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"
181 import PrimPacked ( strLength )
185 import Numeric (fromRat)
188 #if __GLASGOW_HASKELL__ < 503
189 import IOExts ( hPutBufFull )
191 import System.IO ( hPutBuf )
194 #if __GLASGOW_HASKELL__ < 503
195 import PrelBase ( unpackCString# )
197 import GHC.Base ( unpackCString# )
200 import PrimPacked ( Ptr(..) )
202 -- Don't import Util( assertPanic ) because it makes a loop in the module structure
211 *********************************************************
213 \subsection{CPP magic so that we can compile with both GHC and Hugs}
215 *********************************************************
217 The library uses unboxed types to get a bit more speed, but these CPP macros
218 allow you to use either GHC or Hugs. To get GHC, just set the CPP variable
223 #if defined(__GLASGOW_HASKELL__)
227 -- Disable ASSERT checks; they are expensive!
228 #define LOCAL_ASSERT(x)
231 #define IBOX(x) (I# (x))
234 #define NEGATE negateInt#
239 #define DIV `quotInt#`
243 #define MAXINT maxBound
249 #define LOCAL_ASSERT(x)
254 #define NEGATE negate
263 #define MAXINT maxBound
270 *********************************************************
272 \subsection{The interface}
274 *********************************************************
276 The primitive @Doc@ values
280 isEmpty :: Doc -> Bool
281 text :: String -> Doc
284 semi, comma, colon, space, equals :: Doc
285 lparen, rparen, lbrack, rbrack, lbrace, rbrace :: Doc
287 parens, brackets, braces :: Doc -> Doc
288 quotes, doubleQuotes :: Doc -> Doc
291 integer :: Integer -> Doc
292 float :: Float -> Doc
293 double :: Double -> Doc
294 rational :: Rational -> Doc
297 Combining @Doc@ values
300 (<>) :: Doc -> Doc -> Doc -- Beside
301 hcat :: [Doc] -> Doc -- List version of <>
302 (<+>) :: Doc -> Doc -> Doc -- Beside, separated by space
303 hsep :: [Doc] -> Doc -- List version of <+>
305 ($$) :: Doc -> Doc -> Doc -- Above; if there is no
306 -- overlap it "dovetails" the two
307 vcat :: [Doc] -> Doc -- List version of $$
309 cat :: [Doc] -> Doc -- Either hcat or vcat
310 sep :: [Doc] -> Doc -- Either hsep or vcat
311 fcat :: [Doc] -> Doc -- ``Paragraph fill'' version of cat
312 fsep :: [Doc] -> Doc -- ``Paragraph fill'' version of sep
314 nest :: Int -> Doc -> Doc -- Nested
320 hang :: Doc -> Int -> Doc -> Doc
321 punctuate :: Doc -> [Doc] -> [Doc] -- punctuate p [d1, ... dn] = [d1 <> p, d2 <> p, ... dn-1 <> p, dn]
324 Displaying @Doc@ values.
327 instance SHOW Doc where
328 showsPrec prec doc cont = showDoc doc cont
330 render :: Doc -> String -- Uses default style
332 -> Int -- Line length
333 -> Float -- Ribbons per line
334 -> (TextDetails -> a -> a) -- What to do with text
335 -> a -- What to do at the end
339 {- When we start using 1.3
340 renderStyle :: Style -> Doc -> String
341 data Style = Style { lineLength :: Int, -- In chars
342 ribbonsPerLine :: Float, -- Ratio of ribbon length to line length
345 style :: Style -- The default style
346 style = Style { lineLength = 100, ribbonsPerLine = 2.5, mode = PageMode }
349 data Mode = PageMode -- Normal
350 | ZigZagMode -- With zig-zag cuts
351 | LeftMode -- No indentation, infinitely long lines
352 | OneLineMode -- All on one line
357 *********************************************************
359 \subsection{The @Doc@ calculus}
361 *********************************************************
363 The @Doc@ combinators satisfy the following laws:
367 <a1> (x $$ y) $$ z = x $$ (y $$ z)
375 <b1> (x <> y) <> z = x <> (y <> z)
376 <b2> empty <> x = empty
383 <t1> text s <> text t = text (s++t)
384 <t2> text "" <> x = x, if x non-empty
389 <n2> nest k (nest k' x) = nest (k+k') x
390 <n3> nest k (x <> y) = nest k z <> nest k y
391 <n4> nest k (x $$ y) = nest k x $$ nest k y
392 <n5> nest k empty = empty
393 <n6> x <> nest k y = x <> y, if x non-empty
395 ** Note the side condition on <n6>! It is this that
396 ** makes it OK for empty to be a left unit for <>.
