package fmt

You can search for identifiers within the package.

in-package search v0.2.0

On This Page

Standard outputs
Formatting
Formatters
Separators
Sequencing
Boxes
Brackets
Records
Stdlib types
Magnitudes
Binary data
Words, paragraphs, text and lines
HCI fragments
Conditional UTF-8 formatting
Styled formatting
1. Style rendering control
Converting with string value converters
Deprecated
Naming conventions

package fmt

Fmt v0.10.0
- CHANGES
- LICENSE
- README
- Library fmt
  - Fmt
    
    Dump
- Library fmt.cli
  - Fmt_cli
- Library fmt.tty
  - Fmt_tty
- Sources
  - fmt
    
    fmt.ml
  - fmt.cli
    
    fmt_cli.ml
  - fmt.tty
    
    fmt_tty.ml

Legend:
Page
Library
Module
Module type
Parameter
Class
Class type
Source

Module `Fmt`Source

Format pretty-printer combinators.

Consult naming conventions for your pretty-printers.

References

The Format module documentation.
The required reading Format module tutorial.

Standard outputs

Sourceval stdout : Format.formatter

stdout is the standard output formatter.

Sourceval stderr : Format.formatter

stderr is the standard error formatter.

Formatting

Sourceval pf : Format.formatter -> ('a, Format.formatter, unit) format -> 'a

pf is Format.fprintf.

Sourceval pr : ('a, Format.formatter, unit) format -> 'a

pr is pf stdout.

Sourceval epr : ('a, Format.formatter, unit) format -> 'a

epr is pf stderr.

Sourceval str : ('a, Format.formatter, unit, string) format4 -> 'a

str is Format.asprintf.

Note. When using str utf_8 and style_renderer are always respectively set to true and `None. See also str_like.

Source

val kpf : 
  (Format.formatter -> 'a) ->
  Format.formatter ->
  ('b, Format.formatter, unit, 'a) format4 ->
  'b

kpf is Format.kfprintf.

Sourceval kstr : (string -> 'a) -> ('b, Format.formatter, unit, 'a) format4 -> 'b

kstr is like str but continuation based.

Source

val str_like : 
  Format.formatter ->
  ('a, Format.formatter, unit, string) format4 ->
  'a

str_like ppf is like str except its utf_8 and style_renderer settings are those of ppf.

Sourceval with_buffer : ?like:Format.formatter -> Buffer.t -> Format.formatter

with_buffer ~like b is a formatter whose utf_8 and style_renderer settings are copied from those of like (if provided).

Sourceval failwith : ('a, Format.formatter, unit, 'b) format4 -> 'a

failwith is kstr failwith, raises Stdlib.Failure with a pretty-printed string argument.

Sourceval failwith_notrace : ('a, Format.formatter, unit, 'b) format4 -> 'a

failwith_notrace is like failwith but raises with raise_notrace.

Sourceval invalid_arg : ('a, Format.formatter, unit, 'b) format4 -> 'a

invalid_arg is kstr invalid_arg, raises Stdlib.Invalid_argument with a pretty-printed string argument.

Sourceval error : ('b, Format.formatter, unit, ('a, string) result) format4 -> 'b

error fmt ... is kstr (fun s -> Error s) fmt ...

Source

val error_msg : 
  ('b, Format.formatter, unit, ('a, [> `Msg of string ]) result) format4 ->
  'b

error_msg fmt ... is kstr (fun s -> Error (`Msg s)) fmt ...

Formatters

Sourcetype 'a t = Format.formatter -> 'a -> unit

The type for formatters of values of type 'a.

Sourceval flush : 'a t

flush has the effect of Format.pp_print_flush

Sourceval nop : 'a t

nop formats nothing.

Sourceval any : (unit, Format.formatter, unit) format -> 'a t

any fmt ppf v formats any value with the constant format fmt.

Sourceval using : ('a -> 'b) -> 'b t -> 'a t

using f pp ppf v ppf ppf (f v).

Sourceval const : 'a t -> 'a -> 'b t

const pp_v v always formats v using pp_v.

Sourceval if' : bool -> 'a t -> 'a t

if' bool pp is pp if bool is true and nop otherwise.

Sourceval fmt : ('a, Format.formatter, unit) format -> Format.formatter -> 'a

fmt fmt ppf is pf ppf fmt. If fmt is used with a single non-constant formatting directive, generates a value of type t.

