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diff --git a/compiler/utils/Pretty.lhs b/compiler/utils/Pretty.lhs new file mode 100644 index 0000000000..ec8f1e75ad --- /dev/null +++ b/compiler/utils/Pretty.lhs @@ -0,0 +1,1075 @@ +********************************************************************************* +* * +* 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 + $$ = Above + + Then, where I need to get to a "TextBeside" or "NilAbove" form I "force" + the Doc to squeeze out these suspended calls to Beside and Above; but in so + doing I re-associate. It's quite simple, but I'm not satisfied that I've done + the best possible job. I'll send you the code if you are interested. + + * Added new exports: + punctuate, hang + int, integer, float, double, rational, + lparen, rparen, lbrack, rbrack, lbrace, rbrace, + + * fullRender's type signature has changed. Rather than producing a string it + now takes an extra couple of arguments that tells it how to glue fragments + of output together: + + fullRender :: Mode + -> Int -- Line length + -> Float -- Ribbons per line + -> (TextDetails -> a -> a) -- What to do with text + -> a -- What to do at the end + -> Doc + -> a -- Result + + The "fragments" are encapsulated in the TextDetails data type: + data TextDetails = Chr Char + | Str String + | PStr FastString + + The Chr and Str constructors are obvious enough. The PStr constructor has a packed + string (FastString) inside it. It's generated by using the new "ptext" export. + + An advantage of this new setup is that you can get the renderer to do output + directly (by passing in a function of type (TextDetails -> IO () -> IO ()), + rather than producing a string that you then print. + + +Version 2.0 24 April 1997 + * Made empty into a left unit for <> as well as a right unit; + it is also now true that + nest k empty = empty + which wasn't true before. + + * Fixed an obscure bug in sep that occassionally gave very wierd behaviour + + * Added $+$ + + * Corrected and tidied up the laws and invariants + +====================================================================== +Relative to John's original paper, there are the following new features: + +1. There's an empty document, "empty". It's a left and right unit for + both <> and $$, 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 itc 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 $$ + + sep (separate) is either like hsep or like vcat, depending on what fits + + cat is behaves like sep, but it uses <> for horizontal conposition + fcat is behaves like fsep, but it uses <> for horizontal conposition + + These new ones do the obvious things: + char, semi, comma, colon, space, + parens, brackets, braces, + quotes, doubleQuotes + +4. The "above" combinator, $$, 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 + + + +\begin{code} +module Pretty ( + Doc, -- Abstract + Mode(..), TextDetails(..), + + empty, isEmpty, nest, + + text, char, ftext, ptext, + int, integer, float, double, rational, + parens, brackets, braces, quotes, doubleQuotes, + semi, comma, colon, space, equals, + lparen, rparen, lbrack, rbrack, lbrace, rbrace, + + (<>), (<+>), hcat, hsep, + ($$), ($+$), vcat, + sep, cat, + fsep, fcat, + + hang, punctuate, + +-- renderStyle, -- Haskell 1.3 only + render, fullRender, printDoc, showDocWith + ) where + +#include "HsVersions.h" + +import BufWrite +import FastString + +import GLAEXTS + +import Numeric (fromRat) +import IO + +import System.IO ( hPutBuf ) + +import GHC.Base ( unpackCString# ) +import GHC.Ptr ( Ptr(..) ) + +-- Don't import Util( assertPanic ) because it makes a loop in the module structure + +infixl 6 <> +infixl 6 <+> +infixl 5 $$, $+$ +\end{code} + + + +********************************************************* +* * +\subsection{CPP