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"
182 import Numeric (fromRat)
183 import PrimPacked ( strLength )
186 #if __GLASGOW_HASKELL__ < 503
187 import IOExts ( hPutBufFull )
189 import System.IO ( hPutBuf )
192 import PrimPacked ( strLength )
194 -- Don't import Util( assertPanic ) because it makes a loop in the module structure
203 *********************************************************
205 \subsection{CPP magic so that we can compile with both GHC and Hugs}
207 *********************************************************
209 The library uses unboxed types to get a bit more speed, but these CPP macros
210 allow you to use either GHC or Hugs. To get GHC, just set the CPP variable
215 #if defined(__GLASGOW_HASKELL__)
219 -- Disable ASSERT checks; they are expensive!
220 #define LOCAL_ASSERT(x)
223 #define IBOX(x) (I# (x))
226 #define NEGATE negateInt#
231 #define DIV `quotInt#`
235 #define MAXINT maxBound
241 #define LOCAL_ASSERT(x)
246 #define NEGATE negate
255 #define MAXINT maxBound
262 *********************************************************
264 \subsection{The interface}
266 *********************************************************
268 The primitive @Doc@ values
272 isEmpty :: Doc -> Bool
273 text :: String -> Doc
276 semi, comma, colon, space, equals :: Doc
277 lparen, rparen, lbrack, rbrack, lbrace, rbrace :: Doc
279 parens, brackets, braces :: Doc -> Doc
280 quotes, doubleQuotes :: Doc -> Doc
283 integer :: Integer -> Doc
284 float :: Float -> Doc
285 double :: Double -> Doc
286 rational :: Rational -> Doc
289 Combining @Doc@ values
292 (<>) :: Doc -> Doc -> Doc -- Beside
293 hcat :: [Doc] -> Doc -- List version of <>
294 (<+>) :: Doc -> Doc -> Doc -- Beside, separated by space
295 hsep :: [Doc] -> Doc -- List version of <+>
297 ($$) :: Doc -> Doc -> Doc -- Above; if there is no
298 -- overlap it "dovetails" the two
299 vcat :: [Doc] -> Doc -- List version of $$
301 cat :: [Doc] -> Doc -- Either hcat or vcat
302 sep :: [Doc] -> Doc -- Either hsep or vcat
303 fcat :: [Doc] -> Doc -- ``Paragraph fill'' version of cat
304 fsep :: [Doc] -> Doc -- ``Paragraph fill'' version of sep
306 nest :: Int -> Doc -> Doc -- Nested
312 hang :: Doc -> Int -> Doc -> Doc
313 punctuate :: Doc -> [Doc] -> [Doc] -- punctuate p [d1, ... dn] = [d1 <> p, d2 <> p, ... dn-1 <> p, dn]
316 Displaying @Doc@ values.
319 instance SHOW Doc where
320 showsPrec prec doc cont = showDoc doc cont
322 render :: Doc -> String -- Uses default style
324 -> Int -- Line length
325 -> Float -- Ribbons per line
326 -> (TextDetails -> a -> a) -- What to do with text
327 -> a -- What to do at the end
331 {- When we start using 1.3
332 renderStyle :: Style -> Doc -> String
333 data Style = Style { lineLength :: Int, -- In chars
334 ribbonsPerLine :: Float, -- Ratio of ribbon length to line length
337 style :: Style -- The default style
338 style = Style { lineLength = 100, ribbonsPerLine = 2.5, mode = PageMode }
341 data Mode = PageMode -- Normal
342 | ZigZagMode -- With zig-zag cuts
343 | LeftMode -- No indentation, infinitely long lines
344 | OneLineMode -- All on one line
349 *********************************************************
351 \subsection{The @Doc@ calculus}
353 *********************************************************
355 The @Doc@ combinators satisfy the following laws:
359 <a1> (x $$ y) $$ z = x $$ (y $$ z)
367 <b1> (x <> y) <> z = x <> (y <> z)
368 <b2> empty <> x = empty
375 <t1> text s <> text t = text (s++t)
376 <t2> text "" <> x = x, if x non-empty
381 <n2> nest k (nest k' x) = nest (k+k') x
382 <n3> nest k (x <> y) = nest k z <> nest k y
383 <n4> nest k (x $$ y) = nest k x $$ nest k y
384 <n5> nest k empty = empty
385 <n6> x <> nest k y = x <> y, if x non-empty
387 ** Note the side condition on <n6>! It is this that
388 ** makes it OK for empty to be a left unit for <>.
