marketplace-2014/README.md

# Marketplace: Bringing the Network into the Programming Language

Marketplace is a concurrent language able to express communication,
enforce isolation, and manage resources. Network-inspired extensions
to a functional core represent imperative actions as values, giving
side-effects locality and enabling composition of communicating
processes.

Collaborating programs are grouped within task-specific *virtual
machines* (VMs) to scope their interactions. Conversations between
programs are multi-party (using a publish/subscribe medium), and
programs can easily participate in many such conversations at once.

Marketplace makes *presence* notifications an integral part of
pub/sub. Programs react to presence and absence notifications that
report the comings and goings of their peers. Presence serves to
communicate changes in demand for and supply of services, both within
a VM and across *nested VM layers*. Programs can give up
responsibility for maintaining presence information and for scoping
group communications to their containing VM.

## Documentation

A (draft) manual for Marketplace is available
[here](http://tonyg.github.io/marketplace/).

## The code

This repository contains a [Racket](http://racket-lang.org/) package,
`marketplace`, which includes

 - the implementation of the `#lang marketplace` language, in the
   [top directory](https://github.com/tonyg/marketplace/tree/typeless/).

 - a TCP echo server example, in
   [`examples/echo-paper.rkt`](https://github.com/tonyg/marketplace/tree/typeless/examples/echo-paper.rkt).

 - a TCP chat server example, in
   [`examples/chat-paper.rkt`](https://github.com/tonyg/marketplace/tree/typeless/examples/chat-paper.rkt).

 - Haskell, Erlang and Python implementations of the chat server for comparison, in
   [`examples/chat.hs`](https://github.com/tonyg/marketplace/tree/typeless/examples/chat.hs),
   [`chat.erl`](https://github.com/tonyg/marketplace/tree/typeless/examples/chat.erl),
   and
   [`chat.py`](https://github.com/tonyg/marketplace/tree/typeless/examples/chat.py)
   respectively.

## Compiling and running the code

You will need Racket version 6.1.x or later.

Once you have Racket installed, run

    raco pkg install marketplace

to install the package from the Racket package repository, or

    raco pkg install --link `pwd`

from the root directory of the Git checkout to install the package
from a local snapshot. (Alternatively, `make link` does the same thing.)
This will make `#lang marketplace` available to programs.

At this point, you may load and run any of the example `*.rkt` files
in the
[`examples/`](https://github.com/tonyg/marketplace/tree/typeless/examples/)
directory.

Note that both the echo server and chat server examples do not print
any output on standard output: instead, they simply start running and
silently await TCP connections. Once one of the servers is running, in
a separate window, try `telnet localhost 5999`.

Note also that both the echo server and the chat server use port 5999,
so you cannot run both simultaneously.

## Copyright

Copyright © Tony Garnock-Jones 2010, 2011, 2012, 2013, 2014.