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 #if __GLASGOW_HASKELL__ < 503
193 import PrelBase ( unpackCString# )
195 import GHC.Base ( unpackCString# )
198 import PrimPacked ( strLength )
200 #if __GLASGOW_HASKELL__ < 411
201 import PrelAddr ( Addr(..) )
203 import Addr ( Addr(..) )
204 #if __GLASGOW_HASKELL__ < 503
205 import Ptr ( Ptr(..) )
207 import GHC.Ptr ( Ptr(..) )
211 -- Don't import Util( assertPanic ) because it makes a loop in the module structure
220 *********************************************************
222 \subsection{CPP magic so that we can compile with both GHC and Hugs}
224 *********************************************************
226 The library uses unboxed types to get a bit more speed, but these CPP macros
227 allow you to use either GHC or Hugs. To get GHC, just set the CPP variable
232 #if defined(__GLASGOW_HASKELL__)
236 -- Disable ASSERT checks; they are expensive!
237 #define LOCAL_ASSERT(x)
240 #define IBOX(x) (I# (x))
243 #define NEGATE negateInt#
248 #define DIV `quotInt#`
252 #define MAXINT maxBound
258 #define LOCAL_ASSERT(x)
263 #define NEGATE negate
272 #define MAXINT maxBound
279 *********************************************************
281 \subsection{The interface}
283 *********************************************************
285 The primitive @Doc@ values
289 isEmpty :: Doc -> Bool
290 text :: String -> Doc
293 semi, comma, colon, space, equals :: Doc
294 lparen, rparen, lbrack, rbrack, lbrace, rbrace :: Doc
296 parens, brackets, braces :: Doc -> Doc
297 quotes, doubleQuotes :: Doc -> Doc
300 integer :: Integer -> Doc
301 float :: Float -> Doc
302 double :: Double -> Doc
303 rational :: Rational -> Doc
306 Combining @Doc@ values
309 (<>) :: Doc -> Doc -> Doc -- Beside
310 hcat :: [Doc] -> Doc -- List version of <>
311 (<+>) :: Doc -> Doc -> Doc -- Beside, separated by space
312 hsep :: [Doc] -> Doc -- List version of <+>
314 ($$) :: Doc -> Doc -> Doc -- Above; if there is no
315 -- overlap it "dovetails" the two
316 vcat :: [Doc] -> Doc -- List version of $$
318 cat :: [Doc] -> Doc -- Either hcat or vcat
319 sep :: [Doc] -> Doc -- Either hsep or vcat
320 fcat :: [Doc] -> Doc -- ``Paragraph fill'' version of cat
321 fsep :: [Doc] -> Doc -- ``Paragraph fill'' version of sep
323 nest :: Int -> Doc -> Doc -- Nested
329 hang :: Doc -> Int -> Doc -> Doc
330 punctuate :: Doc -> [Doc] -> [Doc] -- punctuate p [d1, ... dn] = [d1 <> p, d2 <> p, ... dn-1 <> p, dn]
333 Displaying @Doc@ values.
336 instance SHOW Doc where
337 showsPrec prec doc cont = showDoc doc cont
339 render :: Doc -> String -- Uses default style
341 -> Int -- Line length
342 -> Float -- Ribbons per line
343 -> (TextDetails -> a -> a) -- What to do with text
344 -> a -- What to do at the end
348 {- When we start using 1.3
349 renderStyle :: Style -> Doc -> String
350 data Style = Style { lineLength :: Int, -- In chars
351 ribbonsPerLine :: Float, -- Ratio of ribbon length to line length
354 style :: Style -- The default style
355 style = Style { lineLength = 100, ribbonsPerLine = 2.5, mode = PageMode }
358 data Mode = PageMode -- Normal
359 | ZigZagMode -- With zig-zag cuts
360 | LeftMode -- No indentation, infinitely long lines
361 | OneLineMode -- All on one line
366 *********************************************************
368 \subsection{The @Doc@ calculus}
370 *********************************************************
372 The @Doc@ combinators satisfy the following laws:
376 <a1> (x $$ y) $$ z = x $$ (y $$ z)
384 <b1> (x <> y) <> z = x <> (y <> z)
385 <b2> empty <> x = empty
392 <t1> text s <> text t = text (s++t)
393 <t2> text "" <> x = x, if x non-empty
398 <n2> nest k (nest k' x) = nest (k+k') x
399 <n3> nest k (x <> y) = nest k z <> nest k y
400 <n4> nest k (x $$ y) = nest k x $$ nest k y
401 <n5> nest k empty = empty
402 <n6> x <> nest k y = x <> y, if x non-empty
404 ** Note the side condition on <n6>! It is this that
405 ** makes it OK for empty to be a left unit for <>.
