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Update README for Eio 1.0
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- Remove the Status section.
- Mention `Eio_js`.
- Simplify the hello-world example.
- Mention `Eio_unix.sleep` in the time section.
- Mention non-determinism only applies to the main Eio API.
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talex5 committed Mar 13, 2024
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33 changes: 17 additions & 16 deletions README.md
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Expand Up @@ -15,8 +15,7 @@ Eio replaces existing concurrency libraries such as Lwt
<!-- vim-markdown-toc GFM -->

* [Motivation](#motivation)
* [Current Status](#current-status)
* [Structure of the Code](#structure-of-the-code)
* [Eio packages](#eio-packages)
* [Getting OCaml 5.1](#getting-ocaml-51)
* [Getting Eio](#getting-eio)
* [Running Eio](#running-eio)
Expand Down Expand Up @@ -80,22 +79,18 @@ Additionally, modern operating systems provide high-performance alternatives to
For example, Linux's io_uring system has applications write the operations they want to perform to a ring buffer,
which Linux handles asynchronously, and Eio can take advantage of this.

## Current Status

See [Eio 1.0 progress tracking](https://github.com/ocaml-multicore/eio/issues/388) for the current status.
Please try porting your programs to use Eio and submit PRs or open issues when you find problems.
Remember that you can always [fall back to using Lwt libraries](#lwt) to provide missing features if necessary.

See [Awesome Multicore OCaml][] for links to work migrating other projects to Eio.

## Structure of the Code
## Eio packages

- [Eio][] provides concurrency primitives (promises, etc.) and a high-level, cross-platform OS API.
- [Eio_posix][] provides a cross-platform backend for these APIs for POSIX-type systems.
- [Eio_linux][] provides a Linux io-uring backend for these APIs,
plus a low-level API that can be used directly (in non-portable code).
- [Eio_linux][] provides a Linux io_uring backend for these APIs.
- [Eio_windows][] is for use on Windows (incomplete - [help wanted](https://github.com/ocaml-multicore/eio/issues/125)).
- [Eio_main][] selects an appropriate backend (e.g. `eio_linux` or `eio_posix`), depending on your platform.
- [Eio_js][] allows Eio code to run in the browser, using `js_of_ocaml`.

## Getting OCaml 5.1

Expand Down Expand Up @@ -138,15 +133,15 @@ prompt and return after each line.)
This function writes a greeting to `stdout` using [Eio.Flow][]:

```ocaml
let main ~stdout =
Eio.Flow.copy_string "Hello, world!\n" stdout
let main out =
Eio.Flow.copy_string "Hello, world!\n" out
```

We use [Eio_main.run][] to run the event loop and call `main` from there:

```ocaml
# Eio_main.run @@ fun env ->
main ~stdout:(Eio.Stdenv.stdout env);;
main (Eio.Stdenv.stdout env);;
Hello, world!
- : unit = ()
```
Expand All @@ -156,7 +151,7 @@ Note that:
- The `env` argument represents the standard environment of a Unix process, allowing it to interact with the outside world.
A program will typically start by extracting from `env` whatever things the program will need and then calling `main` with them.

- The type of the `main` function here tells us that this program only interacts via `stdout`.
- The type of the `main` function here tells us that this program only interacts via the `out` flow.

- `Eio_main.run` automatically calls the appropriate run function for your platform.
For example, on Linux this will call `Eio_linux.run`. For non-portable code you can use the platform-specific library directly.
Expand All @@ -171,7 +166,7 @@ For example, instead of giving `main` the real standard output, we can have it w
```ocaml
# Eio_main.run @@ fun _env ->
let buffer = Buffer.create 20 in
main ~stdout:(Eio.Flow.buffer_sink buffer);
main (Eio.Flow.buffer_sink buffer);
traceln "Main would print %S" (Buffer.contents buffer);;
+Main would print "Hello, world!\n"
- : unit = ()
Expand All @@ -185,8 +180,7 @@ The [Eio_mock][] library provides some convenient pre-built mocks:
```ocaml
# #require "eio.mock";;
# Eio_main.run @@ fun _env ->
let mock_stdout = Eio_mock.Flow.make "mock-stdout" in
main ~stdout:mock_stdout;;
main (Eio_mock.Flow.make "mock-stdout");;
+mock-stdout: wrote "Hello, world!\n"
- : unit = ()
```
Expand Down Expand Up @@ -934,6 +928,9 @@ The mock backend provides a mock clock that advances automatically where there i
- : unit = ()
```

Note: You could also just use `Eio_unix.sleep 5.0` if you don't want to pass a clock around.
This is especially useful if you need to insert a delay for some quick debugging.

## Multicore Support

OCaml allows a program to create multiple *domains* in which to run code, allowing multiple CPUs to be used at once.
Expand Down Expand Up @@ -1593,6 +1590,9 @@ In particular, if you test your code by providing (deterministic) mocks then the
An easy way to write tests is by having the mocks call `traceln` and then comparing the trace output with the expected output.
See Eio's own tests for examples, e.g., [tests/switch.md](tests/switch.md).

Note: this only applies to the high-level APIs in the `Eio` module.
Programs can behave non-deterministically when using `Eio_unix` or the various `Low_level` APIs provided by the backends.

## Provider Interfaces

Eio applications use resources by calling functions (such as `Eio.Flow.write`).
Expand Down Expand Up @@ -1912,3 +1912,4 @@ Some background about the effects system can be found in:
[Olly]: https://github.com/tarides/runtime_events_tools
[eio-trace]: https://github.com/ocaml-multicore/eio-trace
[cap_enter]: https://man.freebsd.org/cgi/man.cgi?query=cap_enter
[eio_js]: https://github.com/ocaml-multicore/eio_js

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