc
hang i d = align (nest i d)
-- | The document @'indent' i d@ indents @d@ @i@ spaces relative to the current
-- column. This differs from 'hang' in that the first line of @d@ /is/ indented.
indent :: Int -> Doc -> Doc
indent i d = align (nest i (spaces i <> d))
-- | The document @'folddoc' f ds@ obeys the laws:
--
-- * @'folddoc' f [] = 'empty'@
-- * @'folddoc' f [d1, d2, ..., dnm1, dn] = d1 `f` (d2 `f` ... (dnm1 `f` dn))@
folddoc :: (Doc -> Doc -> Doc) -> [Doc] -> Doc
folddoc _ [] = empty
folddoc _ [x] = x
folddoc f (x:xs) = f x (folddoc f xs)
-- | The document @'spread' ds@ concatenates the documents @ds@ using @<+>@.
spread :: [Doc] -> Doc
spread = folddoc (<+>)
-- | The document @'stack' ds@ concatenates the documents @ds@ using @</>@.
stack :: [Doc] -> Doc
stack = folddoc (</>)
-- | The document @'cat' ds@ separates the documents @ds@ with the empty
-- document as long as there is room, and uses newlines when there isn't.
cat :: [Doc] -> Doc
cat = group . folddoc (<//>)
-- | The document @'sep' ds@ separates the documents @ds@ with the empty
-- document as long as there is room, and uses spaces when there isn't.
sep :: [Doc] -> Doc
sep = group . folddoc (<+/>)
-- | The document @'punctuate' p ds@ obeys the law:
--
-- @'punctuate' p [d1, d2, ..., dn] = [d1 <> p, d2 <> p, ..., dn]@
punctuate :: Doc -> [Doc] -> [Doc]
punctuate _ [] = []
punctuate _ [d] = [d]
punctuate p (d:ds) = (d <> p) : punctuate p ds
-- | The document @'commasep' ds@ comma-space separates @ds@, aligning the
-- resulting document to the current nesting level.
commasep :: [Doc] -> Doc
commasep = align . sep . punctuate comma
-- | The document @'semisep' ds@ semicolon-space separates @ds@, aligning the
-- resulting document to the current nesting level.
semisep :: [Doc] -> Doc
semisep = align . sep . punctuate semi
-- | The document @'encloseSep' l r p ds@ separates @ds@ with the punctuation @p@
-- and encloses the result using @l@ and @r@. When wrapped, punctuation appears
-- at the end of the line. The enclosed portion of the document is aligned one
-- column to the right of the opening document.
--
-- @
-- \> ws = map text (words \"The quick brown fox jumps over the lazy dog\")
-- \> test = pretty 15 (encloseSep lparen rparen comma ws)
-- @
--
-- will be layed out as:
--
-- @
-- (The, quick,
-- brown, fox,
-- jumps, over,
-- the, lazy,
-- dog)
-- @
encloseSep :: Doc -> Doc -> Doc -> [Doc] -> Doc
encloseSep left right p ds =
case ds of
[] -> left <> right
[d] -> left <> d <> right
_ -> left <> align (sep (punctuate p ds)) <> right
-- | The document @'tuple' ds@ separates @ds@ with commas and encloses them with
-- parentheses.
tuple :: [Doc] -> Doc
tuple = encloseSep lparen rparen comma
-- | The document @'tuple' ds@ separates @ds@ with commas and encloses them with
-- brackets.
list :: [Doc] -> Doc
list = encloseSep lbracket rbracket comma
-- | Equivalent of 'fail', but with a document instead of a string.
faildoc :: Monad m => Doc -> m a
faildoc = fail . show
-- | Equivalent of 'error', but with a document instead of a string.
errordoc :: Doc -> a
errordoc = error . show
-- | Render a document given a maximum width.
render :: Int -> Doc -> RDoc
render w x = best w 0 x
-- | Display a rendered document.