Separators

Sourceval cut : 'a t

cut has the effect of Format.pp_print_cut.

Sourceval sp : 'a t

sp has the effect of Format.pp_print_space.

Sourceval sps : int -> 'a t

sps n has the effect of Format.pp_print_break n 0.

Sourceval comma : 'a t

comma is Fmt.any ",@ ".

Sourceval semi : 'a t

semi is Fmt.any ";@ ".

Sequencing

Sourceval append : 'a t -> 'a t -> 'a t

append pp_v0 pp_v1 ppf v is pp_v0 ppf v; pp_v1 ppf v.

Sourceval (++) : 'a t -> 'a t -> 'a t

( ++ ) is append.

Sourceval concat : ?sep:unit t -> 'a t list -> 'a t

concat ~sep pps formats a value using the formaters pps and separting each format with sep (defaults to cut).

Sourceval iter : ?sep:unit t -> (('a -> unit) -> 'b -> unit) -> 'a t -> 'b t

iter ~sep iter pp_elt formats the iterations of iter over a value using pp_elt. Iterations are separated by sep (defaults to cut).

Source

val iter_bindings : 
  ?sep:unit t ->
  (('a -> 'b -> unit) -> 'c -> unit) ->
  ('a * 'b) t ->
  'c t

iter_bindings ~sep iter pp_binding formats the iterations of iter over a value using pp_binding. Iterations are separated by sep (defaults to cut).

Boxes

Sourceval box : ?indent:int -> 'a t -> 'a t

box ~indent pp ppf wraps pp in a pretty-printing box. The box tries to print as much as possible on every line, while emphasizing the box structure (see Format.pp_open_box). Break hints that lead to a new line add indent to the current indentation (defaults to 0).

Sourceval hbox : 'a t -> 'a t

hbox is like box but is a horizontal box: the line is not split in this box (but may be in sub-boxes). See Format.pp_open_hbox.

Sourceval vbox : ?indent:int -> 'a t -> 'a t

vbox is like box but is a vertical box: every break hint leads to a new line which adds indent to the current indentation (defaults to 0). See Format.pp_open_vbox.

Sourceval hvbox : ?indent:int -> 'a t -> 'a t

hvbox is like hbox if it fits on a single line, or like vbox otherwise. See Format.pp_open_hvbox.

Sourceval hovbox : ?indent:int -> 'a t -> 'a t

hovbox is a condensed box. See Format.pp_open_hovbox.

Brackets

Sourceval parens : 'a t -> 'a t

parens pp_v ppf is pf "@[<1>(%a)@]" pp_v.

Sourceval brackets : 'a t -> 'a t

brackets pp_v ppf is pf "@[<1>[%a]@]" pp_v.

Sourceval braces : 'a t -> 'a t

braces pp_v ppf is pf "@[<1>{%a}@]" pp_v.

Sourceval quote : ?mark:string -> 'a t -> 'a t

quote ~mark pp_v ppf is pf "@[<1>@<1>%s%a@<1>%s@]" mark pp_v mark, mark defaults to "\"", it is always counted as spanning as single column (this allows for UTF-8 encoded marks).

Records

Sourceval id : 'a -> 'a

id is Fun.id.

Source

val field : 
  ?label:string t ->
  ?sep:unit t ->
  string ->
  ('b -> 'a) ->
  'a t ->
  'b t

field ~label ~sep l prj pp_v pretty prints a labelled field value as pf "@[<1>%a%a%a@]" label l sep () (using prj pp_v). label defaults to styled `Yellow string and sep to any ":@ ".

Sourceval record : ?sep:unit t -> 'a t list -> 'a t

record ~sep fields pretty-prints a value using the concatenation of fields, separated by sep (defaults to cut) and framed in a vertical box.

Stdlib types

Formatters for structures give full control to the client over the formatting process and do not wrap the formatted structures with boxes. Use the Dump module to quickly format values for inspection.

Sourceval bool : bool t

bool is Format.pp_print_bool.

Sourceval int : int t

int ppf is pf ppf "%d".

Sourceval nativeint : nativeint t

nativeint ppf is pf ppf "%nd".

Sourceval int32 : int32 t

int32 ppf is pf ppf "%ld".

Sourceval int64 : int64 t

int64 ppf is pf ppf "%Ld".

Sourceval uint : int t

uint ppf is pf ppf "%u".

