| Safe Haskell | Safe-Inferred |
|---|---|
| Language | Haskell2010 |
Prettyprinter.Internal
Description
Warning: internal module! This means that the API may change arbitrarily between versions without notice. Depending on this module may lead to unexpected breakages, so proceed with caution!
For a stable API, use the non-internal modules. For the special case of
writing adaptors to this library’s Doc
Synopsis
- data Doc ann
- class Pretty a where
- pretty :: a -> Doc ann
- prettyList :: [a] -> Doc ann
- viaShow :: Show a => a -> Doc ann
- unsafeViaShow :: Show a => a -> Doc ann
- unsafeTextWithoutNewlines :: Text -> Doc ann
- emptyDoc :: Doc ann
- nest :: Int -> Doc ann -> Doc ann
- line :: Doc ann
- line' :: Doc ann
- softline :: Doc ann
- softline' :: Doc ann
- hardline :: Doc ann
- group :: Doc ann -> Doc ann
- flatAlt :: Doc ann -> Doc ann -> Doc ann
- align :: Doc ann -> Doc ann
- hang :: Int -> Doc ann -> Doc ann
- indent :: Int -> Doc ann -> Doc ann
- encloseSep :: Doc ann -> Doc ann -> Doc ann -> [Doc ann] -> Doc ann
- list :: [Doc ann] -> Doc ann
- tupled :: [Doc ann] -> Doc ann
- (<+>) :: Doc ann -> Doc ann -> Doc ann
- concatWith :: Foldable t => (Doc ann -> Doc ann -> Doc ann) -> t (Doc ann) -> Doc ann
- hsep :: [Doc ann] -> Doc ann
- vsep :: [Doc ann] -> Doc ann
- fillSep :: [Doc ann] -> Doc ann
- sep :: [Doc ann] -> Doc ann
- hcat :: [Doc ann] -> Doc ann
- vcat :: [Doc ann] -> Doc ann
- fillCat :: [Doc ann] -> Doc ann
- cat :: [Doc ann] -> Doc ann
- punctuate :: Doc ann -> [Doc ann] -> [Doc ann]
- column :: (Int -> Doc ann) -> Doc ann
- nesting :: (Int -> Doc ann) -> Doc ann
- width :: Doc ann -> (Int -> Doc ann) -> Doc ann
- pageWidth :: (PageWidth -> Doc ann) -> Doc ann
- fill :: Int -> Doc ann -> Doc ann
- fillBreak :: Int -> Doc ann -> Doc ann
- plural :: (Num amount, Eq amount) => doc -> doc -> amount -> doc
- enclose :: Doc ann -> Doc ann -> Doc ann -> Doc ann
- surround :: Doc ann -> Doc ann -> Doc ann -> Doc ann
- annotate :: ann -> Doc ann -> Doc ann
- unAnnotate :: Doc ann -> Doc xxx
- reAnnotate :: (ann -> ann') -> Doc ann -> Doc ann'
- alterAnnotations :: (ann -> [ann']) -> Doc ann -> Doc ann'
- unAnnotateS :: SimpleDocStream ann -> SimpleDocStream xxx
- reAnnotateS :: (ann -> ann') -> SimpleDocStream ann -> SimpleDocStream ann'
- alterAnnotationsS :: (ann -> Maybe ann') -> SimpleDocStream ann -> SimpleDocStream ann'
- fuse :: FusionDepth -> Doc ann -> Doc ann
- data FusionDepth
- data SimpleDocStream ann
- = SFail
- | SEmpty
- | SChar !Char (SimpleDocStream ann)
- | SText !Int !Text (SimpleDocStream ann)
- | SLine !Int (SimpleDocStream ann)
- | SAnnPush ann (SimpleDocStream ann)
- | SAnnPop (SimpleDocStream ann)
- data PageWidth
- defaultPageWidth :: PageWidth
- newtype LayoutOptions = LayoutOptions {}
- defaultLayoutOptions :: LayoutOptions
- layoutPretty :: LayoutOptions -> Doc ann -> SimpleDocStream ann
- layoutCompact :: Doc ann1 -> SimpleDocStream ann2
- layoutSmart :: LayoutOptions -> Doc ann -> SimpleDocStream ann
- removeTrailingWhitespace :: SimpleDocStream ann -> SimpleDocStream ann
- renderShowS :: SimpleDocStream ann -> ShowS
- textSpaces :: Int -> Text
Documents
The abstract data type Doc annann.
