CCO.Printing

A combinator library for pretty printing.

Inspired by

• S. Doaitse Swierstra, Pablo R. Azero Alcocer, and Joao Saraiva. Designing and implementing combinator languages. In S. Doaitse Swierstra and Pedro Rangel Henriques, and Jose Nuno Oliveira, editors, Advanced Functional Programming, Third International School, Braga, Portugal, September 12-19, 1998, Revised Lectures, volume 1608 of Lecture Notes in Computer Science, pages 150-206. Springer-Verlag, 1999.

Abstract document type

data Doc

The type of documents.

isEmpty :: Doc -> Bool

Indicates whether a document is empty.

Primitive document constructors

empty :: Doc

The empty document. Left and right unit of >-< and >|<.

text :: String -> Doc

text txt produces a document containing the text txt.

wrapped :: String -> Doc

wrapped txt produces a document containing the text txt, possibly wrapping its contents to fit the available space

Elementary document combinators

indent :: Int -> Doc -> Doc

Indents a document by a given amount of space.

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

"Above": puts one document on top of another.

above :: [Doc] -> Doc

Stacks multiple documents: above = foldr (>-<) empty.

(>|<) :: Doc -> Doc -> Doc

"Besides": puts two documents next to eachother by "dovetailing" them.

besides :: [Doc] -> Doc

Queues multiple documents: besides = foldr (>|<) empty.

Parallelisation

(>//<) :: Doc -> Doc -> Doc

"Split": introduces two alternative ("parallel") formattings.

split :: [Doc] -> Doc

Introduces multiple alternative formattings: split = foldr (>//<) empty.

join :: Doc -> Doc

Selects the most space-efficient of all alternative formattings for a document.

(>^<) :: Doc -> Doc -> Doc

Immediate choice: l >^< r = join (l >//< r).

choose :: [Doc] -> Doc

Immediate choice: choose = foldr (>^<) empty.

Punctuation

space :: Doc

A space character: space = text " ".

period :: Doc

A full stop: period = text ".".

comma :: Doc

A comma: comma = text ",".

semicolon :: Doc

A semicolon: semicolon = text ";".

colon :: Doc

A colon: colon = text ":".

sepBy :: [Doc] -> Doc -> Doc

Inserts a delimiter between all adjacent nonempty documents in a list.

(>#<) :: Doc -> Doc -> Doc

Inserts a space between two documents. If one of the documents is empty, the other one is returned: l >#< r = [l, r] `sepBy` space.

lparen :: Doc

Parentheses:

 lparen = text "("
 rparen = text ")"

rparen :: Doc

Parentheses:

 lparen = text "("
 rparen = text ")"

lbracket :: Doc

Square brackets:

 lbracket = text "["
 rbracket = text "]"

rbracket :: Doc

Square brackets:

 lbracket = text "["
 rbracket = text "]"

lbrace :: Doc

Curly braces:

 lbrace = text "{"
 rbrace = text "}"

rbrace :: Doc

Curly braces:

 lbrace = text "{"
 rbrace = text "}"

langle :: Doc

Angle brackets:

 langle = text "<"
 rangle = text ">"

rangle :: Doc

Angle brackets:

 langle = text "<"
 rangle = text ">"

enclose :: Doc -> Doc -> Doc -> Doc

Encloses a document in brackets: enclose l r d = l >|< d >|< r.

parens :: Doc -> Doc

Encloses a document in parentheses: parens = enclose lparen rparen.

brackets :: Doc -> Doc

Encloses a document in square brackets: brackets = enclose lbracket rbracket.

braces :: Doc -> Doc

Encloses a document in curly braces: braces = enclose lbrace rbrace.

angles :: Doc -> Doc

Encloses a document in angle brackets: angles = enclose langle rangle.

Colours

black :: Doc -> Doc

Sets the foreground colour of a document to black.

(Note: colours are only taken into account when a document is rendered by means of renderIO or renderIO_. They are ignored if render or render_ are used.)

red :: Doc -> Doc

Sets the foreground colour of a document to red.

(Note: colours are only taken into account when a document is rendered by means of renderIO or renderIO_. They are ignored if render or render_ are used.)

green :: Doc -> Doc

Sets the foreground colour of a document to green.

(Note: colours are only taken into account when a document is rendered by means of renderIO or renderIO_. They are ignored if render or render_ are used.)

blue :: Doc -> Doc

Sets the foreground colour of a document to blue.

(Note: colours are only taken into account when a document is rendered by means of renderIO or renderIO_. They are ignored if render or render_ are used.)

yellow :: Doc -> Doc

Sets the foreground colour of a document to yellow.

(Note: colours are only taken into account when a document is rendered by means of renderIO or renderIO_. They are ignored if render or render_ are used.)

magenta :: Doc -> Doc

Sets the foreground colour of a document to magenta.

(Note: colours are only taken into account when a document is rendered by means of renderIO or renderIO_. They are ignored if render or render_ are used.)

cyan :: Doc -> Doc

Sets the foreground colour of a document to cyan.

(Note: colours are only taken into account when a document is rendered by means of renderIO or renderIO_. They are ignored if render or render_ are used.)

white :: Doc -> Doc

Sets the foreground colour of a document to white.

(Note: colours are only taken into account when a document is rendered by means of renderIO or renderIO_. They are ignored if render or render_ are used.)

Rendering

render :: Int -> Doc -> Maybe String

Tries to render a document within a specified amount of horizontal space.

render_ :: Int -> Doc -> String

Tries to render a document within a specified amount of horizontal space. If the document cannot be rendered within the given amount of space, the amount of space is, until the document fits, repeatedly enlarged by 10 percent.

renderHeight :: Int -> Doc -> Maybe (String, Int)

Tries to render a document within a specified amount of horizontal space. A resulting rendering is tupled with the number of new lines claimed by the rendering.

renderHeight_ :: Int -> Doc -> (String, Int)

renderIO :: Int -> Doc -> Maybe (IO ())

Tries to render a document within a specified amount of horizontal space and to print it to the standard output channel.

renderIO_ :: Int -> Doc -> IO ()

Tries to render a document within a specified amount of horizontal space and to print it to the standard output channel. If the document cannot be rendered within the given amount of space, the amount of space is, until the document fits, repeatedly enlarged by 10 percent.

renderIOHeight :: Int -> Doc -> Maybe (IO (), Int)

Tries to render a document within a specified amount of horizontal space and to print it to the standard output channel. A resulting rendering is tupled with the number of new lines claimed by the rendering.

renderIOHeight_ :: Int -> Doc -> (IO (), Int)

Tries to render a document within a specified amount of horizontal space and to print it to the standard output channel. If the document cannot be rendered within the given amount of space, the amount of space is, until the document fits, repeatedly enlarged by 10 percent. The resulting rendering is tupled with the number of new lines claimed by the rendering.

The class Printable

class Printable a where

The class Printable. Instances of Printable provide a pretty printer for their values.

A minimal complete definition must supply the method pp.

Methods

pp :: a -> Doc

Retrieves a pretty-printable document for a value.

Instances

Printable Char

Printable Double

Printable Float

Printable Int

Printable Integer

Printable ATerm

Printing showables

showable :: Show a => a -> Doc

Prints a Showable value: showable = text . show.