392 <m1> (text s <> x) $$ y = text s <> ((text "" <> x)) $$
395 <m2> (x $$ y) <> z = x $$ (y <> z)
399 Laws for list versions
400 ~~~~~~~~~~~~~~~~~~~~~~
401 <l1> sep (ps++[empty]++qs) = sep (ps ++ qs)
402 ...ditto hsep, hcat, vcat, fill...
404 <l2> nest k (sep ps) = sep (map (nest k) ps)
405 ...ditto hsep, hcat, vcat, fill...
409 <o1> oneLiner (nest k p) = nest k (oneLiner p)
410 <o2> oneLiner (x <> y) = oneLiner x <> oneLiner y
414 You might think that the following verion of <m1> would
417 <3 NO> (text s <> x) $$ y = text s <> ((empty <> x)) $$
420 But it doesn't work, for if x=empty, we would have
422 text s $$ y = text s <> (empty $$ nest (-length s) y)
423 = text s <> nest (-length s) y
428 *********************************************************
430 \subsection{Simple derived definitions}
432 *********************************************************
447 int n = text (show n)
448 integer n = text (show n)
449 float n = text (show n)
450 double n = text (show n)
451 rational n = text (show (fromRat n))
452 --rational n = text (show (fromRationalX n)) -- _showRational 30 n)
454 quotes p = char '`' <> p <> char '\''
455 doubleQuotes p = char '"' <> p <> char '"'
456 parens p = char '(' <> p <> char ')'
457 brackets p = char '[' <> p <> char ']'
458 braces p = char '{' <> p <> char '}'
461 hcat = foldr (<>) empty
462 hsep = foldr (<+>) empty
463 vcat = foldr ($$) empty
465 hang d1 n d2 = sep [d1, nest n d2]
468 punctuate p (d:ds) = go d ds
471 go d (e:es) = (d <> p) : go e es
475 *********************************************************
477 \subsection{The @Doc@ data type}
479 *********************************************************
481 A @Doc@ represents a {\em set} of layouts. A @Doc@ with
482 no occurrences of @Union@ or @NoDoc@ represents just one layout.
486 | NilAbove Doc -- text "" $$ x
487 | TextBeside TextDetails INT Doc -- text s <> x
488 | Nest INT Doc -- nest k x
489 | Union Doc Doc -- ul `union` ur
490 | NoDoc -- The empty set of documents
491 | Beside Doc Bool Doc -- True <=> space between
492 | Above Doc Bool Doc -- True <=> never overlap
494 type RDoc = Doc -- RDoc is a "reduced Doc", guaranteed not to have a top-level Above or Beside
497 reduceDoc :: Doc -> RDoc
498 reduceDoc (Beside p g q) = beside p g (reduceDoc q)
499 reduceDoc (Above p g q) = above p g (reduceDoc q)
503 data TextDetails = Chr Char
505 | PStr FastString -- a hashed string
506 | LStr Addr# Int# -- a '\0'-terminated array of bytes
512 Here are the invariants:
515 The argument of @NilAbove@ is never @Empty@. Therefore
516 a @NilAbove@ occupies at least two lines.
519 The arugment of @TextBeside@ is never @Nest@.
522 The layouts of the two arguments of @Union@ both flatten to the same string.
525 The arguments of @Union@ are either @TextBeside@, or @NilAbove@.
528 The right argument of a union cannot be equivalent to the empty set (@NoDoc@).
529 If the left argument of a union is equivalent to the empty set (@NoDoc@),
530 then the @NoDoc@ appears in the first line.