409 <m1> (text s <> x) $$ y = text s <> ((text "" <> x)) $$
412 <m2> (x $$ y) <> z = x $$ (y <> z)
416 Laws for list versions
417 ~~~~~~~~~~~~~~~~~~~~~~
418 <l1> sep (ps++[empty]++qs) = sep (ps ++ qs)
419 ...ditto hsep, hcat, vcat, fill...
421 <l2> nest k (sep ps) = sep (map (nest k) ps)
422 ...ditto hsep, hcat, vcat, fill...
426 <o1> oneLiner (nest k p) = nest k (oneLiner p)
427 <o2> oneLiner (x <> y) = oneLiner x <> oneLiner y
431 You might think that the following verion of <m1> would
434 <3 NO> (text s <> x) $$ y = text s <> ((empty <> x)) $$
437 But it doesn't work, for if x=empty, we would have
439 text s $$ y = text s <> (empty $$ nest (-length s) y)
440 = text s <> nest (-length s) y
445 *********************************************************
447 \subsection{Simple derived definitions}
449 *********************************************************
464 int n = text (show n)
465 integer n = text (show n)
466 float n = text (show n)
467 double n = text (show n)
468 rational n = text (show (fromRat n))
469 --rational n = text (show (fromRationalX n)) -- _showRational 30 n)
471 quotes p = char '`' <> p <> char '\''
472 doubleQuotes p = char '"' <> p <> char '"'
473 parens p = char '(' <> p <> char ')'
474 brackets p = char '[' <> p <> char ']'
475 braces p = char '{' <> p <> char '}'
478 hcat = foldr (<>) empty
479 hsep = foldr (<+>) empty
480 vcat = foldr ($$) empty
482 hang d1 n d2 = sep [d1, nest n d2]
485 punctuate p (d:ds) = go d ds
488 go d (e:es) = (d <> p) : go e es
492 *********************************************************
494 \subsection{The @Doc@ data type}
496 *********************************************************
498 A @Doc@ represents a {\em set} of layouts. A @Doc@ with
499 no occurrences of @Union@ or @NoDoc@ represents just one layout.
503 | NilAbove Doc -- text "" $$ x
504 | TextBeside TextDetails INT Doc -- text s <> x
505 | Nest INT Doc -- nest k x
506 | Union Doc Doc -- ul `union` ur
507 | NoDoc -- The empty set of documents
508 | Beside Doc Bool Doc -- True <=> space between
509 | Above Doc Bool Doc -- True <=> never overlap
511 type RDoc = Doc -- RDoc is a "reduced Doc", guaranteed not to have a top-level Above or Beside
514 reduceDoc :: Doc -> RDoc
515 reduceDoc (Beside p g q) = beside p g (reduceDoc q)
516 reduceDoc (Above p g q) = above p g (reduceDoc q)
520 data TextDetails = Chr Char
522 | PStr FastString -- a hashed string
523 | LStr Addr# Int# -- a '\0'-terminated array of bytes
529 Here are the invariants:
532 The argument of @NilAbove@ is never @Empty@. Therefore
533 a @NilAbove@ occupies at least two lines.
536 The arugment of @TextBeside@ is never @Nest@.
539 The layouts of the two arguments of @Union@ both flatten to the same string.
542 The arguments of @Union@ are either @TextBeside@, or @NilAbove@.
545 The right argument of a union cannot be equivalent to the empty set (@NoDoc@).
546 If the left argument of a union is equivalent to the empty set (@NoDoc@),
547 then the @NoDoc@ appears in the first line.
