{-# OPTIONS_HADDOCK not-home #-} {-# LANGUAGE BangPatterns #-} #if __GLASGOW_HASKELL__ >= 701 {-# LANGUAGE Safe #-} #endif ----------------------------------------------------------------------------- -- | -- Module : Text.PrettyPrint.HughesPJ -- Copyright : (c) The University of Glasgow 2001 -- License : BSD-style (see the file LICENSE) -- -- Maintainer : David Terei <dave.terei@gmail.com> -- Stability : stable -- Portability : portable -- -- John Hughes's and Simon Peyton Jones's Pretty Printer Combinators -- -- Based on /The Design of a Pretty-printing Library/ -- in Advanced Functional Programming, -- Johan Jeuring and Erik Meijer (eds), LNCS 925 -- <http://www.cs.chalmers.se/~rjmh/Papers/pretty.ps> -- ----------------------------------------------------------------------------- #ifndef TESTING module Text.PrettyPrint.HughesPJ ( -- * The document type Doc, TextDetails(..), -- * Constructing documents -- ** Converting values into documents char, text, ptext, sizedText, zeroWidthText, int, integer, float, double, rational, -- ** Simple derived documents semi, comma, colon, space, equals, lparen, rparen, lbrack, rbrack, lbrace, rbrace, -- ** Wrapping documents in delimiters parens, brackets, braces, quotes, doubleQuotes, -- ** Combining documents empty, (<>), (<+>), hcat, hsep, ($$), ($+$), vcat, sep, cat, fsep, fcat, nest, hang, punctuate, -- * Predicates on documents isEmpty, -- * Utility functions for documents first, reduceDoc, -- TODO: Should these be exported? Previously they weren't -- * Rendering documents -- ** Default rendering render, -- ** Rendering with a particular style Style(..), style, renderStyle, Mode(..), -- ** General rendering fullRender ) where #endif import Data.Monoid ( Monoid(mempty, mappend) ) import Data.String ( IsString(fromString) ) -- --------------------------------------------------------------------------- -- The Doc calculus {- Laws for $$ ~~~~~~~~~~~ <a1> (x $$ y) $$ z = x $$ (y $$ z) <a2> empty $$ x = x <a3> x $$ empty = x ...ditto $+$... Laws for <> ~~~~~~~~~~~ <b1> (x <> y) <> z = x <> (y <> z) <b2> empty <> x = empty <b3> x <> empty = x ...ditto <+>... Laws for text ~~~~~~~~~~~~~ <t1> text s <> text t = text (s++t) <t2> text "" <> x = x, if x non-empty ** because of law n6, t2 only holds if x doesn't ** start with `nest'. Laws for nest ~~~~~~~~~~~~~ <n1> nest 0 x = x <n2> nest k (nest k' x) = nest (k+k') x <n3> nest k (x <> y) = nest k x <> nest k y <n4> nest k (x $$ y) = nest k x $$ nest k y <n5> nest k empty = empty <n6> x <> nest k y = x <> y, if x non-empty ** Note the side condition on <n6>! It is this that ** makes it OK for empty to be a left unit for <>. Miscellaneous ~~~~~~~~~~~~~ <m1> (text s <> x) $$ y = text s <> ((text "" <> x) $$ nest (-length s) y) <m2> (x $$ y) <> z = x $$ (y <> z) if y non-empty Laws for list versions ~~~~~~~~~~~~~~~~~~~~~~ <l1> sep (ps++[empty]++qs) = sep (ps ++ qs) ...ditto hsep, hcat, vcat, fill... <l2> nest k (sep ps) = sep (map (nest k) ps) ...ditto hsep, hcat, vcat, fill... Laws for oneLiner ~~~~~~~~~~~~~~~~~ <o1> oneLiner (nest k p) = nest k (oneLiner p) <o2> oneLiner (x <> y) = oneLiner x <> oneLiner y You might think that the following verion of <m1> would be neater: <3 NO> (text s <> x) $$ y = text s <> ((empty <> x)) $$ nest (-length s) y) But it doesn't work, for if x=empty, we would have text s $$ y = text s <> (empty $$ nest (-length s) y) = text s <> nest (-length s) y -} -- --------------------------------------------------------------------------- -- Operator fixity infixl 6 <> infixl 6 <+> infixl 5 $$, $+$ -- --------------------------------------------------------------------------- -- The Doc data type -- | The abstract type of documents. -- A Doc represents a *set* of layouts. A Doc with -- no occurrences of Union or NoDoc represents just one layout. data Doc = Empty -- empty | NilAbove Doc -- text "" $$ x | TextBeside !TextDetails {-# UNPACK #-} !Int Doc -- text s <> x | Nest {-# UNPACK #-} !Int Doc -- nest k x | Union Doc Doc -- ul `union` ur | NoDoc -- The empty set of documents | Beside Doc Bool Doc -- True <=> space between | Above Doc Bool Doc -- True <=> never overlap {- Here are the invariants: 1) The argument of NilAbove is never Empty. Therefore a NilAbove occupies at least two lines. 2) The argument of @TextBeside@ is never @Nest@. 3) The layouts of the two arguments of @Union@ both flatten to the same string. 4) The arguments of @Union@ are either @TextBeside@, or @NilAbove@. 5) A @NoDoc@ may only appear on the first line of the left argument of an union. Therefore, the right argument of an union can never be equivalent to the empty set (@NoDoc@). 6) An empty document is always represented by @Empty@. It can't be hidden inside a @Nest@, or a @Union@ of two @Empty@s. 7) The first line of every layout in the left argument of @Union@ is longer than the first line of any layout in the right argument. (1) ensures that the left argument has a first line. In view of (3), this invariant means that the right argument must have at least two lines. Notice the difference between * NoDoc (no documents) * Empty (one empty document; no height and no width) * text "" (a document containing the empty string; one line high, but has no width) -} -- | RDoc is a "reduced GDoc", guaranteed not to have a top-level Above or Beside. type RDoc = Doc -- | The TextDetails data type -- -- A TextDetails represents a fragment of text that will be -- output at some point. data TextDetails = Chr {-# UNPACK #-} !Char -- ^ A single Char fragment | Str String -- ^ A whole String fragment | PStr String -- ^ Used to represent a Fast String fragment -- but now deprecated and identical to the -- Str constructor. -- Combining @Doc@ values instance Monoid Doc where mempty = empty mappend = (<>) instance IsString Doc where fromString = text instance Show Doc where showsPrec _ doc cont = fullRender (mode style) (lineLength style) (ribbonsPerLine style) txtPrinter cont doc -- --------------------------------------------------------------------------- -- Values and Predicates on GDocs and TextDetails -- | A document of height and width 1, containing a literal character. char :: Char -> Doc char c = textBeside_ (Chr c) 1 Empty -- | A document of height 1 containing a literal string. -- 'text' satisfies the following laws: -- -- * @'text' s '<>' 'text' t = 'text' (s'++'t)@ -- -- * @'text' \"\" '<>' x = x@, if @x@ non-empty -- -- The side condition on the last law is necessary because @'text' \"\"@ -- has