1 *********************************************************************************
3 * John Hughes's and Simon Peyton Jones's Pretty Printer Combinators *
5 * based on "The Design of a Pretty-printing Library" *
6 * in Advanced Functional Programming, *
7 * Johan Jeuring and Erik Meijer (eds), LNCS 925 *
8 * http://www.cs.chalmers.se/~rjmh/Papers/pretty.ps *
10 * Heavily modified by Simon Peyton Jones, Dec 96 *
12 *********************************************************************************
14 Version 3.0 28 May 1997
15 * Cured massive performance bug. If you write
17 foldl <> empty (map (text.show) [1..10000])
19 you get quadratic behaviour with V2.0. Why? For just the same reason as you get
20 quadratic behaviour with left-associated (++) chains.
22 This is really bad news. One thing a pretty-printer abstraction should
23 certainly guarantee is insensivity to associativity. It matters: suddenly
24 GHC's compilation times went up by a factor of 100 when I switched to the
27 I fixed it with a bit of a hack (because I wanted to get GHC back on the
28 road). I added two new constructors to the Doc type, Above and Beside:
33 Then, where I need to get to a "TextBeside" or "NilAbove" form I "force"
34 the Doc to squeeze out these suspended calls to Beside and Above; but in so
35 doing I re-associate. It's quite simple, but I'm not satisfied that I've done
36 the best possible job. I'll send you the code if you are interested.
40 int, integer, float, double, rational,
41 lparen, rparen, lbrack, rbrack, lbrace, rbrace,
43 * fullRender's type signature has changed. Rather than producing a string it
44 now takes an extra couple of arguments that tells it how to glue fragments
49 -> Float -- Ribbons per line
50 -> (TextDetails -> a -> a) -- What to do with text
51 -> a -- What to do at the end
55 The "fragments" are encapsulated in the TextDetails data type:
56 data TextDetails = Chr Char
60 The Chr and Str constructors are obvious enough. The PStr constructor has a packed
61 string (FastString) inside it. It's generated by using the new "ptext" export.
63 An advantage of this new setup is that you can get the renderer to do output
64 directly (by passing in a function of type (TextDetails -> IO () -> IO ()),
65 rather than producing a string that you then print.
68 Version 2.0 24 April 1997
69 * Made empty into a left unit for <> as well as a right unit;
70 it is also now true that
72 which wasn't true before.
74 * Fixed an obscure bug in sep that occassionally gave very wierd behaviour
78 * Corrected and tidied up the laws and invariants
80 ======================================================================
81 Relative to John's original paper, there are the following new features:
83 1. There's an empty document, "empty". It's a left and right unit for
84 both <> and $$, and anywhere in the argument list for
85 sep, hcat, hsep, vcat, fcat etc.
87 It is Really Useful in practice.
89 2. There is a paragraph-fill combinator, fsep, that's much like sep,
90 only it keeps fitting things on one line until itc can't fit any more.
92 3. Some random useful extra combinators are provided.
93 <+> puts its arguments beside each other with a space between them,
94 unless either argument is empty in which case it returns the other
97 hcat is a list version of <>
98 hsep is a list version of <+>
99 vcat is a list version of $$
101 sep (separate) is either like hsep or like vcat, depending on what fits
103 cat is behaves like sep, but it uses <> for horizontal conposition
104 fcat is behaves like fsep, but it uses <> for horizontal conposition
106 These new ones do the obvious things:
107 char, semi, comma, colon, space,
108 parens, brackets, braces,
111 4. The "above" combinator, $$, now overlaps its two arguments if the
112 last line of the top argument stops before the first line of the second begins.
113 For example: text "hi" $$ nest 5 "there"
120 There are two places this is really useful
122 a) When making labelled blocks, like this:
123 Left -> code for left
124 Right -> code for right
126 code for longlonglonglabel
127 The block is on the same line as the label if the label is
128 short, but on the next line otherwise.