Sourceval unativeint : nativeint t

unativeint ppf is pf ppf "%nu".

Sourceval uint32 : int32 t

uint32 ppf is pf ppf "%lu".

Sourceval uint64 : int64 t

uint64 ppf is pf ppf "%Lu".

Sourceval float : float t

float ppf is pf ppf "%g".

Sourceval float_dfrac : int -> float t

float_dfrac d rounds the float to the dth decimal fractional digit and formats the result with "%g". Ties are rounded towards positive infinity. The result is only defined for 0 <= d <= 16.

Sourceval float_dsig : int -> float t

float_dsig d rounds the normalized decimal significand of the float to the dth decimal fractional digit and formats the result with "%g". Ties are rounded towards positive infinity. The result is NaN on infinities and only defined for 0 <= d <= 16.

Warning. The current implementation overflows on large d and floats.

Sourceval char : char t

char is Format.pp_print_char.

Sourceval string : string t

string is Format.pp_print_string.

Sourceval buffer : Buffer.t t

buffer formats a Buffer.t value's current contents.

Sourceval exn : exn t

exn formats an exception.

Sourceval exn_backtrace : (exn * Printexc.raw_backtrace) t

exn_backtrace formats an exception backtrace.

Sourceval pair : ?sep:unit t -> 'a t -> 'b t -> ('a * 'b) t

pair ~sep pp_fst pp_snd formats a pair. The first and second projection are formatted using pp_fst and pp_snd and are separated by sep (defaults to cut).

Sourceval option : ?none:unit t -> 'a t -> 'a option t

option ~none pp_v formats an optional value. The Some case uses pp_v and None uses none (defaults to nop).

Sourceval result : ok:'a t -> error:'b t -> ('a, 'b) result t

result ~ok ~error formats a result value using ok for the Ok case and error for the Error case.

Sourceval list : ?sep:unit t -> 'a t -> 'a list t

list sep pp_v formats list elements. Each element of the list is formatted in order with pp_v. Elements are separated by sep (defaults to cut). If the list is empty, this is nop.

Sourceval array : ?sep:unit t -> 'a t -> 'a array t

array sep pp_v formats array elements. Each element of the array is formatted in order with pp_v. Elements are separated by sep (defaults to cut). If the array is empty, this is nop.

Sourceval seq : ?sep:unit t -> 'a t -> 'a Seq.t t

seq sep pp_v formats sequence elements. Each element of the sequence is formatted in order with pp_v. Elements are separated by sep (defaults to cut). If the sequence is empty, this is nop.

Sourceval hashtbl : ?sep:unit t -> ('a * 'b) t -> ('a, 'b) Hashtbl.t t

hashtbl ~sep pp_binding formats the bindings of a hash table. Each binding is formatted with pp_binding and bindings are separated by sep (defaults to cut). If the hash table has multiple bindings for a given key, all bindings are formatted, with the most recent binding first. If the hash table is empty, this is nop.

Sourceval queue : ?sep:unit t -> 'a t -> 'a Queue.t t

queue ~sep pp_v formats queue elements. Each element of the queue is formatted in least recently added order with pp_v. Elements are separated by sep (defaults to cut). If the queue is empty, this is nop.

Sourceval stack : ?sep:unit t -> 'a t -> 'a Stack.t t

stack ~sep pp_v formats stack elements. Each element of the stack is formatted from top to bottom order with pp_v. Elements are separated by sep (defaults to cut). If the stack is empty, this is nop.

Sourcemodule Dump : sig ... end

Formatters for inspecting OCaml values.

Magnitudes

Sourceval si_size : scale:int -> string -> int t

si_size ~scale unit formats a non negative integer representing unit unit at scale 10^{scale * 3}, depending on its magnitude, using power of 3 SI prefixes (i.e. all of them except deca, hector, deci and centi). Only US-ASCII characters are used, µ (10^-6) is written using u.

scale indicates the scale 10^{scale * 3} an integer represents, for example -1 for munit (10^-3), 0 for unit (10⁰), 1 for kunit (10³); it must be in the range [-8;8] or Invalid_argument is raised.

Except at the maximal yotta scale always tries to show three digits of data with trailing fractional zeros omited. Rounds towards positive infinity (over approximates).

Sourceval byte_size : int t

byte_size is si_size ~scale:0 "B".