More specifically, a value of type Doc
The annotation is an arbitrary piece of data associated with (part of) a document. Annotations may be used by the rendering backends in order to display output differently, such as
- color information (e.g. when rendering to the terminal)
- mouseover text (e.g. when rendering to rich HTML)
- whether to show something or not (to allow simple or detailed versions)
The simplest way to display a Doc is via the Show class.
>>>putStrLn (show (vsep ["hello", "world"]))hello world
Constructors
| Fail | Occurs when flattening a line. The layouter will reject this document, choosing a more suitable rendering. |
| Empty | The empty document; conceptually the unit of |
| Char !Char | invariant: not 'n' |
| Text !Int !Text | Invariants: at least two characters long, does not contain 'n'. For
empty documents, there is Since the frequently used |
| Line | Hard line break |
| FlatAlt (Doc ann) (Doc ann) | Lay out the first The layout algorithms work under the assumption that the first alternative is less wide than the flattened second alternative. |
| Cat (Doc ann) (Doc ann) | Concatenation of two documents |
| Nest !Int (Doc ann) | Document indented by a number of columns |
| Union (Doc ann) (Doc ann) | Invariant: The first lines of first document should be longer than the
first lines of the second one, so the layout algorithm can pick the one
that fits best. Used to implement layout alternatives for |
| Column (Int -> Doc ann) | React on the current cursor position, see |
| WithPageWidth (PageWidth -> Doc ann) | React on the document's width, see |
| Nesting (Int -> Doc ann) | React on the current nesting level, see |
| Annotated ann (Doc ann) | Add an annotation to the enclosed |
Instances
Basic functionality
Minimal complete definition
Methods
pretty :: a -> Doc ann Source #
>>>pretty 1 <+> pretty "hello" <+> pretty 1.2341 hello 1.234
prettyList :: [a] -> Doc ann Source #
prettyListinstance
. In normal circumstances only the Pretty a => Pretty [a]pretty
>>>prettyList [1, 23, 456][1, 23, 456]
Instances
| Pretty Bool Source # |
|
| Pretty Char Source # | Instead of
|
| Pretty Double Source # |
|
| Pretty Float Source # |
|
| Pretty Int Source # |
|
| Pretty Int8 Source # | |
| Pretty Int16 Source # | |
| Pretty Int32 Source # | |
| Pretty Int64 Source # | |
| Pretty Integer Source # |
|
| Pretty Natural Source # | |
| Pretty Word Source # | |
| Pretty Word8 Source # | |
| Pretty Word16 Source # | |
| Pretty Word32 Source # | |
| Pretty Word64 Source # | |
| Pretty () Source # |
The argument is not used:
|
Defined in Prettyprinter.Internal | |
| Pretty Void Source # | Finding a good example for printing something that does not exist is hard, so here is an example of printing a list full of nothing.
|
| Pretty Text Source # | (lazy |
| Pretty Text Source # | Automatically converts all newlines to
Note that
Manually use |
| Pretty a => Pretty [a] Source # |
|
Defined in Prettyprinter.Internal | |
| Pretty a => Pretty (Maybe a) Source # | Ignore
|
| Pretty a => Pretty (Identity a) Source # |
|
| Pretty a => Pretty (NonEmpty a) Source # | |
| (Pretty a1, Pretty a2) => Pretty (a1, a2) Source # |
|
Defined in Prettyprinter.Internal | |
| (Pretty a1, Pretty a2, Pretty a3) => Pretty (a1, a2, a3) Source # |
|
Defined in Prettyprinter.Internal | |
| Pretty a => Pretty (Const a b) Source # | |
viaShow :: Show a => a -> Doc ann Source #
Convenience function to convert a Showable value to a Doc. If the
String does not contain newlines, consider using the more performant
unsafeViaShow.
unsafeViaShow :: Show a => a -> Doc ann Source #
unsafeTextWithoutNewlines :: Text -> Doc ann Source #
(unsafeTextWithoutNewlines s) contains the literal string s.
The string must not contain any newline characters, since this is an
invariant of the Text constructor.
( lays out the document nest i x)x with the current nesting level
(indentation of the following lines) increased by i. Negative values are
allowed, and decrease the nesting level accordingly.
