(*
 * BatPervasives - Additional functions
 * Copyright (C) 1996 Xavier Leroy
 *               2003 Nicolas Cannasse
 *               2007 Zheng Li
 *               2008 David Teller
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version,
 * with the special exception on linking described in file LICENSE.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *)

(** Additional functions.

    @author Xavier Leroy (Base module)
    @author Nicolas Cannasse
    @author David Teller
    @author Zheng Li
*)

open BatIO

##V>=5## module Pervasives := Stdlib

(** The initially opened module.

    This module provides the basic operations over the built-in types
    (numbers, booleans, strings, exceptions, references, lists, arrays,
    input-output channels, ...)

    This module is automatically opened at the beginning of each compilation.
    All components of this module can therefore be referred by their short
    name, without prefixing them by [BatPervasives].

    @author Xavier Leroy (Base module)
    @author Nicolas Cannasse
    @author David Teller
    @author Zheng Li
*)

val input_lines : Pervasives.in_channel -> string BatEnum.t
(** Returns an enumeration over lines of an input channel, as read by the
    [input_line] function. *)

val input_chars : Pervasives.in_channel -> char BatEnum.t
(** Returns an enumeration over characters of an input channel. *)

val input_list : Pervasives.in_channel -> string list
(** Returns the list of lines read from an input channel. *)

val input_all : Pervasives.in_channel -> string
(** Return the whole contents of an input channel as a single
    string. *)

val dump : 'a -> string
(** Attempt to convert a value to a string.

    Works well for a lot of cases such as non-empty lists, algebraic
    datatype, and records.

    However, since types are lost at compile-time, the representation
    might not match your type. (0, 1) will be printed as expected, but
    (1, 0) and [1] have the same representation and will get printed
    in the same way. The result of [dump] is unspecified and may
    change in future versions, so you should only use it for debugging
    and never have program behavior depend on the output.

    Here is a list of some of the surprising corner cases of the
    current implementation:

      - (3, 0) is printed [3], (0.5, 0) is printed [0.5], etc.
      - None, false and [] are printed 0

    [dump] may fail for ill-formed values, such as obtained from
    a faulty C binding or crazy uses of [Obj.set_tag].
*)

val print_any : 'b BatIO.output -> 'a -> unit
(** Attempt to print a value to an output.

    Uses [dump] to convert the value to a string and prints that
    string to the output.
*)

(** {1 List operations}

    More list operations are provided in module {!List}.
*)

val ( @ ) : 'a list -> 'a list -> 'a list
(** List concatenation. *)


(** {1 Input/output}

    This section only contains the most common input/output operations.
    More operations may be found in modules {!BatIO} and {!File}.
*)

val stdin : input
(** Standard input, as per Unix/Windows conventions (by default, keyboard).

    Use this input to read what the user is writing on the keyboard.*)

val stdout: unit output
(** Standard output, as per Unix/Windows conventions (by default, console).

    Use this output to display regular messages.*)

val stderr: unit output
(** Standard error output, as per Unix/Windows conventions.

    Use this output to display warnings and error messages.*)

val stdnull: unit output
(** An output which discards everything written to it.

    Use this output to ignore messages.*)

val flush_all : unit -> unit
(** Write all pending data to output channels, ignore all errors.

    It is normally not necessary to call this function, as all pending
    data is written when an output channel is closed or when the
    program itself terminates, either normally or because of an
    uncaught exception. However, this function is useful for
    debugging, as it forces pending data to be written immediately.
*)

(** {2 Output functions on standard output} *)


val print_bool : bool -> unit
(** Print a boolean on standard output. *)

val print_guess : 'a BatIO.output -> 'b -> unit
(** Attempt to print the representation of a runtime value on the
    standard output.  See remarks for {!dump}. This function is
    useful mostly for debugging. As a general rule, it should not be
    used in production code.*)

val print_all : input -> unit
(** Print the contents of an input to the standard output.*)

