Darcs.Util.Printer

A Document is at heart ShowS from the prelude

Essentially, if you give a Doc a string it'll print out whatever it wants followed by that string. So text "foo" makes the Doc that prints "foo" followed by its argument. The combinator names are taken from HughesPJ, although the behaviour of the two libraries is slightly different.

The advantage of Printer over simple string appending/concatenating is that the appends end up associating to the right, e.g.:

  (text "foo" <> text "bar") <> (text "baz" <> text "quux") ""
= \s -> (text "foo" <> text "bar") ((text "baz" <> text "quux") s) ""
= (text "foo" <> text "bar") ((text "baz" <> text "quux") "")
= (\s -> (text "foo") (text "bar" s)) ((text "baz" <> text "quux") "")
= text "foo" (text "bar" ((text "baz" <> text "quux") ""))
= (\s -> "foo" ++ s) (text "bar" ((text "baz" <> text "quux") ""))
= "foo" ++ (text "bar" ((text "baz" <> text "quux") ""))
= "foo" ++ ("bar" ++ ((text "baz" <> text "quux") ""))
= "foo" ++ ("bar" ++ ((\s -> text "baz" (text "quux" s)) ""))
= "foo" ++ ("bar" ++ (text "baz" (text "quux" "")))
= "foo" ++ ("bar" ++ ("baz" ++ (text "quux" "")))
= "foo" ++ ("bar" ++ ("baz" ++ ("quux" ++ "")))

The Empty alternative comes in because you want

text "a" $$ vcat xs $$ text "b"

$$ means above, vcat is the list version of $$ (to be "a\nb" when xs is []), but without the concept of an Empty Document each $$ would add a '\n' and you'd end up with "a\n\nb". Note that Empty /= text "" (the latter would cause two '\\n').

This code was made generic in the element type by Juliusz Chroboczek.

Doc type and structural combinators

newtype Doc

A Doc is a bit of enriched text. Docs are concatenated using <> from class Monoid, which is right-associative.

Constructors

Doc

Fields

• unDoc :: St -> Document

Instances

IsString Doc

Together with the language extension OverloadedStrings, this allows to use string literals where a Doc is expected.

Methods

fromString :: String -> Doc

Monoid Doc

mappend (<>) is concatenation, mempty is the empty Doc

Methods

mempty :: Doc

mappend :: Doc -> Doc -> Doc

mconcat :: [Doc] -> Doc

empty :: Doc

The empty Doc

(<>) :: Monoid m => m -> m -> m infixr 6

An infix synonym for mappend.

Since: 4.5.0.0

(<?>) :: Doc -> Doc -> Doc

a <?> b is a <> b if a is not empty, else empty

(<+>) :: Doc -> Doc -> Doc infixr 6

a <+> b is a followed by a space, then b

($$) :: Doc -> Doc -> Doc infixr 5

a $$ b is a above b

vcat :: [Doc] -> Doc

Pile Docs vertically

vsep :: [Doc] -> Doc

Pile Docs vertically, with a blank line in between

hcat :: [Doc] -> Doc

Concatenate Docs horizontally

hsep :: [Doc] -> Doc

Concatenate Docs horizontally with a space as separator

minus :: Doc

A Doc representing a "-"

newline :: Doc

A Doc representing a newline

plus :: Doc

A Doc representing a "+"

space :: Doc

A Doc representing a space (" ")

backslash :: Doc

A Doc representing a "\"

lparen :: Doc

A Doc that represents "("

rparen :: Doc

A Doc that represents ")"

parens :: Doc -> Doc

parens d = lparen <> d <> rparen

Constructing Docs

text :: String -> Doc

text creates a Doc from a String, using printable.

hiddenText :: String -> Doc

hiddenText creates a Doc containing hidden text from a String

invisibleText :: String -> Doc

invisibleText creates a Doc containing invisible text from a String

wrapText :: Int -> String -> Doc

wrapText n s is a Doc representing s line-wrapped at n characters

quoted :: String -> Doc

Quote a string for screen output

userchunk :: String -> Doc

userchunk creates a Doc containing a user chunk from a String

packedString :: ByteString -> Doc

packedString builds a Doc from a ByteString using printable

prefix :: String -> Doc -> Doc

hiddenPrefix :: String -> Doc -> Doc

insertBeforeLastline :: Doc -> Doc -> Doc

prefixLines :: Doc -> Doc -> Doc

invisiblePS :: ByteString -> Doc

invisiblePS creates a Doc with invisible text from a ByteString

userchunkPS :: ByteString -> Doc

userchunkPS creates a Doc representing a user chunk from a ByteString.

Rrrright. And what, please is that supposed to mean?

Rendering

data RenderMode

Used when rendering a Doc to indicate if the result should be encoded to the current locale or left alone. In practice this only affects output when a relevant DARCS_DONT_ESCAPE_XXX option is set (see Darcs.Util.Printer.Color) If in doubt, choose Standard.

Constructors

Encode

Encode Strings with the current locale. At present ByteStrings are assumed to be in UTF8 and are left alone, so will be mis-encoded in non-UTF8 locales.

