ghc-lib-parser-0.20190402: compiler/utils/Pretty.hs
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE MagicHash #-}
-----------------------------------------------------------------------------
-- |
-- Module : Pretty
-- Copyright : (c) The University of Glasgow 2001
-- License : BSD-style (see the file LICENSE)
--
-- Maintainer : David Terei <code@davidterei.com>
-- Stability : stable
-- Portability : portable
--
-- 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>
--
-----------------------------------------------------------------------------
{-
Note [Differences between libraries/pretty and compiler/utils/Pretty.hs]
For historical reasons, there are two different copies of `Pretty` in the GHC
source tree:
* `libraries/pretty` is a submodule containing
https://github.com/haskell/pretty. This is the `pretty` library as released
on hackage. It is used by several other libraries in the GHC source tree
(e.g. template-haskell and Cabal).
* `compiler/utils/Pretty.hs` (this module). It is used by GHC only.
There is an ongoing effort in https://github.com/haskell/pretty/issues/1 and
https://gitlab.haskell.org/ghc/ghc/issues/10735 to try to get rid of GHC's copy
of Pretty.
Currently, GHC's copy of Pretty resembles pretty-1.1.2.0, with the following
major differences:
* GHC's copy uses `Faststring` for performance reasons.
* GHC's copy has received a backported bugfix for #12227, which was
released as pretty-1.1.3.4 ("Remove harmful $! forcing in beside",
https://github.com/haskell/pretty/pull/35).
Other differences are minor. Both copies define some extra functions and
instances not defined in the other copy. To see all differences, do this in a
ghc git tree:
$ cd libraries/pretty
$ git checkout v1.1.2.0
$ cd -
$ vimdiff compiler/utils/Pretty.hs \
libraries/pretty/src/Text/PrettyPrint/HughesPJ.hs
For parity with `pretty-1.1.2.1`, the following two `pretty` commits would
have to be backported:
* "Resolve foldr-strictness stack overflow bug"
(307b8173f41cd776eae8f547267df6d72bff2d68)
* "Special-case reduce for horiz/vert"
(c57c7a9dfc49617ba8d6e4fcdb019a3f29f1044c)
This has not been done sofar, because these commits seem to cause more
allocation in the compiler (see thomie's comments in
https://github.com/haskell/pretty/pull/9).
-}
module Pretty (
-- * The document type
Doc, TextDetails(..),
-- * Constructing documents
-- ** Converting values into documents
char, text, ftext, ptext, ztext, sizedText, zeroWidthText,
int, integer, float, double, rational, hex,
-- ** Simple derived documents
semi, comma, colon, space, equals,
lparen, rparen, lbrack, rbrack, lbrace, rbrace,
-- ** Wrapping documents in delimiters
parens, brackets, braces, quotes, quote, doubleQuotes,
maybeParens,
-- ** Combining documents
empty,
(<>), (<+>), hcat, hsep,
($$), ($+$), vcat,
sep, cat,
fsep, fcat,
nest,
hang, hangNotEmpty, punctuate,
-- * Predicates on documents
isEmpty,
-- * Rendering documents
-- ** Rendering with a particular style
Style(..),
style,
renderStyle,
Mode(..),
-- ** General rendering
fullRender, txtPrinter,
-- ** GHC-specific rendering
printDoc, printDoc_,
bufLeftRender -- performance hack
) where
import GhcPrelude hiding (error)
import BufWrite
import FastString
import Panic
import System.IO
import Numeric (showHex)
--for a RULES
import GHC.Base ( unpackCString#, unpackNBytes#, Int(..) )
import GHC.Ptr ( Ptr(..) )
-- Don't import Util( assertPanic ) because it makes a loop in the module structure
-- ---------------------------------------------------------------------------
-- The Doc calculus
{-
Laws for $$
~~~~~~~~~~~
<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 non-empty
** because of law n6, t2 only holds if x doesn't
** start with `nest'.
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 x <> 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 non-empty
** 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 non-empty
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
You might think that the following version of <m1> would
be neater:
<3 NO> (text s <> x) $$ y = text s <> ((empty <> x)) $$
nest (-length s) y)
But it doesn't work, for if x=empty, we would have
text s $$ y = text s <> (empty $$ nest (-length s) y)
= text s <> nest (-length s) y
-}
-- ---------------------------------------------------------------------------
-- Operator fixity
infixl 6 <>
infixl 6 <+>
infixl 5 $$, $+$
-- ---------------------------------------------------------------------------
-- The Doc data type
-- | The abstract type of documents.
