{- ********************************************************************************* * * * 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 ( -- * The document type Doc, TextDetails(..), -- * Constructing documents -- ** Converting values into documents char, text, ftext, ptext, ztext, 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, quote, doubleQuotes, maybeParens, -- ** Combining documents empty, (<>), (<+>), hcat, hsep, ($$), ($+$), vcat, sep, cat, fsep, fcat, nest, hang, punctuate, -- * Predicates on documents isEmpty, -- * Rendering documents -- ** Rendering with a particular style Mode(..), -- ** General rendering fullRender, -- ** GHC-specific rendering printDoc, printDoc_, showDoc, bufLeftRender -- performance hack ) where import BufWrite import FastString import FastTypes import Panic import Numeric (fromRat) import System.IO import Prelude hiding (error) --for a RULES import GHC.Base ( unpackCString# ) import GHC.Exts ( Int# ) import GHC.Ptr ( Ptr(..) ) -- Don't import Util( assertPanic ) because it makes a loop in the module structure -- --------------------------------------------------------------------------- -- The Doc calculus {- Laws for $$ ~~~~~~~~~~~ (x $$ y) $$ z = x $$ (y $$ z) empty $$ x = x x $$ empty = x ...ditto $+$... Laws for <> ~~~~~~~~~~~ (x <> y) <> z = x <> (y <> z) empty <> x = empty x <> empty = x ...ditto <+>... Laws for text ~~~~~~~~~~~~~ text s <> text t = text (s++t) text "" <> x = x, if x non-empty ** because of law n6, t2 only holds if x doesn't ** start with `nest'. Laws for nest ~~~~~~~~~~~~~ nest 0 x = x nest k (nest k' x) = nest (k+k') x nest k (x <> y) = nest k x <> 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 ** Note the side condition on ! It is this that ** makes it OK for empty to be a left unit for <>. Miscellaneous ~~~~~~~~~~~~~ (text s <> x) $$ y = text s <> ((text "" <> x) $$ nest (-length s) y) (x $$ y) <> z = x $$ (y <> z) if y non-empty Laws for list versions ~~~~~~~~~~~~~~~~~~~~~~ sep (ps++[empty]++qs) = sep (ps ++ qs) ...ditto hsep, hcat, vcat, fill... nest k (sep ps) = sep (map (nest k) ps) ...ditto hsep, hcat, vcat, fill... Laws for oneLiner ~~~~~~~~~~~~~~~~~ oneLiner (nest k p) = nest k (oneLiner p) oneLiner (x <> y) = oneLiner x <> oneLiner y You might think that the following verion of 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 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 {- 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 FastString -- a hashed string | ZStr FastZString -- a z-encoded string | LStr {-#UNPACK#-}!LitString FastInt -- a '\0'-terminated -- array of bytes instance Show Doc where showsPrec _ doc cont = showDocPlus PageMode 100 doc cont showDoc :: Mode -> Int -> Doc -> String showDoc mode cols doc = showDocPlus mode cols doc "" showDocPlus :: Mode -> Int -> Doc -> String -> String showDocPlus mode cols doc rest = fullRender mode cols 1.5 txtPrinter rest 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) (_ILIT(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 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 -- 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) #-} 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} -- | Some text, but without any width. Use for non-printing text -- such as a HTML or Latex tags zeroWidthText :: String -> Doc zeroWidthText s = textBeside_ (Str s) (_ILIT(0)) Empty -- | 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. spaces :: Int# -> String spaces n | n <=# _ILIT(0) = "" | otherwise = ' ' : spaces (n -# _ILIT(1)) {- 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 (<> 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 '}' spaceText, nlText :: TextDetails spaceText = Chr ' ' nlText = 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 (fromRat n :: Double)) --rational n = text (show (fromRationalX n)) -- _showRational 30 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 @\'...