533 An empty document is always represented by @Empty@.
534 It can't be hidden inside a @Nest@, or a @Union@ of two @Empty@s.
537 The first line of every layout in the left argument of @Union@
538 is longer than the first line of any layout in the right argument.
539 (1) ensures that the left argument has a first line. In view of (3),
540 this invariant means that the right argument must have at least two
545 -- Arg of a NilAbove is always an RDoc
546 nilAbove_ p = LOCAL_ASSERT( ok p ) NilAbove p
551 -- Arg of a TextBeside is always an RDoc
552 textBeside_ s sl p = TextBeside s sl (LOCAL_ASSERT( ok p ) p)
554 ok (Nest _ _) = False
557 -- Arg of Nest is always an RDoc
558 nest_ k p = Nest k (LOCAL_ASSERT( ok p ) p)
563 -- Args of union are always RDocs
564 union_ p q = Union (LOCAL_ASSERT( ok p ) p) (LOCAL_ASSERT( ok q ) q)
566 ok (TextBeside _ _ _) = True
567 ok (NilAbove _) = True
568 ok (Union _ _) = True
573 Notice the difference between
574 * NoDoc (no documents)
575 * Empty (one empty document; no height and no width)
576 * text "" (a document containing the empty string;
577 one line high, but has no width)
581 *********************************************************
583 \subsection{@empty@, @text@, @nest@, @union@}
585 *********************************************************
593 char c = textBeside_ (Chr c) 1# Empty
594 text s = case length s of {IBOX(sl) -> textBeside_ (Str s) sl Empty}
595 ftext s = case lengthFS s of {IBOX(sl) -> textBeside_ (PStr s) sl Empty}
596 ptext (A# s) = case strLength (A# s) of {IBOX(sl) -> textBeside_ (LStr s sl) sl Empty}
598 nest IBOX(k) p = mkNest k (reduceDoc p) -- Externally callable version
600 -- mkNest checks for Nest's invariant that it doesn't have an Empty inside it
601 mkNest k (Nest k1 p) = mkNest (k PLUS k1) p
602 mkNest k NoDoc = NoDoc
603 mkNest k Empty = Empty
604 mkNest ILIT(0) p = p -- Worth a try!
605 mkNest k p = nest_ k p
607 -- mkUnion checks for an empty document
608 mkUnion Empty q = Empty
609 mkUnion p q = p `union_` q
612 *********************************************************
614 \subsection{Vertical composition @$$@}
616 *********************************************************
620 p $$ q = Above p False q
621 p $+$ q = Above p True q
623 above :: Doc -> Bool -> RDoc -> RDoc
624 above (Above p g1 q1) g2 q2 = above p g1 (above q1 g2 q2)
625 above p@(Beside _ _ _) g q = aboveNest (reduceDoc p) g ILIT(0) (reduceDoc q)
626 above p g q = aboveNest p g ILIT(0) (reduceDoc q)
628 aboveNest :: RDoc -> Bool -> INT -> RDoc -> RDoc
629 -- Specfication: aboveNest p g k q = p $g$ (nest k q)
631 aboveNest NoDoc g k q = NoDoc
632 aboveNest (p1 `Union` p2) g k q = aboveNest p1 g k q `union_`
635 aboveNest Empty g k q = mkNest k q
636 aboveNest (Nest k1 p) g k q = nest_ k1 (aboveNest p g (k MINUS k1) q)
637 -- p can't be Empty, so no need for mkNest
639 aboveNest (NilAbove p) g k q = nilAbove_ (aboveNest p g k q)
640 aboveNest (TextBeside s sl p) g k q = textBeside_ s sl rest
644 Empty -> nilAboveNest g k1 q
645 other -> aboveNest p g k1 q
649 nilAboveNest :: Bool -> INT -> RDoc -> RDoc
650 -- Specification: text s <> nilaboveNest g k q
651 -- = text s <> (text "" $g$ nest k q)
653 nilAboveNest g k Empty = Empty -- Here's why the "text s <>" is in the spec!
