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Date: -- (:)
From: Jacques Carette <carette@m...>
Subject: pa_monad 1.0 - syntax extension for monads
We are pleased to announce the release of the stable version our syntax 
extension for monadic expressions in Ocaml.

All the details can be obtained from 
http://www.cas.mcmaster.ca/~carette/pa_monad/ .

Example: A simple but realistic example of the use of a list monad looks 
like this

        bind
          [1; 2; 3]
          (fun a -> bind
                      [3; 4; 5]
                      (fun b -> return (a + b)))

where we assume the appropriate definitions of the functions "bind" and 
"return". With the help of "pa_monad" this can be written as

        perform
          a <-- [1; 2; 3];
          b <-- [3; 4; 5];
          return (a + b)

which is much clearer and thus easier to understand and maintain. By the 
way, the expression evaluates to [4; 5; 6; 5; 6; 7; 6; 7; 8] the sum of 
each pair of values of the input lists.

Highlights:

- Efficient code: The generated code is as efficient as hand-coded.
- Highly flexible: The "bind" and "failwith" functions can be
  specified in various ways
  (a) Binding with default names:
          perform ...
  (b) Binding with user-defined names:
          perform with my_bind and my_failwith in ...
  (c) One-of-a-kind binding:
          perform with fun a f -> f a and ... in ...
  (d) Module-based binding:
          perform with MyMonad in ...
      or with OCaml's local modules:
          let foo ... =
            let module MyMonad = ... in
            perform with MyMonad in ...

The package for this extension contains more examples as well as some 
self-tests and an extensive README with yet more details (including a 
patch to tuareg-mode).  In the source code (and the generated ocamldoc 
html), one can find amongst other things an informal and formal 
description of the grammar of the extension, and a (rewriting) semantics 
for the extension.

This code is licensed under the GNU library general public license, 
compatible with Ocaml's own license.

All feedback welcome,
Jacques Carette, Lydia E. van Dijk and Oleg Kiselyov