550 An empty document is always represented by @Empty@.
551 It can't be hidden inside a @Nest@, or a @Union@ of two @Empty@s.
554 The first line of every layout in the left argument of @Union@
555 is longer than the first line of any layout in the right argument.
556 (1) ensures that the left argument has a first line. In view of (3),
557 this invariant means that the right argument must have at least two
562 -- Arg of a NilAbove is always an RDoc
563 nilAbove_ p = LOCAL_ASSERT( ok p ) NilAbove p
568 -- Arg of a TextBeside is always an RDoc
569 textBeside_ s sl p = TextBeside s sl (LOCAL_ASSERT( ok p ) p)
571 ok (Nest _ _) = False
574 -- Arg of Nest is always an RDoc
575 nest_ k p = Nest k (LOCAL_ASSERT( ok p ) p)
580 -- Args of union are always RDocs
581 union_ p q = Union (LOCAL_ASSERT( ok p ) p) (LOCAL_ASSERT( ok q ) q)
583 ok (TextBeside _ _ _) = True
584 ok (NilAbove _) = True
585 ok (Union _ _) = True
590 Notice the difference between
591 * NoDoc (no documents)
592 * Empty (one empty document; no height and no width)
593 * text "" (a document containing the empty string;
594 one line high, but has no width)
598 *********************************************************
600 \subsection{@empty@, @text@, @nest@, @union@}
602 *********************************************************
610 char c = textBeside_ (Chr c) 1# Empty
611 text s = case length s of {IBOX(sl) -> textBeside_ (Str s) sl Empty}
612 ftext s = case lengthFS s of {IBOX(sl) -> textBeside_ (PStr s) sl Empty}
613 ptext (A# s) = case strLength (A# s) of {IBOX(sl) -> textBeside_ (LStr s sl) sl Empty}
615 -- RULE that turns (text "abc") into (ptext (A# "abc"#)) to avoid the
616 -- intermediate packing/unpacking of the string.
618 "text/str" forall a. text (unpackCString# a) = ptext (A# a)
621 nest IBOX(k) p = mkNest k (reduceDoc p) -- Externally callable version
623 -- mkNest checks for Nest's invariant that it doesn't have an Empty inside it
624 mkNest k (Nest k1 p) = mkNest (k PLUS k1) p
625 mkNest k NoDoc = NoDoc
626 mkNest k Empty = Empty
627 mkNest ILIT(0) p = p -- Worth a try!
628 mkNest k p = nest_ k p
630 -- mkUnion checks for an empty document
631 mkUnion Empty q = Empty
632 mkUnion p q = p `union_` q
635 *********************************************************
637 \subsection{Vertical composition @$$@}
639 *********************************************************
643 p $$ q = Above p False q
644 p $+$ q = Above p True q
646 above :: Doc -> Bool -> RDoc -> RDoc
647 above (Above p g1 q1) g2 q2 = above p g1 (above q1 g2 q2)
648 above p@(Beside _ _ _) g q = aboveNest (reduceDoc p) g ILIT(0) (reduceDoc q)
649 above p g q = aboveNest p g ILIT(0) (reduceDoc q)
651 aboveNest :: RDoc -> Bool -> INT -> RDoc -> RDoc
652 -- Specfication: aboveNest p g k q = p $g$ (nest k q)
654 aboveNest NoDoc g k q = NoDoc
655 aboveNest (p1 `Union` p2) g k q = aboveNest p1 g k q `union_`
658 aboveNest Empty g k q = mkNest k q
659 aboveNest (Nest k1 p) g k q = nest_ k1 (aboveNest p g (k MINUS k1) q)
660 -- p can't be Empty, so no need for mkNest
662 aboveNest (NilAbove p) g k q = nilAbove_ (aboveNest p g k q)
663 aboveNest (TextBeside s sl p) g k q = textBeside_ s sl rest
667 Empty -> nilAboveNest g k1 q
668 other -> aboveNest p g k1 q
672 nilAboveNest :: Bool -> INT -> RDoc -> RDoc
673 -- Specification: text s <> nilaboveNest g k q
674 -- = text s <> (text "" $g$ nest k q)
676 nilAboveNest g k Empty = Empty -- Here's why the "text s <>" is in the spec!