130 b) When laying out lists like this:
135 which some people like. But if the list fits on one line
136 you want [first, second, third]. You can't do this with
137 John's original combinators, but it's quite easy with the
140 The combinator $+$ gives the original "never-overlap" behaviour.
142 5. Several different renderers are provided:
144 * one that uses cut-marks to avoid deeply-nested documents
145 simply piling up in the right-hand margin
146 * one that ignores indentation (fewer chars output; good for machines)
147 * one that ignores indentation and newlines (ditto, only more so)
149 6. Numerous implementation tidy-ups
150 Use of unboxed data types to speed up the implementation
157 Mode(..), TextDetails(..),
159 empty, isEmpty, nest,
161 text, char, ftext, ptext,
162 int, integer, float, double, rational,
163 parens, brackets, braces, quotes, doubleQuotes,
164 semi, comma, colon, space, equals,
165 lparen, rparen, lbrack, rbrack, lbrace, rbrace,
167 (<>), (<+>), hcat, hsep,
174 -- renderStyle, -- Haskell 1.3 only
175 render, fullRender, printDoc, showDocWith
178 #include "HsVersions.h"
185 import Numeric (fromRat)
188 import GHC.Base ( unpackCString# )
189 import GHC.Ptr ( Ptr(..) )
191 -- Don't import Util( assertPanic ) because it makes a loop in the module structure
200 *********************************************************
202 \subsection{CPP magic so that we can compile with both GHC and Hugs}
204 *********************************************************
206 The library uses unboxed types to get a bit more speed, but these CPP macros
207 allow you to use either GHC or Hugs. To get GHC, just set the CPP variable
212 #if defined(__GLASGOW_HASKELL__)
216 -- Disable ASSERT checks; they are expensive!
217 #define LOCAL_ASSERT(x)
220 #define IBOX(x) (I# (x))
223 #define NEGATE negateInt#
229 #define DIV `quotInt#`
233 #define MAXINT maxBound
239 #define LOCAL_ASSERT(x)
244 #define NEGATE negate
253 #define MAXINT maxBound
260 *********************************************************
262 \subsection{The interface}
264 *********************************************************
266 The primitive @Doc@ values
270 isEmpty :: Doc -> Bool
271 text :: String -> Doc
274 semi, comma, colon, space, equals :: Doc
275 lparen, rparen, lbrack, rbrack, lbrace, rbrace :: Doc
277 parens, brackets, braces :: Doc -> Doc
278 quotes, doubleQuotes :: Doc -> Doc
281 integer :: Integer -> Doc
282 float :: Float -> Doc
283 double :: Double -> Doc
284 rational :: Rational -> Doc
287 Combining @Doc@ values
290 (<>) :: Doc -> Doc -> Doc -- Beside
291 hcat :: [Doc] -> Doc -- List version of <>
292 (<+>) :: Doc -> Doc -> Doc -- Beside, separated by space
293 hsep :: [Doc] -> Doc -- List version of <+>
295 ($$) :: Doc -> Doc -> Doc -- Above; if there is no
296 -- overlap it "dovetails" the two
297 vcat :: [Doc] -> Doc -- List version of $$
299 cat :: [Doc] -> Doc -- Either hcat or vcat
300 sep :: [Doc] -> Doc -- Either hsep or vcat
301 fcat :: [Doc] -> Doc -- ``Paragraph fill'' version of cat
302 fsep :: [Doc] -> Doc -- ``Paragraph fill'' version of sep
304 nest :: Int -> Doc -> Doc -- Nested
310 hang :: Doc -> Int -> Doc -> Doc
311 punctuate :: Doc -> [Doc] -> [Doc] -- punctuate p [d1, ... dn] = [d1 <> p, d2 <> p, ... dn-1 <> p, dn]
