{- ********************************************************************************* * * * 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 * * * * Heavily modified by Simon Peyton Jones, Dec 96 * * * ********************************************************************************* Version 3.0 28 May 1997 * Cured massive performance bug. If you write foldl <> empty (map (text.show) [1..10000]) you get quadratic behaviour with V2.0. Why? For just the same reason as you get quadratic behaviour with left-associated (++) chains. This is really bad news. One thing a pretty-printer abstraction should certainly guarantee is insensivity to associativity. It matters: suddenly GHC's compilation times went up by a factor of 100 when I switched to the new pretty printer. I fixed it with a bit of a hack (because I wanted to get GHC back on the road). I added two new constructors to the Doc type, Above and Beside: <> = Beside $$ = Above Then, where I need to get to a "TextBeside" or "NilAbove" form I "force" the Doc to squeeze out these suspended calls to Beside and Above; but in so doing I re-associate. It's quite simple, but I'm not satisfied that I've done the best possible job. I'll send you the code if you are interested. * Added new exports: punctuate, hang int, integer, float, double, rational, lparen, rparen, lbrack, rbrack, lbrace, rbrace, * fullRender's type signature has changed. Rather than producing a string it now takes an extra couple of arguments that tells it how to glue fragments of output together: fullRender :: Mode -> Int -- Line length -> Float -- Ribbons per line -> (TextDetails -> a -> a) -- What to do with text -> a -- What to do at the end -> Doc -> a -- Result The "fragments" are encapsulated in the TextDetails data type: data TextDetails = Chr Char | Str String | PStr FastString The Chr and Str constructors are obvious enough. The PStr constructor has a packed string (FastString) inside it. It's generated by using the new "ptext" export. An advantage of this new setup is that you can get the renderer to do output directly (by passing in a function of type (TextDetails -> IO () -> IO ()), rather than producing a string that you then print. Version 2.0 24 April 1997 * Made empty into a left unit for <> as well as a right unit; it is also now true that nest k empty = empty which wasn't true before. * Fixed an obscure bug in sep that occasionally gave very weird behaviour * Added $+$ * Corrected and tidied up the laws and invariants ====================================================================== Relative to John's original paper, there are the following new features: 1. There's an empty document, "empty". It's a left and right unit for both <> and $$, and anywhere in the argument list for sep, hcat, hsep, vcat, fcat etc. It is Really Useful in practice. 2. There is a paragraph-fill combinator, fsep, that's much like sep, only it keeps fitting things on one line until it can't fit any more. 3. Some random useful extra combinators are provided. <+> puts its arguments beside each other with a space between them, unless either argument is empty in which case it returns the other hcat is a list version of <> hsep is a list version of <+> vcat is a list version of $$ sep (separate) is either like hsep or like vcat, depending on what fits cat is behaves like sep, but it uses <> for horizontal conposition fcat is behaves like fsep, but it uses <> for horizontal conposition These new ones do the obvious things: char, semi, comma, colon, space, parens, brackets, braces, quotes, quote, doubleQuotes 4. The "above" combinator, $$, now overlaps its two arguments if the last line of the top argument stops before the first line of the second begins. For example: text "hi" $$ nest 5 "there" lays out as hi there rather than hi there There are two places this is really useful a) When making labelled blocks, like this: Left -> code for left Right -> code for right LongLongLongLabel -> code for longlonglonglabel The block is on the same line as the label if the label is short, but on the next line otherwise. b) When laying out lists like this: [ first , second , third ] which some people like. But if the list fits on one line you want [first, second, third]. You can't do this with John's original combinators, but it's quite easy with the new $$. The combinator $+$ gives the original "never-overlap" behaviour. 5. Several different renderers are provided: * a standard one * one that uses cut-marks to avoid deeply-nested documents simply piling up in the right-hand margin * one that ignores indentation (fewer chars output; good for machines) * one that ignores indentation and newlines (ditto, only more so) 6. Numerous implementation tidy-ups Use of unboxed data types to speed up the implementation -} {-# LANGUAGE BangPatterns, CPP, MagicHash #-} module Pretty ( Doc, -- Abstract Mode(..), TextDetails(..), empty, isEmpty, nest, char, text, ftext, ptext, ztext, zeroWidthText, int, integer, float, double, rational, parens, brackets, braces, quotes, quote, doubleQuotes, semi, comma, colon, space, equals, lparen, rparen, lbrack, rbrack, lbrace, rbrace, cparen, (<>), (<+>), hcat, hsep, ($$), ($+$), vcat, sep, cat, fsep, fcat, hang, punctuate, fullRender, printDoc, printDoc_, showDoc, bufLeftRender -- performance hack ) where import BufWrite import FastString import FastTypes import Panic import Numeric (fromRat) import System.IO --for a RULES import GHC.Base ( unpackCString# ) import GHC.Exts ( Int# ) import GHC.Ptr ( Ptr(..) ) -- Don't import Util( assertPanic ) because it makes a loop in the module structure infixl 6 <> infixl 6 <+> infixl 5 $$, $+$ -- Disable ASSERT checks; they are expensive! #define LOCAL_ASSERT(x) {- ********************************************************* * * \subsection{The interface} * * ********************************************************* The primitive @Doc@ values -} empty :: Doc isEmpty :: Doc -> Bool -- | Some text, but without any width. Use for non-printing text -- such as a HTML or Latex tags zeroWidthText :: String -> Doc text :: String -> Doc char :: Char -> Doc semi, comma, colon, space, equals :: Doc lparen, rparen, lbrack, rbrack, lbrace, rbrace :: Doc parens, brackets, braces :: Doc -> Doc quotes, quote, doubleQuotes :: Doc -> Doc int :: Int -> Doc integer :: Integer -> Doc float :: Float -> Doc double :: Double -> Doc rational :: Rational -> Doc -- Combining @Doc@ values (<>) :: Doc -> Doc -> Doc -- Beside hcat :: [Doc] -> Doc -- List version of <> (<+>) :: Doc -> Doc -> Doc -- Beside, separated by space hsep :: [Doc] -> Doc -- List version of <+> ($$) :: Doc -> Doc -> Doc -- Above; if there is no -- overlap it "dovetails" the two vcat :: [Doc] -> Doc -- List version of $$ cat :: [Doc] -> Doc -- Either hcat or vcat sep :: [Doc] -> Doc -- Either hsep or vcat fcat :: [Doc] -> Doc -- ``Paragraph fill'' version of cat fsep :: [Doc] -> Doc -- ``Paragraph fill'' version of sep nest :: Int -> Doc -> Doc -- Nested -- GHC-specific ones. hang :: Doc -> Int -> Doc -> Doc punctuate :: Doc -> [Doc] -> [Doc] -- punctuate p [d1, ... dn] = [d1 <> p, d2 <> p, ... dn-1 <> p, dn] -- Displaying @Doc@ values. instance