-- A Doc represents a *set* of layouts. A Doc with
-- no occurrences of Union or NoDoc represents just one layout.
data Doc
= Empty -- empty
| NilAbove Doc -- text "" $$ x
| TextBeside !TextDetails {-# UNPACK #-} !Int Doc -- text s <> x
| Nest {-# UNPACK #-} !Int Doc -- nest k x
| Union Doc Doc -- ul `union` ur
| NoDoc -- The empty set of documents
| Beside Doc Bool Doc -- True <=> space between
| Above Doc Bool Doc -- True <=> never overlap
{-
Here are the invariants:
1) The argument of NilAbove is never Empty. Therefore
a NilAbove occupies at least two lines.
2) The argument of @TextBeside@ is never @Nest@.
3) The layouts of the two arguments of @Union@ both flatten to the same
string.
4) The arguments of @Union@ are either @TextBeside@, or @NilAbove@.
5) A @NoDoc@ may only appear on the first line of the left argument of an
union. Therefore, the right argument of an union can never be equivalent
to the empty set (@NoDoc@).
6) An empty document is always represented by @Empty@. It can't be
hidden inside a @Nest@, or a @Union@ of two @Empty@s.
7) 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.
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)
-}
-- | RDoc is a "reduced GDoc", guaranteed not to have a top-level Above or Beside.
type RDoc = Doc
-- | The TextDetails data type
--
-- A TextDetails represents a fragment of text that will be
-- output at some point.
data TextDetails = Chr {-# UNPACK #-} !Char -- ^ A single Char fragment
| Str String -- ^ A whole String fragment
| PStr FastString -- a hashed string
| ZStr FastZString -- a z-encoded string
| LStr {-# UNPACK #-} !PtrString
-- a '\0'-terminated array of bytes
| RStr {-# UNPACK #-} !Int {-# UNPACK #-} !Char
-- a repeated character (e.g., ' ')
instance Show Doc where
showsPrec _ doc cont = fullRender (mode style) (lineLength style)
(ribbonsPerLine style)
txtPrinter cont doc
-- ---------------------------------------------------------------------------
-- Values and Predicates on GDocs and TextDetails
-- | A document of height and width 1, containing a literal character.
char :: Char -> Doc
char c = textBeside_ (Chr c) 1 Empty
-- | A document of height 1 containing a literal string.
-- 'text' satisfies the following laws:
--
-- * @'text' s '<>' 'text' t = 'text' (s'++'t)@
--
-- * @'text' \"\" '<>' x = x@, if @x@ non-empty
--
-- The side condition on the last law is necessary because @'text' \"\"@
-- has height 1, while 'empty' has no height.
text :: String -> Doc
text s = textBeside_ (Str s) (length s) Empty
{-# NOINLINE [0] text #-} -- Give the RULE a chance to fire
-- It must wait till after phase 1 when
-- the unpackCString first is manifested
-- RULE that turns (text "abc") into (ptext (A# "abc"#)) to avoid the
-- intermediate packing/unpacking of the string.
{-# RULES "text/str"
forall a. text (unpackCString# a) = ptext (mkPtrString# a)
#-}
{-# RULES "text/unpackNBytes#"
forall p n. text (unpackNBytes# p n) = ptext (PtrString (Ptr p) (I# n))
#-}
ftext :: FastString -> Doc
ftext s = textBeside_ (PStr s) (lengthFS s) Empty
ptext :: PtrString -> Doc
ptext s = textBeside_ (LStr s) (lengthPS s) Empty
ztext :: FastZString -> Doc
ztext s = textBeside_ (ZStr s) (lengthFZS s) Empty
-- | Some text with any width. (@text s = sizedText (length s) s@)
sizedText :: Int -> String -> Doc
sizedText l s = textBeside_ (Str s) l Empty
-- | Some text, but without any width. Use for non-printing text
-- such as a HTML or Latex tags
zeroWidthText :: String -> Doc
zeroWidthText = sizedText 0
-- | The empty document, with no height and no width.