(** {2 Output functions on standard error} *)

val prerr_bool : bool -> unit
(** Print a boolean to stderr. *)

val prerr_guess : 'a -> unit
(** Attempt to print the representation of a runtime value on the
    error output.  See remarks for {!dump}. This function is
    useful mostly for debugging.*)

val prerr_all : input -> unit
(** Print the contents of an input to the error output.*)

(** {2 General output functions} *)

val output_file : filename:string -> text:string -> unit
(** creates a filename, write text into it and close it. *)

val open_out : ?mode:(BatFile.open_out_flag list) ->
  ?perm:BatFile.permission           ->
  string -> unit BatIO.output
(** Open the named file for writing, and return a new output channel
    on that file. You will need to close the file once you have
    finished using it.

    You may use optional argument [mode] to decide whether the
    output will overwrite the contents of the file (by default) or
    to add things at the end of the file, whether the file should be
    created if it does not exist yet (the default) or not, whether
    this operation should proceed if the file exists already (the
    default) or not, whether the file should be opened as text
    (the default) or as binary, and whether the file should be
    opened for non-blocking operations.

    You may use optional argument [perm] to specify the permissions
    of the file, as per Unix conventions. By default, files are created
    with default permissions (which depend on your setup).

    @raise Sys_error if the file could not be opened. *)

val open_out_bin : string -> unit BatIO.output
(** Same as {!open_out}, but the file is opened in binary mode, so
    that no translation takes place during writes. On operating
    systems that do not distinguish between text mode and binary
    mode, this function behaves like {!open_out} without any
    [mode] or [perm]. *)

val open_out_gen : open_flag list -> int -> string -> unit BatIO.output
(**
   [open_out_gen mode perm filename] opens the named file for writing,
   as described above. The extra argument [mode]
   specifies the opening mode. The extra argument [perm] specifies
   the file permissions, in case the file must be created.

   @deprecated Use {!open_out instead}*)

val flush : unit BatIO.output -> unit
(** Flush the buffer associated with the given output, performing
    all pending writes on that channel. Interactive programs must be
    careful about flushing standard output and standard error at the
    right time. *)



val output_char : unit BatIO.output -> char -> unit
(** Write the character on the given output channel. *)

val output_string : unit BatIO.output -> string -> unit
(** Write the string on the given output channel. *)

val output : unit BatIO.output -> Bytes.t -> int -> int -> unit
(** [output oc buf pos len] writes [len] characters from byte sequence [buf],
    starting at offset [pos], to the given output channel [oc].
    @raise Invalid_argument if [pos] and [len] do not
    designate a valid subsequence of [buf]. *)

val output_substring : unit BatIO.output -> string -> int -> int -> unit
(** [output_substring oc buf pos len] writes [len] characters from string [buf],
    starting at offset [pos], to the given output channel [oc].
    @raise Invalid_argument if [pos] and [len] do not
    designate a valid substring of [buf]. *)

val output_byte : unit BatIO.output -> int -> unit
(** Write one 8-bit integer (as the single character with that code)
    on the given output channel. The given integer is taken modulo
    256. *)

val output_binary_int : unit BatIO.output -> int -> unit
(** Write one integer in binary format (4 bytes, big-endian)
    on the given output channel.
    The given integer is taken modulo 2{^32}.
    The only reliable way to read it back is through the
    {!Pervasives.input_binary_int} function. The format is compatible across
    all machines for a given version of OCaml. *)

val output_binary_float : unit BatIO.output -> float -> unit
(** Write one float in binary format (8 bytes, IEEE 754 double format)
    on the given output channel.
    The only reliable way to read it back is through the
    {!Pervasives.input_binary_float} function. The format is compatible across
    all machines for a given version of OCaml. *)

val output_value : unit BatIO.output -> 'a -> unit
(** Write the representation of a structured value of any type
    to a channel. Circularities and sharing inside the value
    are detected and preserved. The object can be read back,
    by the function {!input_value}. See the description of module
    {!Marshal} for more information. {!output_value} is equivalent
    to {!Marshal.output} with an empty list of flags. *)


val close_out : unit BatIO.output -> unit
(** Close the given channel, flushing all buffered write operations.
    Output functions raise a [Sys_error] exception when they are
    applied to a closed output channel, except [close_out] and [flush],
    which do nothing when applied to an already closed channel.
    @raise Sys_error if the operating
    system signals an error when flushing or closing. *)

val close_out_noerr : unit BatIO.output -> unit
(** Same as [close_out], but ignore all errors. *)