314 Displaying @Doc@ values.
317 instance SHOW Doc where
318 showsPrec prec doc cont = showDoc doc cont
320 render :: Doc -> String -- Uses default style
322 -> Int -- Line length
323 -> Float -- Ribbons per line
324 -> (TextDetails -> a -> a) -- What to do with text
325 -> a -- What to do at the end
329 {- When we start using 1.3
330 renderStyle :: Style -> Doc -> String
331 data Style = Style { lineLength :: Int, -- In chars
332 ribbonsPerLine :: Float, -- Ratio of ribbon length to line length
335 style :: Style -- The default style
336 style = Style { lineLength = 100, ribbonsPerLine = 2.5, mode = PageMode }
339 data Mode = PageMode -- Normal
340 | ZigZagMode -- With zig-zag cuts
341 | LeftMode -- No indentation, infinitely long lines
342 | OneLineMode -- All on one line
347 *********************************************************
349 \subsection{The @Doc@ calculus}
351 *********************************************************
353 The @Doc@ combinators satisfy the following laws:
357 <a1> (x $$ y) $$ z = x $$ (y $$ z)
365 <b1> (x <> y) <> z = x <> (y <> z)
366 <b2> empty <> x = empty
373 <t1> text s <> text t = text (s++t)
374 <t2> text "" <> x = x, if x non-empty
379 <n2> nest k (nest k' x) = nest (k+k') x
380 <n3> nest k (x <> y) = nest k z <> nest k y
381 <n4> nest k (x $$ y) = nest k x $$ nest k y
382 <n5> nest k empty = empty
383 <n6> x <> nest k y = x <> y, if x non-empty
385 ** Note the side condition on <n6>! It is this that
386 ** makes it OK for empty to be a left unit for <>.
390 <m1> (text s <> x) $$ y = text s <> ((text "" <> x)) $$
393 <m2> (x $$ y) <> z = x $$ (y <> z)
397 Laws for list versions
398 ~~~~~~~~~~~~~~~~~~~~~~
399 <l1> sep (ps++[empty]++qs) = sep (ps ++ qs)
400 ...ditto hsep, hcat, vcat, fill...
402 <l2> nest k (sep ps) = sep (map (nest k) ps)
403 ...ditto hsep, hcat, vcat, fill...
407 <o1> oneLiner (nest k p) = nest k (oneLiner p)
408 <o2> oneLiner (x <> y) = oneLiner x <> oneLiner y
412 You might think that the following verion of <m1> would
415 <3 NO> (text s <> x) $$ y = text s <> ((empty <> x)) $$
418 But it doesn't work, for if x=empty, we would have
420 text s $$ y = text s <> (empty $$ nest (-length s) y)
421 = text s <> nest (-length s) y
426 *********************************************************
428 \subsection{Simple derived definitions}
430 *********************************************************
445 int n = text (show n)
446 integer n = text (show n)
447 float n = text (show n)
448 double n = text (show n)
449 rational n = text (show (fromRat n))
450 --rational n = text (show (fromRationalX n)) -- _showRational 30 n)
452 quotes p = char '`' <> p <> char '\''
453 doubleQuotes p = char '"' <> p <> char '"'
454 parens p = char '(' <> p <> char ')'
455 brackets p = char '[' <> p <> char ']'
456 braces p = char '{' <> p <> char '}'
459 hcat = foldr (<>) empty
460 hsep = foldr (<+>) empty
461 vcat = foldr ($$) empty
463 hang d1 n d2 = sep [d1, nest n d2]
466 punctuate p (d:ds) = go d ds
469 go d (e:es) = (d <> p) : go e es
473 *********************************************************
475 \subsection{The @Doc@ data type}
477 *********************************************************
479 A @Doc@ represents a {\em set} of layouts. A @Doc@ with
480 no occurrences of @Union@ or @NoDoc@ represents just one layout.