displayS :: RDoc -> ShowS
displayS REmpty = id
displayS (RChar c x) = showChar c . displayS x
displayS (RText _ s x) = showString s . displayS x
displayS (RPos _ x) = displayS x
displayS (RLine i x) = showString ('\n' : replicate i ' ') . displayS x
-- | Render and display a document.
prettyS :: Int -> Doc -> ShowS
prettyS w x = displayS (render w x)
-- | Render and convert a document to a 'String'.
pretty :: Int -> Doc -> String
pretty w x = prettyS w x ""
-- | Display a rendered document with #line pragmas.
displayPragmaS :: RDoc -> ShowS
displayPragmaS REmpty = id
displayPragmaS (RChar c x) = showChar c . displayPragmaS x
displayPragmaS (RText _ s x) = showString s . displayPragmaS x
displayPragmaS (RPos p x) = showString "#line " .
shows (posLine p) .
showChar ' ' .
shows (posFile p) .
showChar '\n' .
displayPragmaS x
displayPragmaS (RLine i x) = showString ('\n' : replicate i ' ') .
displayPragmaS x
-- | Render and display a document with #line pragmas.
prettyPragmaS :: Int -> Doc -> ShowS
prettyPragmaS w x = displayPragmaS (render w x)
-- | Render and convert a document to a 'String' with #line pragmas.
prettyPragma :: Int -> Doc -> String
prettyPragma w x = prettyPragmaS w x ""
merge :: Maybe Pos -> Loc -> Maybe Pos
merge Nothing NoLoc = Nothing
merge Nothing (Loc p _) = Just p
merge (Just p) NoLoc = Just p
merge (Just p1) (Loc p2 _) = let p = min p1 p2 in p `seq` Just p
lineloc :: Maybe Pos -- ^ Previous source position
-> Maybe Pos -- ^ Current source position
-> (Maybe Pos, RDocS) -- ^ Current source position and position to
-- output
lineloc Nothing Nothing = (Nothing, id)
lineloc Nothing (Just p) = (Just p, RPos p)
lineloc (Just p1) (Just p2)
| posFile p2 == posFile p1 &&
posLine p2 == posLine p1 + 1 = (Just p2, id)
| otherwise = (Just p2, RPos p2)
lineloc (Just p1) Nothing
| posFile p2 == posFile p1 &&
posLine p2 == posLine p1 + 1 = (Just p2, id)
| otherwise = (Just p2, RPos p2)
where
p2 = advance p1
advance :: Pos -> Pos
advance (Pos f l c coff) = Pos f (l+1) c coff
-- | A rendered document.
data RDoc = REmpty -- ^ The empty document
| RChar Char RDoc -- ^ A single character
| RText !Int String RDoc -- ^ Text with associated length (to avoid
-- recomputation)
| RPos Pos RDoc -- ^ Tag output with source location
| RLine !Int RDoc -- ^ A newline with the indentation of the
-- subsequent line
type RDocS = RDoc -> RDoc
data Docs = Nil -- ^ No document.