(** {2 General input functions} *)

val input_file : ?bin:bool -> string -> string
(** returns the data of a given filename. *)

val open_in : ?mode:(BatFile.open_in_flag list) ->
  ?perm:BatFile.permission ->
  string -> BatIO.input
(** Open the named file for reading. You will need to close the file once you have
    finished using it.

    You may use optional argument [mode] to decide whether the opening
    should fail if the file doesn't exist yet (by default) or whether
    the file should be created if it doesn't exist yet, whether the
    opening should fail if the file already exists or not (by
    default), whether the file should be read as binary (by default)
    or as text, and whether reading should be non-blocking.

    You may use optional argument [perm] to specify the permissions of
    the file, should it be created, as per Unix conventions. By
    default, files are created with default permissions (which depend
    on your setup).

    @raise Sys_error if the file could not be opened. *)


val open_in_bin : string -> BatIO.input
(** Same as {!Pervasives.open_in}, but the file is opened in binary mode,
    so that no translation takes place during reads. On operating
    systems that do not distinguish between text mode and binary
    mode, this function behaves like {!Pervasives.open_in}. *)

val open_in_gen : open_flag list -> int -> string -> BatIO.input
(** [open_in_gen mode perm filename] opens the named file for reading,
    as described above. The extra arguments [mode] and [perm]
    specify the opening mode and file permissions.
    {!Pervasives.open_in} and {!Pervasives.open_in_bin} are special
    cases of this function.

    @deprecated Use {!open_in instead}*)

val input_char : BatIO.input -> char
(** Read one character from the given input channel.
    @raise End_of_file if there are no more characters to read. *)

val input_line : BatIO.input -> string
(** Read characters from the given input channel, until a
    newline character is encountered. Return the string of
    all characters read, without the newline character at the end.
    @raise End_of_file if the end of the file is reached
    at the beginning of line. *)

val input : BatIO.input -> Bytes.t -> int -> int -> int
(** [input ic buf pos len] reads up to [len] characters from the given
    channel [ic], storing them in byte sequence [buf], starting at
    character number [pos].
    It returns the actual number of characters read, between 0 and
    [len] (inclusive).
    A return value of 0 means that the end of file was reached.
    A return value between 0 and [len] exclusive means that
    not all requested [len] characters were read, either because
    no more characters were available at that time, or because
    the implementation found it convenient to do a partial read;
    [input] must be called again to read the remaining characters,
    if desired.  (See also {!Pervasives.really_input} for reading
    exactly [len] characters.)
    @raise Invalid_argument if [pos] and [len]
    do not designate a valid subsequence of [buf]. *)

val really_input : BatIO.input -> Bytes.t -> int -> int -> unit
(** [really_input ic buf pos len] reads [len] characters from channel
    [ic], storing them in byte sequence [buf], starting at character
    number [pos].

    @raise End_of_file if the end of file is reached
    before [len] characters have been read.
    @raise Invalid_argument if
    [pos] and [len] do not designate a valid subsequence of [buf]. *)

val input_byte : BatIO.input -> int
(** Same as {!Pervasives.input_char}, but return the 8-bit integer representing
    the character.
    @raise End_of_file if an end of file was reached. *)

val input_binary_int : BatIO.input -> int
(** Read an integer encoded in binary format (4 bytes, big-endian)
    from the given input channel. See {!Pervasives.output_binary_int}.
    @raise End_of_file if an end of file was reached while reading the
    integer. *)

val input_binary_float : BatIO.input -> float
(** Read a float encoded in binary format (8 bytes, IEEE 754 double format)
    from the given input channel. See {!Pervasives.output_binary_float}.
    @raise End_of_file if an end of file was reached while reading the
    float. *)

