{-# LANGUAGE BangPatterns #-} {-# LANGUAGE MagicHash #-} ----------------------------------------------------------------------------- -- | -- Module : GHC.Utils.Ppr -- Copyright : (c) The University of Glasgow 2001 -- License : BSD-style (see the file LICENSE) -- -- Maintainer : David Terei <code@davidterei.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.cse.chalmers.se/~rjmh/Papers/pretty.ps> -- ----------------------------------------------------------------------------- {- Note [Differences between libraries/pretty and compiler/GHC/Utils/Ppr.hs] For historical reasons, there are two different copies of `Pretty` in the GHC source tree: * `libraries/pretty` is a submodule containing https://github.com/haskell/pretty. This is the `pretty` library as released on hackage. It is used by several other libraries in the GHC source tree (e.g. template-haskell and Cabal). * `compiler/GHC/Utils/Ppr.hs` (this module). It is used by GHC only. There is an ongoing effort in https://github.com/haskell/pretty/issues/1 and https://gitlab.haskell.org/ghc/ghc/issues/10735 to try to get rid of GHC's copy of Pretty. Currently, GHC's copy of Pretty resembles pretty-1.1.2.0, with the following major differences: * GHC's copy uses `Faststring` for performance reasons. * GHC's copy has received a backported bugfix for #12227, which was released as pretty-1.1.3.4 ("Remove harmful $! forcing in beside", https://github.com/haskell/pretty/pull/35). Other differences are minor. Both copies define some extra functions and instances not defined in the other copy. To see all differences, do this in a ghc git tree: $ cd libraries/pretty $ git checkout v1.1.2.0 $ cd - $ vimdiff compiler/GHC/Utils/Ppr.hs \ libraries/pretty/src/Text/PrettyPrint/HughesPJ.hs For parity with `pretty-1.1.2.1`, the following two `pretty` commits would have to be backported: * "Resolve foldr-strictness stack overflow bug" (307b8173f41cd776eae8f547267df6d72bff2d68) * "Special-case reduce for horiz/vert" (c57c7a9dfc49617ba8d6e4fcdb019a3f29f1044c) This has not been done sofar, because these commits seem to cause more allocation in the compiler (see thomie's comments in https://github.com/haskell/pretty/pull/9). -} module GHC.Utils.Ppr ( -- * The document type Doc, TextDetails(..), -- * Constructing documents -- ** Converting values into documents char, text, ftext, ptext, ztext, sizedText, zeroWidthText, int, integer, float, double, rational, hex, -- ** 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, ($$), ($+$), vcat, sep, cat, fsep, fcat, nest, hang, hangNotEmpty, punctuate, -- * Predicates on documents isEmpty, -- * Rendering documents -- ** Rendering with a particular style Style(..), style, renderStyle, Mode(..), -- ** General rendering fullRender, txtPrinter, -- ** GHC-specific rendering printDoc, printDoc_, bufLeftRender -- performance hack ) where import GHC.Prelude hiding (error) import GHC.Utils.BufHandle import GHC.Data.FastString import GHC.Utils.Panic.Plain import System.IO import Numeric (showHex) --for a RULES import GHC.Base ( unpackCString#, unpackNBytes#, Int(..) ) import GHC.Ptr ( Ptr(..) ) -- --------------------------------------------------------------------------- -- The Doc calculus {- Laws for $$ ~~~~~~~~~~~ <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 version 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 FastString -- a hashed string | ZStr FastZString -- a z-encoded string | LStr {-# UNPACK #-} !PtrString -- a '\0'-terminated array of bytes | RStr {-# UNPACK #-} !Int {-# UNPACK #-} !Char -- a repeated character (e.g., ' ') 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 = textBeside_ (Str s) (length s) 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 (mkPtrString# a) #-} {-# RULES "text/unpackNBytes#" forall p n. text (unpackNBytes# p n) = ptext (PtrString (Ptr p) (I# n)) #-} ftext :: FastString -> Doc ftext s = textBeside_ (PStr