400 <m1> (text s <> x) $$ y = text s <> ((text "" <> x)) $$
403 <m2> (x $$ y) <> z = x $$ (y <> z)
407 Laws for list versions
408 ~~~~~~~~~~~~~~~~~~~~~~
409 <l1> sep (ps++[empty]++qs) = sep (ps ++ qs)
410 ...ditto hsep, hcat, vcat, fill...
412 <l2> nest k (sep ps) = sep (map (nest k) ps)
413 ...ditto hsep, hcat, vcat, fill...
417 <o1> oneLiner (nest k p) = nest k (oneLiner p)
418 <o2> oneLiner (x <> y) = oneLiner x <> oneLiner y
422 You might think that the following verion of <m1> would
425 <3 NO> (text s <> x) $$ y = text s <> ((empty <> x)) $$
428 But it doesn't work, for if x=empty, we would have
430 text s $$ y = text s <> (empty $$ nest (-length s) y)
431 = text s <> nest (-length s) y
436 *********************************************************
438 \subsection{Simple derived definitions}
440 *********************************************************
455 int n = text (show n)
456 integer n = text (show n)
457 float n = text (show n)
458 double n = text (show n)
459 rational n = text (show (fromRat n))
460 --rational n = text (show (fromRationalX n)) -- _showRational 30 n)
462 quotes p = char '`' <> p <> char '\''
463 doubleQuotes p = char '"' <> p <> char '"'
464 parens p = char '(' <> p <> char ')'
465 brackets p = char '[' <> p <> char ']'
466 braces p = char '{' <> p <> char '}'
469 hcat = foldr (<>) empty
470 hsep = foldr (<+>) empty
471 vcat = foldr ($$) empty
473 hang d1 n d2 = sep [d1, nest n d2]
476 punctuate p (d:ds) = go d ds
479 go d (e:es) = (d <> p) : go e es
483 *********************************************************
485 \subsection{The @Doc@ data type}
487 *********************************************************
489 A @Doc@ represents a {\em set} of layouts. A @Doc@ with
490 no occurrences of @Union@ or @NoDoc@ represents just one layout.
494 | NilAbove Doc -- text "" $$ x
495 | TextBeside !TextDetails INT Doc -- text s <> x
496 | Nest INT Doc -- nest k x
497 | Union Doc Doc -- ul `union` ur
498 | NoDoc -- The empty set of documents
499 | Beside Doc Bool Doc -- True <=> space between
500 | Above Doc Bool Doc -- True <=> never overlap
502 type RDoc = Doc -- RDoc is a "reduced Doc", guaranteed not to have a top-level Above or Beside
505 reduceDoc :: Doc -> RDoc
506 reduceDoc (Beside p g q) = beside p g (reduceDoc q)
507 reduceDoc (Above p g q) = above p g (reduceDoc q)
511 data TextDetails = Chr Char
513 | PStr FastString -- a hashed string
514 | LStr Addr# Int# -- a '\0'-terminated array of bytes
520 Here are the invariants:
523 The argument of @NilAbove@ is never @Empty@. Therefore
524 a @NilAbove@ occupies at least two lines.
527 The arugment of @TextBeside@ is never @Nest@.
530 The layouts of the two arguments of @Union@ both flatten to the same string.
533 The arguments of @Union@ are either @TextBeside@, or @NilAbove@.
536 The right argument of a union cannot be equivalent to the empty set (@NoDoc@).
537 If the left argument of a union is equivalent to the empty set (@NoDoc@),
538 then the @NoDoc@ appears in the first line.
541 An empty document is always represented by @Empty@.
542 It can't be hidden inside a @Nest@, or a @Union@ of two @Empty@s.
545 The first line of every layout in the left argument of @Union@
546 is longer than the first line of any layout in the right argument.