>>>vsep [nest 4 (vsep ["lorem", "ipsum", "dolor"]), "sit", "amet"]lorem ipsum dolor sit amet
See also
softline behaves like spaceline
Here, we have enough space to put everything in one line:
>>>let doc = "lorem ipsum" <> softline <> "dolor sit amet">>>putDocW 80 doclorem ipsum dolor sit amet
If we narrow the page to width 10, the layouter produces a line break:
>>>putDocW 10 doclorem ipsum dolor sit amet
softline=groupline
softline'softlinememptyspacelineline'softlinesoftline'
With enough space, we get direct concatenation:
>>>let doc = "ThisWord" <> softline' <> "IsWayTooLong">>>putDocW 80 docThisWordIsWayTooLong
If we narrow the page to width 10, the layouter produces a line break:
>>>putDocW 10 docThisWord IsWayTooLong
softline'=groupline'
A hardlinegrouped or
when there is plenty of space. Note that it might still be simply discarded
if it is part of a flatAlt inside a group.
>>>let doc = "lorem ipsum" <> hardline <> "dolor sit amet">>>putDocW 1000 doclorem ipsum dolor sit amet
>>>group doclorem ipsum dolor sit amet
Primitives for alternative layouts
group :: Doc ann -> Doc ann Source #
( tries laying out group x)x into a single line by removing the
contained line breaks; if this does not fit the page, or when a hardline
within x prevents it from being flattened, x is laid out without any
changes.
The group function is key to layouts that adapt to available space nicely.
See vcat, line, or flatAlt for examples that are related, or make good
use of it.
By default, ( renders as flatAlt x y)x. However when grouped,
y will be preferred, with x as the fallback for the case when y
doesn't fit.
>>>let doc = flatAlt "a" "b">>>putDoc doca>>>putDoc (group doc)b>>>putDocW 0 (group doc)a
flatAlt is particularly useful for defining conditional separators such as
softline =group(flatAlthardline" ")
>>>let hello = "Hello" <> softline <> "world!">>>putDocW 12 helloHello world!>>>putDocW 11 helloHello world!
Example: Haskell's do-notation
We can use this to render Haskell's do-notation nicely:
>>>let open = flatAlt "" "{ ">>>let close = flatAlt "" " }">>>let separator = flatAlt "" "; ">>>let prettyDo xs = group ("do" <+> align (encloseSep open close separator xs))>>>let statements = ["name:_ <- getArgs", "let greet = \"Hello, \" <> name", "putStrLn greet"]
This is put into a single line with {;} style if it fits:
>>>putDocW 80 (prettyDo statements)do { name:_ <- getArgs; let greet = "Hello, " <> name; putStrLn greet }
When there is not enough space the statements are broken up into lines nicely:
>>>putDocW 10 (prettyDo statements)do name:_ <- getArgs let greet = "Hello, " <> name putStrLn greet
Notes
Users should be careful to choose x to be less wide than y.
Otherwise, if y turns out not to fit the page, we fall back on an even
wider layout:
>>>let ugly = group (flatAlt "even wider" "too wide")>>>putDocW 7 uglyeven wider
Also note that group will flatten y:
>>>putDoc (group (flatAlt "x" ("y" <> line <> "y")))y y
This also means that an "unflattenable" y which contains a hard linebreak
will never be rendered:
>>>putDoc (group (flatAlt "x" ("y" <> hardline <> "y")))x
Alignment functions
align :: Doc ann -> Doc ann Source #
( lays out the document align x)x with the nesting level set to the
current column. It is used for example to implement hang.
As an example, we will put a document right above another one, regardless of
the current nesting level. Without alignment, the second line is put simply
below everything we've had so far:
>>>"lorem" <+> vsep ["ipsum", "dolor"]lorem ipsum dolor
If we add an align to the mix, the vsep
>>>"lorem" <+> align (vsep ["ipsum", "dolor"])lorem ipsum dolor
Arguments
| :: Int | Change of nesting level, relative to the start of the first line |
| -> Doc ann | |
| -> Doc ann |
( lays out the document hang i x)x with a nesting level set to the
current column plus i. Negative values are allowed, and decrease the
nesting level accordingly.