Standard

Don't encode.

renderString :: RenderMode -> Doc -> String

renders a Doc into a String with control codes for the special features of the doc.

renderStringWith :: Printers' -> RenderMode -> Doc -> String

renders a Doc into a String using a given set of printers.

renderPS :: RenderMode -> Doc -> ByteString

renders a Doc into ByteString with control codes for the special features of the Doc. See also readerString.

renderPSWith :: Printers' -> RenderMode -> Doc -> ByteString

renders a doc into a ByteString using a given set of printers.

renderPSs :: RenderMode -> Doc -> [ByteString]

renders a Doc into a list of PackedStrings, one for each line.

renderPSsWith :: Printers' -> RenderMode -> Doc -> [ByteString]

renders a Doc into a list of PackedStrings, one for each chunk of text that was added to the doc, using the given set of printers.

Printers

type Printers = Handle -> Printers'

data Printers'

A set of printers to print different types of text to a handle.

Constructors

Printers

Fields

• colorP :: !(Color -> Printer)
• invisibleP :: !Printer
• hiddenP :: !Printer
• userchunkP :: !Printer
• defP :: !Printer
• lineColorT :: !(Color -> Doc -> Doc)
• lineColorS :: !([Printable] -> [Printable])

type Printer = Printable -> St -> Document

simplePrinters :: Printers

simplePrinters is a Printers which uses the set 'simplePriners\'' on any handle.

invisiblePrinter :: Printer

invisiblePrinter is the Printer for hidden text. It just replaces the document with empty. It's useful to have a printer that doesn't actually do anything because this allows you to have tunable policies, for example, only printing some text if it's to the terminal, but not if it's to a file or vice-versa.

simplePrinter :: Printer

simplePrinter is the simplest Printer: it just concatenates together the pieces of the Doc

Printables

data Printable

A Printable is either a String, a packed string, or a chunk of text with both representations.

Constructors

S !String

PS !ByteString

Both !String !ByteString

doc :: ([Printable] -> [Printable]) -> Doc

printable :: Printable -> Doc

Creates a Doc from any Printable.

invisiblePrintable :: Printable -> Doc

Creates an invisible Doc from any Printable.

hiddenPrintable :: Printable -> Doc

Creates a hidden Doc from any Printable.

userchunkPrintable :: Printable -> Doc

Creates... WTF is a userchunk???

Constructing colored Docs

data Color

Constructors

Blue

Red

Green

Cyan

Magenta

blueText :: String -> Doc

redText :: String -> Doc

greenText :: String -> Doc

magentaText :: String -> Doc

cyanText :: String -> Doc

colorText :: Color -> String -> Doc

colorText creates a Doc containing colored text from a String

lineColor :: Color -> Doc -> Doc

IO

hPutDoc :: RenderMode -> Handle -> Doc -> IO ()

hputDoc puts a doc on the given handle using simplePrinters

hPutDocLn :: RenderMode -> Handle -> Doc -> IO ()

hputDocLn puts a doc, followed by a newline on the given handle using simplePrinters.

putDoc :: Doc -> IO ()

putDoc puts a doc on stdout using the simple printer simplePrinters.

putDocLn :: Doc -> IO ()

putDocLn puts a doc, followed by a newline on stdout using simplePrinters

hPutDocWith :: Printers -> RenderMode -> Handle -> Doc -> IO ()

hputDocWith puts a doc on the given handle using the given printer.

hPutDocLnWith :: Printers -> RenderMode -> Handle -> Doc -> IO ()

hputDocLnWith puts a doc, followed by a newline on the given handle using the given printer.

putDocWith :: Printers -> Doc -> IO ()

putDocWith puts a doc on stdout using the given printer.

putDocLnWith :: Printers -> Doc -> IO ()

putDocLnWith puts a doc, followed by a newline on stdout using the given printer.

hPutDocCompr :: RenderMode -> Handle -> Doc -> IO ()

like hPutDoc but with compress data before writing

debugDocLn :: Doc -> IO ()

Write a Doc to stderr if debugging is turned on.

ePutDocLn :: Doc -> IO ()

eputDocLn puts a doc, followed by a newline to stderr using simplePrinters. Like putDocLn, it encodes with the user's locale. This function is the recommended way to output messages that should be visible to users on the console, but cannot (or should not) be silenced even when --quiet is in effect.

errorDoc :: Doc -> a

Fail with a stack trace and the given Doc as error message.

Unsafe constructors

unsafeText :: String -> Doc

unsafeText creates a Doc from a String, using simplePrinter directly

unsafeBoth :: String -> ByteString -> Doc

unsafeBoth builds a Doc from a String and a ByteString representing the same text, but does not check that they do.

unsafeBothText :: String -> Doc

unsafeBothText builds a Doc from a String. The string is stored in the Doc as both a String and a ByteString.

unsafeChar :: Char -> Doc

unsafeChar creates a Doc containing just one character.

unsafePackedString :: ByteString -> Doc

unsafePackedString builds a Doc from a ByteString using simplePrinter