Hello World for Core
A simple hello-world project for Core. The intent is to show you how to get started building OCaml projects using OPAM, Core and OCamlbuild. To use this, first get OPAM, and install the "core" package. Also, it's probably doing this:
$ opam switch ocaml-4.00.1+short-types
to get better error messages from the compiler when using Core. (As of 4.01, this compiler variant should be obsolete.)
You can build all the pieces of this project by running:
Or you can build any individual executable by running
$ ./build.sh hello_world.native
There are three basic examples
This executable is
here's an example of it in action.
core-hello-world $ ./hello_world.native Hello World! core-hello-world $ ./hello_world.native -help Hello World hello_world.native === flags === [-hello] The 'hello' of 'hello world' [-world] The 'world' of 'hello world' [-build-info] print info about this build and exit [-version] print the version of this build and exit [-help] print this help text and exit (alias: -?) core-hello-world $ ./hello_world.native -hello "Goodbye" -world "Yellow Brick Road" Goodbye Yellow Brick Road!
Hello World client/server
The next example is a pair of programs:
hello_client.native. The server will accept requests via the
Async.Rpc library, and the client dispatches them. The RPC is
trivial: the client sends a string, and the server attaches " World!"
to the end of it and sends the result back.
This is the most complicated example.
broker_server.native is a
simple message broker that allows you to publish and subscribe to
streams of data.
broker_client.native is a client that lets you do
a few operations, including publishing, subscribing, getting a dump of
the current state of the server, and shutting the server down.
Guide to the files
These are listed in rough dependency order.
hello_world.ml: Command-line tool that prints "Hello World!"
common.ml: Some common utilities for setting up Async-RPC clients and servers
hello_protocol.ml: Async-RPC protocol for communicating between the hello client and server.
hello_server.ml: Async-RPC server for answering "hello" query
hello_client.ml: Async-RPC client fro sending "hello" query
directory.ml: Core datastructur of the Async message broker
broker_protocol.ml: Async-RPC protocol for communicating between the broker client and server.
broker_server.ml: Async-RPC server that handles message broker requests. Backed by the Directory.
broker_client.ml: Async-RPC client that can publish, subscribe, get a dump of the state of the broker, and shut the broker down.
Plus, the build scripts:
_tags: which sets up the build options for
build.sh: For building any target, invoking
build_all.sh: builds all the executable targets. Calls out to
Setting up the toplevel
There's also a file called dot_ocamlinit, which will auto-load Core for you in the toplevel, if you do this:
$ cp dot_ocamlinit ~/.ocamlinit
If you want to use the toplevel, you might want to try installing rlwrap to give you command-line editing, at which point you can run:
$ rlwrap ocaml
and start using Core in the OCaml toplevel.