484 | NilAbove Doc -- text "" $$ x
485 | TextBeside !TextDetails INT Doc -- text s <> x
486 | Nest INT Doc -- nest k x
487 | Union Doc Doc -- ul `union` ur
488 | NoDoc -- The empty set of documents
489 | Beside Doc Bool Doc -- True <=> space between
490 | Above Doc Bool Doc -- True <=> never overlap
492 type RDoc = Doc -- RDoc is a "reduced Doc", guaranteed not to have a top-level Above or Beside
495 reduceDoc :: Doc -> RDoc
496 reduceDoc (Beside p g q) = beside p g (reduceDoc q)
497 reduceDoc (Above p g q) = above p g (reduceDoc q)
501 data TextDetails = Chr {-#UNPACK#-}!Char
503 | PStr FastString -- a hashed string
504 | LStr Addr# Int# -- a '\0'-terminated array of bytes
510 Here are the invariants:
513 The argument of @NilAbove@ is never @Empty@. Therefore
514 a @NilAbove@ occupies at least two lines.
517 The arugment of @TextBeside@ is never @Nest@.
520 The layouts of the two arguments of @Union@ both flatten to the same string.
523 The arguments of @Union@ are either @TextBeside@, or @NilAbove@.
526 The right argument of a union cannot be equivalent to the empty set (@NoDoc@).
527 If the left argument of a union is equivalent to the empty set (@NoDoc@),
528 then the @NoDoc@ appears in the first line.
531 An empty document is always represented by @Empty@.
532 It can't be hidden inside a @Nest@, or a @Union@ of two @Empty@s.
535 The first line of every layout in the left argument of @Union@
536 is longer than the first line of any layout in the right argument.
537 (1) ensures that the left argument has a first line. In view of (3),
538 this invariant means that the right argument must have at least two
543 -- Arg of a NilAbove is always an RDoc
544 nilAbove_ p = LOCAL_ASSERT( ok p ) NilAbove p
549 -- Arg of a TextBeside is always an RDoc
550 textBeside_ s sl p = TextBeside s sl (LOCAL_ASSERT( ok p ) p)
552 ok (Nest _ _) = False
555 -- Arg of Nest is always an RDoc
556 nest_ k p = Nest k (LOCAL_ASSERT( ok p ) p)
561 -- Args of union are always RDocs
562 union_ p q = Union (LOCAL_ASSERT( ok p ) p) (LOCAL_ASSERT( ok q ) q)
564 ok (TextBeside _ _ _) = True
565 ok (NilAbove _) = True
566 ok (Union _ _) = True
571 Notice the difference between
572 * NoDoc (no documents)
573 * Empty (one empty document; no height and no width)
574 * text "" (a document containing the empty string;
575 one line high, but has no width)
579 *********************************************************
581 \subsection{@empty@, @text@, @nest@, @union@}
583 *********************************************************
591 char c = textBeside_ (Chr c) 1# Empty
592 text s = case length s of {IBOX(sl) -> textBeside_ (Str s) sl Empty}
593 ftext s = case lengthFS s of {IBOX(sl) -> textBeside_ (PStr s) sl Empty}
594 ptext (Ptr s) = case strLength (Ptr s) of {IBOX(sl) -> textBeside_ (LStr s sl) sl Empty}
596 -- RULE that turns (text "abc") into (ptext (A# "abc"#)) to avoid the
597 -- intermediate packing/unpacking of the string.
599 "text/str" forall a. text (unpackCString# a) = ptext (Ptr a)
602 nest IBOX(k) p = mkNest k (reduceDoc p) -- Externally callable version
604 -- mkNest checks for Nest's invariant that it doesn't have an Empty inside it
605 mkNest k (Nest k1 p) = mkNest (k PLUS k1) p
606 mkNest k NoDoc = NoDoc
607 mkNest k Empty = Empty
608 mkNest ILIT(0) p = p -- Worth a try!
