%*********************************************************************************
%* *
%* John Hughes's and Simon Peyton Jones's Pretty Printer Combinators *
%* *
%* based on "The Design of a Pretty-printing Library" *
%* in Advanced Functional Programming, *
%* Johan Jeuring and Erik Meijer (eds), LNCS 925 *
%* http://www.cs.chalmers.se/~rjmh/Papers/pretty.ps *
%* *
%* Heavily modified by Simon Peyton Jones, Dec 96 *
%* *
%*********************************************************************************
Version 3.0 28 May 1997
* Cured massive performance bug. If you write
foldl <> empty (map (text.show) [1..10000])
you get quadratic behaviour with V2.0. Why? For just the same reason as you get
quadratic behaviour with leftassociated (++) chains.
This is really bad news. One thing a prettyprinter abstraction should
certainly guarantee is insensivity to associativity. It matters: suddenly
GHC's compilation times went up by a factor of 100 when I switched to the
new pretty printer.
I fixed it with a bit of a hack (because I wanted to get GHC back on the
road). I added two new constructors to the Doc type, Above and Beside:
<> = Beside
$$ = Above
Then, where I need to get to a "TextBeside" or "NilAbove" form I "force"
the Doc to squeeze out these suspended calls to Beside and Above; but in so
doing I reassociate. It's quite simple, but I'm not satisfied that I've done
the best possible job. I'll send you the code if you are interested.
* Added new exports:
punctuate, hang
int, integer, float, double, rational,
lparen, rparen, lbrack, rbrack, lbrace, rbrace,
* fullRender's type signature has changed. Rather than producing a string it
now takes an extra couple of arguments that tells it how to glue fragments
of output together:
fullRender :: Mode
-> Int
-> Float
-> (TextDetails -> a -> a)
-> a
-> Doc
-> a
The "fragments" are encapsulated in the TextDetails data type:
data TextDetails = Chr Char
| Str String
| PStr FastString
The Chr and Str constructors are obvious enough. The PStr constructor has a packed
string (FastString) inside it. It's generated by using the new "ptext" export.
An advantage of this new setup is that you can get the renderer to do output
directly (by passing in a function of type (TextDetails -> IO () -> IO ()),
rather than producing a string that you then print.
Version 2.0 24 April 1997
* Made empty into a left unit for <> as well as a right unit;
it is also now true that
nest k empty = empty
which wasn't true before.
* Fixed an obscure bug in sep that occassionally gave very wierd behaviour
* Added $+$
* Corrected and tidied up the laws and invariants
======================================================================
Relative to John's original paper, there are the following new features:
1. There's an empty document, "empty". It's a left and right unit for
both <> and $$, and anywhere in the argument list for
sep, hcat, hsep, vcat, fcat etc.
It is Really Useful in practice.
2. There is a paragraphfill combinator, fsep, that's much like sep,
only it keeps fitting things on one line until it can't fit any more.
3. Some random useful extra combinators are provided.
<+> puts its arguments beside each other with a space between them,
unless either argument is empty in which case it returns the other
hcat is a list version of <>
hsep is a list version of <+>
vcat is a list version of $$
sep (separate) is either like hsep or like vcat, depending on what fits
cat is behaves like sep, but it uses <> for horizontal conposition
fcat is behaves like fsep, but it uses <> for horizontal conposition
These new ones do the obvious things:
char, semi, comma, colon, space,
parens, brackets, braces,
quotes, doubleQuotes
4. The "above" combinator, $$, now overlaps its two arguments if the
last line of the top argument stops before the first line of the second begins.
For example: text "hi" $$ nest 5 "there"
lays out as
hi there
rather than
hi
there
There are two places this is really useful
a) When making labelled blocks, like this:
Left -> code for left
Right -> code for right
LongLongLongLabel ->
code for longlonglonglabel
The block is on the same line as the label if the label is
short, but on the next line otherwise.
b) When laying out lists like this:
[ first
, second
, third
]
which some people like. But if the list fits on one line
you want [first, second, third]. You can't do this with
John's original combinators, but it's quite easy with the
new $$.
The combinator $+$ gives the original "never-overlap" behaviour.