-- 'empty' is the identity for '<>', '<+>', '$$' and '$+$', and anywhere
-- in the argument list for 'sep', 'hcat', 'hsep', 'vcat', 'fcat' etc.
empty :: Doc
empty = Empty
-- | Returns 'True' if the document is empty
isEmpty :: Doc -> Bool
isEmpty Empty = True
isEmpty _ = False
{-
Q: What is the reason for negative indentation (i.e. argument to indent
is < 0) ?
A:
This indicates an error in the library client's code.
If we compose a <> b, and the first line of b is more indented than some
other lines of b, the law <n6> (<> eats nests) may cause the pretty
printer to produce an invalid layout:
doc |0123345
------------------
d1 |a...|
d2 |...b|
|c...|
d1<>d2 |ab..|
c|....|
Consider a <> b, let `s' be the length of the last line of `a', `k' the
indentation of the first line of b, and `k0' the indentation of the
left-most line b_i of b.
The produced layout will have negative indentation if `k - k0 > s', as
the first line of b will be put on the (s+1)th column, effectively
translating b horizontally by (k-s). Now if the i^th line of b has an
indentation k0 < (k-s), it is translated out-of-page, causing
`negative indentation'.
-}
semi :: Doc -- ^ A ';' character
comma :: Doc -- ^ A ',' character
colon :: Doc -- ^ A ':' character
space :: Doc -- ^ A space character
equals :: Doc -- ^ A '=' character
lparen :: Doc -- ^ A '(' character
rparen :: Doc -- ^ A ')' character
lbrack :: Doc -- ^ A '[' character
rbrack :: Doc -- ^ A ']' character
lbrace :: Doc -- ^ A '{' character
rbrace :: Doc -- ^ A '}' character
semi = char ';'
comma = char ','
colon = char ':'
space = char ' '
equals = char '='
lparen = char '('
rparen = char ')'
lbrack = char '['
rbrack = char ']'
lbrace = char '{'
rbrace = char '}'
spaceText, nlText :: TextDetails
spaceText = Chr ' '
nlText = Chr '\n'
int :: Int -> Doc -- ^ @int n = text (show n)@
integer :: Integer -> Doc -- ^ @integer n = text (show n)@
float :: Float -> Doc -- ^ @float n = text (show n)@
double :: Double -> Doc -- ^ @double n = text (show n)@
rational :: Rational -> Doc -- ^ @rational n = text (show n)@
hex :: Integer -> Doc -- ^ See Note [Print Hexadecimal Literals]
int n = text (show n)
integer n = text (show n)
float n = text (show n)
double n = text (show n)
rational n = text (show n)
hex n = text ('0' : 'x' : padded)
where
str = showHex n ""
strLen = max 1 (length str)
len = 2 ^ (ceiling (logBase 2 (fromIntegral strLen :: Double)) :: Int)
padded = replicate (len - strLen) '0' ++ str
parens :: Doc -> Doc -- ^ Wrap document in @(...)@
brackets :: Doc -> Doc -- ^ Wrap document in @[...]@
braces :: Doc -> Doc -- ^ Wrap document in @{...}@
quotes :: Doc -> Doc -- ^ Wrap document in @\'...\'@
quote :: Doc -> Doc
doubleQuotes :: Doc -> Doc -- ^ Wrap document in @\"...\"@
quotes p = char '`' <> p <> char '\''
quote p = char '\'' <> p
doubleQuotes p = char '"' <> p <> char '"'
parens p = char '(' <> p <> char ')'
brackets p = char '[' <> p <> char ']'
braces p = char '{' <> p <> char '}'
{-
Note [Print Hexadecimal Literals]
Relevant discussions:
* Phabricator: https://phabricator.haskell.org/D4465
* GHC Trac: https://gitlab.haskell.org/ghc/ghc/issues/14872
There is a flag `-dword-hex-literals` that causes literals of
type `Word#` or `Word64#` to be displayed in hexadecimal instead
of decimal when dumping GHC core. It also affects the presentation
of these in GHC's error messages. Additionally, the hexadecimal
encoding of these numbers is zero-padded so that its length is
a power of two. As an example of what this does,
consider the following haskell file `Literals.hs`:
module Literals where
alpha :: Int
alpha = 100 + 200
beta :: Word -> Word
beta x = x + div maxBound 255 + div 0xFFFFFFFF 255 + 0x0202
We get the following dumped core when we compile on a 64-bit
machine with ghc -O2 -fforce-recomp -ddump-simpl -dsuppress-all
-dhex-word-literals literals.hs:
==================== Tidy Core ====================
... omitted for brevity ...