height 1, while 'empty' has no height. text :: String -> Doc text s = case length s of {sl -> textBeside_ (Str s) sl Empty} -- | Same as @text@. Used to be used for Bytestrings. ptext :: String -> Doc ptext s = case length s of {sl -> textBeside_ (PStr s) sl Empty} -- | Some text with any width. (@text s = sizedText (length s) s@) sizedText :: Int -> String -> Doc sizedText l s = textBeside_ (Str s) l Empty -- | Some text, but without any width. Use for non-printing text -- such as a HTML or Latex tags zeroWidthText :: String -> Doc zeroWidthText = sizedText 0 -- | The empty document, with no height and no width. -- 'empty' is the identity for '<>', '<+>', '$$' and '$+$', and anywhere -- in the argument list for 'sep', 'hcat', 'hsep', 'vcat', 'fcat' etc. empty :: Doc empty = Empty -- | Returns 'True' if the document is empty isEmpty :: Doc -> Bool isEmpty Empty = True isEmpty _ = False -- | Produce spacing for indenting the amount specified. -- -- an old version inserted tabs being 8 columns apart in the output. indent :: Int -> String indent !n = replicate n ' ' {- Q: What is the reason for negative indentation (i.e. argument to indent is < 0) ? A: This indicates an error in the library client's code. If we compose a <> b, and the first line of b is more indented than some other lines of b, the law <n6> (<> eats nests) may cause the pretty printer to produce an invalid layout: doc |0123345 ------------------ d1 |a...| d2 |...b| |c...| d1<>d2 |ab..| c|....| Consider a <> b, let `s' be the length of the last line of `a', `k' the indentation of the first line of b, and `k0' the indentation of the left-most line b_i of b. The produced layout will have negative indentation if `k - k0 > s', as the first line of b will be put on the (s+1)th column, effectively translating b horizontally by (k-s). Now if the i^th line of b has an indentation k0 < (k-s), it is translated out-of-page, causing `negative indentation'. -} semi :: Doc -- ^ A ';' character comma :: Doc -- ^ A ',' character colon :: Doc -- ^ A ':' character space :: Doc -- ^ A space character equals :: Doc -- ^ A '=' character lparen :: Doc -- ^ A '(' character rparen :: Doc -- ^ A ')' character lbrack :: Doc -- ^ A '[' character rbrack :: Doc -- ^ A ']' character lbrace :: Doc -- ^ A '{' character rbrace :: Doc -- ^ A '}' character semi = char ';' comma = char ',' colon = char ':' space = char ' ' equals = char '=' lparen = char '(' rparen = char ')' lbrack = char '[' rbrack = char ']' lbrace = char '{' rbrace = char '}' space_text, nl_text :: TextDetails space_text = Chr ' ' nl_text = Chr '\n' int :: Int -> Doc -- ^ @int n = text (show n)@ integer :: Integer -> Doc -- ^ @integer n = text (show n)@ float :: Float -> Doc -- ^ @float n = text (show n)@ double :: Double -> Doc -- ^ @double n = text (show n)@ rational :: Rational -> Doc -- ^ @rational n = text (show n)@ int n = text (show n) integer n = text (show n) float n = text (show n) double n = text (show n) rational n = text (show n) parens :: Doc -> Doc -- ^ Wrap document in @(...)@ brackets :: Doc -> Doc -- ^ Wrap document in @[...]@ braces :: Doc -> Doc -- ^ Wrap document in @{...}@ quotes :: Doc -> Doc -- ^ Wrap document in @\'...\'@ doubleQuotes :: Doc -> Doc -- ^ Wrap document in @\"...