Module Fmlib_pretty.Print

Pretty Printer: Generate nicely formatted ascii text.

Documentation

Pretty Printing Overview

API

Types

type doc

A document which can be pretty printed.

type t

A pretty printed document as a readable character stream.

Layout a Document

val layout : int -> doc -> t

layout width doc Layout the document doc with a the line width into a character stream.

val layout_with_ribbon : int -> int -> doc -> t

layout width ribbon doc Layout the document doc with a the line width and the ribbon width. Note: width is the complete line width and ribbon is the line width minus the indentation of the current line.

Character Stream

val has_more : t -> bool

has_more s Does the stream s have more characters to read? 

val peek : t -> char

peek s The next character in the stream s.

Precondition: has_more s

val advance : t -> t

advance s The character stream s advanced by one position. I.e. the first character popped off the stream.

Precondition: has_more s

val string_of : t -> string

string_of s A string representation of the stream s.

val write_to_channel : Stdlib.out_channel -> t -> unit

write_to_channel oc s Write the stream s to the output channel oc.

Document Combinators

This section describes all combinators which can be used to generate documents and combine them into bigger documents.

Basic Combinators

val empty : doc

An empty document.

val text : string -> doc

text str A document with the unbreakable string str. It is highly recommended that the string does not contain newlines. Newlines in a text string confuse the layouter.

val substring : string -> int -> int -> doc

substring str start length A document with the unbreakable string str starting at position start and having length.

val char : char -> doc

char c A document with the character c.

val fill : int -> char -> doc

fill n c A document with n repetitions of the character c.

val break : string -> doc

break str A break hint with the alternative text str.

val space : doc

space A break hint with a blank as alternative text.

val cut : doc

cut A break hint with an empty alternative text.

val (<+>) : doc -> doc -> doc

doc1 <+> doc2 Concatentate the documents doc1 and doc2.

val (>>) : doc -> (unit -> doc) -> doc

doc >> lazy_doc Concatenate the document doc with the lazy document lazy_doc.

val group : doc -> doc

group doc

Treat all break hints belonging directly to doc consistently. Either print all as newlines or print all with their alternative text.

This is the basic operation to decide break hints.

If the whole group and all text which follows until the next break hint after the group fits on a line, then all break hints (directly or indirectly) in the group are flattened i.e. printed with their alternative texts.

If the whole group does not fit, then all break hints belonging directly to the group are printed as effective newlines. The break hints of inner groups are considered separately.

val nest : int -> doc -> doc

nest n doc

The document doc indented by n blanks.

This is the basic function to indicate a substructure to the pretty printer. The substructure is indented with respect to the parent document.

The indentation is valid after each effective line break. It is usually convenient to group the whole substructure and put a break hint before the group and group the parent structure and the substructure. This makes sure that either the parent and the child fit on a line or the child begins on a newline and is indented. See the function parent_child below which does exactly that.

val with_width : int -> doc -> doc

with_width n doc Format the document doc with line width.

Use this combinator if you want to format the internal document doc with a different line width than the overall document.

val with_ribbon : int -> doc -> doc

with_ribbon n doc Format the document doc with ribbon width.

Use this combinator if you want to format the internal document doc with a different ribbon width than the overall document.

Convenience Combinators

val parent_child : string -> int -> doc -> doc -> doc

parent_child hint indent parent child

Put the parent and the child in a group and separate them by a break hint with the alternative text hint. Furthermore put the child in a separate group.

Equivalent to

parent
<+> break hint
<+> nest indent (group child)
|> group
val cat : doc list -> doc

cat list Concatenate all documents in the list of documents.

val separated_by : doc -> doc list -> doc

separated_by sep list Concatenate all documents in the list of documents separated by sep.

val pack : string -> doc list -> doc

pack str list Pack as much documents of the list of documents as possible into a line. I.e. separate all documents by a break hint with str as an alternative text.

val stack : string -> doc list -> doc

stack str list The same as separated_by (break str) list.

val stack_or_pack : string -> doc list -> doc

stack_or_pack str list Separate all documents of the list by a break hint with alternative text str and either print all break hints as newlines of with the alternative text str.

val wrap_words : string -> doc

wrap_words str Split the string str into words (words are substrings of str not containing blanks) and pack as many of them onto a line.

val paragraphs : doc list -> doc

paragraphs ps

Print the paragraphs in ps separated by newlines. The function works best if each paragraph ends in a newline. paragraphs ps is equivalent to separated_by cut ps.