-- RHS size: {terms: 2, types: 0, coercions: 0, joins: 0/0}
alpha
alpha = I# 300#
-- RHS size: {terms: 12, types: 3, coercions: 0, joins: 0/0}
beta
beta
= \ x_aYE ->
case x_aYE of { W# x#_a1v0 ->
W#
(plusWord#
(plusWord# (plusWord# x#_a1v0 0x0101010101010101##) 0x01010101##)
0x0202##)
}
Notice that the word literals are in hexadecimals and that they have
been padded with zeroes so that their lengths are 16, 8, and 4, respectively.
-}
-- | Apply 'parens' to 'Doc' if boolean is true.
maybeParens :: Bool -> Doc -> Doc
maybeParens False = id
maybeParens True = parens
-- ---------------------------------------------------------------------------
-- Structural operations on GDocs
-- | Perform some simplification of a built up @GDoc@.
reduceDoc :: Doc -> RDoc
reduceDoc (Beside p g q) = p `seq` g `seq` (beside p g $! reduceDoc q)
reduceDoc (Above p g q) = p `seq` g `seq` (above p g $! reduceDoc q)
reduceDoc p = p
-- | List version of '<>'.
hcat :: [Doc] -> Doc
hcat = reduceAB . foldr (beside_' False) empty
-- | List version of '<+>'.
hsep :: [Doc] -> Doc
hsep = reduceAB . foldr (beside_' True) empty
-- | List version of '$$'.
vcat :: [Doc] -> Doc
vcat = reduceAB . foldr (above_' False) empty
-- | Nest (or indent) a document by a given number of positions
-- (which may also be negative). 'nest' satisfies the laws:
--
-- * @'nest' 0 x = x@
--
-- * @'nest' k ('nest' k' x) = 'nest' (k+k') x@
--
-- * @'nest' k (x '<>' y) = 'nest' k z '<>' 'nest' k y@
--
-- * @'nest' k (x '$$' y) = 'nest' k x '$$' 'nest' k y@
--
-- * @'nest' k 'empty' = 'empty'@
--
-- * @x '<>' 'nest' k y = x '<>' y@, if @x@ non-empty
--
-- The side condition on the last law is needed because
-- 'empty' is a left identity for '<>'.
nest :: Int -> Doc -> Doc
nest k p = mkNest k (reduceDoc p)
-- | @hang d1 n d2 = sep [d1, nest n d2]@
hang :: Doc -> Int -> Doc -> Doc
hang d1 n d2 = sep [d1, nest n d2]
-- | Apply 'hang' to the arguments if the first 'Doc' is not empty.
hangNotEmpty :: Doc -> Int -> Doc -> Doc
hangNotEmpty d1 n d2 = if isEmpty d1
then d2
else hang d1 n d2
-- | @punctuate p [d1, ... dn] = [d1 \<> p, d2 \<> p, ... dn-1 \<> p, dn]@
punctuate :: Doc -> [Doc] -> [Doc]
punctuate _ [] = []
punctuate p (x:xs) = go x xs
where go y [] = [y]
go y (z:zs) = (y <> p) : go z zs
-- mkNest checks for Nest's invariant that it doesn't have an Empty inside it
mkNest :: Int -> Doc -> Doc
mkNest k _ | k `seq` False = undefined
mkNest k (Nest k1 p) = mkNest (k + k1) p
mkNest _ NoDoc = NoDoc
mkNest _ Empty = Empty
mkNest 0 p = p
mkNest k p = nest_ k p
-- mkUnion checks for an empty document
mkUnion :: Doc -> Doc -> Doc
mkUnion Empty _ = Empty
mkUnion p q = p `union_` q
beside_' :: Bool -> Doc -> Doc -> Doc
beside_' _ p Empty = p
beside_' g p q = Beside p g q
above_' :: Bool -> Doc -> Doc -> Doc
above_' _ p Empty = p
above_' g p q = Above p g q
reduceAB :: Doc -> Doc
reduceAB (Above Empty _ q) = q
reduceAB (Beside Empty _ q) = q
reduceAB doc = doc
nilAbove_ :: RDoc -> RDoc
nilAbove_ = NilAbove
-- Arg of a TextBeside is always an RDoc
textBeside_ :: TextDetails -> Int -> RDoc -> RDoc
textBeside_ = TextBeside
nest_ :: Int -> RDoc -> RDoc
nest_ = Nest
union_ :: RDoc -> RDoc -> RDoc
union_ = Union
-- ---------------------------------------------------------------------------
-- Vertical composition @$$@
-- | Above, except that if the last line of the first argument stops
-- at least one position before the first line of the second begins,
-- these two lines are overlapped. For example:
--
-- > text "hi" $$ nest 5 (text "there")
--
-- lays out as
--
-- > hi there
--
-- rather than
--
-- > hi
-- > there
--
-- '$$' is associative, with identity 'empty', and also satisfies
--
-- * @(x '$$' y) '<>' z = x '$$' (y '<>' z)@, if @y@ non-empty.