Show Doc where showsPrec _ doc cont = showDocPlus PageMode 100 doc cont fullRender :: Mode -> Int -- Line length -> Float -- Ribbons per line -> (TextDetails -> a -> a) -- What to do with text -> a -- What to do at the end -> Doc -> a -- Result data Mode = PageMode -- Normal | ZigZagMode -- With zig-zag cuts | LeftMode -- No indentation, infinitely long lines | OneLineMode -- All on one line {- ********************************************************* * * \subsection{The @Doc@ calculus} * * ********************************************************* The @Doc@ combinators satisfy the following laws: \begin{verbatim} Laws for $$ ~~~~~~~~~~~ <a1> (x $$ y) $$ z = x $$ (y $$ z) <a2> empty $$ x = x <a3> x $$ empty = x ...ditto $+$... Laws for <> ~~~~~~~~~~~ <b1> (x <> y) <> z = x <> (y <> z) <b2> empty <> x = empty <b3> x <> empty = x ...ditto <+>... Laws for text ~~~~~~~~~~~~~ <t1> text s <> text t = text (s++t) <t2> text "" <> x = x, if x non-empty Laws for nest ~~~~~~~~~~~~~ <n1> nest 0 x = x <n2> nest k (nest k' x) = nest (k+k') x <n3> nest k (x <> y) = nest k z <> nest k y <n4> nest k (x $$ 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 $$ (y <> z) if y non-empty Laws for list versions ~~~~~~~~~~~~~~~~~~~~~~ <l1> sep (ps++[empty]++qs) = sep (ps ++ qs) ...ditto hsep, hcat, vcat, fill... <l2> nest k (sep ps) = sep (map (nest k) ps) ...ditto hsep, hcat, vcat, fill... Laws for oneLiner ~~~~~~~~~~~~~~~~~ <o1> oneLiner (nest k p) = nest k (oneLiner p) <o2> oneLiner (x <> y) = oneLiner x <> oneLiner y \end{verbatim} You might think that the following verion of <m1> would be neater: \begin{verbatim} <3 NO> (text s <> x) $$ y = text s <> ((empty <> x)) $$ nest (-length s) y) \end{verbatim} But it doesn't work, for if x=empty, we would have \begin{verbatim} text s $$ y = text s <> (empty $$ nest (-length s) y) = text s <> nest (-length s) y \end{verbatim} ********************************************************* * * \subsection{Simple derived definitions} * * ********************************************************* -} semi = char ';' colon = char ':' comma = char ',' space = char ' ' equals = char '=' lparen = char '(' rparen = char ')' lbrack = char '[' rbrack = char ']' lbrace = char '{' rbrace = char '}' int n = text (show n) integer n = text (show n) float n = text (show n) double n = text (show n) rational n = text (show (fromRat n :: Double)) --rational n = text (show (fromRationalX n)) -- _showRational 30 n) quotes p = char '`' <> p <> char '\'' quote p = char '\'' <> p doubleQuotes p = char '"' <> p <> char '"' parens p = char '(' <> p <> char ')' brackets p = char '[' <> p <> char ']' braces p = char '{' <> p <> char '}' cparen :: Bool -> Doc -> Doc cparen True = parens cparen False = id hcat = foldr (<>) empty hsep = foldr (<+>) empty vcat = foldr ($$) empty hang d1 n d2 = sep [d1, nest n d2] punctuate _ [] = [] punctuate p (d:ds) = go d ds where go d [] = [d] go d (e:es) = (d <> p) : go e es {- ********************************************************* * * \subsection{The @Doc@ data type} * * ********************************************************* A @Doc@ represents a {\em 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 FastInt Doc -- text s <> x | Nest FastInt 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 type RDoc = Doc -- RDoc is a "reduced Doc", guaranteed not to have a top-level Above or Beside 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 data TextDetails = Chr {-#UNPACK#-}!Char | Str String | PStr FastString -- a hashed string | ZStr FastZString -- a z-encoded string | LStr {-#UNPACK#-}!LitString