val input_value : BatIO.input -> 'a
(** Read the representation of a structured value, as produced
    by {!output_value}, and return the corresponding value.
    This function is identical to {!Marshal.input};
    see the description of module {!Marshal} for more information,
    in particular concerning the lack of type safety. *)

val close_in : BatIO.input -> unit
(** Close the given channel.  Input functions raise a [Sys_error]
    exception when they are applied to a closed input channel,
    except [close_in], which does nothing when applied to an already
    closed channel.
    @raise Sys_error if
    the operating system signals an error. *)

val close_in_noerr : BatIO.input -> unit
(** Same as [close_in], but ignore all errors. *)


(**
   {1 Fundamental functions and operators}
*)

external identity : 'a -> 'a = "%identity"
(** The identity function. *)

val undefined : ?message:string -> 'a -> 'b
  (** The undefined function.

      Evaluating [undefined x] always fails and raises an exception
      "Undefined". Optional argument [message] permits the
      customization of the error message.*)

##V<4## val ( @@ ) : ('a -> 'b) -> 'a -> 'b
##V>=4## external ( @@ ) : ('a -> 'b) -> 'a -> 'b = "%apply"

(** Function application. [f @@ x] is equivalent to [f x].
    However, it binds less tightly (between [::] and [=],[<],[>],etc)
    and is right-associative, which makes it useful for composing sequences of
    function calls without too many parentheses. It is similar to Haskell's [$].
    Note that it replaces pre-2.0 [**>] and [<|]. *)

val ( % ) : ('a -> 'b) -> ('c -> 'a) -> 'c -> 'b
  (** Function composition: the mathematical [o] operator.
      [f % g] is [fun x -> f (g x)]. It is similar to Haskell's [.].

      Examples: the following are equivalent:
      [f (g (h x))], [f @@ g @@ h x], [f % g % h @@ x]. *)

##V<4## val ( |> ) : 'a -> ('a -> 'b) -> 'b
##V>=4## external (|>) : 'a -> ('a -> 'b) -> 'b = "%revapply"
(** The "pipe": function application. [x |> f] is equivalent to [f x].

    This operator is commonly used to write a function composition by
    order of evaluation (the order used in object-oriented
    programming) rather than by inverse order (the order typically
    used in functional programming).

    For instance, [g (f x)] means "apply [f] to [x], then apply [g] to
    the result." The corresponding notation in most object-oriented
    programming languages would be somewhere along the lines of [x.f.g.h()],
    or "starting from [x], apply [f], then apply [g]." In OCaml,
    using the ( |> ) operator, this is written [x |> f |> g |> h].

    This operator may also be useful for composing sequences of
    function calls without too many parentheses. *)

val ( %> ) : ('a -> 'b) -> ('b -> 'c) -> 'a -> 'c
(** Piping function composition. [f %> g] is [fun x -> g (f x)].
    Whereas [f % g] applies [g] first and [f] second, [f %> g]
    applies [f], then [g].
    Note that it plays well with pipes, so for instance
    [x |> f %> g %> h |> i %> j] yields the expected result...
    but in such cases it's still recommended to use [|>] only.
    Note that it replaces pre-2.0 [|-], which {i didn't} integrate with
    pipes.
*)

val ( |? ) : 'a option -> 'a -> 'a
(** Like {!BatOption.default}, with the arguments reversed.
    [None |? 10] returns [10], while [Some "foo" |? "bar"] returns ["foo"].

    {b Note} This operator does not short circuit like [( || )] and [( && )].
    Both arguments will be evaluated.

    @since 2.0 *)

val flip : ( 'a -> 'b -> 'c ) -> 'b -> 'a -> 'c
(** Argument flipping.

    [flip f x y] is [f y x]. Don't abuse this function, it may shorten
    considerably your code but it also has the nasty habit of making
    it harder to read.*)


val curry : ('a * 'b -> 'c) -> 'a -> 'b -> 'c
(** Convert a function which accepts a pair of arguments into a
    function which accepts two arguments.