\'@ quote :: Doc -> Doc doubleQuotes :: Doc -> Doc -- ^ Wrap document in @\"...\"@ 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 '}' -- | Apply 'parens' to 'Doc' if boolean is true. maybeParens :: Bool -> Doc -> Doc maybeParens False = id maybeParens True = parens -- --------------------------------------------------------------------------- -- 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 = foldr (<>) empty -- | List version of '<+>'. hsep :: [Doc] -> Doc hsep = foldr (<+>) empty -- | List version of '$$'. vcat :: [Doc] -> Doc vcat = foldr ($$) empty -- | Nest (or indent) a document by a given number of positions -- (which may also be negative). 'nest' satisfies the laws: -- -- * @'nest' 0 x = x@ -- -- * @'nest' k ('nest' k' x) = 'nest' (k+k') x@ -- -- * @'nest' k (x '<>' y) = 'nest' k z '<>' 'nest' k y@ -- -- * @'nest' k (x '$$' y) = 'nest' k x '$$' 'nest' k y@ -- -- * @'nest' k 'empty' = 'empty'@ -- -- * @x '<>' 'nest' k y = x '<>' y@, if @x@ non-empty -- -- The side condition on the last law is needed because -- 'empty' is a left identity for '<>'. nest :: Int -> Doc -> Doc nest k p = mkNest (iUnbox k) (reduceDoc p) -- | @hang d1 n d2 = sep [d1, nest n d2]@ hang :: Doc -> Int -> Doc -> Doc hang d1 n d2 = sep [d1, nest n d2] -- | @punctuate p [d1, ... dn] = [d1 \<> p, d2 \<> p, ... dn-1 \<> p, dn]@ punctuate :: Doc -> [Doc] -> [Doc] punctuate _ [] = [] punctuate p (x:xs) = go x xs where go y [] = [y] go y (z:zs) = (y <> p) : go z zs -- mkNest checks for Nest's invariant that it doesn't have an Empty inside it mkNest :: Int# -> Doc -> Doc mkNest k (Nest k1 p) = mkNest (k +# k1) p mkNest _ NoDoc = NoDoc mkNest _ Empty = Empty mkNest k p | k ==# _ILIT(0) = p -- Worth a try! mkNest k p = nest_ k p -- mkUnion checks for an empty document mkUnion :: Doc -> Doc -> Doc mkUnion Empty _ = Empty mkUnion p q = p `union_` q nilAbove_ :: RDoc -> RDoc nilAbove_ = NilAbove -- Arg of a TextBeside is always an RDoc textBeside_ :: TextDetails -> FastInt -> RDoc -> RDoc textBeside_ = TextBeside nest_ :: FastInt -> RDoc -> RDoc nest_ = Nest union_ :: RDoc -> RDoc -> RDoc union_ = Union -- --------------------------------------------------------------------------- -- Vertical composition @$$@ -- | 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 -> 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) -- Specfication: aboveNest p g k q = p $g$ (nest k q) aboveNest :: RDoc -> Bool -> FastInt -> RDoc -> RDoc 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 -> FastInt -> RDoc -> RDoc 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) -- --------------------------------------------------------------------------- -- 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 -- Specification: beside g p q = p 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 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 -- Specification: text "" <> nilBeside g p -- = text "" 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_ spaceText (_ILIT(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) (_ILIT(0)) ps -- Specification: sep1 g k ys = sep (x : map (nest k) ys) -- = oneLiner (x nest k (hsep ys)) -- `union` x $$ nest k (vcat ys) sep1 :: Bool -> RDoc -> FastInt -> [Doc] -> RDoc sep1 _ NoDoc _ _ = NoDoc sep1 g (p `Union` q) k ys = sep1 g p k ys `union_` aboveNest q False k (reduceDoc (vcat ys)) sep1 g Empty k ys = mkNest k (sepX g ys) sep1 g (Nest n p) k ys = nest_ n (sep1 g p (k -# n) ys) sep1 _ (NilAbove p) k ys = nilAbove_ (aboveNest p False k (reduceDoc (vcat ys))) sep1 g (TextBeside s sl p) k ys = textBeside_ s sl (sepNB g p (k -# sl) ys) sep1 _ (Above {}) _ _ = error "sep1 Above" sep1 _ (Beside {}) _ _ = error "sep1 Beside" -- Specification: sepNB p k ys = sep1 (text "" <> p) k ys -- Called when we have already found some text in the first item -- We have to eat up nests sepNB :: Bool -> Doc -> FastInt -> [Doc] -> Doc sepNB g (Nest _ p) k ys = sepNB g p k ys -- Never triggered, because of invariant (2) sepNB g Empty k ys = oneLiner (nilBeside g (reduceDoc rest)) `mkUnion` -- XXX: TODO: PRETTY: Used to use True here (but GHC used False...) nilAboveNest False k (reduceDoc (vcat ys)) where rest | g = hsep ys | otherwise = hcat ys sepNB g p k ys = sep1 g p k ys -- --------------------------------------------------------------------------- -- @fill@ -- | \"Paragraph fill\" version of 'cat'. fcat :: [Doc] -> Doc fcat = fill False -- | \"Paragraph fill\" version of 'sep'. fsep :: [Doc] -> Doc fsep = fill True -- Specification: -- -- fill g docs = fillIndent 0 docs -- -- fillIndent k [] = [] -- fillIndent k [p] = p -- fillIndent k (p1:p2:ps) = -- oneLiner p1 fillIndent (k + length p1 + g ? 1 : 0) -- (remove_nests (oneLiner p2) : ps) -- `Union` -- (p1 $*$ nest (-k) (fillIndent 0 ps)) -- -- $*$ is defined for layouts (not Docs) as -- layout1 $*$ layout2 | hasMoreThanOneLine layout1 = layout1 $$ layout2 -- | otherwise = layout1 $+$ layout2 fill :: Bool -> [Doc] -> RDoc fill _ [] = empty fill g (p:ps) = fill1 g (reduceDoc p) (_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 _ (Above {}) _ _ = error "fill1 Above" fill1 _ (Beside {}) _ _ = error "fill1 Beside" fillNB :: Bool -> Doc -> Int# -> [Doc] -> Doc fillNB g (Nest _ p) k ys = fillNB g p k ys -- Never triggered, because of invariant (2) fillNB _ Empty _ [] = Empty fillNB g Empty k (y:ys) = nilBeside g (fill1 g (oneLiner (reduceDoc y)) k' ys) `mkUnion` nilAboveNest False k (fill g (y:ys)) where !k' | g = k -# _ILIT(1) | otherwise = k fillNB g p k ys = fill1 g p k ys -- --------------------------------------------------------------------------- -- 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 _ (Above {}) = error "best get Above" get _ (Beside {}) = error "best get Beside" 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 _ _ (Above {}) = error "best get1 Above" get1 _ _ (Beside {}) = error "best get1 Beside" 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 _ (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 -- | Rendering mode. data Mode = PageMode -- ^ Normal | ZigZagMode -- ^ With zig-zag cuts | LeftMode -- ^ No indentation, infinitely long lines | OneLineMode -- ^ All on one line -- | Default TextDetails printer txtPrinter :: TextDetails -> String -> String txtPrinter (Chr c) s = c:s txtPrinter (Str s1) s2 = s1 ++ s2 txtPrinter (PStr s1) s2 = unpackFS s1 ++ s2 txtPrinter (ZStr s1) s2 = zString s1 ++ s2 txtPrinter (LStr s1 _) s2 = unpackLitString 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 = 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) = spaceText `txt` lay p -- NoDoc always on first line lay (TextBeside s _ p) = s `txt` lay p lay (Above {}) = error "fullRender/OneLineMode Above" lay (Beside {}) = error "fullRender/OneLineMode Beside" 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) = nlText `txt` lay p -- NoDoc always on first line lay (TextBeside s _ p) = s `txt` lay p lay (Above {}) = error "fullRender/LeftMode Above" lay (Beside {}) = error "fullRender/LeftMode Beside" 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 display :: Mode -> Int -> Int -> (TextDetails -> a -> a) -> a -> Doc -> a display m 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) = nlText `txt` lay k p lay k (TextBeside s sl p) = case m of ZigZagMode | k >=# gap_width -> nlText `txt` ( Str (multi_ch shift '/') `txt` ( nlText `txt` lay1 (k -# shift) s sl p )) | k <# _ILIT(0) -> nlText `txt` ( Str (multi_ch shift '\\') `txt` ( nlText `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 = indent k (s `txt` lay2 (k +# sl) p) lay2 k (NilAbove p) = nlText `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" -- 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 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" -- Define error=panic, for easier comparison with libraries/pretty. error :: String -> a error = panic