PPrint Library Reference

lhs <^> rhs is the concatenation of the documents lhs and rhs. For example, txt "a" <^> txt "b" renders as ab.

Note: This is the same as the operator <> used in the original Haskell libraries. In F#, the <> operator is already used.

Concatenates the given documents with a space in between. lhs <+> rhs is equivalent to lhs <^> space <^> rhs. For example, txt "a" <+> txt "b" renders as a b.

Concatenates the given documents with a line in between. lhs <.> rhs is equivalent to lhs <^> line <^> rhs.

For example

txt "a" <.> txt "b"

renders as

a
b

and

txt "a" <.> txt "b" |> group

renders as

a b

Note: In the original Haskell libraries, the symbol <$> was used for this operation, but it is not a legal symbol in F#.

Concatenates the given documents with a softline in between. lhs </> rhs is equivalent to lhs <^> softline <^> rhs.

Concatenates the given documents with a linebreak in between. lhs <..> rhs is equivalent to lhs <^> linebreak <^> rhs.

For example

txt "a" <..> txt "b"

renders as

a
b

and

txt "a" <..> txt "b" |> group

renders as

ab

Concatenates the given documents with a softbreak in between. lhs <//> rhs is equivalent to lhs <^> softbreak <^> rhs.

Output actions.

abstract Line: unit -> unit

default Line: unit -> unit

abstract User: obj -> unit

default User: obj -> unit

abstract Write: string -> unit

Outputs the document using the given output actions.

Outputs the document using the given output function.

Outputs the document using the given text writer.

Renders the document as a string.

The empty document is equivalent to txt "".

chr c renders to the character c. The character shouldn't be a newline. For example, chr 'x' renders to x.

txt s renders to the string s. The string shouldn't contain any newline characters. For example, txt "hello" renders to hello.

fmt ... is equivalent to txt <| sprintf .... For example, to format an integer i, one could write fmt "%d" i.

doc |> nest n renders document doc indented by n more columns. See also: gnest and nestBy.

For example

[txt "x"; txt "y"; txt "z"]
|> punctuate comma
|> vsep
|> parens
|> nest 1

renders as

(x,
 y,
 z)

Note that in order for nest n doc to have any effect, you must have lines or linebreaks in the doc.

doc |> nestBy prefix renders document doc with given prefix added after line breaks. See also: nest.

For example

[txt "a"; txt "b"; txt "c"]
|> vsep
|> nestBy " * "
|> enclose (txt "(* ", line <^> txt " *)")

renders as

(* a
 * b
 * c
 *)

Advances to the next line and indents, unless undone by group in which case line behaves like txt " ".

For example

[txt "a"; line; txt "b"]
|> hcat
|> nest 2

renders as

a
  b

while

[txt "a"; line; txt "b"]
|> hcat
|> nest 2
|> group

renders as

a b

Advances to the next line and indents, unless undone by group in which case linebreak behaves like empty.

For example

[txt "a"; linebreak; txt "b"]
|> hcat
|> nest 2

renders as

a
  b

while

[txt "a"; linebreak; txt "b"]
|> hcat
|> nest 2
|> group

renders as

ab

Used to specify alternative layouts. group doc undoes all line breaks in document doc. The resulting line of text is added to the current output if it fits. Otherwise, the document is rendered without changes (with line breaks).

For example

txt "a" <.> txt "b"

renders as

a
b

while

txt "a" <.> txt "b" |> group

renders as

a b

except when it wouldn't fit within the desired number of columns.

doc |> gnest n is equivalent to doc |> group |> nest n which is equivalent to doc |> nest n |> group. nest is frequently combined with group.

Used to specify alternative documents. The wide document is added to the current output line if it fits. Otherwise, the narrow document is rendered.

This combinator is not available in the original Haskell libraries. It allows one to create documents whose rendering may not produce optimal or easily predictable results. Nevertheless, careful use of this combinator can produce useful results. The initial use case for this combinator was to format Standard ML string literals so that they are either formatted onto a single line or onto multiple lines using line continuation characters.