\"@ quotes p = char '\'' <> p <> char '\'' doubleQuotes p = char '"' <> p <> char '"' parens p = char '(' <> p <> char ')' brackets p = char '[' <> p <> char ']' braces p = char '{' <> p <> char '}' -- --------------------------------------------------------------------------- -- Structural operations on GDocs -- | Perform some simplification of a built up @GDoc@. reduceDoc :: Doc -> RDoc reduceDoc (Beside p g q) = beside p g (reduceDoc q) reduceDoc (Above p g q) = above p g (reduceDoc q) reduceDoc p = p -- | List version of '<>'. hcat :: [Doc] -> Doc hcat = reduceAB . foldr (beside_' False) empty -- | List version of '<+>'. hsep :: [Doc] -> Doc hsep = reduceAB . foldr (beside_' True) empty -- | List version of '$$'. vcat :: [Doc] -> Doc vcat = reduceAB . foldr (above_' False) empty -- | Nest (or indent) a document by a given number of positions -- (which may also be negative). 'nest' satisfies the laws: -- -- * @'nest' 0 x = x@ -- -- * @'nest' k ('nest' k' x) = 'nest' (k+k') x@ -- -- * @'nest' k (x '<>' y) = 'nest' k z '<>' 'nest' k y@ -- -- * @'nest' k (x '$$' y) = 'nest' k x '$$' 'nest' k y@ -- -- * @'nest' k 'empty' = 'empty'@ -- -- * @x '<>' 'nest' k y = x '<>' y@, if @x@ non-empty -- -- The side condition on the last law is needed because -- 'empty' is a left identity for '<>'. nest :: Int -> Doc -> Doc nest k p = mkNest k (reduceDoc p) -- | @hang d1 n d2 = sep [d1, nest n d2]@ hang :: Doc -> Int -> Doc -> Doc hang d1 n d2 = sep [d1, nest n d2] -- | @punctuate p [d1, ... dn] = [d1 \<> p, d2 \<> p, ... dn-1 \<> p, dn]@ punctuate :: Doc -> [Doc] -> [Doc] punctuate _ [] = [] punctuate p (x:xs) = go x xs where go y [] = [y] go y (z:zs) = (y <> p) : go z zs -- mkNest checks for Nest's invariant that it doesn't have an Empty inside it mkNest :: Int -> Doc -> Doc mkNest k _ | k `seq` False = undefined mkNest k (Nest k1 p) = mkNest (k + k1) p mkNest _ NoDoc = NoDoc mkNest _ Empty = Empty mkNest 0 p = p mkNest k p = nest_ k p -- mkUnion checks for an empty document mkUnion :: Doc -> Doc -> Doc mkUnion Empty _ = Empty mkUnion p q = p `union_` q beside_' :: Bool -> Doc -> Doc -> Doc beside_' _ p Empty = p beside_' g p q = Beside p g q above_' :: Bool -> Doc -> Doc -> Doc above_' _ p Empty = p above_' g p q = Above p g q reduceAB :: Doc -> Doc reduceAB (Above Empty _ q) = q reduceAB (Beside Empty _ q) = q reduceAB doc = doc nilAbove_ :: RDoc -> RDoc nilAbove_ p = NilAbove p -- Arg of a TextBeside is always an RDoc textBeside_ :: TextDetails -> Int -> RDoc -> RDoc textBeside_ s sl p = TextBeside s sl p nest_ :: Int -> RDoc -> RDoc nest_ k p = Nest k p union_ :: RDoc -> RDoc -> RDoc union_ p q = Union p q -- --------------------------------------------------------------------------- -- Vertical composition @$$@ -- | Above, except that if the last line of the first argument stops -- at least one position before the first line of the second begins, -- these two lines are overlapped. For example: -- -- > text "hi" $$ nest 5 (text "there") -- -- lays out as -- -- > hi there -- -- rather than -- -- > hi -- > there -- -- '$$' is associative, with identity 'empty', and also satisfies -- -- * @(x '$$' y) '<>' z = x '$$' (y '<>' z)@, if @y@ non-empty. -- ($$) :: Doc -> Doc -> Doc p $$ q = above_ p False q -- | Above, with no overlapping. -- '$+$' is associative, with identity 'empty'. ($+$) :: Doc -> Doc -> Doc p $+$ q = above_ p True q above_ :: Doc -> Bool -> Doc -> Doc above_ p _ Empty = p above_ Empty _ q = q above_ p g q = Above p g q above :: Doc -> Bool -> RDoc -> RDoc above (Above p g1 q1) g2 q2 = above p g1 (above q1 g2 q2) above p@(Beside _ _ _) g q = aboveNest (reduceDoc p) g 0 (reduceDoc q) above p g q = aboveNest p g 0 (reduceDoc q) -- Specfication: aboveNest p g k q = p $g$ (nest k q) aboveNest :: RDoc -> Bool -> Int -> RDoc -> RDoc aboveNest _ _ k _ | k `seq` False = undefined aboveNest NoDoc _ _ _ = NoDoc aboveNest (p1 `Union` p2) g k q = aboveNest p1 g k q `union_` aboveNest p2 g k q aboveNest Empty _ k q = mkNest k q aboveNest (Nest k1 p) g k q = nest_ k1 (aboveNest p g (k - k1) q) -- p can't be Empty, so no need for mkNest aboveNest (NilAbove p) g k q = nilAbove_ (aboveNest p g k q) aboveNest (TextBeside s sl p) g k q = textBeside_ s sl rest where !k1 = k - sl rest = case p of Empty -> nilAboveNest g k1 q _ -> aboveNest p g k1 q aboveNest (Above {}) _ _ _ = error "aboveNest Above" aboveNest (Beside {}) _ _ _ = error "aboveNest Beside" -- Specification: text s <> nilaboveNest g k q -- = text s <> (text "" $g$ nest k q) nilAboveNest :: Bool -> Int -> RDoc -> RDoc nilAboveNest _ k _ | k `seq` False = undefined nilAboveNest _ _ Empty = Empty -- Here's why the "text s <>" is in the spec! nilAboveNest g k (Nest k1 q) = nilAboveNest g (k + k1) q nilAboveNest g k q | not g && k > 0 -- No newline if no overlap = textBeside_ (Str (indent k)) k q | otherwise -- Put them really above = nilAbove_ (mkNest k q) -- --------------------------------------------------------------------------- -- Horizontal composition @<>@ -- We intentionally avoid Data.Monoid.(<>) here due to interactions of -- Data.Monoid.(<>) and (<+>). See -- http://www.haskell.org/pipermail/libraries/2011-November/017066.html -- | Beside. -- '<>' is associative, with identity 'empty'. (<>) :: Doc -> Doc -> Doc p <> q = beside_ p False q -- | Beside, separated by space, unless one of the arguments is 'empty'. -- '<+>' is associative, with identity 'empty'. (<+>) :: Doc -> Doc -> Doc p <+> q = beside_ p True q beside_ :: Doc -> Bool -> Doc -> Doc beside_ p _ Empty = p beside_ Empty _ q = q beside_ p g q = Beside p g q -- Specification: beside g p q = p <g> q beside :: Doc -> Bool -> RDoc -> RDoc beside NoDoc _ _ = NoDoc beside (p1 `Union` p2) g q = beside p1 g q `union_` beside p2 g q beside Empty _ q = q beside (Nest k p) g q = nest_ k $! beside p g q beside p@(Beside p1 g1 q1) g2 q2 | g1 == g2 = beside p1 g1 $! beside q1 g2 q2 | otherwise = beside (reduceDoc p) g2 q2 beside p@(Above _ _ _) g q = let !d = reduceDoc p in beside d g q beside (NilAbove p) g q = nilAbove_ $! beside p g q beside (TextBeside s sl p) g q = textBeside_ s sl $! rest where rest = case p of Empty -> nilBeside g q _ -> beside p g q -- Specification: text "" <> nilBeside g p -- = text "" <g> p nilBeside :: Bool -> RDoc -> RDoc nilBeside _ Empty = Empty -- Hence the text "" in the spec nilBeside g (Nest _ p) = nilBeside g p nilBeside g p | g = textBeside_ space_text 1 p | otherwise = p -- --------------------------------------------------------------------------- -- Separate, @sep@ -- Specification: sep ps = oneLiner (hsep ps) -- `union` -- vcat ps -- | Either 'hsep' or 'vcat'. sep :: [Doc] -> Doc sep = sepX True -- Separate with spaces -- | Either 'hcat' or 'vcat'. cat :: [Doc] -> Doc cat = sepX False -- Don't sepX :: Bool -> [Doc] -> Doc sepX _ [] = empty sepX x (p:ps) = sep1 x (reduceDoc p) 0 ps -- Specification: sep1 g k ys = sep (x : map (nest k) ys) -- = oneLiner (x <g> nest k (hsep ys)) -- `union` x $$ nest k (vcat ys) sep1 :: Bool -> RDoc -> Int -> [Doc] -> RDoc sep1 _ _ k _ | k `seq` False = undefined sep1 _ NoDoc _ _ = NoDoc sep1 g (p `Union` q) k ys = sep1 g p k ys `union_` aboveNest q False k (reduceDoc (vcat ys)) sep1 g Empty k ys = mkNest k (sepX g ys) sep1 g (Nest n p) k ys = nest_ n (sep1 g p (k - n) ys) sep1 _ (NilAbove p) k ys = nilAbove_ (aboveNest p False k (reduceDoc (vcat ys))) sep1 g (TextBeside s sl p) k ys = textBeside_ s sl (sepNB g p (k - sl) ys) sep1 _ (Above {}) _ _ = error "sep1 Above" sep1 _ (Beside {}) _ _ = error "sep1 Beside" -- Specification: sepNB p k ys = sep1 (text "" <> p) k ys -- Called when we have already found some text in the first item -- We have to eat up nests sepNB :: Bool -> Doc -> Int -> [Doc] -> Doc sepNB g (Nest _ p) k ys = sepNB g p k ys -- Never triggered, because of invariant (2) sepNB g Empty k ys = oneLiner (nilBeside g (reduceDoc rest)) `mkUnion` -- XXX: TODO: PRETTY: Used to use True here (but GHC used False...) nilAboveNest False k (reduceDoc (vcat ys)) where rest | g = hsep ys | otherwise = hcat ys sepNB g p k ys = sep1 g p k ys -- --------------------------------------------------------------------------- -- @fill@ -- | \"Paragraph fill\" version of 'cat'. fcat :: [Doc] -> Doc fcat = fill False -- | \"Paragraph fill\" version of 'sep'. fsep :: [Doc] -> Doc fsep = fill True -- Specification: -- -- fill g docs = fillIndent 0 docs -- -- fillIndent k [] = [] -- fillIndent k [p] = p -- fillIndent k (p1:p2:ps) = -- oneLiner p1 <g> fillIndent (k + length p1 + g ? 1 : 0) -- (remove_nests (oneLiner p2) : ps) -- `Union` -- (p1 $*$ nest (-k) (fillIndent 0 ps)) -- -- $*$ is defined for layouts (not Docs) as -- layout1 $*$ layout2 | hasMoreThanOneLine layout1 = layout1 $$ layout2 -- | otherwise = layout1 $+$ layout2 fill :: Bool -> [Doc] -> RDoc fill _ [] = empty fill g (p:ps) = fill1 g (reduceDoc p) 0 ps fill1 :: Bool -> RDoc -> Int -> [Doc] -> Doc fill1 _ _ k _ | k `seq` False = undefined fill1 _ NoDoc _ _ = NoDoc fill1 g (p `Union` q) k ys = fill1 g p k ys `union_` aboveNest q False k (fill g ys) fill1 g Empty k ys = mkNest k (fill g ys) fill1 g (Nest n p) k ys = nest_ n (fill1 g p (k - n) ys) fill1 g (NilAbove p) k ys = nilAbove_ (aboveNest p False k (fill g ys)) fill1 g (TextBeside s sl p) k ys = textBeside_ s sl (fillNB g p (k - sl) ys) fill1 _ (Above {}) _ _ = error "fill1 Above" fill1 _ (Beside {}) _ _ = error "fill1 Beside" fillNB :: Bool -> Doc -> Int -> [Doc] -> Doc fillNB _ _ k _ | k `seq` False = undefined fillNB g (Nest _ p) k ys = fillNB g p k ys -- Never triggered, because of invariant (2) fillNB _ Empty _ [] = Empty fillNB g Empty k (Empty:ys) = fillNB g Empty k ys fillNB g Empty k (y:ys) = fillNBE g k y ys fillNB g p k ys = fill1 g p k ys fillNBE :: Bool -> Int -> Doc -> [Doc] -> Doc fillNBE g k y ys = nilBeside g (fill1 g ((elideNest . oneLiner . reduceDoc) y) k' ys) -- XXX: TODO: PRETTY: Used to use True here (but GHC used False...) `mkUnion` nilAboveNest False k (fill g (y:ys)) where k' = if g then k - 1 else k elideNest :: Doc -> Doc elideNest (Nest _ d) = d elideNest d = d -- --------------------------------------------------------------------------- -- Selecting the best layout best :: Int -- Line length -> Int -- Ribbon length -> RDoc -> RDoc -- No unions in here! best w0 r p0 = get w0 p0 where get w _ | w == 0 && False = undefined get _ Empty = Empty get _ NoDoc = NoDoc get w (NilAbove p) = nilAbove_ (get w p) get w (TextBeside s sl p) = textBeside_ s sl (get1 w sl p) get w (Nest k p) = nest_ k (get (w - k) p) get w (p `Union` q) = nicest w r (get w p) (get w q) get _ (Above {}) = error "best get Above" get _ (Beside {}) = error "best get Beside" get1 w _ _ | w == 0 && False = undefined get1 _ _ Empty = Empty get1 _ _ NoDoc = NoDoc get1 w sl (NilAbove p) = nilAbove_ (get (w - sl) p) get1 w sl (TextBeside t tl p) = textBeside_ t tl (get1 w (sl + tl) p) get1 w sl (Nest _ p) = get1 w sl p get1 w sl (p `Union` q) = nicest1 w r sl (get1 w sl p) (get1 w sl q) get1 _ _ (Above {}) = error "best get1 Above" get1 _ _ (Beside {}) = error "best get1 Beside" nicest :: Int -> Int -> Doc -> Doc -> Doc nicest !w !r p q = nicest1 w r 0 p q nicest1 :: Int -> Int -> Int -> Doc -> Doc -> Doc nicest1 !w !r !sl p q | fits ((w `min` r) - sl) p = p | otherwise = q fits :: Int -- Space available -> Doc -> Bool -- True if *first line* of Doc fits in space available fits n _ | n < 0 = False fits _ NoDoc = False fits _ Empty = True fits _ (NilAbove _) = True fits n (TextBeside _ sl p) = fits (n - sl) p fits _ (Above {}) = error "fits Above" fits _ (Beside {}) = error "fits Beside" fits _ (Union {}) = error "fits Union" fits _ (Nest {}) = error "fits Nest" -- | @first@ returns its first argument if it is non-empty, otherwise its second. first :: Doc -> Doc -> Doc first p q | nonEmptySet p = p -- unused, because (get OneLineMode) is unused | otherwise = q nonEmptySet :: Doc -> Bool nonEmptySet NoDoc = False nonEmptySet (_ `Union` _) = True nonEmptySet Empty = True nonEmptySet (NilAbove _) = True nonEmptySet (TextBeside _ _ p) = nonEmptySet p nonEmptySet (Nest _ p) = nonEmptySet p nonEmptySet (Above {}) = error "nonEmptySet Above" nonEmptySet (Beside {}) = error "nonEmptySet Beside" -- @oneLiner@ returns the one-line members of the given set of @GDoc@s. oneLiner :: Doc -> Doc oneLiner NoDoc = NoDoc oneLiner Empty = Empty oneLiner (NilAbove _) = NoDoc oneLiner (TextBeside s sl p) = textBeside_ s sl (oneLiner p) oneLiner (Nest k p) = nest_ k (oneLiner p) oneLiner (p `Union` _) = oneLiner p oneLiner (Above {}) = error "oneLiner Above" oneLiner (Beside {}) = error "oneLiner Beside" -- --------------------------------------------------------------------------- -- Rendering -- | A rendering style. data Style = Style { mode :: Mode -- ^ The rendering mode , lineLength :: Int -- ^ Length of line, in chars , ribbonsPerLine :: Float -- ^ Ratio of ribbon length to line length } -- | The default style (@mode=PageMode, lineLength=100, ribbonsPerLine=1.5@). style :: Style