    [curry f] is [fun x y -> f (x,y)]*)

val uncurry : ('a -> 'b -> 'c) -> 'a * 'b -> 'c
(** Convert a function which accepts two arguments into a function
    which accepts a pair of arguments.

    [uncurry f] is [fun (x, y) -> f x y]*)

val neg : ('a -> bool) -> 'a -> bool
(** [neg p] returns a new predicate that is the negation of the given
    predicate.  That is, the new predicate returns [false] when the
    input predicate returns [true] and vice versa.  This is for
    predicates with one argument.

    [neg p] is [fun x -> not (p x)]
*)

val neg2 : ('a -> 'b -> bool) -> 'a -> 'b -> bool
(** as [neg] but for predicates with two arguments *)

val const : 'a -> (_ -> 'a)
(** Ignore its second argument.

    [const x] is the function which always returns [x].*)

val unique : unit -> int
(** Returns an unique identifier every time it is called.

    {b Note} This is thread-safe.*)

val tap : ('a -> unit) -> 'a -> 'a
(** Allows application of a function in the middle of a pipe
    sequence without disturbing the sequence.  [x |> tap f]
    evaluates to [x], but has the side effect of [f x].  Useful for
    debugging. *)

val finally : (unit -> unit) -> ('a -> 'b) -> 'a -> 'b
(** [finally fend f x] calls [f x] and then [fend()] even if [f x] raised
    an exception. *)

val with_dispose : dispose:('a -> unit) -> ('a -> 'b) -> 'a -> 'b
(** [with_dispose dispose f x] invokes [f] on [x], calling [dispose x]
    when [f] terminates (either with a return value or an
    exception). *)

val forever : ('a -> 'b) -> 'a -> unit
(** [forever f x] invokes [f] on [x] repeatedly (until an exception occurs). *)

val ignore_exceptions : ('a -> 'b) -> 'a -> unit
(** [ignore_exceptions f x] invokes [f] on [x], ignoring both the returned value
    and the exceptions that may be raised. *)

val verify_arg : bool -> string -> unit
(** [verify_arg condition message] will raise [Invalid_argument message] if
    [condition] is false, otherwise it does nothing.

    @since 2.0 *)

val args : unit -> string BatEnum.t
(** An enumeration of the arguments passed to this program through the command line.

    [args ()] is given by the elements of [Sys.argv], minus the first element.*)

(**/**)
val invisible_args : int ref
(** The number of arguments which must never be returned by [args]

    Typically, [invisible_args] is [1], to drop the name of the executable. However,
    in some circumstances, it may be useful to pretend that some arguments need not
    be parsed.
*)
(**/**)


val exe  : string
(** The name of the current executable.

    [exe] is given by the first argument of [Sys.argv]*)


(**
   {1 Enumerations}

   In OCaml Batteries Included, all data structures are enumerable,
   which means that they support a number of standard operations,
   transformations, etc. The general manner of {i enumerating} the
   contents of a data structure is to invoke the [enum] function of
   your data structure.

   For instance, you may use the {!foreach} loop to apply a function
   [f] to all the consecutive elements of a string [s]. For this
   purpose, you may write either [foreach (String.enum s) f] or [open
   String in foreach (enum s) f]. Either possibility states that you
   are enumerating through a character string [s]. Should you prefer
   your enumeration to proceed from the end of the string to the
   beginning, you may replace {! String.enum} with {!
   String.backwards}. Therefore, either [foreach (String.backwards s)
   f] or [open String in foreach (backwards s) f] will apply [f]
   to all the consecutive elements of string [s], from the last to
   the first.

   Similarly, you may use {!List.enum} instead of {!String.enum} to
   visit the elements of a list in the usual order, or
   {!List.backwards} instead of {!String.backwards} to visit them
   in the opposite order, or {!Hashtbl.enum} for hash tables, etc.

   More operations on enumerations are defined in module {!BatEnum},
   including the necessary constructors to make your own structures
   enumerable.