5. Several different renderers are provided:
* a standard one
* one that uses cutmarks to avoid deeplynested documents
simply piling up in the righthand margin
* one that ignores indentation (fewer chars output; good for machines)
* one that ignores indentation and newlines (ditto, only more so)
6. Numerous implementation tidyups
Use of unboxed data types to speed up the implementation
\begin{code}
module Pretty (
Doc,
Mode(..), TextDetails(..),
empty, isEmpty, nest,
char, text, ftext, ptext,
int, integer, float, double, rational,
parens, brackets, braces, quotes, doubleQuotes,
semi, comma, colon, space, equals,
lparen, rparen, lbrack, rbrack, lbrace, rbrace, cparen,
(<>), (<+>), hcat, hsep,
($$), ($+$), vcat,
sep, cat,
fsep, fcat,
hang, punctuate,
render, fullRender, printDoc, showDocWith,
bufLeftRender
) where
import BufWrite
import FastString
import FastTypes
import Panic
import Numeric (fromRat)
import System.IO
#if defined(__GLASGOW_HASKELL__)
import GHC.Base ( unpackCString# )
import GHC.Exts ( Int# )
import GHC.Ptr ( Ptr(..) )
#endif
infixl 6 <>
infixl 6 <+>
infixl 5 $$, $+$
\end{code}
\begin{code}
#define LOCAL_ASSERT(x)
\end{code}
%*********************************************************
%* *
\subsection{The interface}
%* *
%*********************************************************
The primitive @Doc@ values
\begin{code}
empty :: Doc
isEmpty :: Doc -> Bool
text :: String -> Doc
char :: Char -> Doc
semi, comma, colon, space, equals :: Doc
lparen, rparen, lbrack, rbrack, lbrace, rbrace :: Doc
parens, brackets, braces :: Doc -> Doc
quotes, doubleQuotes :: Doc -> Doc
int :: Int -> Doc
integer :: Integer -> Doc
float :: Float -> Doc
double :: Double -> Doc
rational :: Rational -> Doc
\end{code}
Combining @Doc@ values
\begin{code}
(<>) :: Doc -> Doc -> Doc
hcat :: [Doc] -> Doc
(<+>) :: Doc -> Doc -> Doc
hsep :: [Doc] -> Doc
($$) :: Doc -> Doc -> Doc
vcat :: [Doc] -> Doc
cat :: [Doc] -> Doc
sep :: [Doc] -> Doc
fcat :: [Doc] -> Doc
fsep :: [Doc] -> Doc
nest :: Int -> Doc -> Doc
\end{code}
GHCspecific ones.
\begin{code}
hang :: Doc -> Int -> Doc -> Doc
punctuate :: Doc -> [Doc] -> [Doc]
\end{code}
Displaying @Doc@ values.
\begin{code}
instance Show Doc where
showsPrec _ doc cont = showDoc doc cont
render :: Doc -> String
fullRender :: Mode
-> Int
-> Float
-> (TextDetails -> a -> a)
-> a
-> Doc
-> a
data Mode = PageMode
| ZigZagMode
| LeftMode
| OneLineMode
\end{code}
%*********************************************************
%* *
\subsection{The @Doc@ calculus}
%* *
%*********************************************************
The @Doc@ combinators satisfy the following laws:
\begin{verbatim}
Laws for $$
~~~~~~~~~~~
<a1> (x $$ y) $$ z = x $$ (y $$ z)
<a2> empty $$ x = x
<a3> x $$ empty = x
...ditto $+$...
Laws for <>
~~~~~~~~~~~
<b1> (x <> y) <> z = x <> (y <> z)
<b2> empty <> x = empty
<b3> x <> empty = x
...ditto <+>...
Laws for text
~~~~~~~~~~~~~
<t1> text s <> text t = text (s++t)
<t2> text "" <> x = x, if x nonempty
Laws for nest
~~~~~~~~~~~~~
<n1> nest 0 x = x
<n2> nest k (nest k' x) = nest (k+k') x
<n3> nest k (x <> y) = nest k z <> nest k y
<n4> nest k (x $$ y) = nest k x $$ nest k y
<n5> nest k empty = empty
<n6> x <> nest k y = x <> y, if x nonempty
Note the side condition on <n6>! It is this that
makes it OK for empty to be a left unit for <>.
Miscellaneous
~~~~~~~~~~~~~
<m1> (text s <> x) $$ y = text s <> ((text "" <> x)) $$
nest (length s) y)
<m2> (x $$ y) <> z = x $$ (y <> z)
if y nonempty
Laws for list versions
~~~~~~~~~~~~~~~~~~~~~~
<l1> sep (ps++[empty]++qs) = sep (ps ++ qs)
...ditto hsep, hcat, vcat, fill...
