Copyright	(c) The University of Glasgow 2001
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	David Terei <dave.terei@gmail.com>
Stability	stable
Portability	portable
Safe Haskell	Safe
Language	Haskell98

Text.PrettyPrint.HughesPJ

Contents

The document type
Constructing documents
Predicates on documents
Rendering documents

Description

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 (December 1996).

Synopsis

The document type

data Doc Source

The abstract type of documents. The Show instance is equivalent to using render.

Instances

Show Doc Source
IsString Doc Source
Monoid Doc Source

Constructing documents

Converting values into documents

char :: Char -> Doc Source

A document of height and width 1, containing a literal character.

text :: String -> Doc Source

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.

ptext :: String -> Doc Source

An obsolete function, now identical to text.

sizedText :: Int -> String -> Doc Source

Some text with any width. (text s = sizedText (length s) s)

zeroWidthText :: String -> Doc Source

Some text, but without any width. Use for non-printing text such as a HTML or Latex tags

int :: Int -> Doc Source

int n = text (show n)

integer :: Integer -> Doc Source

integer n = text (show n)

float :: Float -> Doc Source

float n = text (show n)

double :: Double -> Doc Source

double n = text (show n)

rational :: Rational -> Doc Source

rational n = text (show n)

Simple derived documents

semi :: Doc Source

A ';' character

comma :: Doc Source

A ',' character

colon :: Doc Source

A : character

space :: Doc Source

A space character

equals :: Doc Source

A '=' character

lparen :: Doc Source

A '(' character

rparen :: Doc Source

A ')' character

lbrack :: Doc Source

A '[' character

rbrack :: Doc Source

A ']' character

lbrace :: Doc Source

A '{' character

rbrace :: Doc Source

A '}' character

Wrapping documents in delimiters

parens :: Doc -> Doc Source

Wrap document in (...)

brackets :: Doc -> Doc Source

Wrap document in [...]

braces :: Doc -> Doc Source

Wrap document in {...}

quotes :: Doc -> Doc Source

Wrap document in '...'

doubleQuotes :: Doc -> Doc Source

Wrap document in "..."

Combining documents

empty :: Doc Source

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.

(<>) :: Doc -> Doc -> Doc infixl 6 Source

Beside. <> is associative, with identity empty.

(<+>) :: Doc -> Doc -> Doc infixl 6 Source

Beside, separated by space, unless one of the arguments is empty. <+> is associative, with identity empty.

hcat :: [Doc] -> Doc Source

List version of <>.

hsep :: [Doc] -> Doc Source

List version of <+>.

($$) :: Doc -> Doc -> Doc infixl 5 Source

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 infixl 5 Source

Above, with no overlapping. $+$ is associative, with identity empty.

vcat :: [Doc] -> Doc Source

List version of $$.

sep :: [Doc] -> Doc Source

Either hsep or vcat.

cat :: [Doc] -> Doc Source

Either hcat or vcat.

fsep :: [Doc] -> Doc Source

"Paragraph fill" version of sep.

fcat :: [Doc] -> Doc Source

"Paragraph fill" version of cat.

nest :: Int -> Doc -> Doc Source

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 <>.

hang :: Doc -> Int -> Doc -> Doc Source

hang d1 n d2 = sep [d1, nest n d2]

punctuate :: Doc -> [Doc] -> [Doc] Source

punctuate p [d1, ... dn] = [d1 <> p, d2 <> p, ... dn-1 <> p, dn]

Predicates on documents

isEmpty :: Doc -> Bool Source

Returns True if the document is empty

Rendering documents

Default rendering

render :: Doc -> String Source

Renders the document as a string using the default style.

Rendering with a particular style

data Style Source

A rendering style.

Constructors

Style
Fields mode :: Mode The rendering mode lineLength :: Int Length of line, in chars ribbonsPerLine :: Float Ratio of ribbon length to line length

style :: Style Source

The default style (mode=PageMode, lineLength=100, ribbonsPerLine=1.5).

renderStyle :: Style -> Doc -> String Source

Render the document as a string using a specified style.

General rendering

fullRender Source

Arguments

:: 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

The general rendering interface.

data Mode Source

Rendering mode.

Constructors

PageMode	Normal
ZigZagMode	With zig-zag cuts
LeftMode	No indentation, infinitely long lines
OneLineMode	All on one line

data TextDetails Source

The TextDetails data type

A TextDetails represents a fragment of text that will be output at some point.

Constructors

Chr Char	A single Char fragment
Str String	A whole String fragment
PStr String	Used to represent a Fast String fragment but now deprecated and identical to the Str constructor.