Module Pretty

module Pretty: sig .. end
Utility functions for pretty-printing. The major features provided by this module are Pretty-printing occurs in two stages: The formatting algorithm is not optimal but it does a pretty good job while still operating in linear time. The original version was based on a pretty printer by Philip Wadler which turned out to not scale to large jobs.

type doc 
The type of unformated documents. Elements of this type can be constructed in two ways. Either with a number of constructor shown below, or using the Pretty.dprintf function with a printf-like interface. The Pretty.dprintf method is slightly slower so we do not use it for large jobs such as the output routines for a compiler. But we use it for small jobs such as logging and error messages.

Constructors for the doc type.
val nil : doc
Constructs an empty document
val (++) : doc -> doc -> doc
Concatenates two documents. This is an infix operator that associates to the left.
val concat : doc -> doc -> doc
val text : string -> doc
A document that prints the given string
val num : int -> doc
A document that prints an integer in decimal form
val num64 : int64 -> doc
A document that prints a 64-bit int in decimal form
val real : float -> doc
A document that prints a real number
val chr : char -> doc
A document that prints a character. This is just like Pretty.text with a one-character string.
val line : doc
A document that consists of a mandatory newline. This is just like (text "\n"). The new line will be indented to the current indentation level, unless you use Pretty.leftflush right after this.
val leftflush : doc
Use after a Pretty.line to prevent the indentation. Whatever follows next will be flushed left. Indentation resumes on the next line.
val break : doc
A document that consists of either a space or a line break. Also called an optional line break. Such a break will be taken only if necessary to fit the document in a given width. If the break is not taken a space is printed instead.
val align : doc
Mark the current column as the current indentation level. Does not print anything. All taken line breaks will align to this column. The previous alignment level is saved on a stack.
val unalign : doc
Reverts to the last saved indentation level.
val mark : doc
Mark the beginning of a markup section. The width of a markup section is considered 0 for the purpose of computing identation
val unmark : doc
The end of a markup section

Syntactic sugar
val indent : int -> doc -> doc
Indents the document. Same as ((text " ") ++ align ++ doc ++ unalign), with the specified number of spaces.
val markup : doc -> doc
Prints a document as markup. The marked document cannot contain line breaks or alignment constructs.
val seq : sep:doc -> doit:('a -> doc) -> elements:'a list -> doc
Formats a sequence. sep is a separator, doit is a function that converts an element to a document.
val docList : ?sep:doc -> ('a -> doc) -> unit -> 'a list -> doc
An alternative function for printing a list. The unit argument is there to make this function more easily usable with the Pretty.dprintf interface. The first argument is a separator, by default a comma.
val d_list : string -> (unit -> 'a -> doc) -> unit -> 'a list -> doc
sm: Yet another list printer. This one accepts the same kind of printing function that Pretty.dprintf does, and itself works in the dprintf context. Also accepts a string as the separator since that's by far the most common.
val docArray : ?sep:doc ->
(int -> 'a -> doc) -> unit -> 'a array -> doc
Formats an array. A separator and a function that prints an array element. The default separator is a comma.
val docOpt : ('a -> doc) -> unit -> 'a option -> doc
Prints an 'a option with None or Some
val d_int32 : int32 -> doc
Print an int32
val f_int32 : unit -> int32 -> doc
val d_int64 : int64 -> doc
val f_int64 : unit -> int64 -> doc
module MakeMapPrinter: 
functor (Map : sig
type key 
type 'a t 
val fold : (key -> 'a -> 'b -> 'b) ->
'a t -> 'b -> 'b
end) -> sig .. end
Format maps.
module MakeSetPrinter: 
functor (Set : sig
type elt 
type t 
val fold : (elt -> 'a -> 'a) ->
t -> 'a -> 'a
end) -> sig .. end
Format sets.
val insert : unit -> doc -> doc
A function that is useful with the printf-like interface
val dprintf : ('a, unit, doc, doc) format4 -> 'a
This function provides an alternative method for constructing doc objects. The first argument for this function is a format string argument (of type ('a, unit, doc) format; if you insist on understanding what that means see the module Printf). The format string is like that for the printf function in C, except that it understands a few more formatting controls, all starting with the @ character.

See the gprintf function if you want to pipe the result of dprintf into some other functions.

The following special formatting characters are understood (these do not correspond to arguments of the function):

In addition to the usual printf % formatting characters the following two new characters are supported:
dprintf "Name=%s, SSN=%7d, Children=@[%a@]\n"
    pers.ssn (docList (chr ',' ++ break) text)

The result of dprintf is a Pretty.doc. You can format the document and emit it using the functions Pretty.fprint and Pretty.sprint.

val gprintf : (doc -> 'a) -> ('b, unit, doc, 'a) format4 -> 'b
Like Pretty.dprintf but more general. It also takes a function that is invoked on the constructed document but before any formatting is done. The type of the format argument means that 'a is the type of the parameters of this function, unit is the type of the first argument to %a and %t formats, doc is the type of the intermediate result, and 'b is the type of the result of gprintf.
val fprint : out_channel -> width:int -> doc -> unit
Format the document to the given width and emit it to the given channel
val sprint : width:int -> doc -> string
Format the document to the given width and emit it as a string
val fprintf : out_channel -> ('a, unit, doc) format -> 'a
Like Pretty.dprintf followed by Pretty.fprint
val printf : ('a, unit, doc) format -> 'a
Like Pretty.fprintf applied to stdout
val eprintf : ('a, unit, doc) format -> 'a
Like Pretty.fprintf applied to stderr
val withPrintDepth : int -> (unit -> unit) -> unit
Invokes a thunk, with printDepth temporarily set to the specified value

The following variables can be used to control the operation of the printer
val printDepth : int ref
Specifies the nesting depth of the align/unalign pairs at which everything is replaced with ellipsis
val printIndent : bool ref
If false then does not indent
val fastMode : bool ref
If set to true then optional breaks are taken only when the document has exceeded the given width. This means that the printout will looked more ragged but it will be faster
val flushOften : bool ref
If true the it flushes after every print
val flattenBeforePrint : bool ref
Whether to rebalance doc before printing it to avoid stack-overflows
val countNewLines : int ref
Keep a running count of the taken newlines. You can read and write this from the client code if you want
val auto_printer : string -> 'a
A function that when used at top-level in a module will direct the pa_prtype module generate automatically the printing functions for a type