   The various kinds of loops are detailed further in this documentation.
*)

val foreach: 'a BatEnum.t -> ('a -> unit) ->  unit
(** Imperative loop on an enumeration.

    [foreach e f] applies function [f] to each successive element of [e].
    For instance, [foreach (1 -- 10) print_int] invokes function [print_int]
    on [1], [2], ..., [10], printing [12345678910].

    {b Note} This function is one of the many loops available on
    enumerations.  Other commonly used loops are {!iter} (same usage
    scenario as [foreach], but with different notations), {!map}
    (convert an enumeration to another enumeration) or {!fold}
    (flatten an enumeration by applying an operation to each
    element).

*)

(**
   {2 General-purpose loops}

   The following functions are the three main general-purpose loops
   available in OCaml. By opposition to the loops available in
   imperative languages, OCaml loops are regular functions, which
   may be passed, composed, currified, etc. In particular, each
   of these loops may be considered either as a manner of applying
   a function to a data structure or as transforming a function
   into another function which will act on a whole data structure.

   For instance, if [f] is a function operating on one value, you may
   lift this function to operate on all values of an enumeration (and
   consequently on all values of any data structure of OCaml Batteries
   Included) by applying {!iter}, {!map} or {!fold} to this function.
*)


val iter : ('a -> unit) -> 'a BatEnum.t -> unit
(** Imperative loop on an enumeration. This loop is typically used
    to lift a function with an effect but no meaningful result and
    get it to work on enumerations.

    If [f] is a function [iter f] is a function which behaves as [f]
    but acts upon enumerations rather than individual elements. As
    indicated in the type of [iter], [f] must produce values of type
    [unit] (i.e. [f] has no meaningful result) the resulting function
    produces no meaningful result either.

    In other words, [iter f] is a function which, when applied upon
    an enumeration [e], calls [f] with each element of [e] in turn.

    For instance, [iter f (1 -- 10)] invokes function [f] on [1],
    [2], ..., [10] and produces value [()].
*)

val map : ('a -> 'b) -> 'a BatEnum.t -> 'b BatEnum.t
(** Transformation loop on an enumeration, used to build an enumeration
    from another enumeration. This loop is typically used to transform
    an enumeration into another enumeration with the same number of
    elements, in the same order.

    If [f] is a function, [map f e] is a function which behaves as
    [f] but acts upon enumerations rather than individual elements --
    and builds a new enumeration from the results of each application.

    In other words, [map f] is a function which, when applied
    upon an enumeration containing elements [e0], [e1], ...,
    produces enumeration [f e0], [f e1], ...

    For instance, if [odd] is the function which returns [true]
    when applied to an odd number or [false] when applied to
    an even number, [map odd (1 -- 10)] produces enumeration
    [true], [false], [true], ..., [false].

    Similarly, if [square] is the function [fun x -> x * x],
    [map square (1 -- 10)] produces the enumeration of the
    square numbers of all numbers between [1] and [10].
*)


val filter_map : ('a -> 'b option) -> 'a BatEnum.t -> 'b BatEnum.t
(** Similar to a map, except that you can skip over some items of the
    incoming enumeration by returning None instead of Some value.
    Think of it as a {!filter} combined with a {!map}.
*)


val reduce : ('a -> 'a -> 'a) -> 'a BatEnum.t -> 'a
(** Transformation loop on an enumeration, used to build a single value
    from an enumeration.

    If [f] is a function and [e] is an enumeration, [reduce f e] applies
    function [f] to the first two elements of [e], then to the result of this
    expression and to the third element of [e], then to the result of this
    new expression and to the fourth element of [e]...

    In other words, [reduce f e] returns [a0] if [e] contains only
    one element [a0], otherwise [f (... (f (f a0) a1) ...) aN] where
    [a0,a1..aN] are the elements of [e].

    @raise Not_found if [e] is empty.