style = Style { lineLength = 100, ribbonsPerLine = 1.5, mode = PageMode } -- | Rendering mode. data Mode = PageMode -- ^ Normal | ZigZagMode -- ^ With zig-zag cuts | LeftMode -- ^ No indentation, infinitely long lines | OneLineMode -- ^ All on one line -- | Render the @Doc@ to a String using the default @Style@. render :: Doc -> String render doc = fullRender (mode style) (lineLength style) (ribbonsPerLine style) txtPrinter "" doc -- | Render the @Doc@ to a String using the given @Style@. renderStyle :: Style -> Doc -> String renderStyle s doc = fullRender (mode s) (lineLength s) (ribbonsPerLine s) txtPrinter "" doc -- | Default TextDetails printer txtPrinter :: TextDetails -> String -> String txtPrinter (Chr c) s = c:s txtPrinter (Str s1) s2 = s1 ++ s2 txtPrinter (PStr s1) s2 = s1 ++ s2 -- | The general rendering interface. fullRender :: Mode -- ^ Rendering mode -> Int -- ^ Line length -> Float -- ^ Ribbons per line -> (TextDetails -> a -> a) -- ^ What to do with text -> a -- ^ What to do at the end -> Doc -- ^ The document -> a -- ^ Result fullRender OneLineMode _ _ txt end doc = easy_display space_text (\_ y -> y) txt end (reduceDoc doc) fullRender LeftMode _ _ txt end doc = easy_display nl_text first txt end (reduceDoc doc) fullRender m lineLen ribbons txt rest doc = display m lineLen ribbonLen txt rest doc' where doc' = best bestLineLen ribbonLen (reduceDoc doc) bestLineLen, ribbonLen :: Int ribbonLen = round (fromIntegral lineLen / ribbons) bestLineLen = case m of ZigZagMode -> maxBound _ -> lineLen easy_display :: TextDetails -> (Doc -> Doc -> Doc) -> (TextDetails -> a -> a) -> a -> Doc -> a easy_display nl_space_text choose txt end doc = lay doc where lay NoDoc = error "easy_display: NoDoc" lay (Union p q) = lay (choose p q) lay (Nest _ p) = lay p lay Empty = end lay (NilAbove p) = nl_space_text `txt` lay p lay (TextBeside s _ p) = s `txt` lay p lay (Above {}) = error "easy_display Above" lay (Beside {}) = error "easy_display Beside" display :: Mode -> Int -> Int -> (TextDetails -> a -> a) -> a -> Doc -> a display m !page_width !ribbon_width txt end doc = case page_width - ribbon_width of { gap_width -> case gap_width `quot` 2 of { shift -> let lay k _ | k `seq` False = undefined lay k (Nest k1 p) = lay (k + k1) p lay _ Empty = end lay k (NilAbove p) = nl_text `txt` lay k p lay k (TextBeside s sl p) = case m of ZigZagMode | k >= gap_width -> nl_text `txt` ( Str (replicate shift '/') `txt` ( nl_text `txt` lay1 (k - shift) s sl p )) | k < 0 -> nl_text `txt` ( Str (replicate shift '\\') `txt` ( nl_text `txt` lay1 (k + shift) s sl p )) _ -> lay1 k s sl p lay _ (Above {}) = error "display lay Above" lay _ (Beside {}) = error "display lay Beside" lay _ NoDoc = error "display lay NoDoc" lay _ (Union {}) = error "display lay Union" lay1 !k s !sl p = let !r = k + sl in Str (indent k) `txt` (s `txt` lay2 r p) lay2 k _ | k `seq` False = undefined lay2 k (NilAbove p) = nl_text `txt` lay k p lay2 k (TextBeside s sl p) = s `txt` lay2 (k + sl) p lay2 k (Nest _ p) = lay2 k p lay2 _ Empty = end lay2 _ (Above {}) = error "display lay2 Above" lay2 _ (Beside {}) = error "display lay2 Beside" lay2 _ NoDoc = error "display lay2 NoDoc" lay2 _ (Union {}) = error "display lay2 Union" in lay 0 doc }}