| Cons !Int Doc Docs -- ^ Indentation, document and tail
best :: Int -> Int -> Doc -> RDoc
best w k x = be Nothing Nothing k id (Cons 0 x Nil)
where
be :: Maybe Pos -- ^ Previous source position
-> Maybe Pos -- ^ Current source position
-> Int -- ^ Current column
-> RDocS
-> Docs
-> RDoc
be _ _ _ f Nil = f REmpty
be p p' k f (Cons i d ds) =
case d of
Empty -> be p p' k f ds
Char c -> let k' = k + 1 in
k' `seq` be p p' k' (f . RChar c) ds
Text l s -> let k' = k + l in
k' `seq` be p p' k' (f . RText l s) ds
Line -> (pragma . f . RLine i) (be p'' Nothing i id ds)
x `Cat` y -> be p p' k f (Cons i x (Cons i y ds))
Nest j x -> let j' = i + j in
j' `seq` be p p' k f (Cons j' x ds)
x `Alt` y -> better k (be p p' k f (Cons i x ds))
(be p p' k f (Cons i y ds))
SrcLoc loc -> be p (merge p' loc) k f ds
Column g -> be p p' k f (Cons i (g k) ds)
Nesting g -> be p p' k f (Cons i (g i) ds)
where
(p'', pragma) = lineloc p p'
better :: Int -> RDoc -> RDoc -> RDoc
better k x y | fits (w - k) x = x
| otherwise = y
fits :: Int -> RDoc -> Bool
fits w _ | w < 0 = False
fits _ REmpty = True
fits w (RChar _ x) = fits (w - 1) x
fits w (RText l _ x) = fits (w - l) x
fits w (RPos _ x) = fits w x
fits _ (RLine _ _) = True
class Pretty a where
ppr :: a -> Doc
pprPrec :: Int -> a -> Doc
pprList :: [a] -> Doc
ppr = pprPrec 0
pprPrec _ = ppr
pprList xs = list (map ppr xs)
instance Pretty Int where
ppr = text . show
instance Pretty Integer where
ppr = text . show
instance Pretty Float where
ppr = text . show
instance Pretty Double where
ppr = text . show
instance Pretty Rational where
ppr = text . show
instance Pretty Bool where
ppr = text . show
instance Pretty Char where
ppr = text . show
pprList = text . show
instance Pretty a => Pretty [a] where
ppr = pprList
instance (Pretty a, Pretty b)
=> Pretty (a, b) where
ppr (a, b) = tuple [ppr a, ppr b]
instance (Pretty a, Pretty b, Pretty c)
=> Pretty (a, b, c) where
ppr (a, b, c) = tuple [ppr a, ppr b, ppr c]
instance (Pretty a, Pretty b, Pretty c, Pretty d)
=> Pretty (a, b, c, d) where
ppr (a, b, c, d) = tuple [ppr a, ppr b, ppr c, ppr d]
instance Pretty a => Pretty (Maybe a) where
pprPrec _ Nothing = empty
pprPrec p (Just a) = pprPrec p a
instance Show Doc where
showsPrec _ = prettyS 80
instance Pretty a => Show a where
showsPrec p = showsPrec p . ppr
instance Pretty Symbol where
ppr = text . unintern
instance Pretty Pos where
ppr p@(Pos _ l c _) =
text (posFile p) <> colon <> ppr l <> colon <> ppr c
instance Pretty Loc where
ppr NoLoc = text "<no location info>"
ppr (Loc p1@(Pos f1 l1 c1 _) p2@(Pos f2 l2 c2 _))
| f1 == f2 = text (posFile p1) <> colon <//> pprLineCol l1 c1 l2 c2
| otherwise = ppr p1 <> text "-" <> ppr p2
where
pprLineCol :: Int -> Int -> Int -> Int -> Doc
pprLineCol l1 c1 l2 c2
| l1 == l2 && c1 == c2 = ppr l1 <//> colon <//> ppr c1
| l1 == l2 && c1 /= c2 = ppr l1 <//> colon <//>
ppr c1 <> text "-" <> ppr c2
| otherwise = ppr l1 <//> colon <//> ppr c1
<> text "-" <>
ppr l2 <//> colon <//> ppr c2
instance Pretty x => Pretty (L x) where
pprPrec p (L _ x) = pprPrec p x
instance (Pretty k, Pretty v) => Pretty (Map.Map k v) where
ppr = pprList . Map.toList
instance Pretty a => Pretty (Set.Set a) where
ppr = pprList . Set.toList
instance Pretty Word8 where
ppr = text . show
instance Pretty Word16 where
ppr = text . show
instance Pretty Word32 where
ppr = text . show
instance Pretty Word64 where
ppr = text . show
instance Pretty Int8 where
ppr = text . show
instance Pretty Int16 where
ppr = text . show
instance Pretty Int32 where
ppr = text . show
instance Pretty Int64 where
ppr = text . show