--
($$) :: Doc -> Doc -> Doc
p $$ q = above_ p False q
-- | Above, with no overlapping.
-- '$+$' is associative, with identity 'empty'.
($+$) :: Doc -> Doc -> Doc
p $+$ q = above_ p True q
above_ :: Doc -> Bool -> Doc -> Doc
above_ p _ Empty = p
above_ Empty _ q = q
above_ p g q = Above p g 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 0 (reduceDoc q)
above p g q = aboveNest p g 0 (reduceDoc q)
-- Specification: aboveNest p g k q = p $g$ (nest k q)
aboveNest :: RDoc -> Bool -> Int -> RDoc -> RDoc
aboveNest _ _ k _ | k `seq` False = undefined
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)
-- p can't be Empty, so no need for mkNest
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 (Above {}) _ _ _ = error "aboveNest Above"
aboveNest (Beside {}) _ _ _ = error "aboveNest Beside"
-- Specification: text s <> nilaboveNest g k q
-- = text s <> (text "" $g$ nest k q)
nilAboveNest :: Bool -> Int -> RDoc -> RDoc
nilAboveNest _ k _ | k `seq` False = undefined
nilAboveNest _ _ Empty = Empty
-- Here's why the "text s <>" is in the spec!
nilAboveNest g k (Nest k1 q) = nilAboveNest g (k + k1) q
nilAboveNest g k q | not g && k > 0 -- No newline if no overlap
= textBeside_ (RStr k ' ') k q
| otherwise -- Put them really above
= nilAbove_ (mkNest k q)
-- ---------------------------------------------------------------------------
-- Horizontal composition @<>@
-- We intentionally avoid Data.Monoid.(<>) here due to interactions of
-- Data.Monoid.(<>) and (<+>). See
-- http://www.haskell.org/pipermail/libraries/2011-November/017066.html
-- | Beside.
-- '<>' is associative, with identity 'empty'.
(<>) :: Doc -> Doc -> Doc
p <> q = beside_ p False q
-- | Beside, separated by space, unless one of the arguments is 'empty'.
-- '<+>' is associative, with identity 'empty'.
(<+>) :: Doc -> Doc -> Doc
p <+> q = beside_ p True q
beside_ :: Doc -> Bool -> Doc -> Doc
beside_ p _ Empty = p
beside_ Empty _ q = q
beside_ p g q = Beside p g q
-- Specification: beside g p q = p <g> 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 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
-- Specification: text "" <> nilBeside g p
-- = text "" <g> p
nilBeside :: Bool -> RDoc -> RDoc
nilBeside _ Empty = Empty -- Hence the text "" in the spec
nilBeside g (Nest _ p) = nilBeside g p
nilBeside g p | g = textBeside_ spaceText 1 p
| otherwise = p
-- ---------------------------------------------------------------------------
-- Separate, @sep@
-- Specification: sep ps = oneLiner (hsep ps)
-- `union`
-- vcat ps
-- | Either 'hsep' or 'vcat'.
sep :: [Doc] -> Doc
sep = sepX True -- Separate with spaces
-- | Either 'hcat' or 'vcat'.
