🚀 go-pugleaf

In article <91849@netnews.upenn.edu>, freeman@linc.cis.upenn.edu (Jon Freeman) writes:

|> 
|> I never even thought that writing a pretty-printer for SML was a
|> feasible undertaking.  Consider the following program:
|> 
|> --------------------------------------------------------------
|> datatype foo = Alpha of int | Beta of real | Gamma of string;
|> datatype bar = Happy of int | Dopey of real | Grumpy of string;
|> 
|> fun testcase (x,y) =
|>   case x of
|>     Alpha _ => ()
|>   | Beta _ =>
|>       case y of
|>         Happy _ => ()
|>       | Dopey _ => ()
|>       | Grumpy _ => ()
|>   | Gamma _ => ();       (* Hmmm... *)
|> --------------------------------------------------------------
|> 
|> Any pretty-printer that can correctly indent the last line of testcase
|> has to be able to discriminate between the constructors of foo and the
|> constructors of bar!!  Does your pretty-printer really do this?  If
|> so, I'm very impressed.

That would be clever, but doesn't the definition say that matches extend as far
to the right as possible? In this example, the last line would be parsed as part
of the inner case expression, and the program contains a type error.

--brian

-- 
Internet: brian@comp.vuw.ac.nz
Postal: Brian Boutel, Computer Science Dept, Victoria University of Wellington,
        PO Box 600, Wellington, New Zealand
Phone: +64 4 471-5328   Fax: +64 4 495-5232