magic so that we can compile with both GHC and Hugs} +* * +********************************************************* + +The library uses unboxed types to get a bit more speed, but these CPP macros +allow you to use either GHC or Hugs. To get GHC, just set the CPP variable + __GLASGOW_HASKELL__ + +\begin{code} + +#if defined(__GLASGOW_HASKELL__) + +-- Glasgow Haskell + +-- Disable ASSERT checks; they are expensive! +#define LOCAL_ASSERT(x) + +#define ILIT(x) (x#) +#define IBOX(x) (I# (x)) +#define INT Int# +#define MINUS -# +#define NEGATE negateInt# +#define PLUS +# +#define GR ># +#define GREQ >=# +#define LT <# +#define DIV `quotInt#` + + +#define SHOW Show +#define MAXINT maxBound + +#else + +-- Standard Haskell + +#define LOCAL_ASSERT(x) + +#define INT Int +#define IBOX(x) x +#define MINUS - +#define NEGATE negate +#define PLUS + +#define GR > +#define GREQ >= +#define LT < +#define DIV `quot` +#define ILIT(x) x + +#define SHOW Show +#define MAXINT maxBound + +#endif + +\end{code} + + +********************************************************* +* * +\subsection{The interface} +* * +********************************************************* + +The primitive @Doc@ values + +\begin{code} +empty :: Doc +isEmpty :: Doc -> Bool +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, doubleQuotes :: Doc -> Doc + +int :: Int -> Doc +integer :: Integer -> Doc +float :: Float -> Doc +double :: Double -> Doc +rational :: Rational -> Doc +\end{code} + +Combining @Doc@ values + +\begin{code} +(<>) :: 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 +\end{code} + +GHC-specific ones. + +\begin{code} +hang :: Doc -> Int -> Doc -> Doc +punctuate :: Doc -> [Doc] -> [Doc] -- punctuate p [d1, ... dn] = [d1 <> p, d2 <> p, ... dn-1 <> p, dn] +\end{code} + +Displaying @Doc@ values. + +\begin{code} +instance SHOW Doc where + showsPrec prec doc cont = showDoc doc cont + +render :: Doc -> String -- Uses default style +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 + +{- When we start using 1.3 +renderStyle :: Style -> Doc -> String +data Style = Style { lineLength :: Int, -- In chars + ribbonsPerLine :: Float, -- Ratio of ribbon length to line length + mode :: Mode + } +style :: Style -- The default style +style = Style { lineLength = 100, ribbonsPerLine = 2.5, mode = PageMode } +-} + +data Mode = PageMode -- Normal + | ZigZagMode -- With zig-zag cuts + | LeftMode -- No indentation, infinitely long lines + | OneLineMode -- All on one line + +\end{code} + + +********************************************************* +* * +\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 $$ nest (-length s) y) + = text s <> nest (-length s) y +\end{verbatim} + + + +********************************************************* +* * +\subsection{Simple derived definitions} +* * +********************************************************* + +\begin{code} +semi = char ';' +colon = char ':' +comma = char ',' +space = char ' ' +equals = char '=' +lparen = char '(' +rparen = char ')' +lbrack = char '[' +rbrack = char ']' +lbrace = char '{' +rbrace = char '}' + +int n = text (show n) +integer n = text (show n) +float n = text (show n) +double n = text (show n) +rational n = text (show (fromRat n)) +--rational n = text (show (fromRationalX n)) -- _showRational 30 n) + +quotes p = char '`' <> p <> char '\'' +doubleQuotes p = char '"' <> p <> char '"' +parens p = char '(' <> p <> char ')' +brackets p = char '[' <> p <> char ']' +braces p = char '{' <> p <> char '}' + + +hcat = foldr (<>) empty +hsep = foldr (<+>) empty +vcat = foldr ($$) empty + +hang d1 n d2 = sep [d1, nest n d2] + +punctuate p [] = [] +punctuate p (d:ds) = go d ds + where + go d [] = [d] + go d (e:es) = (d <> p) : go e es +\end{code} + + +********************************************************* +* * +\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. +\begin{code} +data Doc + = Empty -- empty + | NilAbove Doc -- text "" $$ x + | TextBeside !TextDetails INT Doc -- text s <> x + | Nest 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 + +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 + | LStr Addr# Int# -- a '\0'-terminated array of bytes + +space_text = Chr ' ' +nl_text = Chr '\n' +\end{code} + +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} + +\begin{code} + -- Arg of a NilAbove is always an RDoc +nilAbove_ p = LOCAL_ASSERT( ok p ) NilAbove p + where + ok Empty = False + ok other = True + + -- Arg of a TextBeside is always an RDoc +textBeside_ s sl p = TextBeside s sl (LOCAL_ASSERT( ok p ) p) + where + ok (Nest _ _) = False + ok other = True + + -- Arg of Nest is always an RDoc +nest_ k p = Nest k (LOCAL_ASSERT( ok p ) p) + where + ok Empty = False + ok other = True + + -- Args of union are always RDocs +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 other = False +\end{code} + + +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@} +* * +********************************************************* + +\begin{code} +empty = Empty + +isEmpty Empty = True +isEmpty _ = False + +char c = textBeside_ (Chr c) 1# Empty +text s = case length s of {IBOX(sl) -> textBeside_ (Str s) sl Empty} +ftext s = case lengthFS s of {IBOX(sl) -> textBeside_ (PStr s) sl Empty} +ptext (Ptr s) = case strLength (Ptr s) of {IBOX(sl) -> textBeside_ (LStr s sl) sl 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 IBOX(k) p = mkNest k (reduceDoc p) -- Externally callable version + +-- mkNest checks for Nest's invariant that it doesn't have an Empty inside it +mkNest k (Nest k1 p) = mkNest (k PLUS k1) p +mkNest k NoDoc = NoDoc +mkNest k Empty = Empty +mkNest ILIT(0) p = p -- Worth a try! +mkNest k p = nest_ k p + +-- mkUnion checks for an empty document +mkUnion Empty q = Empty +mkUnion p q = p `union_` q +\end{code} + +********************************************************* +* * +\subsection{Vertical composition @$$@} +* * +********************************************************* + + +\begin{code} +p $$ q = Above p False q +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 -> INT -> RDoc -> RDoc +-- Specfication: aboveNest p g k q = p $g$ (nest k q) + +aboveNest NoDoc g k q = NoDoc +aboveNest (p1 `Union` p2) g k q = aboveNest p1 g k q `union_` + aboveNest p2 g k q + +aboveNest Empty g k q = mkNest k q +aboveNest (Nest k1 p) g k q = nest_ k1 (aboveNest p g (k MINUS 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 MINUS sl + rest = case p of + Empty -> nilAboveNest g k1 q + other -> aboveNest p g k1 q +\end{code} + +\begin{code} +nilAboveNest :: Bool -> INT -> RDoc -> RDoc +-- Specification: text s <> nilaboveNest g k q +-- = text s <> (text "" $g$ nest k q) + +nilAboveNest g k Empty = Empty -- Here's why the "text s <>" is in the spec! +nilAboveNest g k (Nest k1 q) = nilAboveNest g (k PLUS k1) q + +nilAboveNest g k q | (not g) && (k GR ILIT(0)) -- No newline if no overlap + = textBeside_ (Str (spaces k)) k q + | otherwise -- Put them really above + = nilAbove_ (mkNest k q) +\end{code} + + +********************************************************* +* * +\subsection{Horizontal composition @<>@} +* * +********************************************************* + +\begin{code} +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 g q = NoDoc +beside (p1 `Union` p2) g q = (beside p1 g q) `union_` (beside p2 g q) +beside Empty g 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 + other -> beside p g q +\end{code} + +\begin{code} +nilBeside :: Bool -> RDoc -> RDoc +-- Specification: text "" <> nilBeside g p +-- = text "" <g> p + +nilBeside g 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 +\end{code} + +********************************************************* +* * +\subsection{Separate, @sep@, Hughes version} +* * +********************************************************* + +\begin{code} +-- Specification: sep ps = oneLiner (hsep ps) +-- `union` +-- vcat ps + +sep = sepX True -- Separate with spaces +cat = sepX False -- Don't + +sepX x [] = 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 -> INT -> [Doc] -> RDoc +sep1 g NoDoc k ys = 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 MINUS n) ys) + +sep1 g (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 MINUS sl) ys) + +-- 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 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 +\end{code} + +********************************************************* +* * +\subsection{@fill@} +* * +********************************************************* + +\begin{code} +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 g [] = empty +fill g (p:ps) = fill1 g (reduceDoc p) ILIT(0) ps + + +fill1 :: Bool -> RDoc -> INT -> [Doc] -> Doc +fill1 g NoDoc k ys = 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 MINUS 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 MINUS sl) ys) + +fillNB g (Nest _ p) k ys = fillNB g p k ys +fillNB g Empty k [] = 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 MINUS ILIT(1) + | otherwise = k + +fillNB g p k ys = fill1 g p k ys +\end{code} + + +********************************************************* +* * +\subsection{Selecting the best layout} +* * +********************************************************* + +\begin{code} +best :: Int -- Line length + -> Int -- Ribbon length + -> RDoc + -> RDoc -- No unions in here! + +best IBOX(w) IBOX(r) p + = get w p + where + get :: INT -- (Remaining) width of line + -> Doc -> Doc + get w Empty = Empty + get w 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 MINUS k) p) + get w (p `Union` q) = nicest w r (get w p) (get w q) + + 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 sl Empty = Empty + get1 w sl NoDoc = NoDoc + get1 w sl (NilAbove p) = nilAbove_ (get (w MINUS sl) p) + get1 w sl (TextBeside t tl p) = textBeside_ t tl (get1 w (sl PLUS tl) p) + get1 w sl (Nest k p) = get1 w sl p + get1 w sl (p `Union` q) = nicest1 w r sl (get1 w sl p) + (get1 w sl q) + +nicest w r p q = nicest1 w r ILIT(0) p q +nicest1 w r sl p q | fits ((w `minn` r) MINUS sl) p = p + | otherwise = q + +fits :: INT -- Space available + -> Doc + -> Bool -- True if *first line* of Doc fits in space available + +fits n p | n LT ILIT(0) = False +fits n NoDoc = False +fits n Empty = True +fits n (NilAbove _) = True +fits n (TextBeside _ sl p) = fits (n MINUS sl) p + +minn x y | x LT y = x + | otherwise = y +\end{code} + +@first@ and @nonEmptySet@ are similar to @nicest@ and @fits@, only simpler. +@first@ returns its first argument if it is non-empty, otherwise its second. + +\begin{code} +first p q | nonEmptySet p = p + | otherwise = q + +nonEmptySet NoDoc = False +nonEmptySet (p `Union` q) = True +nonEmptySet Empty = True +nonEmptySet (NilAbove p) = True -- NoDoc always in first line +nonEmptySet (TextBeside _ _ p) = nonEmptySet p +nonEmptySet (Nest _ p) = nonEmptySet p +\end{code} + +@oneLiner@ returns the one-line members of the given set of @Doc@s. + +\begin{code} +oneLiner :: Doc -> Doc +oneLiner NoDoc = NoDoc +oneLiner Empty = Empty +oneLiner (NilAbove p) = NoDoc +oneLiner (TextBeside s sl p) = textBeside_ s sl (oneLiner p) +oneLiner (Nest k p) = nest_ k (oneLiner p) +oneLiner (p `Union` q) = oneLiner p +\end{code} + + + +********************************************************* +* * +\subsection{Displaying the best layout} +* * +********************************************************* + + +\begin{code} +{- +renderStyle