cat :: [Doc] -> Doc
cat = sepX False -- Don't
sepX :: Bool -> [Doc] -> Doc
sepX _ [] = empty
sepX x (p:ps) = sep1 x (reduceDoc p) 0 ps
-- Specification: sep1 g k ys = sep (x : map (nest k) ys)
-- = oneLiner (x <g> nest k (hsep ys))
-- `union` x $$ nest k (vcat ys)
sep1 :: Bool -> RDoc -> Int -> [Doc] -> RDoc
sep1 _ _ k _ | k `seq` False = undefined
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 _ (Above {}) _ _ = error "sep1 Above"
sep1 _ (Beside {}) _ _ = error "sep1 Beside"
-- Specification: sepNB p k ys = sep1 (text "" <> p) k ys
-- Called when we have already found some text in the first item
-- We have to eat up nests
sepNB :: Bool -> Doc -> Int -> [Doc] -> Doc
sepNB g (Nest _ p) k ys
= sepNB g p k ys -- Never triggered, because of invariant (2)
sepNB g Empty k ys
= oneLiner (nilBeside g (reduceDoc rest)) `mkUnion`
-- XXX: TODO: PRETTY: Used to use True here (but GHC used False...)
nilAboveNest False k (reduceDoc (vcat ys))
where
rest | g = hsep ys
| otherwise = hcat ys
sepNB g p k ys
= sep1 g p k ys
-- ---------------------------------------------------------------------------
-- @fill@
-- | \"Paragraph fill\" version of 'cat'.
fcat :: [Doc] -> Doc
fcat = fill False
-- | \"Paragraph fill\" version of 'sep'.
fsep :: [Doc] -> Doc
fsep = fill True
-- Specification:
--
-- fill g docs = fillIndent 0 docs
--
-- fillIndent k [] = []
-- fillIndent k [p] = p
-- fillIndent k (p1:p2:ps) =
-- oneLiner p1 <g> fillIndent (k + length p1 + g ? 1 : 0)
-- (remove_nests (oneLiner p2) : ps)
-- `Union`
-- (p1 $*$ nest (-k) (fillIndent 0 ps))
--
-- $*$ is defined for layouts (not Docs) as
-- layout1 $*$ layout2 | hasMoreThanOneLine layout1 = layout1 $$ layout2
-- | otherwise = layout1 $+$ layout2
fill :: Bool -> [Doc] -> RDoc
fill _ [] = empty
fill g (p:ps) = fill1 g (reduceDoc p) 0 ps
fill1 :: Bool -> RDoc -> Int -> [Doc] -> Doc
fill1 _ _ k _ | k `seq` False = undefined
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 _ (Above {}) _ _ = error "fill1 Above"
fill1 _ (Beside {}) _ _ = error "fill1 Beside"
fillNB :: Bool -> Doc -> Int -> [Doc] -> Doc
fillNB _ _ k _ | k `seq` False = undefined
fillNB g (Nest _ p) k ys = fillNB g p k ys
-- Never triggered, because of invariant (2)
fillNB _ Empty _ [] = Empty
fillNB g Empty k (Empty:ys) = fillNB g Empty k ys
fillNB g Empty k (y:ys) = fillNBE g k y ys
fillNB g p k ys = fill1 g p k ys
fillNBE :: Bool -> Int -> Doc -> [Doc] -> Doc
fillNBE g k y ys
= nilBeside g (fill1 g ((elideNest . oneLiner . reduceDoc) y) k' ys)
-- XXX: TODO: PRETTY: Used to use True here (but GHC used False...)
`mkUnion` nilAboveNest False k (fill g (y:ys))
where k' = if g then k - 1 else k
elideNest :: Doc -> Doc
elideNest (Nest _ d) = d
elideNest d = d
-- ---------------------------------------------------------------------------
-- Selecting the best layout
best :: Int -- Line length
-> Int -- Ribbon length
-> RDoc
-> RDoc -- No unions in here!
best w0 r = get w0
where
get :: Int -- (Remaining) width of line
-> Doc -> Doc
get w _ | w == 0 && False = undefined
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 _ (Above {}) = error "best get Above"
get _ (Beside {}) = error "best get Beside"
get1 :: Int -- (Remaining) width of line
-> Int -- Amount of first line already eaten up
-> Doc -- This is an argument to TextBeside => eat Nests
-> Doc -- No unions in here!
