# Module Extlib.Std

    module Std: BatPervasives

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`.

    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.

Since types are lost at compile time, the representation might not match your type. For example, None will be printed 0 since they share the same runtime representation.

`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.

###### List operations

More list operations are provided in module `List`.

    val (@) : 'a list -> 'a list -> 'a list

List concatenation.

###### Input/output

This section only contains the most common input/output operations. More operations may be found in modules `BatIO` and `File`.

    val stdin : BatIO.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 BatIO.output

Standard output, as per Unix/Windows conventions (by default, console).

Use this output to display regular messages.

    val stderr : unit BatIO.output

Standard error output, as per Unix/Windows conventions.

Use this output to display warnings and error messages.

    val stdnull : unit BatIO.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.

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 `BatPervasives.dump`. This function is useful mostly for debugging. As a general rule, it should not be used in production code.

    val print_all : BatIO.input -> unit

Print the contents of an input to the standard output.
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 `BatPervasives.dump`. This function is useful mostly for debugging.

    val prerr_all : BatIO.input -> unit

Print the contents of an input to the error output.
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).
Raises `Sys_error` if the file could not be opened.

    val open_out_bin : string -> unit BatIO.output

Same as `BatPervasives.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 `BatPervasives.open_out` without any `mode` or `perm`.

    val open_out_gen : Pervasives.open_flag list -> int -> string -> unit BatIO.output

Deprecated.Use `open_out instead`
`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.

    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 -> string -> int -> int -> unit

`output oc buf pos len` writes `len` characters from string `buf`, starting at offset `pos`, to the given output channel `oc`.
Raises `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 232. 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 `BatPervasives.input_value`. See the description of module `Marshal` for more information. `BatPervasives.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.
Raises `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.
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).
Raises `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 : Pervasives.open_flag list -> int -> string -> BatIO.input

Deprecated.Use `open_in instead`
`open_in 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.

    val input_char : BatIO.input -> char

Read one character from the given input channel.
Raises `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.
Raises `End_of_file` if the end of the file is reached at the beginning of line.

    val input : BatIO.input -> string -> int -> int -> int

`input ic buf pos len` reads up to `len` characters from the given channel `ic`, storing them in string `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.)
Raises `Invalid_argument` if `pos` and `len` do not designate a valid substring of `buf`.

    val really_input : BatIO.input -> string -> int -> int -> unit

`really_input ic buf pos len` reads `len` characters from channel `ic`, storing them in string `buf`, starting at character number `pos`.
Raises

- `End_of_file` if the end of file is reached before `len` characters have been read.
- `Invalid_argument` if `pos` and `len` do not designate a valid substring of `buf`.

    val input_byte : BatIO.input -> int

Same as `Pervasives.input_char`, but return the 8-bit integer representing the character.
Raises `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`.
Raises `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`.
Raises `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 `BatPervasives.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.
Raises `Sys_error` if the operating system signals an error.

    val close_in_noerr : BatIO.input -> unit

Same as `close_in`, but ignore all errors.

###### Fundamental functions and operators

    val identity : 'a -> 'a

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.

    val (@@) : ('a -> 'b) -> 'a -> 'b

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`.

    val (|>) : 'a -> ('a -> 'b) -> 'b

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 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"`.

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 a 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 -> 'b -> '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.

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 exe : string

The name of the current executable.

`exe` is given by the first argument of `Sys.argv`

###### 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 enumerating the contents of a data structure is to invoke the `enum` function of your data structure.

For instance, you may use the `BatPervasives.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`.

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

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 `BatPervasives.iter`, `BatPervasives.map` or `BatPervasives.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 `BatPervasives.filter` combined with a `BatPervasives.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`.
Raises `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 `BatPervasives.fold` which returns not only the final result of `BatPervasives.fold` but the enumeration of all the intermediate results of `BatPervasives.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 `BatPervasives.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 `BatPervasives.filter_map`.
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

`exists 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.
Raises `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.

###### Results

    type ('a, 'b) result = ('a, 'b) BatInnerPervasives.result =

`|` | `Ok of `'a``
`|` | `Bad of `'b`` | `(*` | The result of a computation - either an `Ok` with the normal result or a `Bad` with some value (often an exception) containing failure information | `*)`

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 `Bad`.

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.

    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 `Bad` 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 `Bad` 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 `Bad` exception.

###### 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 Pervasives.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.