>>>let doc = reflow "Indenting these words with hang">>>putDocW 24 ("prefix" <+> hang 4 doc)prefix Indenting these words with hang
This differs from nest, which is based on the current nesting level plus
i. When you're not sure, try the more efficient nest first. In our
example, this would yield
>>>let doc = reflow "Indenting these words with nest">>>putDocW 24 ("prefix" <+> nest 4 doc)prefix Indenting these words with nest
hangi doc =align(nesti doc)
Arguments
| :: Doc ann | left delimiter |
| -> Doc ann | right delimiter |
| -> Doc ann | separator |
| -> [Doc ann] | input documents |
| -> Doc ann |
( concatenates the documents encloseSep l r sep xs)xs separated by
sep, and encloses the resulting document by l and r.
The documents are laid out horizontally if that fits the page:
>>>let doc = "list" <+> align (encloseSep lbracket rbracket comma (map pretty [1,20,300,4000]))>>>putDocW 80 doclist [1,20,300,4000]
If there is not enough space, then the input is split into lines entry-wise therwise they are laid out vertically, with separators put in the front:
>>>putDocW 10 doclist [1 ,20 ,300 ,4000]
Note that doc contains an explicit call to align so that the list items
are aligned vertically.
For putting separators at the end of entries instead, have a look at
punctuate.
list :: [Doc ann] -> Doc ann Source #
Haskell-inspired variant of encloseSep with braces and comma as
separator.
>>>let doc = list (map pretty [1,20,300,4000])
>>>putDocW 80 doc[1, 20, 300, 4000]
>>>putDocW 10 doc[ 1 , 20 , 300 , 4000 ]
tupled :: [Doc ann] -> Doc ann Source #
Haskell-inspired variant of encloseSep with parentheses and comma as
separator.
>>>let doc = tupled (map pretty [1,20,300,4000])
>>>putDocW 80 doc(1, 20, 300, 4000)
>>>putDocW 10 doc( 1 , 20 , 300 , 4000 )
Binary functions
List functions
concatWith :: Foldable t => (Doc ann -> Doc ann -> Doc ann) -> t (Doc ann) -> Doc ann Source #
Concatenate all documents element-wise with a binary function.
concatWith_ [] =memptyconcatWith(**) [x,y,z] = x ** y ** z
Multiple convenience definitions based on concatWith are already predefined,
for example:
hsep=concatWith(<+>)fillSep=concatWith(\x y -> x<>softline<>y)
This is also useful to define customized joiners:
>>>concatWith (surround dot) ["Prettyprinter", "Render", "Text"]Prettyprinter.Render.Text
sep family
hsep :: [Doc ann] -> Doc ann Source #
( concatenates all documents hsep xs)xs horizontally with <+>
>>>let docs = Util.words "lorem ipsum dolor sit amet"
>>>hsep docslorem ipsum dolor sit amet
hsep
>>>putDocW 5 (hsep docs)lorem ipsum dolor sit amet
For automatic line breaks, consider using fillSep instead.
vsep :: [Doc ann] -> Doc ann Source #
( concatenates all documents vsep xs)xs above each other. If a
group undoes the line breaks inserted by vsep, the documents are
separated with a space instead.
Using vsep alone yields
>>>"prefix" <+> vsep ["text", "to", "lay", "out"]prefix text to lay out
grouping a vsep separates the documents with a space if it fits the
page (and does nothing otherwise). See the sep
The align function can be used to align the documents under their first
element:
>>>"prefix" <+> align (vsep ["text", "to", "lay", "out"])prefix text to lay out
Since grouping a vsep is rather common, sep is a built-in for doing
that.
fillSep :: [Doc ann] -> Doc ann Source #
( concatenates the documents fillSep xs)xs horizontally with <+>linexs. (linegrouped, the documents
are separated with a space instead of newlines. Use fillCat if you do not
want a space.)
Let's print some words to fill the line:
>>>let docs = take 20 (cycle ["lorem", "ipsum", "dolor", "sit", "amet"])>>>putDocW 80 ("Docs:" <+> fillSep docs)Docs: lorem ipsum dolor sit amet lorem ipsum dolor sit amet lorem ipsum dolor sit amet lorem ipsum dolor sit amet
The same document, printed at a width of only 40, yields
>>>putDocW 40 ("Docs:" <+> fillSep docs)Docs: lorem ipsum dolor sit amet lorem ipsum dolor sit amet lorem ipsum dolor sit amet lorem ipsum dolor sit amet
sep :: [Doc ann] -> Doc ann Source #
( tries laying out the documents sep xs)xs separated with spaces,
and if this does not fit the page, separates them with newlines. This is what
differentiates it from vsep, which always lays out its contents beneath
each other.