get1 w _ _ | w == 0 && False = undefined
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 _ _ (Above {}) = error "best get1 Above"
get1 _ _ (Beside {}) = error "best get1 Beside"
nicest :: Int -> Int -> Doc -> Doc -> Doc
nicest !w !r = nicest1 w r 0
nicest1 :: Int -> Int -> Int -> Doc -> Doc -> Doc
nicest1 !w !r !sl p q | fits ((w `min` r) - sl) p = p
| otherwise = q
fits :: Int -- Space available
-> Doc
-> Bool -- True if *first line* of Doc fits in space available
fits n _ | n < 0 = False
fits _ NoDoc = False
fits _ Empty = True
fits _ (NilAbove _) = True
fits n (TextBeside _ sl p) = fits (n - sl) p
fits _ (Above {}) = error "fits Above"
fits _ (Beside {}) = error "fits Beside"
fits _ (Union {}) = error "fits Union"
fits _ (Nest {}) = error "fits Nest"
-- | @first@ returns its first argument if it is non-empty, otherwise its second.
first :: Doc -> Doc -> Doc
first p q | nonEmptySet p = p -- unused, because (get OneLineMode) is unused
| 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 (Above {}) = error "nonEmptySet Above"
nonEmptySet (Beside {}) = error "nonEmptySet Beside"
-- @oneLiner@ returns the one-line members of the given set of @GDoc@s.
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 (Above {}) = error "oneLiner Above"
oneLiner (Beside {}) = error "oneLiner Beside"
-- ---------------------------------------------------------------------------
-- Rendering
-- | A rendering style.
data Style
= Style { mode :: Mode -- ^ The rendering mode
, lineLength :: Int -- ^ Length of line, in chars
, ribbonsPerLine :: Float -- ^ Ratio of line length to ribbon length
}
-- | The default style (@mode=PageMode, lineLength=100, ribbonsPerLine=1.5@).
style :: Style
style = Style { lineLength = 100, ribbonsPerLine = 1.5, mode = PageMode }
-- | Rendering mode.
data Mode = PageMode -- ^ Normal
| ZigZagMode -- ^ With zig-zag cuts
| LeftMode -- ^ No indentation, infinitely long lines
| OneLineMode -- ^ All on one line
-- | Render the @Doc@ to a String using the given @Style@.
renderStyle :: Style -> Doc -> String
renderStyle s = fullRender (mode s) (lineLength s) (ribbonsPerLine s)
txtPrinter ""
-- | Default TextDetails printer
txtPrinter :: TextDetails -> String -> String
txtPrinter (Chr c) s = c:s
txtPrinter (Str s1) s2 = s1 ++ s2
txtPrinter (PStr s1) s2 = unpackFS s1 ++ s2
txtPrinter (ZStr s1) s2 = zString s1 ++ s2
txtPrinter (LStr s1) s2 = unpackPtrString s1 ++ s2
txtPrinter (RStr n c) s2 = replicate n c ++ s2
-- | The general rendering interface.