547 (1) ensures that the left argument has a first line. In view of (3),
548 this invariant means that the right argument must have at least two
553 -- Arg of a NilAbove is always an RDoc
554 nilAbove_ p = LOCAL_ASSERT( ok p ) NilAbove p
559 -- Arg of a TextBeside is always an RDoc
560 textBeside_ s sl p = TextBeside s sl (LOCAL_ASSERT( ok p ) p)
562 ok (Nest _ _) = False
565 -- Arg of Nest is always an RDoc
566 nest_ k p = Nest k (LOCAL_ASSERT( ok p ) p)
571 -- Args of union are always RDocs
572 union_ p q = Union (LOCAL_ASSERT( ok p ) p) (LOCAL_ASSERT( ok q ) q)
574 ok (TextBeside _ _ _) = True
575 ok (NilAbove _) = True
576 ok (Union _ _) = True
581 Notice the difference between
582 * NoDoc (no documents)
583 * Empty (one empty document; no height and no width)
584 * text "" (a document containing the empty string;
585 one line high, but has no width)
589 *********************************************************
591 \subsection{@empty@, @text@, @nest@, @union@}
593 *********************************************************
601 char c = textBeside_ (Chr c) 1# Empty
602 text s = case length s of {IBOX(sl) -> textBeside_ (Str s) sl Empty}
603 ftext s = case lengthFS s of {IBOX(sl) -> textBeside_ (PStr s) sl Empty}
604 ptext (Ptr s) = case strLength (Ptr s) of {IBOX(sl) -> textBeside_ (LStr s sl) sl Empty}
606 -- RULE that turns (text "abc") into (ptext (A# "abc"#)) to avoid the
607 -- intermediate packing/unpacking of the string.
609 "text/str" forall a. text (unpackCString# a) = ptext (Ptr a)
612 nest IBOX(k) p = mkNest k (reduceDoc p) -- Externally callable version
614 -- mkNest checks for Nest's invariant that it doesn't have an Empty inside it
615 mkNest k (Nest k1 p) = mkNest (k PLUS k1) p
616 mkNest k NoDoc = NoDoc
617 mkNest k Empty = Empty
618 mkNest ILIT(0) p = p -- Worth a try!
619 mkNest k p = nest_ k p
621 -- mkUnion checks for an empty document
622 mkUnion Empty q = Empty
623 mkUnion p q = p `union_` q
626 *********************************************************
628 \subsection{Vertical composition @$$@}
630 *********************************************************
634 p $$ q = Above p False q
635 p $+$ q = Above p True q
637 above :: Doc -> Bool -> RDoc -> RDoc
638 above (Above p g1 q1) g2 q2 = above p g1 (above q1 g2 q2)
639 above p@(Beside _ _ _) g q = aboveNest (reduceDoc p) g ILIT(0) (reduceDoc q)
640 above p g q = aboveNest p g ILIT(0) (reduceDoc q)
642 aboveNest :: RDoc -> Bool -> INT -> RDoc -> RDoc
643 -- Specfication: aboveNest p g k q = p $g$ (nest k q)
645 aboveNest NoDoc g k q = NoDoc
646 aboveNest (p1 `Union` p2) g k q = aboveNest p1 g k q `union_`
649 aboveNest Empty g k q = mkNest k q
650 aboveNest (Nest k1 p) g k q = nest_ k1 (aboveNest p g (k MINUS k1) q)
651 -- p can't be Empty, so no need for mkNest
653 aboveNest (NilAbove p) g k q = nilAbove_ (aboveNest p g k q)
654 aboveNest (TextBeside s sl p) g k q = textBeside_ s sl rest
658 Empty -> nilAboveNest g k1 q
659 other -> aboveNest p g k1 q
663 nilAboveNest :: Bool -> INT -> RDoc -> RDoc
664 -- Specification: text s <> nilaboveNest g k q
665 -- = text s <> (text "" $g$ nest k q)
667 nilAboveNest g k Empty = Empty -- Here's why the "text s <>" is in the spec!