677 nilAboveNest g k (Nest k1 q) = nilAboveNest g (k PLUS k1) q
679 nilAboveNest g k q | (not g) && (k GR ILIT(0)) -- No newline if no overlap
680 = textBeside_ (Str (spaces k)) k q
681 | otherwise -- Put them really above
682 = nilAbove_ (mkNest k q)
686 *********************************************************
688 \subsection{Horizontal composition @<>@}
690 *********************************************************
693 p <> q = Beside p False q
694 p <+> q = Beside p True q
696 beside :: Doc -> Bool -> RDoc -> RDoc
697 -- Specification: beside g p q = p <g> q
699 beside NoDoc g q = NoDoc
700 beside (p1 `Union` p2) g q = (beside p1 g q) `union_` (beside p2 g q)
702 beside (Nest k p) g q = nest_ k (beside p g q) -- p non-empty
703 beside p@(Beside p1 g1 q1) g2 q2
704 {- (A `op1` B) `op2` C == A `op1` (B `op2` C) iff op1 == op2
705 [ && (op1 == <> || op1 == <+>) ] -}
706 | g1 == g2 = beside p1 g1 (beside q1 g2 q2)
707 | otherwise = beside (reduceDoc p) g2 q2
708 beside p@(Above _ _ _) g q = beside (reduceDoc p) g q
709 beside (NilAbove p) g q = nilAbove_ (beside p g q)
710 beside (TextBeside s sl p) g q = textBeside_ s sl rest
713 Empty -> nilBeside g q
714 other -> beside p g q
718 nilBeside :: Bool -> RDoc -> RDoc
719 -- Specification: text "" <> nilBeside g p
722 nilBeside g Empty = Empty -- Hence the text "" in the spec
723 nilBeside g (Nest _ p) = nilBeside g p
724 nilBeside g p | g = textBeside_ space_text ILIT(1) p
728 *********************************************************
730 \subsection{Separate, @sep@, Hughes version}
732 *********************************************************
735 -- Specification: sep ps = oneLiner (hsep ps)
739 sep = sepX True -- Separate with spaces
740 cat = sepX False -- Don't
743 sepX x (p:ps) = sep1 x (reduceDoc p) ILIT(0) ps
746 -- Specification: sep1 g k ys = sep (x : map (nest k) ys)
747 -- = oneLiner (x <g> nest k (hsep ys))
748 -- `union` x $$ nest k (vcat ys)
750 sep1 :: Bool -> RDoc -> INT -> [Doc] -> RDoc
751 sep1 g NoDoc k ys = NoDoc
752 sep1 g (p `Union` q) k ys = sep1 g p k ys
754 (aboveNest q False k (reduceDoc (vcat ys)))
756 sep1 g Empty k ys = mkNest k (sepX g ys)
757 sep1 g (Nest n p) k ys = nest_ n (sep1 g p (k MINUS n) ys)
759 sep1 g (NilAbove p) k ys = nilAbove_ (aboveNest p False k (reduceDoc (vcat ys)))
760 sep1 g (TextBeside s sl p) k ys = textBeside_ s sl (sepNB g p (k MINUS sl) ys)
762 -- Specification: sepNB p k ys = sep1 (text "" <> p) k ys
763 -- Called when we have already found some text in the first item
764 -- We have to eat up nests
766 sepNB g (Nest _ p) k ys = sepNB g p k ys
768 sepNB g Empty k ys = oneLiner (nilBeside g (reduceDoc rest))
770 nilAboveNest False k (reduceDoc (vcat ys))
773 | otherwise = hcat ys
775 sepNB g p k ys = sep1 g p k ys
778 *********************************************************
782 *********************************************************
791 -- fill (p1:p2:ps) = oneLiner p1 <#> nest (length p1)
792 -- (fill (oneLiner p2 : ps))
797 fill g (p:ps) = fill1 g (reduceDoc p) ILIT(0) ps
800 fill1 :: Bool -> RDoc -> INT -> [Doc] -> Doc
801 fill1 g NoDoc k ys = NoDoc
802 fill1 g (p `Union` q) k ys = fill1 g p k ys
804 (aboveNest q False k (fill g ys))
806 fill1 g Empty k ys = mkNest k (fill g ys)
807 fill1 g (Nest n p) k ys = nest_ n (fill1 g p (k MINUS n) ys)
809 fill1 g (NilAbove p) k ys = nilAbove_ (aboveNest p False k (fill g ys))
810 fill1 g (TextBeside s sl p) k ys = textBeside_ s sl (fillNB g p (k MINUS sl) ys)
812 fillNB g (Nest _ p) k ys = fillNB g p k ys
813 fillNB g Empty k [] = Empty
814 fillNB g Empty k (y:ys) = nilBeside g (fill1 g (oneLiner (reduceDoc y)) k1 ys)
816 nilAboveNest False k (fill g (y:ys))
818 k1 | g = k MINUS ILIT(1)
821 fillNB g p k ys = fill1 g p k ys
825 *********************************************************
827 \subsection{Selecting the best layout}
829 *********************************************************
832 best :: Int -- Line length
833 -> Int -- Ribbon length
835 -> RDoc -- No unions in here!