s) (lengthFS s) Empty ptext :: PtrString -> Doc ptext s = textBeside_ (LStr s) (lengthPS s) Empty ztext :: FastZString -> Doc ztext s = textBeside_ (ZStr s) (lengthFZS s) 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 {- 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 '}' 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)@ hex :: Integer -> Doc -- ^ See Note [Print Hexadecimal Literals] 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) hex n = text ('0' : 'x' : padded) where str = showHex n "" strLen = max 1 (length str) len = 2 ^ (ceiling (logBase 2 (fromIntegral strLen :: Double)) :: Int) padded = replicate (len - strLen) '0' ++ str 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 '}' {- Note [Print Hexadecimal Literals] Relevant discussions: * Phabricator: https://phabricator.haskell.org/D4465 * GHC Trac: https://gitlab.haskell.org/ghc/ghc/issues/14872 There is a flag `-dword-hex-literals` that causes literals of type `Word#` or `Word64#` to be displayed in hexadecimal instead of decimal when dumping GHC core. It also affects the presentation of these in GHC's error messages. Additionally, the hexadecimal encoding of these numbers is zero-padded so that its length is a power of two. As an example of what this does, consider the following haskell file `Literals.hs`: module Literals where alpha :: Int alpha = 100 + 200 beta :: Word -> Word beta x = x + div maxBound 255 + div 0xFFFFFFFF 255 + 0x0202 We get the following dumped core when we compile on a 64-bit machine with ghc -O2 -fforce-recomp -ddump-simpl -dsuppress-all -dhex-word-literals literals.hs: ==================== Tidy Core ==================== ... omitted for brevity ... -- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0} alpha alpha = I# 300# -- RHS size: {terms: 12, types: 3, coercions: 0, joins: 0/0} beta beta = \ x_aYE -> case x_aYE of { W# x#_a1v0 -> W# (plusWord# (plusWord# (plusWord# x#_a1v0 0x0101010101010101##) 0x01010101##) 0x0202##) } Notice that the word literals are in hexadecimals and that they have been padded with zeroes so that their lengths are 16, 8, and 4, respectively. -} -- | 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) = p `seq` g `seq` (beside p g $! reduceDoc q) reduceDoc (Above p g q) = p `seq` g `seq` (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] -- | Apply 'hang' to the arguments if the first 'Doc' is not empty. hangNotEmpty :: Doc -> Int -> Doc -> Doc hangNotEmpty d1 n d2 = if isEmpty d1 then d2 else hang d1 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_ = NilAbove -- Arg of a TextBeside is always an RDoc textBeside_ :: TextDetails -> Int -> RDoc -> RDoc textBeside_ = TextBeside nest_ :: Int -> 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 -> 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) -- Specification: 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_ (RStr 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_ spaceText 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 = get w0 where get :: Int -- (Remaining) width of line -> Doc -> Doc 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 :: Int -- (Remaining) width of line -> Int -- Amount of first line already eaten up -> Doc -- This is an argument to TextBeside => eat Nests -> Doc -- No unions in here! 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 = nicest1 w r 0 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 line length to ribbon length } -- | The default style (@mode=PageMode False, lineLength=100, ribbonsPerLine=1.5@). style :: Style style = Style { lineLength = 100, ribbonsPerLine = 1.5, mode = PageMode False } -- | Rendering mode. data Mode = PageMode { asciiSpace :: Bool } -- ^ Normal | ZigZagMode -- ^ With zig-zag cuts | LeftMode -- ^ No indentation, infinitely long lines | OneLineMode -- ^ All on one line -- | Can we output an ascii space character for spaces? -- Mostly true, but not for