654 nilAboveNest g k (Nest k1 q) = nilAboveNest g (k PLUS k1) q
656 nilAboveNest g k q | (not g) && (k GR ILIT(0)) -- No newline if no overlap
657 = textBeside_ (Str (spaces k)) k q
658 | otherwise -- Put them really above
659 = nilAbove_ (mkNest k q)
663 *********************************************************
665 \subsection{Horizontal composition @<>@}
667 *********************************************************
670 p <> q = Beside p False q
671 p <+> q = Beside p True q
673 beside :: Doc -> Bool -> RDoc -> RDoc
674 -- Specification: beside g p q = p <g> q
676 beside NoDoc g q = NoDoc
677 beside (p1 `Union` p2) g q = (beside p1 g q) `union_` (beside p2 g q)
679 beside (Nest k p) g q = nest_ k (beside p g q) -- p non-empty
680 beside p@(Beside p1 g1 q1) g2 q2
681 {- (A `op1` B) `op2` C == A `op1` (B `op2` C) iff op1 == op2
682 [ && (op1 == <> || op1 == <+>) ] -}
683 | g1 == g2 = beside p1 g1 (beside q1 g2 q2)
684 | otherwise = beside (reduceDoc p) g2 q2
685 beside p@(Above _ _ _) g q = beside (reduceDoc p) g q
686 beside (NilAbove p) g q = nilAbove_ (beside p g q)
687 beside (TextBeside s sl p) g q = textBeside_ s sl rest
690 Empty -> nilBeside g q
691 other -> beside p g q
695 nilBeside :: Bool -> RDoc -> RDoc
696 -- Specification: text "" <> nilBeside g p
699 nilBeside g Empty = Empty -- Hence the text "" in the spec
700 nilBeside g (Nest _ p) = nilBeside g p
701 nilBeside g p | g = textBeside_ space_text ILIT(1) p
705 *********************************************************
707 \subsection{Separate, @sep@, Hughes version}
709 *********************************************************
712 -- Specification: sep ps = oneLiner (hsep ps)
716 sep = sepX True -- Separate with spaces
717 cat = sepX False -- Don't
720 sepX x (p:ps) = sep1 x (reduceDoc p) ILIT(0) ps
723 -- Specification: sep1 g k ys = sep (x : map (nest k) ys)
724 -- = oneLiner (x <g> nest k (hsep ys))
725 -- `union` x $$ nest k (vcat ys)
727 sep1 :: Bool -> RDoc -> INT -> [Doc] -> RDoc
728 sep1 g NoDoc k ys = NoDoc
729 sep1 g (p `Union` q) k ys = sep1 g p k ys
731 (aboveNest q False k (reduceDoc (vcat ys)))
733 sep1 g Empty k ys = mkNest k (sepX g ys)
734 sep1 g (Nest n p) k ys = nest_ n (sep1 g p (k MINUS n) ys)
736 sep1 g (NilAbove p) k ys = nilAbove_ (aboveNest p False k (reduceDoc (vcat ys)))
737 sep1 g (TextBeside s sl p) k ys = textBeside_ s sl (sepNB g p (k MINUS sl) ys)
739 -- Specification: sepNB p k ys = sep1 (text "" <> p) k ys
740 -- Called when we have already found some text in the first item
741 -- We have to eat up nests
743 sepNB g (Nest _ p) k ys = sepNB g p k ys
745 sepNB g Empty k ys = oneLiner (nilBeside g (reduceDoc rest))
747 nilAboveNest False k (reduceDoc (vcat ys))
750 | otherwise = hcat ys
752 sepNB g p k ys = sep1 g p k ys
755 *********************************************************
759 *********************************************************
768 -- fill (p1:p2:ps) = oneLiner p1 <#> nest (length p1)
769 -- (fill (oneLiner p2 : ps))
774 fill g (p:ps) = fill1 g (reduceDoc p) ILIT(0) ps
777 fill1 :: Bool -> RDoc -> INT -> [Doc] -> Doc
778 fill1 g NoDoc k ys = NoDoc
779 fill1 g (p `Union` q) k ys = fill1 g p k ys
781 (aboveNest q False k (fill g ys))
783 fill1 g Empty k ys = mkNest k (fill g ys)
784 fill1 g (Nest n p) k ys = nest_ n (fill1 g p (k MINUS n) ys)
786 fill1 g (NilAbove p) k ys = nilAbove_ (aboveNest p False k (fill g ys))
787 fill1 g (TextBeside s sl p) k ys = textBeside_ s sl (fillNB g p (k MINUS sl) ys)
789 fillNB g (Nest _ p) k ys = fillNB g p k ys
790 fillNB g Empty k [] = Empty
791 fillNB g Empty k (y:ys) = nilBeside g (fill1 g (oneLiner (reduceDoc y)) k1 ys)
793 nilAboveNest False k (fill g (y:ys))
795 k1 | g = k MINUS ILIT(1)
798 fillNB g p k ys = fill1 g p k ys
802 *********************************************************
804 \subsection{Selecting the best layout}
806 *********************************************************
809 best :: Int -- Line length
810 -> Int -- Ribbon length
812 -> RDoc -- No unions in here!