609 mkNest k p = nest_ k p
611 -- mkUnion checks for an empty document
612 mkUnion Empty q = Empty
613 mkUnion p q = p `union_` q
616 *********************************************************
618 \subsection{Vertical composition @$$@}
620 *********************************************************
624 p $$ q = Above p False q
625 p $+$ q = Above p True q
627 above :: Doc -> Bool -> RDoc -> RDoc
628 above (Above p g1 q1) g2 q2 = above p g1 (above q1 g2 q2)
629 above p@(Beside _ _ _) g q = aboveNest (reduceDoc p) g ILIT(0) (reduceDoc q)
630 above p g q = aboveNest p g ILIT(0) (reduceDoc q)
632 aboveNest :: RDoc -> Bool -> INT -> RDoc -> RDoc
633 -- Specfication: aboveNest p g k q = p $g$ (nest k q)
635 aboveNest NoDoc g k q = NoDoc
636 aboveNest (p1 `Union` p2) g k q = aboveNest p1 g k q `union_`
639 aboveNest Empty g k q = mkNest k q
640 aboveNest (Nest k1 p) g k q = nest_ k1 (aboveNest p g (k MINUS k1) q)
641 -- p can't be Empty, so no need for mkNest
643 aboveNest (NilAbove p) g k q = nilAbove_ (aboveNest p g k q)
644 aboveNest (TextBeside s sl p) g k q = textBeside_ s sl rest
648 Empty -> nilAboveNest g k1 q
649 other -> aboveNest p g k1 q
653 nilAboveNest :: Bool -> INT -> RDoc -> RDoc
654 -- Specification: text s <> nilaboveNest g k q
655 -- = text s <> (text "" $g$ nest k q)
657 nilAboveNest g k Empty = Empty -- Here's why the "text s <>" is in the spec!
658 nilAboveNest g k (Nest k1 q) = nilAboveNest g (k PLUS k1) q
660 nilAboveNest g k q | (not g) && (k GR ILIT(0)) -- No newline if no overlap
661 = textBeside_ (Str (spaces k)) k q
662 | otherwise -- Put them really above
663 = nilAbove_ (mkNest k q)
667 *********************************************************
669 \subsection{Horizontal composition @<>@}
671 *********************************************************
674 p <> q = Beside p False q
675 p <+> q = Beside p True q
677 beside :: Doc -> Bool -> RDoc -> RDoc
678 -- Specification: beside g p q = p <g> q
680 beside NoDoc g q = NoDoc
681 beside (p1 `Union` p2) g q = (beside p1 g q) `union_` (beside p2 g q)
683 beside (Nest k p) g q = nest_ k $! beside p g q -- p non-empty
684 beside p@(Beside p1 g1 q1) g2 q2
685 {- (A `op1` B) `op2` C == A `op1` (B `op2` C) iff op1 == op2
686 [ && (op1 == <> || op1 == <+>) ] -}
687 | g1 == g2 = beside p1 g1 $! beside q1 g2 q2
688 | otherwise = beside (reduceDoc p) g2 q2
689 beside p@(Above _ _ _) g q = let d = reduceDoc p in d `seq` beside d g q
690 beside (NilAbove p) g q = nilAbove_ $! beside p g q
691 beside (TextBeside s sl p) g q = textBeside_ s sl $! rest
694 Empty -> nilBeside g q
695 other -> beside p g q
699 nilBeside :: Bool -> RDoc -> RDoc
700 -- Specification: text "" <> nilBeside g p
703 nilBeside g Empty = Empty -- Hence the text "" in the spec
704 nilBeside g (Nest _ p) = nilBeside g p
705 nilBeside g p | g = textBeside_ space_text ILIT(1) p
709 *********************************************************
711 \subsection{Separate, @sep@, Hughes version}
713 *********************************************************
716 -- Specification: sep ps = oneLiner (hsep ps)
720 sep = sepX True -- Separate with spaces
721 cat = sepX False -- Don't
724 sepX x (p:ps) = sep1 x (reduceDoc p) ILIT(0) ps
727 -- Specification: sep1 g k ys = sep (x : map (nest k) ys)
728 -- = oneLiner (x <g> nest k (hsep ys))