668 nilAboveNest g k (Nest k1 q) = nilAboveNest g (k PLUS k1) q
670 nilAboveNest g k q | (not g) && (k GR ILIT(0)) -- No newline if no overlap
671 = textBeside_ (Str (spaces k)) k q
672 | otherwise -- Put them really above
673 = nilAbove_ (mkNest k q)
677 *********************************************************
679 \subsection{Horizontal composition @<>@}
681 *********************************************************
684 p <> q = Beside p False q
685 p <+> q = Beside p True q
687 beside :: Doc -> Bool -> RDoc -> RDoc
688 -- Specification: beside g p q = p <g> q
690 beside NoDoc g q = NoDoc
691 beside (p1 `Union` p2) g q = (beside p1 g q) `union_` (beside p2 g q)
693 beside (Nest k p) g q = nest_ k (beside p g q) -- p non-empty
694 beside p@(Beside p1 g1 q1) g2 q2
695 {- (A `op1` B) `op2` C == A `op1` (B `op2` C) iff op1 == op2
696 [ && (op1 == <> || op1 == <+>) ] -}
697 | g1 == g2 = beside p1 g1 (beside q1 g2 q2)
698 | otherwise = beside (reduceDoc p) g2 q2
699 beside p@(Above _ _ _) g q = beside (reduceDoc p) g q
700 beside (NilAbove p) g q = nilAbove_ (beside p g q)
701 beside (TextBeside s sl p) g q = textBeside_ s sl rest
704 Empty -> nilBeside g q
705 other -> beside p g q
709 nilBeside :: Bool -> RDoc -> RDoc
710 -- Specification: text "" <> nilBeside g p
713 nilBeside g Empty = Empty -- Hence the text "" in the spec
714 nilBeside g (Nest _ p) = nilBeside g p
715 nilBeside g p | g = textBeside_ space_text ILIT(1) p
719 *********************************************************
721 \subsection{Separate, @sep@, Hughes version}
723 *********************************************************
726 -- Specification: sep ps = oneLiner (hsep ps)
730 sep = sepX True -- Separate with spaces
731 cat = sepX False -- Don't
734 sepX x (p:ps) = sep1 x (reduceDoc p) ILIT(0) ps
737 -- Specification: sep1 g k ys = sep (x : map (nest k) ys)
738 -- = oneLiner (x <g> nest k (hsep ys))
739 -- `union` x $$ nest k (vcat ys)
741 sep1 :: Bool -> RDoc -> INT -> [Doc] -> RDoc
742 sep1 g NoDoc k ys = NoDoc
743 sep1 g (p `Union` q) k ys = sep1 g p k ys
745 (aboveNest q False k (reduceDoc (vcat ys)))
747 sep1 g Empty k ys = mkNest k (sepX g ys)
748 sep1 g (Nest n p) k ys = nest_ n (sep1 g p (k MINUS n) ys)
750 sep1 g (NilAbove p) k ys = nilAbove_ (aboveNest p False k (reduceDoc (vcat ys)))
751 sep1 g (TextBeside s sl p) k ys = textBeside_ s sl (sepNB g p (k MINUS sl) ys)
753 -- Specification: sepNB p k ys = sep1 (text "" <> p) k ys
754 -- Called when we have already found some text in the first item
755 -- We have to eat up nests
757 sepNB g (Nest _ p) k ys = sepNB g p k ys
759 sepNB g Empty k ys = oneLiner (nilBeside g (reduceDoc rest))
761 nilAboveNest False k (reduceDoc (vcat ys))
764 | otherwise = hcat ys
766 sepNB g p k ys = sep1 g p k ys
769 *********************************************************
773 *********************************************************
782 -- fill (p1:p2:ps) = oneLiner p1 <#> nest (length p1)
783 -- (fill (oneLiner p2 : ps))
788 fill g (p:ps) = fill1 g (reduceDoc p) ILIT(0) ps
791 fill1 :: Bool -> RDoc -> INT -> [Doc] -> Doc
792 fill1 g NoDoc k ys = NoDoc
793 fill1 g (p `Union` q) k ys = fill1 g p k ys
795 (aboveNest q False k (fill g ys))
797 fill1 g Empty k ys = mkNest k (fill g ys)
798 fill1 g (Nest n p) k ys = nest_ n (fill1 g p (k MINUS n) ys)
800 fill1 g (NilAbove p) k ys = nilAbove_ (aboveNest p False k (fill g ys))
801 fill1 g (TextBeside s sl p) k ys = textBeside_ s sl (fillNB g p (k MINUS sl) ys)
803 fillNB g (Nest _ p) k ys = fillNB g p k ys
804 fillNB g Empty k [] = Empty
805 fillNB g Empty k (y:ys) = nilBeside g (fill1 g (oneLiner (reduceDoc y)) k1 ys)
807 nilAboveNest False k (fill g (y:ys))
809 k1 | g = k MINUS ILIT(1)
812 fillNB g p k ys = fill1 g p k ys
816 *********************************************************
818 \subsection{Selecting the best layout}
820 *********************************************************
823 best :: Int -- Line length
824 -> Int -- Ribbon length
826 -> RDoc -- No unions in here!
