containers

A modular, clean and powerful extension of the OCaml standard library
IN THIS PACKAGE
Module CCFun

Combinators

val id : 'a -> 'a

id is the identity function. For any argument x, id x is x.

val const : 'a -> _ -> 'a

const c is a function that always returns the value c. For any argument x, (const c) x is c.

val flip : ( 'a -> 'b -> 'c ) -> 'b -> 'a -> 'c

flip f reverses the argument order of the binary function f. For any arguments x and y, (flip f) x y is f y x.

val negate : ( 'a -> bool ) -> 'a -> bool

negate p is the negation of the predicate function p. For any argument x, (negate p) x is not (p x).

Exception handling

val protect : finally:( unit -> unit ) -> ( unit -> 'a ) -> 'a

protect ~finally work invokes work () and then finally () before work () returns with its value or an exception. In the latter case the exception is re-raised after finally (). If finally () raises an exception, then the exception Finally_raised is raised instead.

protect can be used to enforce local invariants whether work () returns normally or raises an exception. However, it does not protect against unexpected exceptions raised inside finally () such as Stdlib.Out_of_memory, Stdlib.Stack_overflow, or asynchronous exceptions raised by signal handlers (e.g. Sys.Break).

Note: It is a programming error if other kinds of exceptions are raised by finally, as any exception raised in work () will be lost in the event of a Finally_raised exception. Therefore, one should make sure to handle those inside the finally.

exception Finally_raised of exn

Finally_raised exn is raised by protect ~finally work when finally raises an exception exn. This exception denotes either an unexpected exception or a programming error. As a general rule, one should not catch a Finally_raised exception except as part of a catch-all handler.

val compose : ( 'a -> 'b ) -> ( 'b -> 'c ) -> 'a -> 'c

compose f g x is g (f x). Composition.

val compose_binop : ( 'a -> 'b ) -> ( 'b -> 'b -> 'c ) -> 'a -> 'a -> 'c

compose_binop f g is fun x y -> g (f x) (f y). Example (partial order): List.sort (compose_binop fst CCInt.compare) [1, true; 2, false; 1, false].

  • since 0.6
val curry : ( ('a * 'b) -> 'c ) -> 'a -> 'b -> 'c

curry f x y is f (x,y). Convert a function which accepts a pair of arguments into a function which accepts two arguments.

val uncurry : ( 'a -> 'b -> 'c ) -> ('a * 'b) -> 'c

uncurry f (x,y) is f x y. Convert a function which accepts a two arguments into a function which accepts a pair of arguments.

val tap : ( 'a -> _ ) -> 'a -> 'a

tap f x evaluates f x, discards it, then returns x. Useful in a pipeline, for instance:

CCArray.(1 -- 10)
|> tap CCArray.shuffle
|> tap @@ CCArray.sort Stdlib.compare
val lexicographic : ( 'a -> 'a -> int ) -> ( 'a -> 'a -> int ) -> 'a -> 'a -> int

Lexicographic combination of comparison functions.

val finally : h:( unit -> _ ) -> f:( unit -> 'a ) -> 'a

finally ~h f calls f () and returns its result. If it raises, the same exception is raised; in any case, h () is called after f () terminates. If h () raises an exception, then this exception will be passed on and any exception that may have been raised by f () is lost.

val finally1 : h:( unit -> _ ) -> ( 'a -> 'b ) -> 'a -> 'b

finally1 ~h f x is the same as f x, but after the computation, h () is called whether f x rose an exception or not. If h () raises an exception, then this exception will be passed on and any exception that may have been raised by f () is lost.

  • since 0.16
val finally2 : h:( unit -> _ ) -> ( 'a -> 'b -> 'c ) -> 'a -> 'b -> 'c

finally2 ~h f x y is the same as f x y, but after the computation, h () is called whether f x y rose an exception or not. If h () raises an exception, then this exception will be passed on and any exception that may have been raised by f () is lost.

  • since 0.16
val opaque_identity : 'a -> 'a

opaque_identity x is like x, but prevents Flambda from using x's definition for optimizing it. (flambda is an optimization/inlining pass in OCaml >= 4.03).

  • since 0.18
val iterate : int -> ( 'a -> 'a ) -> 'a -> 'a

iterate n f is f iterated n times. That is to say, iterate 0 f x is x, iterate 1 f x is f x, iterate 2 f x is f (f x), etc.

  • since 2.1

Infix

Infix operators.

module Infix : sig ... end
include module type of Infix
val (|>) : 'a -> ( 'a -> 'b ) -> 'b

x |> f is the same as f x. A 'pipe' operator.

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

f @@ x is the same as f x, but right-associative.

  • since 0.5
val (%>) : ( 'a -> 'b ) -> ( 'b -> 'c ) -> 'a -> 'c

(f %> g) x or (%>) f g x is g (f x). Alias to compose.

val (%) : ( 'b -> 'c ) -> ( 'a -> 'b ) -> 'a -> 'c

(f % g) x or (%) f g x is f (g x). Mathematical composition.

Monad

Functions with a fixed domain are monads in their codomain.

module Monad (X : sig ... end) : sig ... end