e.g. UTF16 -- See Note [putSpaces optimizations] for why we bother -- to track this. hasAsciiSpace :: Mode -> Bool hasAsciiSpace mode = case mode of PageMode asciiSpace -> asciiSpace _ -> False -- | Render the @Doc@ to a String using the given @Style@. renderStyle :: Style -> Doc -> String renderStyle s = fullRender (mode s) (lineLength s) (ribbonsPerLine s) txtPrinter "" -- | 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 = unpackPtrString s1 ++ s2 txtPrinter (RStr n c) s2 = replicate n c ++ 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 = easyDisplay spaceText (\_ y -> y) txt end (reduceDoc doc) fullRender LeftMode _ _ txt end doc = easyDisplay nlText 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 easyDisplay :: TextDetails -> (Doc -> Doc -> Doc) -> (TextDetails -> a -> a) -> a -> Doc -> a easyDisplay nlSpaceText choose txt end = lay where lay NoDoc = error "easyDisplay: NoDoc" lay (Union p q) = lay (choose p q) lay (Nest _ p) = lay p lay Empty = end lay (NilAbove p) = nlSpaceText `txt` lay p lay (TextBeside s _ p) = s `txt` lay p lay (Above {}) = error "easyDisplay Above" lay (Beside {}) = error "easyDisplay 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) = nlText `txt` lay k p lay k (TextBeside s sl p) = case m of ZigZagMode | k >= gap_width -> nlText `txt` ( Str (replicate shift '/') `txt` ( nlText `txt` lay1 (k - shift) s sl p )) | k < 0 -> nlText `txt` ( Str (replicate 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 = let !r = k + sl in indent k (s `txt` lay2 r p) lay2 k _ | k `seq` False = undefined 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" indent !n r = RStr n ' ' `txt` r in lay 0 doc }} printDoc :: Mode -> Int -> Handle -> Doc -> IO () -- printDoc adds a newline to the end printDoc mode cols hdl doc = printDoc_ mode cols hdl (doc $$ text "") {- Note [putSpaces optimizations] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When using dump flags a lot of what we are dumping ends up being whitespace. This is especially true for Core/Stg dumps. Enough so that it's worth optimizing. Especially in the common case of writing to an UTF8 or similarly encoded file where space is equal to ascii space we use hPutBuf to write a preallocated buffer to the file. This avoids a fair bit of allocation. For other cases we fall back to the old and slow path for simplicity. -} 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) next = hPutPtrString hdl s >> next put (RStr n c) next | c == ' ' = putSpaces n >> next | otherwise = hPutStr hdl (replicate n c) >> next putSpaces n -- If we use ascii spaces we are allowed to use hPutBuf -- See Note [putSpaces optimizations] | hasAsciiSpace mode , n <= 100 = hPutBuf hdl (Ptr spaces') n | hasAsciiSpace mode , n > 100 = hPutBuf hdl (Ptr spaces') 100 >> putSpaces (n-100) | otherwise = hPutStr hdl (replicate n ' ') done = return () -- hPutChar hdl '\n' -- 100 spaces, so we avoid the allocation of replicate n ' ' spaces' = " "# -- some versions of hPutBuf will barf if the length is zero hPutPtrString :: Handle -> PtrString -> IO () hPutPtrString _handle (PtrString _ 0) = return () hPutPtrString handle (PtrString a l) = hPutBuf handle a 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. 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) layLeft :: BufHandle -> Doc -> IO () layLeft b _ | b `seq` False = undefined -- make it strict in b layLeft _ NoDoc = error "layLeft: NoDoc" layLeft b (Union p q) = layLeft b $! first p q layLeft b (Nest _ p) = layLeft b $! p layLeft b Empty = bPutChar b '\n' layLeft b (NilAbove p) = p `seq` (bPutChar b '\n' >> layLeft b p) layLeft b (TextBeside s _ p) = s `seq` (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) = bPutPtrString b s put b (RStr n c) = bPutReplicate b n c layLeft _ _ = panic "layLeft: Unhandled case" -- Define error=panic, for easier comparison with libraries/pretty. error :: String -> a error = panic