828 best IBOX(w) IBOX(r) p
831 get :: INT -- (Remaining) width of line
835 get w (NilAbove p) = nilAbove_ (get w p)
836 get w (TextBeside s sl p) = textBeside_ s sl (get1 w sl p)
837 get w (Nest k p) = nest_ k (get (w MINUS k) p)
838 get w (p `Union` q) = nicest w r (get w p) (get w q)
840 get1 :: INT -- (Remaining) width of line
841 -> INT -- Amount of first line already eaten up
842 -> Doc -- This is an argument to TextBeside => eat Nests
843 -> Doc -- No unions in here!
845 get1 w sl Empty = Empty
846 get1 w sl NoDoc = NoDoc
847 get1 w sl (NilAbove p) = nilAbove_ (get (w MINUS sl) p)
848 get1 w sl (TextBeside t tl p) = textBeside_ t tl (get1 w (sl PLUS tl) p)
849 get1 w sl (Nest k p) = get1 w sl p
850 get1 w sl (p `Union` q) = nicest1 w r sl (get1 w sl p)
853 nicest w r p q = nicest1 w r ILIT(0) p q
854 nicest1 w r sl p q | fits ((w `minn` r) MINUS sl) p = p
857 fits :: INT -- Space available
859 -> Bool -- True if *first line* of Doc fits in space available
861 fits n p | n LT ILIT(0) = False
864 fits n (NilAbove _) = True
865 fits n (TextBeside _ sl p) = fits (n MINUS sl) p
867 minn x y | x LT y = x
871 @first@ and @nonEmptySet@ are similar to @nicest@ and @fits@, only simpler.
872 @first@ returns its first argument if it is non-empty, otherwise its second.
875 first p q | nonEmptySet p = p
878 nonEmptySet NoDoc = False
879 nonEmptySet (p `Union` q) = True
880 nonEmptySet Empty = True
881 nonEmptySet (NilAbove p) = True -- NoDoc always in first line
882 nonEmptySet (TextBeside _ _ p) = nonEmptySet p
883 nonEmptySet (Nest _ p) = nonEmptySet p
886 @oneLiner@ returns the one-line members of the given set of @Doc@s.
889 oneLiner :: Doc -> Doc
890 oneLiner NoDoc = NoDoc
891 oneLiner Empty = Empty
892 oneLiner (NilAbove p) = NoDoc
893 oneLiner (TextBeside s sl p) = textBeside_ s sl (oneLiner p)
894 oneLiner (Nest k p) = nest_ k (oneLiner p)
895 oneLiner (p `Union` q) = oneLiner p
900 *********************************************************
902 \subsection{Displaying the best layout}
904 *********************************************************
909 renderStyle Style{mode, lineLength, ribbonsPerLine} doc
910 = fullRender mode lineLength ribbonsPerLine doc ""
913 render doc = showDocWith PageMode doc
914 showDoc doc rest = showDocWithAppend PageMode doc rest
916 showDocWithAppend :: Mode -> Doc -> String -> String
917 showDocWithAppend mode doc rest = fullRender mode 100 1.5 string_txt rest doc
919 showDocWith :: Mode -> Doc -> String
920 showDocWith mode doc = showDocWithAppend mode doc ""
922 string_txt (Chr c) s = c:s
923 string_txt (Str s1) s2 = s1 ++ s2
924 string_txt (PStr s1) s2 = unpackFS s1 ++ s2
925 string_txt (LStr s1 _) s2 = unpackLitString s1 ++ s2
927 unpackLitString addr =
931 | ch `eqChar#` '\0'# = []
932 | otherwise = C# ch : unpack (nh +# 1#)
934 ch = indexCharOffAddr# addr nh
939 fullRender OneLineMode _ _ txt end doc
940 = lay (reduceDoc doc)
942 lay NoDoc = cant_fail
943 lay (Union p q) = (lay q) -- Second arg can't be NoDoc
944 lay (Nest k p) = lay p
946 lay (NilAbove p) = space_text `txt` lay p -- NoDoc always on first line