FastInt -- a '\0'-terminated -- array of bytes space_text :: TextDetails space_text = Chr ' ' nl_text :: TextDetails nl_text = Chr '\n' {- Here are the invariants: \begin{itemize} \item The argument of @NilAbove@ is never @Empty@. Therefore a @NilAbove@ occupies at least two lines. \item The arugment of @TextBeside@ is never @Nest@. \item The layouts of the two arguments of @Union@ both flatten to the same string. \item The arguments of @Union@ are either @TextBeside@, or @NilAbove@. \item The right argument of a union cannot be equivalent to the empty set (@NoDoc@). If the left argument of a union is equivalent to the empty set (@NoDoc@), then the @NoDoc@ appears in the first line. \item An empty document is always represented by @Empty@. It can't be hidden inside a @Nest@, or a @Union@ of two @Empty@s. \item 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. \end{itemize} -} -- Arg of a NilAbove is always an RDoc nilAbove_ :: Doc -> Doc nilAbove_ p = LOCAL_ASSERT( _ok p ) NilAbove p where _ok Empty = False _ok _ = True -- Arg of a TextBeside is always an RDoc textBeside_ :: TextDetails -> FastInt -> Doc -> Doc textBeside_ s sl p = TextBeside s sl (LOCAL_ASSERT( _ok p ) p) where _ok (Nest _ _) = False _ok _ = True -- Arg of Nest is always an RDoc nest_ :: FastInt -> Doc -> Doc nest_ k p = Nest k (LOCAL_ASSERT( _ok p ) p) where _ok Empty = False _ok _ = True -- Args of union are always RDocs union_ :: Doc -> Doc -> Doc union_ p q = Union (LOCAL_ASSERT( _ok p ) p) (LOCAL_ASSERT( _ok q ) q) where _ok (TextBeside _ _ _) = True _ok (NilAbove _) = True _ok (Union _ _) = True _ok _ = False {- 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) ********************************************************* * * \subsection{@empty@, @text@, @nest@, @union@} * * ********************************************************* -} empty = Empty isEmpty Empty = True isEmpty _ = False char c = textBeside_ (Chr c) (_ILIT(1)) Empty text s = case iUnbox (length s) of {sl -> textBeside_ (Str s) sl Empty} {-# NOINLINE [0] text #-} -- Give the RULE a chance to fire -- It must wait till after phase 1 when -- the unpackCString first is manifested ftext :: FastString -> Doc ftext s = case iUnbox (lengthFS s) of {sl -> textBeside_ (PStr s) sl Empty} ptext :: LitString -> Doc ptext s = case iUnbox (lengthLS s) of {sl -> textBeside_ (LStr s sl) sl Empty} ztext :: FastZString -> Doc ztext s = case iUnbox (lengthFZS s) of {sl -> textBeside_ (ZStr s) sl Empty} zeroWidthText s = textBeside_ (Str s) (_ILIT(0)) Empty -- RULE that turns (text "abc") into (ptext (A# "abc"#)) to avoid the -- intermediate packing/unpacking of the string. {-# RULES "text/str" forall a. text (unpackCString# a) = ptext (Ptr a) #-} nest k p = mkNest (iUnbox k) (reduceDoc p) -- Externally callable version -- mkNest checks for Nest's invariant that it doesn't have an Empty inside it mkNest :: Int# -> Doc -> Doc mkNest k (Nest k1 p) = mkNest (k +# k1) p mkNest _ NoDoc = NoDoc mkNest _ Empty = Empty mkNest k p | k ==# _ILIT(0) = p -- Worth a try! 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 {- ********************************************************* * * \subsection{Vertical composition @$$@} * * ********************************************************* -} p $$ q = Above p False q ($+$) :: Doc -> Doc -> Doc p $+$ q = Above p True 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 (_ILIT(0)) (reduceDoc q) above p g q = aboveNest p g (_ILIT(0)) (reduceDoc q) aboveNest :: RDoc -> Bool -> FastInt -> RDoc -> RDoc -- Specfication: aboveNest p g k q = p $g$ (nest k q) 