<l2> nest k (sep ps) = sep (map (nest k) ps)
...ditto hsep, hcat, vcat, fill...
Laws for oneLiner
~~~~~~~~~~~~~~~~~
<o1> oneLiner (nest k p) = nest k (oneLiner p)
<o2> oneLiner (x <> y) = oneLiner x <> oneLiner y
\end{verbatim}
You might think that the following verion of <m1> would
be neater:
\begin{verbatim}
<3 NO> (text s <> x) $$ y = text s <> ((empty <> x)) $$
nest (length s) y)
\end{verbatim}
But it doesn't work, for if x=empty, we would have
\begin{verbatim}
text s $$ y = text s <> (empty $$ nest (length s) y)
= text s <> nest (length s) y
\end{verbatim}
%*********************************************************
%* *
\subsection{Simple derived definitions}
%* *
%*********************************************************
\begin{code}
semi = char ';'
colon = char ':'
comma = char ','
space = char ' '
equals = char '='
lparen = char '('
rparen = char ')'
lbrack = char '['
rbrack = char ']'
lbrace = char '{'
rbrace = char '}'
int n = text (show n)
integer n = text (show n)
float n = text (show n)
double n = text (show n)
rational n = text (show (fromRat n :: Double))
quotes p = char '`' <> p <> char '\''
doubleQuotes p = char '"' <> p <> char '"'
parens p = char '(' <> p <> char ')'
brackets p = char '[' <> p <> char ']'
braces p = char '{' <> p <> char '}'
cparen :: Bool -> Doc -> Doc
cparen True = parens
cparen False = id
hcat = foldr (<>) empty
hsep = foldr (<+>) empty
vcat = foldr ($$) empty
hang d1 n d2 = sep [d1, nest n d2]
punctuate _ [] = []
punctuate p (d:ds) = go d ds
where
go d [] = [d]
go d (e:es) = (d <> p) : go e es
\end{code}
%*********************************************************
%* *
\subsection{The @Doc@ data type}
%* *
%*********************************************************
A @Doc@ represents a {\em set} of layouts. A @Doc@ with
no occurrences of @Union@ or @NoDoc@ represents just one layout.
\begin{code}
data Doc
= Empty
| NilAbove Doc
| TextBeside !TextDetails FastInt Doc
| Nest FastInt Doc
| Union Doc Doc
| NoDoc
| Beside Doc Bool Doc
| Above Doc Bool Doc
type RDoc = Doc
reduceDoc :: Doc -> RDoc
reduceDoc (Beside p g q) = beside p g (reduceDoc q)
reduceDoc (Above p g q) = above p g (reduceDoc q)
reduceDoc p = p
data TextDetails = Chr !Char
| Str String
| PStr FastString
| LStr !LitString FastInt
space_text :: TextDetails
space_text = Chr ' '
nl_text :: TextDetails
nl_text = Chr '\n'
\end{code}
Here are the invariants:
\begin{itemize}
\item
The argument of @NilAbove@ is never @Empty@. Therefore
a @NilAbove@ occupies at least two lines.
\item
The arugment of @TextBeside@ is never @Nest@.
\item
The layouts of the two arguments of @Union@ both flatten to the same string.
\item
The arguments of @Union@ are either @TextBeside@, or @NilAbove@.
\item
The right argument of a union cannot be equivalent to the empty set (@NoDoc@).
If the left argument of a union is equivalent to the empty set (@NoDoc@),
then the @NoDoc@ appears in the first line.
\item
An empty document is always represented by @Empty@.
It can't be hidden inside a @Nest@, or a @Union@ of two @Empty@s.
\item
The first line of every layout in the left argument of @Union@
is longer than the first line of any layout in the right argument.
(1) ensures that the left argument has a first line. In view of (3),
this invariant means that the right argument must have at least two
lines.
