package batteries

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A community-maintained standard library extension

Install

Dune Dependency

github.com Readme Edit opam file Versions (14)

Authors

O

OCaml batteries-included team

Maintainers

Sources

v3.7.2.tar.gz

md5=1fd7bddce07cf5d244fc9427f7b5e4d4

sha512=c0f2a0fdc8253e0ea999d8d4c58bfbf32b18d251a2e1d9656bf279de5f01a33e9aabac3af4d95f465f8b671e7711ebd37218043face233340a0c11b08fa62f78

doc/batteries.unthreaded/BatReturn/index.html

Module `BatReturn`Source

Local exceptions/labels/goto/return.

This module defines a mechanism akin to SML's exception generators or to a generalization of C's return, i.e. the ability to define local labels, which may be used for immediately terminating an expression and returning a value. By opposition to usual OCaml exceptions, this mechanism

allows polymorphic return values
makes accidental exception catching slightly harder (while a local exception can escape its scope, it cannot be caught again by accident from this module).

Example:

  let find_in_array a e =
    label (fun label ->
      for i = 0 to Array.length a - 1 do
        if Array.get a i = e then return label (Some i)
      done;
      None)

author David Teller

@documents Return

Sourcetype 'a t

A label which may be used to return values of type 'a

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

label f creates a new label x and invokes f x. If, during the execution of f, return x v is invoked, the execution of f x stops immediately and label f returns v. Otherwise, if f x terminates normally and returns y, label f returns y.

Calling return x v from outside scope f is a run-time error and causes termination of the program.

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

as label

Sourceval return : 'a t -> 'a -> _

Return to a label. return l v returns to the point where label l was obtained and produces value l.

Calling return l v from outside the scope of l (i.e. the call to function label which produced l) is a run-time error and causes termination of the program.