The Pp module

type doc

doc represents documents which can be pretty printed. They are constructed from functions provided by this module.

val empty : doc

empty is the empty document.

val (^^) : doc -> doc -> doc

d1 ^^ d2 is the concatenation of documents d1 and d2.

val text : string -> doc

text "hello" creates a document containing the string "hello". This operators simply turns strings into documents.

val break : doc

break represents a point where the pretty printer can decide whether to begin a new line or not. In the former case a newline is printed, followed by a number of spaces to indent the next line. The number of spaces is controlled by the nest operator. When the pretty printer does not begin a new line a single space is printed for the break.

val breakWith : string -> doc

breakWith s acts like break except that it is not turned into a space or a newline but into s or a newline (followed by spaces).

val nest : int -> doc -> doc

nest i doc: all breaks inside doc which are turned into newlines will be followed by additional i spaces. Nesting adds up: when doc contains another nest j operator the breaks inside its document will follwed by i+j spaces.

val hgrp : doc -> doc

breaks inside a hgrp (horizontal group) are never turned into newlines, so they always come out as spaces.

val vgrp : doc -> doc

breaks inside a vgrp (vertical group) are always turned onto newlines (which are followed by spaces as indicated by nest).

val agrp : doc -> doc

The automatic group agrp is the most versatile: when the whole group including all subgroups fits into one line breaks come out as spaces. Otherwise breaks come out as newlines. However, this does not affect subgroups: their breaks are considered seperately.

val fgrp : doc -> doc

The break policy inside an agrp is fixed for all breaks of the group. Inside a flexible group fgrp each break is considered individually: when the document up to the next break fits into the current line the break comes out as space. Otherwise it comes out as newline followed by spaces.

val ppToString : int -> doc -> string

ppToString w doc formats doc for line length w (> 0) and returns it as string. This is not efficient and should be avoided for large documents. The document is considered to be surrounded by a virtual agrp - if this is not desried it should have itself a different group at its outermost level to protect itself from the agrp.

val ppToFile : out_channel -> int -> doc -> unit

ppToFile oc w doc pretty prints doc for line length w into an output channel oc. The document is considered to be surrounded by a virtual agrp - if this is not desried it should have itself a different group at its outermost level to protect itself from this agrp.

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