Style{mode, lineLength, ribbonsPerLine} doc + = fullRender mode lineLength ribbonsPerLine doc "" +-} + +render doc = showDocWith PageMode doc +showDoc doc rest = showDocWithAppend PageMode doc rest + +showDocWithAppend :: Mode -> Doc -> String -> String +showDocWithAppend mode doc rest = fullRender mode 100 1.5 string_txt rest doc + +showDocWith :: Mode -> Doc -> String +showDocWith mode doc = showDocWithAppend mode doc "" + +string_txt (Chr c) s = c:s +string_txt (Str s1) s2 = s1 ++ s2 +string_txt (PStr s1) s2 = unpackFS s1 ++ s2 +string_txt (LStr s1 _) s2 = unpackLitString s1 ++ s2 + +unpackLitString addr = + unpack 0# + where + unpack nh + | ch `eqChar#` '\0'# = [] + | otherwise = C# ch : unpack (nh +# 1#) + where + ch = indexCharOffAddr# addr nh +\end{code} + +\begin{code} + +fullRender OneLineMode _ _ txt end doc + = lay (reduceDoc doc) + where + lay NoDoc = cant_fail + lay (Union p q) = (lay q) -- Second arg can't be NoDoc + lay (Nest k p) = lay p + lay Empty = end + lay (NilAbove p) = space_text `txt` lay p -- NoDoc always on first line + lay (TextBeside s sl p) = s `txt` lay p + +fullRender LeftMode _ _ txt end doc + = lay (reduceDoc doc) + where + lay NoDoc = cant_fail + lay (Union p q) = lay (first p q) + lay (Nest k p) = lay p + lay Empty = end + lay (NilAbove p) = nl_text `txt` lay p -- NoDoc always on first line + lay (TextBeside s sl p) = s `txt` lay p + +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 -> MAXINT; other -> line_length } + +display mode IBOX(page_width) IBOX(ribbon_width) txt end doc + = case page_width MINUS ribbon_width of { gap_width -> + case gap_width DIV ILIT(2) of { shift -> + let + lay k (Nest k1 p) = lay (k PLUS k1) p + lay k Empty = end + + lay k (NilAbove p) = nl_text `txt` lay k p + + lay k (TextBeside s sl p) + = case mode of + ZigZagMode | k GREQ gap_width + -> nl_text `txt` ( + Str (multi_ch shift '/') `txt` ( + nl_text `txt` ( + lay1 (k MINUS shift) s sl p))) + + | k LT ILIT(0) + -> nl_text `txt` ( + Str (multi_ch shift '\\') `txt` ( + nl_text `txt` ( + lay1 (k PLUS shift) s sl p ))) + + other -> lay1 k s sl p + + lay1 k s sl p = Str (indent k) `txt` (s `txt` lay2 (k PLUS sl) p) + + lay2 k (NilAbove p) = nl_text `txt` lay k p + lay2 k (TextBeside s sl p) = s `txt` (lay2 (k PLUS sl) p) + lay2 k (Nest _ p) = lay2 k p + lay2 k Empty = end + in + lay ILIT(0) doc + }} + +cant_fail = error "easy_display: NoDoc" + +indent n | n GREQ ILIT(8) = '\t' : indent (n MINUS ILIT(8)) + | otherwise = spaces n + +multi_ch ILIT(0) ch = "" +multi_ch n ch = ch : multi_ch (n MINUS ILIT(1)) ch + +spaces ILIT(0) = "" +spaces n = ' ' : spaces (n MINUS ILIT(1)) +\end{code} + +\begin{code} +pprCols = (120 :: Int) -- could make configurable + +printDoc :: Mode -> Handle -> Doc -> IO () +printDoc LeftMode hdl doc + = do { printLeftRender hdl doc; hFlush hdl } +printDoc mode 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 = hPutFS hdl s >> next + put (LStr s l) next = hPutLitString hdl s l >> next + + done = hPutChar hdl '\n' + + -- some versions of hPutBuf will barf if the length is zero +hPutLitString handle a# 0# = return () +hPutLitString handle a# l# +#if __GLASGOW_HASKELL__ < 411 + = hPutBuf handle (A# a#) (I# l#) +#else + = hPutBuf handle (Ptr a#) (I# l#) +#endif + +-- 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 + layLeft b (reduceDoc doc) + bFlush b + +-- 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 b _ | b `seq` False = undefined -- make it strict in b +layLeft b NoDoc = cant_fail +layLeft b (Union p q) = return () >> layLeft b (first p q) +layLeft b (Nest k 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 sl 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 (LStr s l) = bPutLitString b s l + +#if __GLASGOW_HASKELL__ < 503 +hPutBuf = hPutBufFull +#endif + +\end{code} |