Pippo takes a document in any format, and executes any code found between
{%=optok%} and {%=cltok%} in an OCaml top-level session. Anything outside of
these sections is printed on the standard output transparently.
There is only one top-level session per file, meaning that the OCaml sections
are threaded, as if you were entering the commands in a top-level yourself. In
order to be useful, the OCaml code should use print_* statements; the output
of these statements will be interleaved with the non-OCaml sections.
Pippo can be downloaded from github. The project contains a sample Makefile that allows you to pre-process a Markdown file, namely the tutorial that you're reading. Because Pippo uses compiler internal modules, it currently only works with OCaml 4.01.0 (in RC at the time of this writing).
The {%=optok%} and {%=cltok%} markers must be on a single, non-indented, Unix-style line.
For instance, writing:
This is some markdown code.
{%=optok%}
for i = 1 to 10 do
Printf.printf "%d<br>" i
done
{%=cltok%}
In a Markdown document, such as the present one, will result in:
This is some markdown code.
{%
for i = 1 to 10 do
Printf.printf "%d
" i
done
%}
The pippo.ml file contains a special inject_value function. It
allows you to make any value defined in pippo.ml available in the OCaml
sections. Just pass it the name of the value, its type, and the OCaml value
itself. As an example, pippo.ml contains the following code:
inject_value
"__version"
"unit -> unit"
(fun () ->
print_endline "This is pippo v0.1");meaning that if one writes in a document, such as this one:
{%=optok%}
__version ();
{%=cltok%}
then the result is:
{% __version (); %}
You are encouraged to customize pippo.ml and add your own useful functions. Of
course, one can always do:
{%=optok%}
#load "mylib.cma"
{%=cltok%}
but it's more fun playing with the compiler internals.