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https://github.com/eatonphil/mod_ocaml

Apache module to allow embedded OCAML.
https://github.com/eatonphil/mod_ocaml

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Apache module to allow embedded OCAML.

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README 

        
WHAT IS OCAML?

==============



OCAML [1] is derived from the CAML language. We include the description

from its home at INRIA here:



Caml is a programming language, easy to learn, easy to use, and yet

amazingly powerful. 



It is developed and distributed by INRIA (the main French research institute

for computer science), since 1984. It is freely available for Unix, PC or

Macintosh.



Objective Caml (OCAML) is a general purpose programming language that combines

functional, imperative, and object-oriented programming. The language is

statically typed; its type system ensures the correct evaluation of

programs. Types are automatically inferred. The language offers powerful

constructions such as user-definable data-types, the ability to define

functions by pattern-matching, and an exception mechanism. Programming in

the large is facilitated by a full-fledge class-based object-oriented layer

and an expressive module system. 



NOW, WHAT IS MOD_OCAML?

=======================



Generally, mod_ocaml is a flexible module for use with the famous Apache

Web Server[2]. Probably you know how to benefit of other modules with

unbelievable capabilities, like PHP (mod_php4) or Perl (mod_perl).



One of the advantages of the Apache Server is the possibility to extend its

features by adding modules to your configuration. At this point, mod_ocaml

comes up.



mod_ocaml is designed to work with the 1.3 family of Apache's all over the

world.



HOW DOES IT WORK?

=================



Thanks to a appropriate "AddHandler" directive in your httpd.conf, all

OCAML-Pages (usually with the file extension .ocml) will be handed to mod_ocaml

for further processing.



mod_ocaml requires the OCAML interpreter to be installed on your system. You

get it on OCAML's virtual home[1].

Every time a page is rendered by the mod_ocaml parser, the interpreter is

called to evaluate the OCAML commands generated by mod_ocaml.



Much like PHP, mod_ocaml gives you the facility to mix up HTML and OCAML

code on your pages. mod_ocaml features a sort of preprocessor (parser) which

extracts the parts of your page and converts them into OCAML commands. For

example, the HTML parts of your page are built into printf()-commands that

are understandable for the OCAML interpreter.



Oh, and we wondered how to make code defined in a fictive OCAML statement #1

available in the OCAML statements #2 ... #n, too: More than one call to the

interpreter would destroy this, because the single OCAML parts of the page

would not know about each other. Then we had the idea to just convert the

separating HTML blocks into OCAML and calling the interpreter only once. In

consequence, you can define some functions, variables, etc. on top of your

page and use them on bottom without further work.



"Problematic" characters like " are escaped automatically, and the OCAML

interpreter doesn't complain about them. Don't worry about this, mod_ocaml

will do it for you.



PRACTICAL USE

=============



You simply write poor old HTML code and save it under your webserver root.

Choose the extension you entered at the "AddHandler" directive in

httpd.conf (per default, this is .ocml). So you save a file named, e. g.

test.ocml.



Until now, you didn't use any of the mod_ocaml benefits. Try to include OCAML

code, and it will be displayed "as is". Since you want your OCAML code to be

interpreted and evaluated, you have to inform mod_ocaml of this:



As you can see, the init tag for your OCAML parts is "". As said before: It is much like PHP, but it's OCAML with all

its advantages and possibilities of functional and imperative programming.

Everything that is located on the outside of these OCAML blocks will be

displayed "as is". 



This solution makes it also possible to include HTML code within a loop

statement like "while" or "for", e. g. when outputting big HTML tables with

many cells and columns. But don't forget about the functional focus of OCAML

when using things like that ;-)



INTEROPERABILITY

================



Sure. You want to process GET requests within your mod_ocaml pages. You call

your pages like http://www.some.where/mypage.ocml?a=foo&b=bar. After that,

you have two variables a and b which are fully available to your OCAML code.

Just include them with $a and $b, like this:



	Printf.printf ("$n");;



Please note: YOU (as web developer, programmer, ...) are responsible for

proper implementing these external vars, e. g. including in quotation for

strings, etc. Also take care of input checking if you're expecting lists

and other cool data types from the "outside" ;-)



We didn't want to check this external input. Not because we were too lazy,

but you shall have all the possibilities to do with mod_ocaml what YOU want.

Additionally, OCAML is a typed language and you just have to pay attention

to what you are doing. When we set up the concept of mod_ocaml, we didn't

want to destroy this intention.



JUST MORE

=========



You are currently reading the README file of mod_ocaml. But mod_ocaml is

more than a website-scripting-wrapper to the OCAML interpreter: You can use

almost every interpreter with it.



AUTHORS

=======



We both are students of computer science at the Technical University of Munich,

Germany[3]. In October 2002, we heard of OCAML for the first time. Our

prof, Prof. Dr. Alois Knoll[4] tries quite hard to make us familiar with

functional programming, and he really loves OCAML and its powerful features.



You can reach us best via e-mail:



	Andreas Brandmaier

	 or 



	Leonhard Fellermayr

	 or 



BUGS

====



... are always and everywhere. So please provide us with your bug reports.

We tried hard to avoid bugs and we will try even harder to remove what is

left of them.



LICENSE

=======



mod_ocaml is released under the terms of the GNU Public License, which is

included with this package. We hope mod_ocaml is useful for you. Enjoy!



REFERENCES

==========

[1] http://caml.inria.fr/

[2] http://httpd.apache.org/

[3] http://www.in.tum.de/

[4] http://wwwknoll.informatik.tu-muenchen.de/~knoll/