package links

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Links is a functional programming language designed to make web programming easier.


Dune Dependency






Links eases building interactive web applications with significant client- and server-side components.

A typical, modern web program involves many "tiers": part of the program runs in the web browser, part runs on a web server, and part runs in back-end systems such as a relational database. To create such a program, the programmer must master a myriad of languages: the logic is written in a mixture of Java, Python, and Perl; the presentation in HTML; the GUI behavior in Javascript; and the queries are written in SQL or XQuery. There is no easy way to link these, for example, to be sure that an HTML form or an SQL query produces the type of data that the Java code expects. This problem is called the impedance mismatch problem.

Links eases the impedance mismatch problem by providing a single language for all three tiers. The system generates code for each tier; for instance, translating some code into Javascript for the browser, some into a bytecode for the server, and some into SQL for the database.

Links incorporates proven ideas from other programming languages: database-query support from Kleisli, web-interaction proposals from PLT Scheme, and distributed-computing support from Erlang. On top of this, it adds some new web-centric features of its own.

Published: 31 Jan 2017



# Installing Links

Links requires OCaml 4.04.0. We recommend installing Links using the
OPAM tool, available from:

If you wish to use Links' database functionality, you should first
install PostgreSQL, the supported DBMS.

You can then install Links simply by issuing the command:

  $ opam install postgresql links

Alternatively, if you don't have PostgreSQL installed then do:

  $ opam install links

This will put Links and its files into your OPAM switch, typically
located at $HOME/.opam/SWITCH_VERSION, where $HOME is your home
directory and SWITCH_VERSION is the compiler version that you're using
(eg. 4.04.0).  Links files install to several locations inside an OPAM

* The executable is called `linx` and goes into `bin`
* The Links prelude and JavaScript libraries go into `lib/links`
* The example Links programs go into `share/links`
* Links configuration file goes into `etc/links`

# Running Links.

Beginning with the Gorgie (0.6) release, Links supports two methods of running
applications: either via the standalone application server, or via the CGI
interpreter used in previous releases. The executable name is `linx`.

## Application Server

# Examples (without a database)

To run the examples that don't use the database with the Links
application server go into share/links directory inside your OPAM
switch and invoke the following command:

  linx -m --path=examples:examples/games

(This version just displays the source code for examples that use the

The default port is 8080, so you should now be able to access the
examples by pointing your browser at:


# Examples (with a database)

To run the examples using the Links application server go into
share/links directory inside your OPAM switch and invoke the following

  linx -m

* The -m flag enables support for Links' module system, new in Gorgie.
* The --path flag says that files can be found in the following directories:
  - examples
  - examples/games
  - examples/dictionary
* Finally examples/webserver/examples.links is the file to run, which imports
  the example modules and sets up the application server.

But first you need to do a few things.

  1) By default Links uses a config file inside etc/links directory.  Use
     --config=/custom/config/file flag to use a different configuration file.

  2) The default config file should contain paths to JavaScript libraries:


     Where SWITCH_PATH is the actual path on your system. To use
     database examples you need to add a database configuration to the
     config file:


     The database user fred should exist. With postgres, perhaps the
     easiest way to do this is to tie fred to your unix username and
     then no separate authentication is required.

  3) Create appropriate databases. Scripts are included to populate
     tables for some of the examples, but not all of them. We also
     don't have the actual data. We will make sample database dumps
     available for the next point release.

## Documentation

Some (outdated) documentation can be built by running the Makefile in
the doc directory.

Some very incomplete documentation is available on the links wiki:

Dependencies (7)

  1. cohttp < "0.99.0"
  2. base64 < "3.0.0"
  3. cgi
  4. lwt
  5. deriving build
  6. ocamlfind build
  7. ocaml >= "4.04.0" & < "4.06"

Dev Dependencies


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