Sourceval bi_byte_size : int t

bi_byte_size formats a byte size according to its magnitude using binary prefixes up to pebi bytes (2¹⁵).

Sourceval uint64_ns_span : int64 t

uint64_ns_span formats an unsigned nanosecond time span according to its magnitude using SI prefixes on seconds and accepted non-SI units. Years are counted in Julian years (365.25 SI-accepted days) as defined by the International Astronomical Union (IAU). Only US-ASCII characters are used (us is used for µs).

Binary data

Sourcetype 'a vec = int * (int -> 'a)

The type for random addressable, sized sequences. Each (n, f) represents the sequence f 0, ..., f (n - 1).

Sourceval on_bytes : char vec t -> bytes t

on_bytes pp is pp adapted to format (entire) bytes.

Sourceval on_string : char vec t -> string t

on_string pp is pp adapted to format (entire) strings.

Sourceval ascii : ?w:int -> ?subst:unit t -> unit -> char vec t

ascii ~w ~subst () formats character sequences by printing characters in the printable US-ASCII range ([0x20];[0x7E]) as is, and replacing the rest with subst (defaults to fmt "."). w causes the output to be right padded to the size of formatting at least w sequence elements (defaults to 0).

Sourceval octets : ?w:int -> ?sep:unit t -> unit -> char vec t

octets ~w ~sep () formats character sequences as hexadecimal digits. It prints groups of successive characters of unspecified length together, separated by sep (defaults to sp). w causes the output to be right padded to the size of formatting at least w sequence elements (defaults to 0).

Sourceval addresses : ?addr:int t -> ?w:int -> 'a vec t -> 'a vec t

addresses pp formats sequences by applying pp to consecutive subsequences of length w (defaults to 16). addr formats subsequence offsets (defaults to an unspecified hexadecimal format).

Sourceval hex : ?w:int -> unit -> char vec t

hex ~w () formats character sequences as traditional hex dumps, matching the output of xxd and forcing line breaks after every w characters (defaults to 16).

Words, paragraphs, text and lines

Note. These functions only work on US-ASCII strings and/or with newlines ('\n'). If you are dealing with UTF-8 strings or different kinds of line endings you should use the pretty-printers from Uuseg_string.

White space. White space is one of the following US-ASCII characters: space ' ' (0x20), tab '\t' (0x09), newline '\n' (0x0A), vertical tab (0x0B), form feed (0x0C), carriage return '\r' (0x0D).

Sourceval words : string t

words formats words by suppressing initial and trailing white space and replacing consecutive white space with a single Format.pp_print_space.

Sourceval paragraphs : string t

paragraphs formats paragraphs by suppressing initial and trailing spaces and newlines, replacing blank lines (a line made only of white space) by a two Format.pp_force_newline and remaining consecutive white space with a single Format.pp_print_space.

Sourceval text : string t

text formats text by respectively replacing spaces and newlines in the string with Format.pp_print_space and Format.pp_force_newline.

Sourceval lines : string t

lines formats lines by replacing newlines ('\n') in the string with calls to Format.pp_force_newline.

Sourceval truncated : max:int -> string t

truncated ~max formats a string using at most max characters. If the string doesn't fit, it is truncated and ended with three consecutive dots which do count towards max.

Sourceval text_loc : ((int * int) * (int * int)) t

text_loc formats a line-column text range according to GNU conventions.

HCI fragments

Sourceval one_of : ?empty:unit t -> 'a t -> 'a list t

one_of ~empty pp_v ppf l formats according to the length of l

0, formats empty (defaults to nop).
1, formats the element with pp_v.
2, formats "either %a or %a" with the list elements
n, formats "one of %a, ... or %a" with the list elements

Source

val did_you_mean : 
  ?pre:unit t ->
  ?post:unit t ->
  kind:string ->
  'a t ->
  ('a * 'a list) t

did_you_mean ~pre kind ~post pp_v formats a faulty value v of kind kind and a list of hints that v could have been mistaken for.

pre defaults to unit "Unknown", post to nop they surround the faulty value before the "did you mean" part as follows "%a %s %a%a." pre () kind pp_v v post (). If hints is empty no "did you mean" part is printed.

Conditional UTF-8 formatting

Note. Since Format is not UTF-8 aware using UTF-8 output may derail the pretty printing process. Use the pretty-printers from Uuseg_string if you are serious about UTF-8 formatting.