729 -- `union` x $$ nest k (vcat ys)
731 sep1 :: Bool -> RDoc -> INT -> [Doc] -> RDoc
732 sep1 g NoDoc k ys = NoDoc
733 sep1 g (p `Union` q) k ys = sep1 g p k ys
735 (aboveNest q False k (reduceDoc (vcat ys)))
737 sep1 g Empty k ys = mkNest k (sepX g ys)
738 sep1 g (Nest n p) k ys = nest_ n (sep1 g p (k MINUS n) ys)
740 sep1 g (NilAbove p) k ys = nilAbove_ (aboveNest p False k (reduceDoc (vcat ys)))
741 sep1 g (TextBeside s sl p) k ys = textBeside_ s sl (sepNB g p (k MINUS sl) ys)
743 -- Specification: sepNB p k ys = sep1 (text "" <> p) k ys
744 -- Called when we have already found some text in the first item
745 -- We have to eat up nests
747 sepNB g (Nest _ p) k ys = sepNB g p k ys
749 sepNB g Empty k ys = oneLiner (nilBeside g (reduceDoc rest))
751 nilAboveNest False k (reduceDoc (vcat ys))
754 | otherwise = hcat ys
756 sepNB g p k ys = sep1 g p k ys
759 *********************************************************
763 *********************************************************
772 -- fill (p1:p2:ps) = oneLiner p1 <#> nest (length p1)
773 -- (fill (oneLiner p2 : ps))
778 fill g (p:ps) = fill1 g (reduceDoc p) ILIT(0) ps
781 fill1 :: Bool -> RDoc -> INT -> [Doc] -> Doc
782 fill1 g NoDoc k ys = NoDoc
783 fill1 g (p `Union` q) k ys = fill1 g p k ys
785 (aboveNest q False k (fill g ys))
787 fill1 g Empty k ys = mkNest k (fill g ys)
788 fill1 g (Nest n p) k ys = nest_ n (fill1 g p (k MINUS n) ys)
790 fill1 g (NilAbove p) k ys = nilAbove_ (aboveNest p False k (fill g ys))
791 fill1 g (TextBeside s sl p) k ys = textBeside_ s sl (fillNB g p (k MINUS sl) ys)
793 fillNB g (Nest _ p) k ys = fillNB g p k ys
794 fillNB g Empty k [] = Empty
795 fillNB g Empty k (y:ys) = nilBeside g (fill1 g (oneLiner (reduceDoc y)) k1 ys)
797 nilAboveNest False k (fill g (y:ys))
799 k1 | g = k MINUS ILIT(1)
802 fillNB g p k ys = fill1 g p k ys
806 *********************************************************
808 \subsection{Selecting the best layout}
810 *********************************************************
813 best :: Int -- Line length
814 -> Int -- Ribbon length
816 -> RDoc -- No unions in here!
818 best IBOX(w) IBOX(r) p
821 get :: INT -- (Remaining) width of line
825 get w (NilAbove p) = nilAbove_ (get w p)
826 get w (TextBeside s sl p) = textBeside_ s sl (get1 w sl p)
827 get w (Nest k p) = nest_ k (get (w MINUS k) p)
828 get w (p `Union` q) = nicest w r (get w p) (get w q)
830 get1 :: INT -- (Remaining) width of line
831 -> INT -- Amount of first line already eaten up
832 -> Doc -- This is an argument to TextBeside => eat Nests
833 -> Doc -- No unions in here!
835 get1 w sl Empty = Empty
836 get1 w sl NoDoc = NoDoc
837 get1 w sl (NilAbove p) = nilAbove_ (get (w MINUS sl) p)
838 get1 w sl (TextBeside t tl p) = textBeside_ t tl (get1 w (sl PLUS tl) p)
839 get1 w sl (Nest k p) = get1 w sl p
840 get1 w sl (p `Union` q) = nicest1 w r sl (get1 w sl p)
843 nicest w r p q = nicest1 w r ILIT(0) p q
844 nicest1 w r sl p q | fits ((w `minn` r) MINUS sl) p = p
847 fits :: INT -- Space available
849 -> Bool -- True if *first line* of Doc fits in space available
851 fits n p | n LT ILIT(0) = False
854 fits n (NilAbove _) = True
855 fits n (TextBeside _ sl p) = fits (n MINUS sl) p
857 minn x y | x LT y = x
861 @first@ and @nonEmptySet@ are similar to @nicest@ and @fits@, only simpler.