947 lay (TextBeside s sl p) = s `txt` lay p
949 fullRender LeftMode _ _ txt end doc
950 = lay (reduceDoc doc)
952 lay NoDoc = cant_fail
953 lay (Union p q) = lay (first p q)
954 lay (Nest k p) = lay p
956 lay (NilAbove p) = nl_text `txt` lay p -- NoDoc always on first line
957 lay (TextBeside s sl p) = s `txt` lay p
959 fullRender mode line_length ribbons_per_line txt end doc
960 = display mode line_length ribbon_length txt end best_doc
962 best_doc = best hacked_line_length ribbon_length (reduceDoc doc)
964 hacked_line_length, ribbon_length :: Int
965 ribbon_length = round (fromIntegral line_length / ribbons_per_line)
966 hacked_line_length = case mode of { ZigZagMode -> MAXINT; other -> line_length }
968 display mode IBOX(page_width) IBOX(ribbon_width) txt end doc
969 = case page_width MINUS ribbon_width of { gap_width ->
970 case gap_width DIV ILIT(2) of { shift ->
972 lay k (Nest k1 p) = lay (k PLUS k1) p
975 lay k (NilAbove p) = nl_text `txt` lay k p
977 lay k (TextBeside s sl p)
979 ZigZagMode | k GREQ gap_width
981 Str (multi_ch shift '/') `txt` (
983 lay1 (k MINUS shift) s sl p)))
987 Str (multi_ch shift '\\') `txt` (
989 lay1 (k PLUS shift) s sl p )))
991 other -> lay1 k s sl p
993 lay1 k s sl p = Str (indent k) `txt` (s `txt` lay2 (k PLUS sl) p)
995 lay2 k (NilAbove p) = nl_text `txt` lay k p
996 lay2 k (TextBeside s sl p) = s `txt` (lay2 (k PLUS sl) p)
997 lay2 k (Nest _ p) = lay2 k p
1003 cant_fail = error "easy_display: NoDoc"
1005 indent n | n GREQ ILIT(8) = '\t' : indent (n MINUS ILIT(8))
1006 | otherwise = spaces n
1008 multi_ch ILIT(0) ch = ""
1009 multi_ch n ch = ch : multi_ch (n MINUS ILIT(1)) ch
1012 spaces n = ' ' : spaces (n MINUS ILIT(1))
1016 pprCols = (120 :: Int) -- could make configurable
1018 printDoc :: Mode -> Handle -> Doc -> IO ()
1019 printDoc LeftMode hdl doc
1020 = do { printLeftRender hdl doc; hFlush hdl }
1021 printDoc mode hdl doc
1022 = do { fullRender mode pprCols 1.5 put done doc ;
1025 put (Chr c) next = hPutChar hdl c >> next
1026 put (Str s) next = hPutStr hdl s >> next
1027 put (PStr s) next = hPutFS hdl s >> next
1028 put (LStr s l) next = hPutLitString hdl s l >> next
1030 done = hPutChar hdl '\n'
1032 -- basically a specialised version of fullRender for LeftMode with IO output.
1033 printLeftRender :: Handle -> Doc -> IO ()
1034 printLeftRender hdl doc = lay (reduceDoc doc)
1036 lay NoDoc = cant_fail
1037 lay (Union p q) = lay (first p q)
1038 lay (Nest k p) = lay p
1039 lay Empty = hPutChar hdl '\n'
1040 lay (NilAbove p) = hPutChar hdl '\n' >> lay p
1041 lay (TextBeside s sl p) = put s >> lay p
1043 put (Chr c) = hPutChar hdl c
1044 put (Str s) = hPutStr hdl s
1045 put (PStr s) = hPutFS hdl s
1046 put (LStr s l) = hPutLitString hdl s l
1048 #if __GLASGOW_HASKELL__ < 503
1049 hPutBuf = hPutBufFull
1052 -- some versions of hPutBuf will barf if the length is zero
1053 hPutLitString handle a# 0# = return ()
1054 hPutLitString handle a# l#
1055 #if __GLASGOW_HASKELL__ < 411
1056 = hPutBuf handle (A# a#) (I# l#)
1058 = hPutBuf handle (Ptr a#) (I# l#)