>>>let doc = "prefix" <+> sep ["text", "to", "lay", "out"]>>>putDocW 80 docprefix text to lay out
With a narrower layout, the entries are separated by newlines:
>>>putDocW 20 docprefix text to lay out
sep=group.vsep
cat family
vcat :: [Doc ann] -> Doc ann Source #
( vertically concatenates the documents vcat xs)xs. If it is
grouped, the line breaks are removed.
In other words vcatvsepspaces.
>>>let docs = Util.words "lorem ipsum dolor">>>vcat docslorem ipsum dolor>>>group (vcat docs)loremipsumdolor
Since grouping a vcat is rather common, cat is a built-in shortcut for
it.
fillCat :: [Doc ann] -> Doc ann Source #
( concatenates documents fillCat xs)xs horizontally with <>line'xs. This is similar to how an ordinary word processor
lays out the text if you just keep typing after you hit the maximum line
length.
(line'grouped, the documents are separated with nothing
instead of newlines. See fillSep if you want a space instead.)
Observe the difference between fillSep and fillCat. fillSep
concatenates the entries spaced when grouped:
>>>let docs = take 20 (cycle (["lorem", "ipsum", "dolor", "sit", "amet"]))>>>putDocW 40 ("Grouped:" <+> group (fillSep docs))Grouped: lorem ipsum dolor sit amet lorem ipsum dolor sit amet lorem ipsum dolor sit amet lorem ipsum dolor sit amet
On the other hand, fillCat concatenates the entries directly when
grouped:
>>>putDocW 40 ("Grouped:" <+> group (fillCat docs))Grouped: loremipsumdolorsitametlorem ipsumdolorsitametloremipsumdolorsitamet loremipsumdolorsitamet
cat :: [Doc ann] -> Doc ann Source #
( tries laying out the documents cat xs)xs separated with nothing,
and if this does not fit the page, separates them with newlines. This is what
differentiates it from vcat, which always lays out its contents beneath
each other.
>>>let docs = Util.words "lorem ipsum dolor">>>putDocW 80 ("Docs:" <+> cat docs)Docs: loremipsumdolor
When there is enough space, the documents are put above one another:
>>>putDocW 10 ("Docs:" <+> cat docs)Docs: lorem ipsum dolor
cat=group.vcat
Others
( appends punctuate p xs)p to all but the last document in xs.
>>>let docs = punctuate comma (Util.words "lorem ipsum dolor sit amet")>>>putDocW 80 (hsep docs)lorem, ipsum, dolor, sit, amet
The separators are put at the end of the entries, which we can see if we position the result vertically:
>>>putDocW 20 (vsep docs)lorem, ipsum, dolor, sit, amet
If you want put the commas in front of their elements instead of at the end,
you should use tupled or, in general, encloseSep.
Reactive/conditional layouts
column :: (Int -> Doc ann) -> Doc ann Source #
Layout a document depending on which column it starts at. align is
implemented in terms of column.
>>>column (\l -> "Columns are" <+> pretty l <> "-based.")Columns are 0-based.
>>>let doc = "prefix" <+> column (\l -> "| <- column" <+> pretty l)>>>vsep [indent n doc | n <- [0,4,8]]prefix | <- column 7 prefix | <- column 11 prefix | <- column 15
width :: Doc ann -> (Int -> Doc ann) -> Doc ann Source #
( lays out the document width doc f)doc, and makes the column width
of it available to a function.
>>>let annotate doc = width (brackets doc) (\w -> " <- width:" <+> pretty w)>>>align (vsep (map annotate ["---", "------", indent 3 "---", vsep ["---", indent 4 "---"]]))[---] <- width: 5 [------] <- width: 8 [ ---] <- width: 8 [--- ---] <- width: 8
pageWidth :: (PageWidth -> Doc ann) -> Doc ann Source #
Layout a document depending on the page width, if one has been specified.