862 @first@ returns its first argument if it is non-empty, otherwise its second.
865 first p q | nonEmptySet p = p
868 nonEmptySet NoDoc = False
869 nonEmptySet (p `Union` q) = True
870 nonEmptySet Empty = True
871 nonEmptySet (NilAbove p) = True -- NoDoc always in first line
872 nonEmptySet (TextBeside _ _ p) = nonEmptySet p
873 nonEmptySet (Nest _ p) = nonEmptySet p
876 @oneLiner@ returns the one-line members of the given set of @Doc@s.
879 oneLiner :: Doc -> Doc
880 oneLiner NoDoc = NoDoc
881 oneLiner Empty = Empty
882 oneLiner (NilAbove p) = NoDoc
883 oneLiner (TextBeside s sl p) = textBeside_ s sl (oneLiner p)
884 oneLiner (Nest k p) = nest_ k (oneLiner p)
885 oneLiner (p `Union` q) = oneLiner p
890 *********************************************************
892 \subsection{Displaying the best layout}
894 *********************************************************
899 renderStyle Style{mode, lineLength, ribbonsPerLine} doc
900 = fullRender mode lineLength ribbonsPerLine doc ""
903 render doc = showDocWith PageMode doc
904 showDoc doc rest = showDocWithAppend PageMode doc rest
906 showDocWithAppend :: Mode -> Doc -> String -> String
907 showDocWithAppend mode doc rest = fullRender mode 100 1.5 string_txt rest doc
909 showDocWith :: Mode -> Doc -> String
910 showDocWith mode doc = showDocWithAppend mode doc ""
912 string_txt (Chr c) s = c:s
913 string_txt (Str s1) s2 = s1 ++ s2
914 string_txt (PStr s1) s2 = unpackFS s1 ++ s2
915 string_txt (LStr s1 _) s2 = unpackLitString s1 ++ s2
917 unpackLitString addr =
921 | ch `eqChar#` '\0'# = []
922 | otherwise = C# ch : unpack (nh +# 1#)
924 ch = indexCharOffAddr# addr nh
929 fullRender OneLineMode _ _ txt end doc
930 = lay (reduceDoc doc)
932 lay NoDoc = cant_fail
933 lay (Union p q) = (lay q) -- Second arg can't be NoDoc
934 lay (Nest k p) = lay p
936 lay (NilAbove p) = space_text `txt` lay p -- NoDoc always on first line
937 lay (TextBeside s sl p) = s `txt` lay p
939 fullRender LeftMode _ _ txt end doc
940 = lay (reduceDoc doc)
942 lay NoDoc = cant_fail
943 lay (Union p q) = lay (first p q)
944 lay (Nest k p) = lay p
946 lay (NilAbove p) = nl_text `txt` lay p -- NoDoc always on first line
947 lay (TextBeside s sl p) = s `txt` lay p
949 fullRender mode line_length ribbons_per_line txt end doc
950 = display mode line_length ribbon_length txt end best_doc
952 best_doc = best hacked_line_length ribbon_length (reduceDoc doc)
954 hacked_line_length, ribbon_length :: Int
955 ribbon_length = round (fromIntegral line_length / ribbons_per_line)
956 hacked_line_length = case mode of { ZigZagMode -> MAXINT; other -> line_length }
958 display mode IBOX(page_width) IBOX(ribbon_width) txt end doc
959 = case page_width MINUS ribbon_width of { gap_width ->
960 case gap_width DIV ILIT(2) of { shift ->
962 lay k (Nest k1 p) = lay (k PLUS k1) p
965 lay k (NilAbove p) = nl_text `txt` lay k p
967 lay k (TextBeside s sl p)
969 ZigZagMode | k GREQ gap_width
971 Str (multi_ch shift '/') `txt` (
973 lay1 (k MINUS shift) s sl p)))