fullRender :: Mode -- ^ Rendering mode
-> Int -- ^ Line length
-> Float -- ^ Ribbons per line
-> (TextDetails -> a -> a) -- ^ What to do with text
-> a -- ^ What to do at the end
-> Doc -- ^ The document
-> a -- ^ Result
fullRender OneLineMode _ _ txt end doc
= easyDisplay spaceText (\_ y -> y) txt end (reduceDoc doc)
fullRender LeftMode _ _ txt end doc
= easyDisplay nlText first txt end (reduceDoc doc)
fullRender m lineLen ribbons txt rest doc
= display m lineLen ribbonLen txt rest doc'
where
doc' = best bestLineLen ribbonLen (reduceDoc doc)
bestLineLen, ribbonLen :: Int
ribbonLen = round (fromIntegral lineLen / ribbons)
bestLineLen = case m of
ZigZagMode -> maxBound
_ -> lineLen
easyDisplay :: TextDetails
-> (Doc -> Doc -> Doc)
-> (TextDetails -> a -> a)
-> a
-> Doc
-> a
easyDisplay nlSpaceText choose txt end
= lay
where
lay NoDoc = error "easyDisplay: NoDoc"
lay (Union p q) = lay (choose p q)
lay (Nest _ p) = lay p
lay Empty = end
lay (NilAbove p) = nlSpaceText `txt` lay p
lay (TextBeside s _ p) = s `txt` lay p
lay (Above {}) = error "easyDisplay Above"
lay (Beside {}) = error "easyDisplay Beside"
display :: Mode -> Int -> Int -> (TextDetails -> a -> a) -> a -> Doc -> a
display m !page_width !ribbon_width txt end doc
= case page_width - ribbon_width of { gap_width ->
case gap_width `quot` 2 of { shift ->
let
lay k _ | k `seq` False = undefined
lay k (Nest k1 p) = lay (k + k1) p
lay _ Empty = end
lay k (NilAbove p) = nlText `txt` lay k p
lay k (TextBeside s sl p)
= case m of
ZigZagMode | k >= gap_width
-> nlText `txt` (
Str (replicate shift '/') `txt` (
nlText `txt`
lay1 (k - shift) s sl p ))
| k < 0
-> nlText `txt` (
Str (replicate shift '\\') `txt` (
nlText `txt`
lay1 (k + shift) s sl p ))
_ -> lay1 k s sl p
lay _ (Above {}) = error "display lay Above"
lay _ (Beside {}) = error "display lay Beside"
lay _ NoDoc = error "display lay NoDoc"
lay _ (Union {}) = error "display lay Union"
lay1 !k s !sl p = let !r = k + sl
in indent k (s `txt` lay2 r p)
lay2 k _ | k `seq` False = undefined
lay2 k (NilAbove p) = nlText `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 _ (Above {}) = error "display lay2 Above"
lay2 _ (Beside {}) = error "display lay2 Beside"
lay2 _ NoDoc = error "display lay2 NoDoc"
lay2 _ (Union {}) = error "display lay2 Union"
indent !n r = RStr n ' ' `txt` r
in
lay 0 doc
}}
printDoc :: Mode -> Int -> Handle -> Doc -> IO ()
-- printDoc adds a newline to the end
printDoc mode cols hdl doc = printDoc_ mode cols hdl (doc $$ text "")
printDoc_ :: Mode -> Int -> Handle -> Doc -> IO ()
-- printDoc_ does not add a newline at the end, so that
-- successive calls can output stuff on the same line
-- Rather like putStr vs putStrLn
printDoc_ LeftMode _ hdl doc
= do { printLeftRender hdl doc; hFlush hdl }
printDoc_ mode pprCols 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
-- NB. not hPutFS, we want this to go through
-- the I/O library's encoding layer. (#3398)
put (ZStr s) next = hPutFZS hdl s >> next
put (LStr s) next = hPutPtrString hdl s >> next
put (RStr n c) next = hPutStr hdl (replicate n c) >> next
done = return () -- hPutChar hdl '\n'
-- some versions of hPutBuf will barf if the length is zero
hPutPtrString :: Handle -> PtrString -> IO ()
hPutPtrString _handle (PtrString _ 0) = return ()
hPutPtrString handle (PtrString a l) = hPutBuf handle a l
-- Printing output in LeftMode is performance critical: it's used when
-- dumping C and assembly output, so we allow ourselves a few dirty
-- hacks:
--
-- (1) we specialise fullRender for LeftMode with IO output.
--
-- (2) we add a layer of buffering on top of Handles. Handles
-- don't perform well with lots of hPutChars, which is mostly
-- what we're doing here, because Handles have to be thread-safe
-- and async exception-safe. We only have a single thread and don't
-- care about exceptions, so we add a layer of fast buffering
-- over the Handle interface.
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 -- make it strict in b
layLeft _ NoDoc = error "layLeft: NoDoc"
layLeft b (Union p q) = layLeft b $! first p q
layLeft b (Nest _ p) = layLeft b $! p
layLeft b Empty = bPutChar b '\n'
layLeft b (NilAbove p) = p `seq` (bPutChar b '\n' >> layLeft b p)
layLeft b (TextBeside s _ p) = s `seq` (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 (ZStr s) = bPutFZS b s
put b (LStr s) = bPutPtrString b s
put b (RStr n c) = bPutReplicate b n c
layLeft _ _ = panic "layLeft: Unhandled case"
-- Define error=panic, for easier comparison with libraries/pretty.
error :: String -> a
error = panic