837 best IBOX(w) IBOX(r) p
840 get :: INT -- (Remaining) width of line
844 get w (NilAbove p) = nilAbove_ (get w p)
845 get w (TextBeside s sl p) = textBeside_ s sl (get1 w sl p)
846 get w (Nest k p) = nest_ k (get (w MINUS k) p)
847 get w (p `Union` q) = nicest w r (get w p) (get w q)
849 get1 :: INT -- (Remaining) width of line
850 -> INT -- Amount of first line already eaten up
851 -> Doc -- This is an argument to TextBeside => eat Nests
852 -> Doc -- No unions in here!
854 get1 w sl Empty = Empty
855 get1 w sl NoDoc = NoDoc
856 get1 w sl (NilAbove p) = nilAbove_ (get (w MINUS sl) p)
857 get1 w sl (TextBeside t tl p) = textBeside_ t tl (get1 w (sl PLUS tl) p)
858 get1 w sl (Nest k p) = get1 w sl p
859 get1 w sl (p `Union` q) = nicest1 w r sl (get1 w sl p)
862 nicest w r p q = nicest1 w r ILIT(0) p q
863 nicest1 w r sl p q | fits ((w `minn` r) MINUS sl) p = p
866 fits :: INT -- Space available
868 -> Bool -- True if *first line* of Doc fits in space available
870 fits n p | n LT ILIT(0) = False
873 fits n (NilAbove _) = True
874 fits n (TextBeside _ sl p) = fits (n MINUS sl) p
876 minn x y | x LT y = x
880 @first@ and @nonEmptySet@ are similar to @nicest@ and @fits@, only simpler.
881 @first@ returns its first argument if it is non-empty, otherwise its second.
884 first p q | nonEmptySet p = p
887 nonEmptySet NoDoc = False
888 nonEmptySet (p `Union` q) = True
889 nonEmptySet Empty = True
890 nonEmptySet (NilAbove p) = True -- NoDoc always in first line
891 nonEmptySet (TextBeside _ _ p) = nonEmptySet p
892 nonEmptySet (Nest _ p) = nonEmptySet p
895 @oneLiner@ returns the one-line members of the given set of @Doc@s.