>>>let prettyPageWidth (AvailablePerLine l r) = "Width:" <+> pretty l <> ", ribbon fraction:" <+> pretty r>>>let doc = "prefix" <+> pageWidth (brackets . prettyPageWidth)>>>putDocW 32 (vsep [indent n doc | n <- [0,4,8]])prefix [Width: 32, ribbon fraction: 1.0] prefix [Width: 32, ribbon fraction: 1.0] prefix [Width: 32, ribbon fraction: 1.0]
Filler functions
( lays out the document fill i x)x. It then appends spaces until
the width is equal to i. If the width of x is already larger, nothing is
appended.
This function is quite useful in practice to output a list of bindings:
>>>let types = [("empty","Doc"), ("nest","Int -> Doc -> Doc"), ("fillSep","[Doc] -> Doc")]>>>let ptype (name, tp) = fill 5 (pretty name) <+> "::" <+> pretty tp>>>"let" <+> align (vcat (map ptype types))let empty :: Doc nest :: Int -> Doc -> Doc fillSep :: [Doc] -> Doc
( first lays out the document fillBreak i x)x. It then appends spaces
until the width is equal to i. If the width of x is already larger than
i, the nesting level is increased by i and a line is appended. When we
redefine ptype in the example given in fill to use fillBreak
>>>let types = [("empty","Doc"), ("nest","Int -> Doc -> Doc"), ("fillSep","[Doc] -> Doc")]>>>let ptype (name, tp) = fillBreak 5 (pretty name) <+> "::" <+> pretty tp>>>"let" <+> align (vcat (map ptype types))let empty :: Doc nest :: Int -> Doc -> Doc fillSep :: [Doc] -> Doc
General convenience
( is plural n one many)one if n is 1, and many otherwise. A
typical use case is adding a plural "s".
>>>let things = [True]>>>let amount = length things>>>pretty things <+> "has" <+> pretty amount <+> plural "entry" "entries" amount[True] has 1 entry
Annotations
annotate :: ann -> Doc ann -> Doc ann Source #
Add an annotation to a Doc
This function is only relevant for custom formats with their own annotations, and not relevant for basic prettyprinting. The predefined renderers, e.g. Prettyprinter.Render.Text, should be enough for the most common needs.
unAnnotate :: Doc ann -> Doc xxx Source #
Remove all annotations.
Although unAnnotate is idempotent with respect to rendering,
unAnnotate.unAnnotate=unAnnotate
it should not be used without caution, for each invocation traverses the
entire contained document. If possible, it is preferrable to unannotate after
producing the layout by using unAnnotateS.
reAnnotate :: (ann -> ann') -> Doc ann -> Doc ann' Source #
Change the annotation of a Document.
Useful in particular to embed documents with one form of annotation in a more generally annotated document.
Since this traverses the entire DocreAnnotateS
Since reAnnotate'reAnnotate id = id',
it is used to define the FunctorDoc
alterAnnotations :: (ann -> [ann']) -> Doc ann -> Doc ann' Source #
Change the annotations of a Document. Individual annotations can be
removed, changed, or replaced by multiple ones.
This is a general function that combines unAnnotate and reAnnotate, and
it is useful for mapping semantic annotations (such as »this is a keyword«)
to display annotations (such as »this is red and underlined«), because some
backends may not care about certain annotations, while others may.
Annotations earlier in the new list will be applied earlier, i.e. returning
[Bold, Green] will result in a bold document that contains green text, and
not vice-versa.
Since this traverses the entire DocalterAnnotationsS
unAnnotateS :: SimpleDocStream ann -> SimpleDocStream xxx Source #
Remove all annotations. unAnnotate for SimpleDocStream.
reAnnotateS :: (ann -> ann') -> SimpleDocStream ann -> SimpleDocStream ann' Source #
Change the annotation of a document. reAnnotate for SimpleDocStream.
alterAnnotationsS :: (ann -> Maybe ann') -> SimpleDocStream ann -> SimpleDocStream ann' Source #
Change the annotation of a document to a different annotation, or none at
all. alterAnnotations for SimpleDocStream.
Note that the Doc version is more flexible, since it allows changing a
single annotation to multiple ones.
(SimpleDocTree restores
this flexibility again.)