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 _ _ _ _ = panic "aboveNest: Unhandled case" nilAboveNest :: Bool -> FastInt -> RDoc -> RDoc -- Specification: text s <> nilaboveNest g k q -- = text s <> (text "" $g$ nest k q) 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 ># _ILIT(0)) -- No newline if no overlap = textBeside_ (Str (spaces k)) k q | otherwise -- Put them really above = nilAbove_ (mkNest k q) {- ********************************************************* * * \subsection{Horizontal composition @<>@} * * ********************************************************* -} p <> q = Beside p False q p <+> q = Beside p True q beside :: Doc -> Bool -> RDoc -> RDoc -- Specification: beside g p q = p <g> q 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 -- p non-empty beside p@(Beside p1 g1 q1) g2 q2 {- (A `op1` B) `op2` C == A `op1` (B `op2` C) iff op1 == op2 [ && (op1 == <> || op1 == <+>) ] -} | 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 d `seq` 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 nilBeside :: Bool -> RDoc -> RDoc -- Specification: text "" <> nilBeside g p -- = text "" <g> p nilBeside _ Empty = Empty -- Hence the text "" in the spec nilBeside g (Nest _ p) = nilBeside g p nilBeside g p | g = textBeside_ space_text (_ILIT(1)) p | otherwise = p {- ********************************************************* * * \subsection{Separate, @sep@, Hughes version} * * ********************************************************* -} -- Specification: sep ps = oneLiner (hsep ps) -- `union` -- vcat ps sep = sepX True -- Separate with spaces cat = sepX False -- Don't sepX :: Bool -> [Doc] -> Doc sepX _ [] = empty sepX x (p:ps) = sep1 x (reduceDoc p) (_ILIT(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 -> FastInt -> [Doc] -> RDoc 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 _ _ _ _ = panic "sep1: Unhandled case" -- 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 -> FastInt -> [Doc] -> Doc sepNB g (Nest _ p) k ys = sepNB g p k ys sepNB g Empty k ys = oneLiner (nilBeside g (reduceDoc rest)) `mkUnion` nilAboveNest False k (reduceDoc (vcat ys)) where rest | g = hsep ys | otherwise = hcat ys sepNB g p k ys = sep1 g p k ys {- ********************************************************* * * \subsection{@fill@} * * ********************************************************* -} fsep = fill True fcat = fill False -- Specification: -- fill [] = empty -- fill [p] = p -- fill (p1:p2:ps) = oneLiner p1 <#> nest (length p1) -- (fill (oneLiner p2 : ps)) -- `union` -- p1 $$ fill ps fill :: Bool -> [Doc] -> Doc fill _ [] = empty fill g (p:ps) = fill1 g (reduceDoc p) (_ILIT(0)) ps fill1 :: Bool -> RDoc -> FastInt -> [Doc] -> Doc 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 _ _ _ _ = panic "fill1: Unhandled case" fillNB :: Bool -> Doc -> Int# -> [Doc] -> Doc fillNB g (Nest _ p) k ys = fillNB g p k ys fillNB _ Empty _ [] = Empty fillNB g Empty k (y:ys) = nilBeside g (fill1 g (oneLiner (reduceDoc y)) k1 ys) `mkUnion` nilAboveNest False k (fill g (y:ys)) where !k1 | g = k -# _ILIT(1) | otherwise = k fillNB g p k ys = fill1 g p k ys {- ********************************************************* * * \subsection{Selecting the best layout} * * ********************************************************* -} best :: Int -- Line length -> Int -- Ribbon length -> RDoc -> RDoc -- No unions in here! best w_ r_ p = get (iUnbox w_) p where !r = iUnbox r_ get :: FastInt -- (Remaining) width of line -> Doc -> Doc 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 _ _ = panic "best/get: Unhandled case" get1 :: FastInt -- (Remaining) width of line -> FastInt -- Amount of first line already eaten up -> Doc -- This is an argument to TextBeside => eat Nests -> Doc -- No unions in here! 