    For instance, if [add] is the function [fun x y -> x + y],
    [reduce add] is the function which computes the sum of the
    elements of an enumeration -- and doesn't work on empty
    enumerations. Therefore, [reduce add (1 -- 10)]
    produces result [55].
*)

val fold : ('b -> 'a -> 'b) -> 'b -> 'a BatEnum.t -> 'b
(** Transformation loop on an enumeration, used to build a single value
    from an enumeration. This is the most powerful general-purpose
    loop and also the most complex.

    If [f] is a function, [fold f v e] applies [f v] to the first
    element of [e], then, calling [acc_1] the result of this
    operation, applies [f acc_1] to the second element of [e], then,
    calling [acc_2] the result of this operation, applies [f acc_2]
    to the third element of [e]...

    In other words, [fold f v e] returns [v] if [e] is empty,
    otherwise [f (... (f (f v a0) a1) ...) aN] where a0,a1..aN are
    the elements of [e].

    For instance, if [add] is the function [fun x y -> x + y],
    [fold add 0] is the function which computes the sum of the
    elements of an enumeration. Therefore, [fold add 0 (1 -- 10)]
    produces result [55].
*)

val scanl : ('b -> 'a -> 'b) -> 'b -> 'a BatEnum.t -> 'b BatEnum.t
(** Functional loop on an enumeration, used to build an enumeration
    from both an enumeration and an initial value. This function may
    be seen as a variant of {!fold} which returns not only the final
    result of {!fold} but the enumeration of all the intermediate
    results of {!fold}.

    If [f] is a function, [scanl f v e] is applies [f v] to the first
    element of [e], then, calling [acc_1] the result of this
    operation, applies [f acc_1] to the second element of [e], then,
    calling [acc_2] the result of this operation, applies [f acc_2]
    to the third element of [e]...

    For instance, if [add] is the function [fun x y -> x + y],
    [scanl add 0] is the function which computes the sum of the
    elements of an enumeration. Therefore, [scanl add 0 (1 -- 10)]
    produces result the enumeration with elements [0, 1, 3, 6, 10,
    15, 21, 28, 36, 45, 55].  *)

val ( /@ ) : 'a BatEnum.t -> ('a -> 'b) -> 'b BatEnum.t

val ( @/ ) : ('a -> 'b) -> 'a BatEnum.t -> 'b BatEnum.t
(**
   Mapping operators.

   These operators have the same meaning as function {!map} but are
   sometimes more readable than this function, when chaining
   several transformations in a row.
*)

val ( //@ ) : 'a BatEnum.t -> ('a -> 'b option) -> 'b BatEnum.t

val ( @// ) : ('a -> 'b option) -> 'a BatEnum.t -> 'b BatEnum.t
(**
   Map combined with filter. Same as {!filter_map}.
*)

(**
   {2 Other operations on enumerations}
*)

val exists: ('a -> bool) -> 'a BatEnum.t -> bool
(** [exists f e] returns [true] if there is some [x] in [e] such
    that [f x]*)

val for_all: ('a -> bool) -> 'a BatEnum.t -> bool
(** [for_all f e] returns [true] if for every [x] in [e], [f x] is true*)



val find : ('a -> bool) -> 'a BatEnum.t -> 'a
(** [find f e] returns the first element [x] of [e] such that [f x] returns
    [true], consuming the enumeration up to and including the
    found element, or, raises [Not_found] if no such element exists
    in the enumeration, consuming the whole enumeration in the search.

    Since [find] consumes a prefix of the enumeration, it can be used several
    times on the same enumeration to find the next element.

    @raise Not_found if no element in the whole enumeration satisfies the predicate *)

val peek : 'a BatEnum.t -> 'a option
(** [peek e] returns [None] if [e] is empty or [Some x] where [x] is
    the next element of [e]. The element is not removed from the
    enumeration. *)

val get : 'a BatEnum.t -> 'a option
(** [get e] returns [None] if [e] is empty or [Some x] where [x] is
    the next element of [e], in which case the element is removed
    from the enumeration. *)

val push : 'a BatEnum.t -> 'a -> unit
(** [push e x] will add [x] at the beginning of [e]. *)

val junk : 'a BatEnum.t -> unit
(** [junk e] removes the first element from the enumeration, if any. *)

val filter : ('a -> bool) -> 'a BatEnum.t -> 'a BatEnum.t
(** [filter f e] returns an enumeration over all elements [x] of [e] such
    as [f x] returns [true]. *)

val ( // ) : 'a BatEnum.t -> ('a -> bool) -> 'a BatEnum.t
(** Filtering (pronounce this operator name "such that").