977 Str (multi_ch shift '\\') `txt` (
979 lay1 (k PLUS shift) s sl p )))
981 other -> lay1 k s sl p
983 lay1 k s sl p = Str (indent k) `txt` (s `txt` lay2 (k PLUS sl) p)
985 lay2 k (NilAbove p) = nl_text `txt` lay k p
986 lay2 k (TextBeside s sl p) = s `txt` (lay2 (k PLUS sl) p)
987 lay2 k (Nest _ p) = lay2 k p
993 cant_fail = error "easy_display: NoDoc"
995 indent n | n GREQ ILIT(8) = '\t' : indent (n MINUS ILIT(8))
996 | otherwise = spaces n
998 multi_ch n ch | n LTEQ ILIT(0) = ""
999 | otherwise = ch : multi_ch (n MINUS ILIT(1)) ch
1001 spaces n | n LTEQ ILIT(0) = ""
1002 | otherwise = ' ' : spaces (n MINUS ILIT(1))
1006 pprCols = (120 :: Int) -- could make configurable
1008 printDoc :: Mode -> Handle -> Doc -> IO ()
1009 printDoc LeftMode hdl doc
1010 = do { printLeftRender hdl doc; hFlush hdl }
1011 printDoc mode hdl doc
1012 = do { fullRender mode pprCols 1.5 put done doc ;
1015 put (Chr c) next = hPutChar hdl c >> next
1016 put (Str s) next = hPutStr hdl s >> next
1017 put (PStr s) next = hPutFS hdl s >> next
1018 put (LStr s l) next = hPutLitString hdl s l >> next
1020 done = hPutChar hdl '\n'
1022 -- some versions of hPutBuf will barf if the length is zero
1023 hPutLitString handle a# 0# = return ()
1024 hPutLitString handle a# l#
1025 #if __GLASGOW_HASKELL__ < 411
1026 = hPutBuf handle (A# a#) (I# l#)
1028 = hPutBuf handle (Ptr a#) (I# l#)
1031 -- Printing output in LeftMode is performance critical: it's used when
1032 -- dumping C and assembly output, so we allow ourselves a few dirty
1035 -- (1) we specialise fullRender for LeftMode with IO output.
1037 -- (2) we add a layer of buffering on top of Handles. Handles
1038 -- don't perform well with lots of hPutChars, which is mostly
1039 -- what we're doing here, because Handles have to be thread-safe
1040 -- and async exception-safe. We only have a single thread and don't
1041 -- care about exceptions, so we add a layer of fast buffering
1042 -- over the Handle interface.
1044 -- (3) a few hacks in layLeft below to convince GHC to generate the right
1047 printLeftRender :: Handle -> Doc -> IO ()
1048 printLeftRender hdl doc = do
1049 b <- newBufHandle hdl
1050 layLeft b (reduceDoc doc)
1053 -- HACK ALERT! the "return () >>" below convinces GHC to eta-expand
1054 -- this function with the IO state lambda. Otherwise we end up with
1055 -- closures in all the case branches.
1056 layLeft b _ | b `seq` False = undefined -- make it strict in b
1057 layLeft b NoDoc = cant_fail
1058 layLeft b (Union p q) = return () >> layLeft b (first p q)
1059 layLeft b (Nest k p) = return () >> layLeft b p
1060 layLeft b Empty = bPutChar b '\n'
1061 layLeft b (NilAbove p) = bPutChar b '\n' >> layLeft b p
1062 layLeft b (TextBeside s sl p) = put b s >> layLeft b p
1064 put b _ | b `seq` False = undefined
1065 put b (Chr c) = bPutChar b c
1066 put b (Str s) = bPutStr b s
1067 put b (PStr s) = bPutFS b s
1068 put b (LStr s l) = bPutLitString b s l
1070 #if __GLASGOW_HASKELL__ < 503
1071 hPutBuf = hPutBufFull