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 _ _ _ = panic "best/get1: Unhandled case" nicest :: FastInt -> FastInt -> Doc -> Doc -> Doc nicest w r p q = nicest1 w r (_ILIT(0)) p q nicest1 :: FastInt -> FastInt -> Int# -> Doc -> Doc -> Doc nicest1 w r sl p q | fits ((w `minFastInt` r) -# sl) p = p | otherwise = q fits :: FastInt -- Space available -> Doc -> Bool -- True if *first line* of Doc fits in space available fits n _ | n <# _ILIT(0) = False fits _ NoDoc = False fits _ Empty = True fits _ (NilAbove _) = True fits n (TextBeside _ sl p) = fits (n -# sl) p fits _ _ = panic "fits: Unhandled case" {- @first@ and @nonEmptySet@ are similar to @nicest@ and @fits@, only simpler. @first@ returns its first argument if it is non-empty, otherwise its second. -} first :: Doc -> Doc -> Doc first p q | nonEmptySet p = p | otherwise = q nonEmptySet :: Doc -> Bool nonEmptySet NoDoc = False nonEmptySet (_ `Union` _) = True nonEmptySet Empty = True nonEmptySet (NilAbove _) = True -- NoDoc always in first line nonEmptySet (TextBeside _ _ p) = nonEmptySet p nonEmptySet (Nest _ p) = nonEmptySet p nonEmptySet _ = panic "nonEmptySet: Unhandled case" -- @oneLiner@ returns the one-line members of the given set of @Doc@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 _ = panic "oneLiner: Unhandled case" {- ********************************************************* * * \subsection{Displaying the best layout} * * ********************************************************* -} showDocPlus :: Mode -> Int -> Doc -> String -> String showDocPlus mode cols doc rest = fullRender mode cols 1.5 string_txt rest doc showDoc :: Mode -> Int -> Doc -> String showDoc mode cols doc = showDocPlus mode cols doc "" string_txt :: TextDetails -> String -> String string_txt (Chr c) s = c:s string_txt (Str s1) s2 = s1 ++ s2 string_txt (PStr s1) s2 = unpackFS s1 ++ s2 string_txt (ZStr s1) s2 = zString s1 ++ s2 string_txt (LStr s1 _) s2 = unpackLitString s1 ++ s2 fullRender OneLineMode _ _ txt end doc = lay (reduceDoc doc) where lay NoDoc = cant_fail lay (Union _ q) = lay q -- Second arg can't be NoDoc lay (Nest _ p) = lay p lay Empty = end lay (NilAbove p) = space_text `txt` lay p -- NoDoc always on -- first line lay (TextBeside s _ p) = s `txt` lay p lay _ = panic "fullRender/OneLineMode/lay: Unhandled case" fullRender LeftMode _ _ txt end doc = lay (reduceDoc doc) where lay NoDoc = cant_fail lay (Union p q) = lay (first p q) lay (Nest _ p) = lay p lay Empty = end lay (NilAbove p) = nl_text `txt` lay p -- NoDoc always on first line lay (TextBeside s _ p) = s `txt` lay p lay _ = panic "fullRender/LeftMode/lay: Unhandled case" fullRender mode line_length ribbons_per_line txt end doc = display mode line_length ribbon_length txt end best_doc where best_doc = best hacked_line_length ribbon_length (reduceDoc doc) hacked_line_length, ribbon_length :: Int ribbon_length = round (fromIntegral line_length / ribbons_per_line) hacked_line_length = case mode of ZigZagMode -> maxBound _ -> line_length display :: Mode -> Int -> Int -> (TextDetails -> t -> t) -> t -> Doc -> t display mode page_width ribbon_width txt end doc = case (iUnbox page_width) -# (iUnbox ribbon_width) of { gap_width -> case gap_width `quotFastInt` _ILIT(2) of { shift -> let 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 mode of ZigZagMode | k >=# gap_width -> nl_text `txt` ( Str (multi_ch shift '/') `txt` ( nl_text `txt` ( lay1 (k -# shift) s sl p))) | k <# _ILIT(0) -> nl_text `txt` ( Str (multi_ch shift '\\') `txt` ( nl_text `txt` ( lay1 (k +# shift) s sl p ))) _ -> lay1 k s sl p lay _ _ = panic "display/lay: Unhandled case" lay1 k s sl p = indent k (s `txt` lay2 (k +# sl) p) 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 _ _ = panic "display/lay2: Unhandled case" -- optimise long indentations using LitString chunks of 8 spaces indent n r | n >=# _ILIT(8) = LStr (sLit " ") (_ILIT(8)) `txt` indent (n -# _ILIT(8)) r | otherwise = Str (spaces n) `txt` r in lay (_ILIT(0)) doc }} cant_fail :: a cant_fail = error "easy_display: NoDoc" multi_ch :: Int# -> Char -> String multi_ch n ch | n <=# _ILIT(0) = "" | otherwise = ch : multi_ch (n -# _ILIT(1)) ch spaces :: Int# -> String spaces n | n <=# _ILIT(0) = "" | otherwise = ' ' : spaces (n -# _ILIT(1)) printDoc :: Mode -> Int -> Handle -> Doc -> IO () -- printDoc adds a newline to the end printDoc mode cols hdl doc = printDoc_ mode cols hdl (doc $$ text "") printDoc_ :: Mode -> Int -> Handle -> Doc -> IO () -- printDoc_ does not add a newline at the end, so that -- successive calls can output stuff on the same line -- Rather like putStr vs putStrLn printDoc_ LeftMode _ hdl doc = do { printLeftRender hdl doc; hFlush hdl } printDoc_ mode pprCols hdl doc = do { fullRender mode pprCols 1.5 put done doc ; hFlush hdl } where put (Chr c) next = hPutChar hdl c >> next put (Str s) next = hPutStr hdl s >> next put (PStr s) next = hPutStr hdl (unpackFS s) >> next -- NB. not hPutFS, we want this to go through -- the I/O library's encoding layer. (#3398) put (ZStr s) next = hPutFZS hdl s >> next put (LStr s l) next = hPutLitString hdl s l >> next done = return () -- hPutChar hdl '\n' -- some versions of hPutBuf will barf if the length is zero hPutLitString :: Handle -> Ptr a -> Int# -> IO () hPutLitString handle a l = if l ==# _ILIT(0) then return () else hPutBuf handle a (iBox l) -- Printing output in LeftMode is performance critical: it's used when -- dumping C and assembly output, so we allow ourselves a few dirty -- hacks: -- -- (1) we specialise fullRender for LeftMode with IO output. -- -- (2) we add a layer of buffering on top of Handles. Handles -- don't perform well with lots of hPutChars, which is mostly -- what we're doing here, because Handles have to be thread-safe -- and async exception-safe. We only have a single thread and don't -- care about exceptions, so we add a layer of fast buffering -- over the Handle interface. -- -- (3) a few hacks in layLeft below to convince GHC to generate the right -- code. printLeftRender :: Handle -> Doc -> IO () printLeftRender hdl doc = do b <- newBufHandle hdl bufLeftRender b doc bFlush b bufLeftRender :: BufHandle -> Doc -> IO () bufLeftRender b doc = layLeft b (reduceDoc doc) -- HACK ALERT! the "return () >>" below convinces GHC to eta-expand -- this function with the IO state lambda. Otherwise we end up with -- closures in all the case branches. layLeft :: BufHandle -> Doc -> IO () layLeft b _ | b `seq` False = undefined -- make it strict in b layLeft _ NoDoc = cant_fail layLeft b (Union p q) = return () >> layLeft b (first p q) layLeft b (Nest _ p) = return () >> layLeft b p layLeft b Empty = bPutChar b '\n' layLeft b (NilAbove p) = bPutChar b '\n' >> layLeft b p layLeft b (TextBeside s _ p) = put b s >> layLeft b p where put b _ | b `seq` False = undefined put b (Chr c) = bPutChar b c put b (Str s) = bPutStr b s put b (PStr s) = bPutFS b s put b (ZStr s) = bPutFZS b s put b (LStr s l) = bPutLitString b s l layLeft _ _ = panic "layLeft: Unhandled case"