Optimization
fuse :: FusionDepth -> Doc ann -> Doc ann Source #
( combines text nodes so they can be rendered more
efficiently. A fused document is always laid out identical to its unfused
version.fuse depth doc)
When laying a Document out to a SimpleDocStream, every component of the
input is translated directly to the simpler output format. This sometimes
yields undesirable chunking when many pieces have been concatenated together.
For example
>>>"a" <> "b" <> pretty 'c' <> "d"abcd
results in a chain of four entries in a SimpleDocStream, although this is fully
equivalent to the tightly packed
>>>"abcd" :: Doc annabcd
which is only a single SimpleDocStream entry, and can be processed faster.
It is therefore a good idea to run fuse on concatenations of lots of small
strings that are used many times:
>>>let oftenUsed = fuse Shallow ("a" <> "b" <> pretty 'c' <> "d")>>>hsep (replicate 5 oftenUsed)abcd abcd abcd abcd abcd
data FusionDepth Source #
Fusion depth parameter, used by fuse.
Constructors
| Shallow | Do not dive deep into nested documents, fusing mostly concatenations of text nodes together. |
| Deep | Recurse into all parts of the This value should only be used if profiling shows it is significantly
faster than using |
Instances
| Eq FusionDepth Source # | |
Defined in Prettyprinter.Internal | |
| Ord FusionDepth Source # | |
Defined in Prettyprinter.Internal Methods compare :: FusionDepth -> FusionDepth -> Ordering # (<) :: FusionDepth -> FusionDepth -> Bool # (<=) :: FusionDepth -> FusionDepth -> Bool # (>) :: FusionDepth -> FusionDepth -> Bool # (>=) :: FusionDepth -> FusionDepth -> Bool # max :: FusionDepth -> FusionDepth -> FusionDepth # min :: FusionDepth -> FusionDepth -> FusionDepth # | |
| Show FusionDepth Source # | |
Defined in Prettyprinter.Internal Methods showsPrec :: Int -> FusionDepth -> ShowS # show :: FusionDepth -> String # showList :: [FusionDepth] -> ShowS # | |
Layout
data SimpleDocStream ann Source #
The data type SimpleDocStream represents laid out documents and is used
by the display functions.
A simplified view is that Doc = [SimpleDocStream]SimpleDocStreams based on which one fits the
layout constraints best. This means that SimpleDocStream has all complexity
contained in Doc resolved, making it very easy to convert it to other
formats, such as plain text or terminal output.
To write your own DocSimpleDocStream
Constructors
| SFail | |
| SEmpty | |
| SChar !Char (SimpleDocStream ann) | |
| SText !Int !Text (SimpleDocStream ann) | |
| SLine !Int (SimpleDocStream ann) |
|
| SAnnPush ann (SimpleDocStream ann) | Add an annotation to the remaining document. |
| SAnnPop (SimpleDocStream ann) | Remove a previously pushed annotation. |
Instances
Maximum number of characters that fit in one line. The layout algorithms
will try not to exceed the set limit by inserting line breaks when applicable
(e.g. via softline').
Constructors
| AvailablePerLine !Int !Double | Layouters should not exceed the specified space per line.
|
| Unbounded | Layouters should not introduce line breaks on their own. |
Instances
| Eq PageWidth Source # | |
| Ord PageWidth Source # | |
| Show PageWidth Source # | |
newtype LayoutOptions Source #
Options to influence the layout algorithms.
Constructors
| LayoutOptions | |
Fields | |
Instances
| Eq LayoutOptions Source # | |
Defined in Prettyprinter.Internal Methods (==) :: LayoutOptions -> LayoutOptions -> Bool # (/=) :: LayoutOptions -> LayoutOptions -> Bool # | |
| Ord LayoutOptions Source # | |
Defined in Prettyprinter.Internal Methods compare :: LayoutOptions -> LayoutOptions -> Ordering # (<) :: LayoutOptions -> LayoutOptions -> Bool # (<=) :: LayoutOptions -> LayoutOptions -> Bool # (>) :: LayoutOptions -> LayoutOptions -> Bool # (>=) :: LayoutOptions -> LayoutOptions -> Bool # max :: LayoutOptions -> LayoutOptions -> LayoutOptions # min :: LayoutOptions -> LayoutOptions -> LayoutOptions # | |
| Show LayoutOptions Source # | |
Defined in Prettyprinter.Internal Methods showsPrec :: Int -> LayoutOptions -> ShowS # show :: LayoutOptions -> String # showList :: [LayoutOptions] -> ShowS # | |
defaultLayoutOptions :: LayoutOptions Source #
The default layout options, suitable when you just want some output, and
don’t particularly care about the details. Used by the Show instance, for
example.