\end{itemize}
\begin{code}
nilAbove_ :: Doc -> Doc
nilAbove_ p = LOCAL_ASSERT( _ok p ) NilAbove p
where
_ok Empty = False
_ok _ = True
textBeside_ :: TextDetails -> FastInt -> Doc -> Doc
textBeside_ s sl p = TextBeside s sl (LOCAL_ASSERT( _ok p ) p)
where
_ok (Nest _ _) = False
_ok _ = True
nest_ :: FastInt -> Doc -> Doc
nest_ k p = Nest k (LOCAL_ASSERT( _ok p ) p)
where
_ok Empty = False
_ok _ = True
union_ :: Doc -> Doc -> Doc
union_ p q = Union (LOCAL_ASSERT( _ok p ) p) (LOCAL_ASSERT( _ok q ) q)
where
_ok (TextBeside _ _ _) = True
_ok (NilAbove _) = True
_ok (Union _ _) = True
_ok _ = False
\end{code}
Notice the difference between
* NoDoc (no documents)
* Empty (one empty document; no height and no width)
* text "" (a document containing the empty string;
one line high, but has no width)
%*********************************************************
%* *
\subsection{@empty@, @text@, @nest@, @union@}
%* *
%*********************************************************
\begin{code}
empty = Empty
isEmpty Empty = True
isEmpty _ = False
char c = textBeside_ (Chr c) (_ILIT(1)) Empty
text s = case iUnbox (length s) of {sl -> textBeside_ (Str s) sl Empty}
ftext :: FastString -> Doc
ftext s = case iUnbox (lengthFS s) of {sl -> textBeside_ (PStr s) sl Empty}
ptext :: LitString -> Doc
ptext s_= case iUnbox (lengthLS s) of {sl -> textBeside_ (LStr s sl) sl Empty}
where s = s_
#if defined(__GLASGOW_HASKELL__)
#endif
nest k p = mkNest (iUnbox k) (reduceDoc p)
mkNest :: Int# -> Doc -> Doc
mkNest k (Nest k1 p) = mkNest (k +# k1) p
mkNest _ NoDoc = NoDoc
mkNest _ Empty = Empty
mkNest k p | k ==# _ILIT(0) = p
mkNest k p = nest_ k p
mkUnion :: Doc -> Doc -> Doc
mkUnion Empty _ = Empty
mkUnion p q = p `union_` q
\end{code}
%*********************************************************
%* *
\subsection{Vertical composition @$$@}
%* *
%*********************************************************
\begin{code}
p $$ q = Above p False q
($+$) :: Doc -> Doc -> Doc
p $+$ q = Above p True q
above :: Doc -> Bool -> RDoc -> RDoc
above (Above p g1 q1) g2 q2 = above p g1 (above q1 g2 q2)
above p@(Beside _ _ _) g q = aboveNest (reduceDoc p) g (_ILIT(0)) (reduceDoc q)
above p g q = aboveNest p g (_ILIT(0)) (reduceDoc q)
aboveNest :: RDoc -> Bool -> FastInt -> RDoc -> RDoc
aboveNest NoDoc _ _ _ = NoDoc
aboveNest (p1 `Union` p2) g k q = aboveNest p1 g k q `union_`
aboveNest p2 g k q
aboveNest Empty _ k q = mkNest k q
aboveNest (Nest k1 p) g k q = nest_ k1 (aboveNest p g (k -# k1) q)
aboveNest (NilAbove p) g k q = nilAbove_ (aboveNest p g k q)
aboveNest (TextBeside s sl p) g k q = textBeside_ s sl rest
where
!k1 = k -# sl
rest = case p of
Empty -> nilAboveNest g k1 q
_ -> aboveNest p g k1 q
aboveNest _ _ _ _ = panic "aboveNest: Unhandled case"
\end{code}
\begin{code}
nilAboveNest :: Bool -> FastInt -> RDoc -> RDoc
nilAboveNest _ _ Empty = Empty
nilAboveNest g k (Nest k1 q) = nilAboveNest g (k +# k1) q
nilAboveNest g k q | (not g) && (k ># _ILIT(0))
= textBeside_ (Str (spaces k)) k q
| otherwise
= nilAbove_ (mkNest k q)
\end{code}
%*********************************************************
%* *
\subsection{Horizontal composition @<>@}
%* *
%*********************************************************
\begin{code}
p <> q = Beside p False q