For example, given

let wide = txt "\\\"a\\nb\\nc\\\""
let narrow = vsep [txt "\"a\\n\""; txt "\"b\\n\""; txt "\"c\""]

then

choice wide narrow

renders as the wide version

"a\nb\nc"

when it fits and as the narrow version

"a\n"
"b\n"
"c"

when the wide version does not fit.

Creates a lazily computed document. delay <| fun () -> doc is equivalent to doc except that the expression doc may not be evaluated at all.

Note: This is primarily useful for specifying the narrow alternative to choice - unless, of course, there is a chance that the whole document will not be rendered at all.

Behaves like space if the resulting output fits, otherwise behaves like line.

Behaves like empty if the resulting output fits, otherwise behaves like line.

user any is equivalent to empty except that the created document carries the given user attribute object any. The object is otherwise ignored by the library, but is carried throughout the layout computation and passed to the Actions.User rendering action at the point when everything before it has been rendered. This can be used to implement features such outputing ANSI control sequences to produce output with special effects.

column f calls f with the current column during rendering to create a document to render.

column f calls f with the current nesting during the layout process to create a document to render.

doc |> indent n indents doc by n columns.

doc |> hang n renders doc with nesting level set to the current column plus n.

doc |> align renders doc with the nesting level set to the current column.

For example

txt "foo" <^>
([txt "bar"; txt "baz"; txt "foobar"]
 |> punctuate comma
 |> vsep
 |> align
 |> parens)

renders as

foo(bar,
    baz,
    foobar)

width lhs rhs calls rhs with the width of lhs to create the document to concatenate to the right of lhs.

For example

width <| txt "foo" <| fun n ->
  [txt "bar"; txt "baz"; txt "foobar"]
  |> punctuate comma
  |> vsep
  |> parens
  |> nest (n+1)

renders to

foo(bar,
    baz,
    foobar)

Note that align can produce the above layout more directly, but other effects can be achieved with width.

doc |> fillBreak width first renders doc and then appends spaces until the width of the output is at least width. If the width is already more than width, the nesting level is increased by width and a line is appended after doc.

doc |> fill width first renders doc and then appends spaces until the width is at least width.

joinSep sep is equivalent to joinWith <| fun l r -> l <^> sep <^> r.

Concatenate a sequence of documents using the given binary operator.

docs |> sep is equivalent to docs |> vsep |> group.

docs |> cat is equivalent to docs |> vcat |> group.

docs |> punctuate punc concatenates punc to the right of each document in docs except the last one.

For example

[txt "a"; txt "b"; txt "c"]
|> punctuate comma
|> hsep

renders to

a, b, c

Concatenates the documents using <+>.

For example

hsep [txt "a"; txt "b"; txt "c"]

renders to

a b c

Concatenates the documents using <.>.

For example

vsep [txt "a"; txt "b"; txt "c"]

renders to

a
b
c

Concatenates the documents using </>.

Concatenates the documents using <^>.

For example

hcat [txt "a"; txt "b"; txt "c"]

renders to

abc

Concatenates the documents using <..>.

Concatenates the documents using <//>.

doc |> enclose (lhs, rhs) is equivalent to lhs <^> doc <^> rhs

squotes doc is equivalent to enclose lrsquote doc.

dquotes doc is equivalent to enclose lrdquote doc.

parens doc is equivalent to enclose lrparen doc.

angles doc is equivalent to enclose lrangle doc.

braces doc is equivalent to enclose lrbrace doc.

brackets doc is equivalent to enclose lrbracket doc.

Equivalent to (squote, squote)

Equivalent to (dquote, dquote)

Equivalent to (lparen, rparen)

Equivalent to (langle, rangle)

Equivalent to (lbrace, rbrace)

Equivalent to (lbracket, rbracket)

Equivalent to txt "(".

Equivalent to txt ")".

Equivalent to txt "<".

Equivalent to txt ">".

Equivalent to txt "{".

Equivalent to txt "}".

Equivalent to txt "[".

Equivalent to txt "]".

Equivalent to txt "'".

Equivalent to txt "\"".

Equivalent to txt ";".

Equivalent to txt ":".

Equivalent to txt ",".

Equivalent to txt " ".

Equivalent to txt ".".

Equivalent to txt "\\".

Equivalent to txt "=".