898 oneLiner :: Doc -> Doc
899 oneLiner NoDoc = NoDoc
900 oneLiner Empty = Empty
901 oneLiner (NilAbove p) = NoDoc
902 oneLiner (TextBeside s sl p) = textBeside_ s sl (oneLiner p)
903 oneLiner (Nest k p) = nest_ k (oneLiner p)
904 oneLiner (p `Union` q) = oneLiner p
909 *********************************************************
911 \subsection{Displaying the best layout}
913 *********************************************************
918 renderStyle Style{mode, lineLength, ribbonsPerLine} doc
919 = fullRender mode lineLength ribbonsPerLine doc ""
922 render doc = showDocWith PageMode doc
923 showDoc doc rest = showDocWithAppend PageMode doc rest
925 showDocWithAppend :: Mode -> Doc -> String -> String
926 showDocWithAppend mode doc rest = fullRender mode 100 1.5 string_txt rest doc
928 showDocWith :: Mode -> Doc -> String
929 showDocWith mode doc = showDocWithAppend mode doc ""
931 string_txt (Chr c) s = c:s
932 string_txt (Str s1) s2 = s1 ++ s2
933 string_txt (PStr s1) s2 = unpackFS s1 ++ s2
934 string_txt (LStr s1 _) s2 = unpackLitString s1 ++ s2
936 unpackLitString addr =
940 | ch `eqChar#` '\0'# = []
941 | otherwise = C# ch : unpack (nh +# 1#)
943 ch = indexCharOffAddr# addr nh
948 fullRender OneLineMode _ _ txt end doc
949 = lay (reduceDoc doc)
951 lay NoDoc = cant_fail
952 lay (Union p q) = (lay q) -- Second arg can't be NoDoc
953 lay (Nest k p) = lay p
955 lay (NilAbove p) = space_text `txt` lay p -- NoDoc always on first line
956 lay (TextBeside s sl p) = s `txt` lay p
958 fullRender LeftMode _ _ txt end doc
959 = lay (reduceDoc doc)
961 lay NoDoc = cant_fail
962 lay (Union p q) = lay (first p q)
963 lay (Nest k p) = lay p
965 lay (NilAbove p) = nl_text `txt` lay p -- NoDoc always on first line
966 lay (TextBeside s sl p) = s `txt` lay p
968 fullRender mode line_length ribbons_per_line txt end doc
969 = display mode line_length ribbon_length txt end best_doc
971 best_doc = best hacked_line_length ribbon_length (reduceDoc doc)
973 hacked_line_length, ribbon_length :: Int
974 ribbon_length = round (fromIntegral line_length / ribbons_per_line)
975 hacked_line_length = case mode of { ZigZagMode -> MAXINT; other -> line_length }
977 display mode IBOX(page_width) IBOX(ribbon_width) txt end doc
978 = case page_width MINUS ribbon_width of { gap_width ->
979 case gap_width DIV ILIT(2) of { shift ->
981 lay k (Nest k1 p) = lay (k PLUS k1) p
984 lay k (NilAbove p) = nl_text `txt` lay k p
986 lay k (TextBeside s sl p)
988 ZigZagMode | k GREQ gap_width
990 Str (multi_ch shift '/') `txt` (
992 lay1 (k MINUS shift) s sl p)))
996 Str (multi_ch shift '\\') `txt` (
998 lay1 (k PLUS shift) s sl p )))
1000 other -> lay1 k s sl p
1002 lay1 k s sl p = Str (indent k) `txt` (s `txt` lay2 (k PLUS sl) p)
1004 lay2 k (NilAbove p) = nl_text `txt` lay k p
1005 lay2 k (TextBeside s sl p) = s `txt` (lay2 (k PLUS sl) p)
1006 lay2 k (Nest _ p) = lay2 k p
1012 cant_fail = error "easy_display: NoDoc"
1014 indent n | n GREQ ILIT(8) = '\t' : indent (n MINUS ILIT(8))
1015 | otherwise = spaces n
1017 multi_ch ILIT(0) ch = ""
1018 multi_ch n ch = ch : multi_ch (n MINUS ILIT(1)) ch
1021 spaces n = ' ' : spaces (n MINUS ILIT(1))
1025 pprCols = (100 :: Int) -- could make configurable
1027 printDoc :: Mode -> Handle -> Doc -> IO ()
1028 printDoc mode hdl doc
1029 = fullRender mode pprCols 1.5 put done doc
1031 put (Chr c) next = hPutChar hdl c >> next
1032 put (Str s) next = hPutStr hdl s >> next
1033 put (PStr s) next = hPutFS hdl s >> next
1034 put (LStr s l) next = hPutLitString hdl s l >> next
1036 done = hPutChar hdl '\n'
1038 #if __GLASGOW_HASKELL__ < 503
1039 hPutBuf = hPutBufFull
1042 hPutLitString handle a# l#
1043 #if __GLASGOW_HASKELL__ < 411
1044 = hPutBuf handle (A# a#) (I# l#)
1046 = hPutBuf handle (Ptr a#) (I# l#)