p <+> q = Beside p True q
beside :: Doc -> Bool -> RDoc -> RDoc
beside NoDoc _ _ = NoDoc
beside (p1 `Union` p2) g q = (beside p1 g q) `union_` (beside p2 g q)
beside Empty _ q = q
beside (Nest k p) g q = nest_ k $! beside p g q
beside p@(Beside p1 g1 q1) g2 q2
| g1 == g2 = beside p1 g1 $! beside q1 g2 q2
| otherwise = beside (reduceDoc p) g2 q2
beside p@(Above _ _ _) g q = let d = reduceDoc p in d `seq` beside d g q
beside (NilAbove p) g q = nilAbove_ $! beside p g q
beside (TextBeside s sl p) g q = textBeside_ s sl $! rest
where
rest = case p of
Empty -> nilBeside g q
_ -> beside p g q
\end{code}
\begin{code}
nilBeside :: Bool -> RDoc -> RDoc
nilBeside _ Empty = Empty
nilBeside g (Nest _ p) = nilBeside g p
nilBeside g p | g = textBeside_ space_text (_ILIT(1)) p
| otherwise = p
\end{code}
%*********************************************************
%* *
\subsection{Separate, @sep@, Hughes version}
%* *
%*********************************************************
\begin{code}
sep = sepX True
cat = sepX False
sepX :: Bool -> [Doc] -> Doc
sepX _ [] = empty
sepX x (p:ps) = sep1 x (reduceDoc p) (_ILIT(0)) ps
sep1 :: Bool -> RDoc -> FastInt -> [Doc] -> RDoc
sep1 _ NoDoc _ _ = NoDoc
sep1 g (p `Union` q) k ys = sep1 g p k ys
`union_`
(aboveNest q False k (reduceDoc (vcat ys)))
sep1 g Empty k ys = mkNest k (sepX g ys)
sep1 g (Nest n p) k ys = nest_ n (sep1 g p (k -# n) ys)
sep1 _ (NilAbove p) k ys = nilAbove_ (aboveNest p False k (reduceDoc (vcat ys)))
sep1 g (TextBeside s sl p) k ys = textBeside_ s sl (sepNB g p (k -# sl) ys)
sep1 _ _ _ _ = panic "sep1: Unhandled case"
sepNB :: Bool -> Doc -> FastInt -> [Doc] -> Doc
sepNB g (Nest _ p) k ys = sepNB g p k ys
sepNB g Empty k ys = oneLiner (nilBeside g (reduceDoc rest))
`mkUnion`
nilAboveNest False k (reduceDoc (vcat ys))
where
rest | g = hsep ys
| otherwise = hcat ys
sepNB g p k ys = sep1 g p k ys
\end{code}
%*********************************************************
%* *
\subsection{@fill@}
%* *
%*********************************************************
\begin{code}
fsep = fill True
fcat = fill False
fill :: Bool -> [Doc] -> Doc
fill _ [] = empty
fill g (p:ps) = fill1 g (reduceDoc p) (_ILIT(0)) ps
fill1 :: Bool -> RDoc -> FastInt -> [Doc] -> Doc
fill1 _ NoDoc _ _ = NoDoc
fill1 g (p `Union` q) k ys = fill1 g p k ys
`union_`
(aboveNest q False k (fill g ys))
fill1 g Empty k ys = mkNest k (fill g ys)
fill1 g (Nest n p) k ys = nest_ n (fill1 g p (k -# n) ys)
fill1 g (NilAbove p) k ys = nilAbove_ (aboveNest p False k (fill g ys))
fill1 g (TextBeside s sl p) k ys = textBeside_ s sl (fillNB g p (k -# sl) ys)
fill1 _ _ _ _ = panic "fill1: Unhandled case"
fillNB :: Bool -> Doc -> Int# -> [Doc] -> Doc
fillNB g (Nest _ p) k ys = fillNB g p k ys
fillNB _ Empty _ [] = Empty
fillNB g Empty k (y:ys) = nilBeside g (fill1 g (oneLiner (reduceDoc y)) k1 ys)
`mkUnion`
nilAboveNest False k (fill g (y:ys))
where
!k1 | g = k -# _ILIT(1)
| otherwise = k
fillNB g p k ys = fill1 g p k ys
\end{code}
%*********************************************************
%* *
\subsection{Selecting the best layout}
%* *
%*********************************************************
\begin{code}
best :: Int
-> Int
-> RDoc
-> RDoc
best w_ r_ p
= get (iUnbox w_) p
where
!r = iUnbox r_
get :: FastInt