>>>defaultLayoutOptionsLayoutOptions {layoutPageWidth = AvailablePerLine 80 1.0}
layoutPretty :: LayoutOptions -> Doc ann -> SimpleDocStream ann Source #
This is the default layout algorithm, and it is used by show, putDoc
and hPutDoc.
layoutPrettySimpleDocStream element lookahead when rendering. Consider using the
smarter, but a bit less performant, layoutSmart
layoutCompact :: Doc ann1 -> SimpleDocStream ann2 Source #
(layoutCompact x) lays out the document x without adding any
indentation and without preserving annotations.
Since no 'pretty' printing is involved, this layouter is very
fast. The resulting output contains fewer characters than a prettyprinted
version and can be used for output that is read by other programs.
>>>let doc = hang 4 (vsep ["lorem", "ipsum", hang 4 (vsep ["dolor", "sit"])])>>>doclorem ipsum dolor sit
>>>let putDocCompact = renderIO System.IO.stdout . layoutCompact>>>putDocCompact doclorem ipsum dolor sit
layoutSmart :: LayoutOptions -> Doc ann -> SimpleDocStream ann Source #
A layout algorithm with more lookahead than layoutPretty, that introduces
line breaks earlier if the content does not (or will not, rather) fit into
one line.
Consider the following python-ish document,
>>>let fun x = hang 2 ("fun(" <> softline' <> x) <> ")">>>let doc = (fun . fun . fun . fun . fun) (align (list ["abcdef", "ghijklm"]))
which we’ll be rendering using the following pipeline (where the layout algorithm has been left open):
>>>import Data.Text.IO as T>>>import Prettyprinter.Render.Text>>>let hr = pipe <> pretty (replicate (26-2) '-') <> pipe>>>let go layouter x = (T.putStrLn . renderStrict . layouter (LayoutOptions (AvailablePerLine 26 1))) (vsep [hr, x, hr])
If we render this using layoutPretty with a page width of 26 characters
per line, all the fun calls fit into the first line so they will be put
there:
>>>go layoutPretty doc|------------------------| fun(fun(fun(fun(fun( [ abcdef , ghijklm ]))))) |------------------------|
Note that this exceeds the desired 26 character page width. The same
document, rendered with layoutSmart
>>>go layoutSmart doc|------------------------| fun( fun( fun( fun( fun( [ abcdef , ghijklm ]))))) |------------------------|
The key difference between layoutPretty and layoutSmart is that the
latter will check the potential document until it encounters a line with the
same indentation or less than the start of the document. Any line encountered
earlier is assumed to belong to the same syntactic structure.
layoutPretty checks only the first line.
Consider for example the question of whether the As fit into the document
below:
1 A 2 A 3 A 4 B 5 B
layoutPretty will check only line 1, ignoring whether e.g. line 2 might
already be too wide.
By contrast, layoutSmart stops only once it reaches line 4, where the B
has the same indentation as the first A.
removeTrailingWhitespace :: SimpleDocStream ann -> SimpleDocStream ann Source #
Remove all trailing space characters.
This has some performance impact, because it does an entire additional pass
over the SimpleDocStream.
No trimming will be done inside annotations, which are considered to contain
no (trimmable) whitespace, since the annotation might actually be about the
whitespace, for example a renderer that colors the background of trailing
whitespace, as e.g. git diff can be configured to do.
Historical note: Since v1.7.0, layoutPretty and layoutSmart avoid
producing the trailing whitespace that was the original motivation for
creating removeTrailingWhitespace.
See https://github.com/quchen/prettyprinter/pull/139 for some background
info.
Rendering
renderShowS :: SimpleDocStream ann -> ShowS Source #
Render a SimpleDocStream to a ShowS, useful to write Show instances
based on the prettyprinter.
instanceShowMyType whereshowsPrec_ =renderShowS.layoutPrettydefaultLayoutOptions.pretty
Internal helpers
textSpaces :: Int -> Text Source #
A utility for producing indentation etc.
>>>textSpaces 3" "
This produces much better Core than the equivalent
T.replicate n " "