814 best IBOX(w) IBOX(r) p
817 get :: INT -- (Remaining) width of line
821 get w (NilAbove p) = nilAbove_ (get w p)
822 get w (TextBeside s sl p) = textBeside_ s sl (get1 w sl p)
823 get w (Nest k p) = nest_ k (get (w MINUS k) p)
824 get w (p `Union` q) = nicest w r (get w p) (get w q)
826 get1 :: INT -- (Remaining) width of line
827 -> INT -- Amount of first line already eaten up
828 -> Doc -- This is an argument to TextBeside => eat Nests
829 -> Doc -- No unions in here!
831 get1 w sl Empty = Empty
832 get1 w sl NoDoc = NoDoc
833 get1 w sl (NilAbove p) = nilAbove_ (get (w MINUS sl) p)
834 get1 w sl (TextBeside t tl p) = textBeside_ t tl (get1 w (sl PLUS tl) p)
835 get1 w sl (Nest k p) = get1 w sl p
836 get1 w sl (p `Union` q) = nicest1 w r sl (get1 w sl p)
839 nicest w r p q = nicest1 w r ILIT(0) p q
840 nicest1 w r sl p q | fits ((w `minn` r) MINUS sl) p = p
843 fits :: INT -- Space available
845 -> Bool -- True if *first line* of Doc fits in space available
847 fits n p | n LT ILIT(0) = False
850 fits n (NilAbove _) = True
851 fits n (TextBeside _ sl p) = fits (n MINUS sl) p
853 minn x y | x LT y = x
857 @first@ and @nonEmptySet@ are similar to @nicest@ and @fits@, only simpler.
858 @first@ returns its first argument if it is non-empty, otherwise its second.
861 first p q | nonEmptySet p = p
864 nonEmptySet NoDoc = False
865 nonEmptySet (p `Union` q) = True
866 nonEmptySet Empty = True
867 nonEmptySet (NilAbove p) = True -- NoDoc always in first line
868 nonEmptySet (TextBeside _ _ p) = nonEmptySet p
869 nonEmptySet (Nest _ p) = nonEmptySet p
872 @oneLiner@ returns the one-line members of the given set of @Doc@s.