-> Doc -> Doc
get _ Empty = Empty
get _ NoDoc = NoDoc
get w (NilAbove p) = nilAbove_ (get w p)
get w (TextBeside s sl p) = textBeside_ s sl (get1 w sl p)
get w (Nest k p) = nest_ k (get (w -# k) p)
get w (p `Union` q) = nicest w r (get w p) (get w q)
get _ _ = panic "best/get: Unhandled case"
get1 :: FastInt
-> FastInt
-> Doc
-> Doc
get1 _ _ Empty = Empty
get1 _ _ NoDoc = NoDoc
get1 w sl (NilAbove p) = nilAbove_ (get (w -# sl) p)
get1 w sl (TextBeside t tl p) = textBeside_ t tl (get1 w (sl +# tl) p)
get1 w sl (Nest _ p) = get1 w sl p
get1 w sl (p `Union` q) = nicest1 w r sl (get1 w sl p)
(get1 w sl q)
get1 _ _ _ = panic "best/get1: Unhandled case"
nicest :: FastInt -> FastInt -> Doc -> Doc -> Doc
nicest w r p q = nicest1 w r (_ILIT(0)) p q
nicest1 :: FastInt -> FastInt -> Int# -> Doc -> Doc -> Doc
nicest1 w r sl p q | fits ((w `minFastInt` r) -# sl) p = p
| otherwise = q
fits :: FastInt
-> Doc
-> Bool
fits n _ | n <# _ILIT(0) = False
fits _ NoDoc = False
fits _ Empty = True
fits _ (NilAbove _) = True
fits n (TextBeside _ sl p) = fits (n -# sl) p
fits _ _ = panic "fits: Unhandled case"
\end{code}
@first@ and @nonEmptySet@ are similar to @nicest@ and @fits@, only simpler.
@first@ returns its first argument if it is nonempty, otherwise its second.
\begin{code}
first :: Doc -> Doc -> Doc
first p q | nonEmptySet p = p
| otherwise = q
nonEmptySet :: Doc -> Bool
nonEmptySet NoDoc = False
nonEmptySet (_ `Union` _) = True
nonEmptySet Empty = True
nonEmptySet (NilAbove _) = True
nonEmptySet (TextBeside _ _ p) = nonEmptySet p
nonEmptySet (Nest _ p) = nonEmptySet p
nonEmptySet _ = panic "nonEmptySet: Unhandled case"
\end{code}
@oneLiner@ returns the oneline members of the given set of @Doc@s.
\begin{code}
oneLiner :: Doc -> Doc
oneLiner NoDoc = NoDoc
oneLiner Empty = Empty
oneLiner (NilAbove _) = NoDoc
oneLiner (TextBeside s sl p) = textBeside_ s sl (oneLiner p)
oneLiner (Nest k p) = nest_ k (oneLiner p)
oneLiner (p `Union` _) = oneLiner p
oneLiner _ = panic "oneLiner: Unhandled case"
\end{code}
%*********************************************************
%* *
\subsection{Displaying the best layout}
%* *
%*********************************************************
\begin{code}
render doc = showDocWith PageMode doc
showDoc :: Doc -> String -> String
showDoc doc rest = showDocWithAppend PageMode doc rest
showDocWithAppend :: Mode -> Doc -> String -> String
showDocWithAppend mode doc rest = fullRender mode 100 1.5 string_txt rest doc
showDocWith :: Mode -> Doc -> String
showDocWith mode doc = showDocWithAppend mode doc ""
string_txt :: TextDetails -> String -> String
string_txt (Chr c) s = c:s
string_txt (Str s1) s2 = s1 ++ s2
string_txt (PStr s1) s2 = unpackFS s1 ++ s2
string_txt (LStr s1 _) s2 = unpackLitString s1 ++ s2
\end{code}
\begin{code}
fullRender OneLineMode _ _ txt end doc
= lay (reduceDoc doc)
where
lay NoDoc = cant_fail
lay (Union _ q) = lay q
lay (Nest _ p) = lay p
lay Empty = end
lay (NilAbove p) = space_text `txt` lay p
lay (TextBeside s _ p) = s `txt` lay p
lay _ = panic "fullRender/OneLineMode/lay: Unhandled case"
fullRender LeftMode _ _ txt end doc
= lay (reduceDoc doc)
where
lay NoDoc = cant_fail
lay (Union p q) = lay (first p q)
lay (Nest _ p) = lay p
lay Empty = end
lay (NilAbove p) = nl_text `txt` lay p
