[Caml-list] ANN: "The Whitespace Thing" for OCaml

[Mike Lin‏]

Hi all,

Brace yourselves for "The Whitespace Thing". This is an OCaml
preprocessor that uses your indentation to group expressions, like in
Python and Haskell. Effectively, the preprocessor auto-parenthesizes
expressions that are split over multiple lines, using your indentation
as clues. This eliminates syntax clutter such as multi-line
parenthesizations, the sequencing operators ; and ;; , and the
keywords done, end, and begin.

http://people.csail.mit.edu/mikelin/ocaml+twt/

Mike

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[David Baelde‏]

Nice job!

I'm especially impressed by the removal of the sequence operator, and
how you also use whitespace for multiple-lines applications.
Is it really not ambiguous ?

Thanks.
--
David

[Mike Lin‏]

> I'm especially impressed by the removal of the sequence operator, and
> how you also use whitespace for multiple-lines applications.
> Is it really not ambiguous ?

Yes...the preprocessor uses rules such as: if an indented block
follows a let, if, try, etc., it's a sequence -- if it follows an
indentifier, then it's an application. This is sound, as far as I can
tell. There is a restriction that a multi-line expression has to start
on its own line, which lets me get away without actually building a
full AST for the source. Ideally that's how it would eventually work,
but...80/20.

Mike