    For instance, [(1 -- 37) // odd] is the enumeration of all odd
    numbers between 1 and 37.*)

val concat : 'a BatEnum.t BatEnum.t -> 'a BatEnum.t
(** [concat e] returns an enumeration over all elements of all enumerations
    of [e]. *)


val ( -- ) : int -> int -> int BatEnum.t
(** Enumerate numbers.

    [5 -- 10] is the enumeration 5,6,7,8,9,10.
    [10 -- 5] is the empty enumeration*)

val ( --^ ) : int -> int -> int BatEnum.t
(** Enumerate numbers, without the right endpoint

    [5 -- 10] is the enumeration 5,6,7,8,9.
*)

val ( --. ) : (float * float) -> float -> float BatEnum.t
(** [(a, step) --. b)] creates a float enumeration from [a] to [b] with an
    increment of [step] between elements.

    [(5.0, 1.0) --. 10.0] is the enumeration 5.0,6.0,7.0,8.0,9.0,10.0.
    [(10.0, -1.0) --. 5.0] is the enumeration 10.0,9.0,8.0,7.0,6.0,5.0.
    [(10.0, 1.0) --. 1.0] is the empty enumeration. *)

val ( --- ) : int -> int -> int BatEnum.t
(** As [--], but accepts enumerations in reverse order.

    [5 --- 10] is the enumeration 5,6,7,8,9,10.
    [10 --- 5] is the enumeration 10,9,8,7,6,5.*)

val ( --~ ) : char -> char -> char BatEnum.t
(** As ( -- ), but for characters.*)

val print :  ?first:string -> ?last:string -> ?sep:string -> ('a BatInnerIO.output -> 'b -> unit) -> 'a BatInnerIO.output -> 'b BatEnum.t -> unit
(** Print and consume the contents of an enumeration.*)

(**
   {1 Results}
*)

(** This type represents the outcome of a function which has the
    possibility of failure.  Normal results of type ['a] are marked
    with [Ok], while failure values of type ['b] are marked with
    [Error].

    This is intended to be a safer alternative to functions raising
    exceptions to signal failure.  It is safer in that the possibility
    of failure has to be handled before the result of that computation
    can be used.

    For more functions related to this type, see the {!BatResult} module.
*)
type ('a, 'e) result = ('a, 'e) BatInnerPervasives.result =
  | Ok  of 'a
  | Error of 'e
  (** The result of a computation - either an [Ok] with the normal
      result or a [Error] with some value (often an exception) containing
      failure information*)

val ignore_ok : ('a, exn) result -> unit
(** [ignore_ok (f x)] ignores the result of [f x] if it's ok, but
    throws the exception contained if [Error] is returned. *)

val ok : ('a, exn) result -> 'a
(** [f x |> ok] unwraps the [Ok] result of [f x] and returns it, or
    throws the exception contained if [Error] is returned. *)

val wrap : ('a -> 'b) -> 'a -> ('b, exn) result
(** [wrap f x] wraps a function that would normally throw an exception
    on failure such that it now returns a result with either the [Ok]
    return value or the [Error] exception. *)


(**
   {1 Thread-safety internals}

   Unless you are attempting to adapt Batteries Included to a new model of
   concurrency, you probably won't need this.
*)

val lock: BatConcurrent.lock ref
  (**
     A lock used to synchronize internal operations.

     By default, this is {!BatConcurrent.nolock}. However, if you're
     using a version of Batteries compiled in threaded mode, this uses
     {!BatMutex}. If you're attempting to use Batteries with another
     concurrency model, set the lock appropriately.
  *)