lay (TextBeside s _ p) = s `txt` lay p
lay _ = panic "fullRender/LeftMode/lay: Unhandled case"
fullRender mode line_length ribbons_per_line txt end doc
= display mode line_length ribbon_length txt end best_doc
where
best_doc = best hacked_line_length ribbon_length (reduceDoc doc)
hacked_line_length, ribbon_length :: Int
ribbon_length = round (fromIntegral line_length / ribbons_per_line)
hacked_line_length = case mode of
ZigZagMode -> maxBound
_ -> line_length
display :: Mode -> Int -> Int -> (TextDetails -> t -> t) -> t -> Doc -> t
display mode page_width ribbon_width txt end doc
= case (iUnbox page_width) -# (iUnbox ribbon_width) of { gap_width ->
case gap_width `quotFastInt` _ILIT(2) of { shift ->
let
lay k (Nest k1 p) = lay (k +# k1) p
lay _ Empty = end
lay k (NilAbove p) = nl_text `txt` lay k p
lay k (TextBeside s sl p)
= case mode of
ZigZagMode | k >=# gap_width
-> nl_text `txt` (
Str (multi_ch shift '/') `txt` (
nl_text `txt` (
lay1 (k -# shift) s sl p)))
| k <# _ILIT(0)
-> nl_text `txt` (
Str (multi_ch shift '\\') `txt` (
nl_text `txt` (
lay1 (k +# shift) s sl p )))
_ -> lay1 k s sl p
lay _ _ = panic "display/lay: Unhandled case"
lay1 k s sl p = indent k (s `txt` lay2 (k +# sl) p)
lay2 k (NilAbove p) = nl_text `txt` lay k p
lay2 k (TextBeside s sl p) = s `txt` (lay2 (k +# sl) p)
lay2 k (Nest _ p) = lay2 k p
lay2 _ Empty = end
lay2 _ _ = panic "display/lay2: Unhandled case"
indent n r | n >=# _ILIT(8) = LStr (sLit " ") (_ILIT(8)) `txt`
indent (n -# _ILIT(8)) r
| otherwise = Str (spaces n) `txt` r
in
lay (_ILIT(0)) doc
}}
cant_fail :: a
cant_fail = error "easy_display: NoDoc"
multi_ch :: Int# -> Char -> String
multi_ch n ch | n <=# _ILIT(0) = ""
| otherwise = ch : multi_ch (n -# _ILIT(1)) ch
spaces :: Int# -> String
spaces n | n <=# _ILIT(0) = ""
| otherwise = ' ' : spaces (n -# _ILIT(1))
\end{code}
\begin{code}
pprCols :: Int
pprCols = 100
printDoc :: Mode -> Handle -> Doc -> IO ()
printDoc LeftMode hdl doc
= do { printLeftRender hdl doc; hFlush hdl }
printDoc mode hdl doc
= do { fullRender mode pprCols 1.5 put done doc ;
hFlush hdl }
where
put (Chr c) next = hPutChar hdl c >> next
put (Str s) next = hPutStr hdl s >> next
put (PStr s) next = hPutStr hdl (unpackFS s) >> next
put (LStr s l) next = hPutLitString hdl s l >> next
done = hPutChar hdl '\n'
hPutLitString :: Handle -> Ptr a -> Int# -> IO ()
hPutLitString handle a l = if l ==# _ILIT(0)
then return ()
else hPutBuf handle a (iBox l)
printLeftRender :: Handle -> Doc -> IO ()
printLeftRender hdl doc = do
b <- newBufHandle hdl
bufLeftRender b doc
bFlush b
bufLeftRender :: BufHandle -> Doc -> IO ()
bufLeftRender b doc = layLeft b (reduceDoc doc)
layLeft :: BufHandle -> Doc -> IO ()
layLeft b _ | b `seq` False = undefined
layLeft _ NoDoc = cant_fail
layLeft b (Union p q) = return () >> layLeft b (first p q)
layLeft b (Nest _ p) = return () >> layLeft b p
layLeft b Empty = bPutChar b '\n'
layLeft b (NilAbove p) = bPutChar b '\n' >> layLeft b p
layLeft b (TextBeside s _ p) = put b s >> layLeft b p
where
put b _ | b `seq` False = undefined
put b (Chr c) = bPutChar b c
put b (Str s) = bPutStr b s
put b (PStr s) = bPutFS b s
put b (LStr s l) = bPutLitString b s l
layLeft _ _ = panic "layLeft: Unhandled case"
\end{code}