Sourceval if_utf_8 : 'a t -> 'a t -> 'a t

if_utf_8 pp_u pp ppf v is:

pp_u ppf v if utf_8 ppf is true.
pp ppf v otherwise.

Sourceval utf_8 : Format.formatter -> bool

utf_8 ppf is true if UTF-8 output is enabled on ppf. If set_utf_8 hasn't been called on ppf this is true.

Sourceval set_utf_8 : Format.formatter -> bool -> unit

set_utf_8 ppf b enables or disables conditional UTF-8 formatting on ppf.

raises Invalid_argument
if ppf is Format.str_formatter: it is is always UTF-8 enabled.

Styled formatting

Sourcetype color = [

| `Black
| `Blue
| `Cyan
| `Green
| `Magenta
| `Red
| `White
| `Yellow

]

The type for colors.

Sourcetype style = [

| `None
| `Bold
| `Faint
| `Italic
| `Underline
| `Reverse
| `Fg of [ color | `Hi of color ]
| `Bg of [ color | `Hi of color ]
| color

]

The type for styles:

`None resets the styling.
`Bold, `Faint, `Italic, `Underline and `Reverse are display attributes.
`Fg _ is the foreground color or high-intensity color on `Hi _.
`Bg _ is the background color or high-intensity color on `Hi _.
#color is the foreground color, deprecated use `Fg #color instead.

Sourceval styled : style -> 'a t -> 'a t

styled s pp formats like pp but styled with s.

Style rendering control

Sourcetype style_renderer = [

| `Ansi_tty
| `None

]

The type for style renderers.

`Ansi_tty, renders styles using ANSI escape sequences.
`None, styled rendering has no effect.

Sourceval style_renderer : Format.formatter -> style_renderer

style_renderer ppf is the style renderer used by ppf. If set_style_renderer has never been called on ppf this is `None.

Sourceval set_style_renderer : Format.formatter -> style_renderer -> unit

set_style_renderer ppf r sets the style renderer of ppf to r.

raises Invalid_argument
if ppf is Format.str_formatter: its renderer is always `None.

Converting with string value converters

Sourceval of_to_string : ('a -> string) -> 'a t

of_to_string f ppf v is string ppf (f v).

Sourceval to_to_string : 'a t -> 'a -> string

to_to_string pp_v v is strf "%a" pp_v v.

Deprecated

Sourceval strf : ('a, Format.formatter, unit, string) format4 -> 'a

deprecated
use str instead.

Sourceval kstrf : (string -> 'a) -> ('b, Format.formatter, unit, 'a) format4 -> 'b

deprecated
use kstr instead.

Source

val strf_like : 
  Format.formatter ->
  ('a, Format.formatter, unit, string) format4 ->
  'a

deprecated
use str_like instead.

Sourceval always : (unit, Format.formatter, unit) format -> 'a t

deprecated
use any instead.

Sourceval unit : (unit, Format.formatter, unit) format -> unit t

deprecated
use any.

Sourceval prefix : unit t -> 'a t -> 'a t

deprecated
use (++).

Sourceval suffix : unit t -> 'a t -> 'a t

deprecated
use (++).

Sourceval styled_unit : style -> (unit, Format.formatter, unit) format -> unit t

deprecated
use styled s (any fmt) instead

Naming conventions

Given a type ty use:

pp_ty for a pretty printer that provides full control to the client and does not wrap the formatted value in an enclosing box. See these examples.
pp_dump_ty for a pretty printer that provides little control over the pretty-printing process, wraps the rendering in an enclosing box and tries as much as possible to respect the OCaml syntax. These pretty-printers should make it easy to inspect and understand values of the given type, they are mainly used for quick printf debugging and/or toplevel interaction. See these examples.

If you are in a situation where making a difference between dump_ty and pp_ty doesn't make sense then use pp_ty.

For a type ty that is the main type of the module (the "M.t" convention) drop the suffix, that is simply use M.pp and M.pp_dump.

package fmt

Module FmtSource

Standard outputs

Formatting

Formatters

Separators

Sequencing

Boxes

Brackets

Records

Stdlib types

Magnitudes

Binary data

Words, paragraphs, text and lines

HCI fragments

Conditional UTF-8 formatting

Styled formatting

Style rendering control

Converting with string value converters

Deprecated

Naming conventions

Module `Fmt`Source