875 oneLiner :: Doc -> Doc
876 oneLiner NoDoc = NoDoc
877 oneLiner Empty = Empty
878 oneLiner (NilAbove p) = NoDoc
879 oneLiner (TextBeside s sl p) = textBeside_ s sl (oneLiner p)
880 oneLiner (Nest k p) = nest_ k (oneLiner p)
881 oneLiner (p `Union` q) = oneLiner p
886 *********************************************************
888 \subsection{Displaying the best layout}
890 *********************************************************
895 renderStyle Style{mode, lineLength, ribbonsPerLine} doc
896 = fullRender mode lineLength ribbonsPerLine doc ""
899 render doc = showDocWith PageMode doc
900 showDoc doc rest = showDocWithAppend PageMode doc rest
902 showDocWithAppend :: Mode -> Doc -> String -> String
903 showDocWithAppend mode doc rest = fullRender mode 100 1.5 string_txt rest doc
905 showDocWith :: Mode -> Doc -> String
906 showDocWith mode doc = showDocWithAppend mode doc ""
908 string_txt (Chr c) s = c:s
909 string_txt (Str s1) s2 = s1 ++ s2
910 string_txt (PStr s1) s2 = unpackFS s1 ++ s2
911 string_txt (LStr s1 _) s2 = unpackLitString s1 ++ s2
913 unpackLitString addr =
917 | ch `eqChar#` '\0'# = []
918 | otherwise = C# ch : unpack (nh +# 1#)
920 ch = indexCharOffAddr# addr nh
925 fullRender OneLineMode _ _ txt end doc
926 = lay (reduceDoc doc)
928 lay NoDoc = cant_fail
929 lay (Union p q) = (lay q) -- Second arg can't be NoDoc
930 lay (Nest k p) = lay p
932 lay (NilAbove p) = space_text `txt` lay p -- NoDoc always on first line
933 lay (TextBeside s sl p) = s `txt` lay p
935 fullRender LeftMode _ _ txt end doc
936 = lay (reduceDoc doc)
938 lay NoDoc = cant_fail
939 lay (Union p q) = lay (first p q)
940 lay (Nest k p) = lay p
942 lay (NilAbove p) = nl_text `txt` lay p -- NoDoc always on first line
943 lay (TextBeside s sl p) = s `txt` lay p
945 fullRender mode line_length ribbons_per_line txt end doc
946 = display mode line_length ribbon_length txt end best_doc
948 best_doc = best hacked_line_length ribbon_length (reduceDoc doc)
950 hacked_line_length, ribbon_length :: Int
951 ribbon_length = round (fromIntegral line_length / ribbons_per_line)
952 hacked_line_length = case mode of { ZigZagMode -> MAXINT; other -> line_length }
954 display mode IBOX(page_width) IBOX(ribbon_width) txt end doc
955 = case page_width MINUS ribbon_width of { gap_width ->
956 case gap_width DIV ILIT(2) of { shift ->
958 lay k (Nest k1 p) = lay (k PLUS k1) p
961 lay k (NilAbove p) = nl_text `txt` lay k p
963 lay k (TextBeside s sl p)
965 ZigZagMode | k GREQ gap_width
967 Str (multi_ch shift '/') `txt` (
969 lay1 (k MINUS shift) s sl p)))
973 Str (multi_ch shift '\\') `txt` (
975 lay1 (k PLUS shift) s sl p )))
977 other -> lay1 k s sl p
979 lay1 k s sl p = Str (indent k) `txt` (s `txt` lay2 (k PLUS sl) p)
981 lay2 k (NilAbove p) = nl_text `txt` lay k p
982 lay2 k (TextBeside s sl p) = s `txt` (lay2 (k PLUS sl) p)
983 lay2 k (Nest _ p) = lay2 k p
989 cant_fail = error "easy_display: NoDoc"
991 indent n | n GREQ ILIT(8) = '\t' : indent (n MINUS ILIT(8))
992 | otherwise = spaces n
994 multi_ch ILIT(0) ch = ""
995 multi_ch n ch = ch : multi_ch (n MINUS ILIT(1)) ch
998 spaces n = ' ' : spaces (n MINUS ILIT(1))
1002 pprCols = (100 :: Int) -- could make configurable
1004 printDoc :: Mode -> Handle -> Doc -> IO ()
1005 printDoc mode hdl doc
1006 = fullRender mode pprCols 1.5 put done doc
1008 put (Chr c) next = hPutChar hdl c >> next
1009 put (Str s) next = hPutStr hdl s >> next
1010 put (PStr s) next = hPutFS hdl s >> next
1011 put (LStr s l) next = hPutLitString hdl s l >> next
1013 done = hPutChar hdl '\n'
1015 #if __GLASGOW_HASKELL__ < 503
1016 hPutBuf = hPutBufFull
1019 hPutLitString handle a# l#
1020 #if __GLASGOW_HASKELL__ < 411
1021 = hPutBuf handle (A# a#) (I# l#)
1023 = hPutBuf handle (Ptr a#) (I# l#)