🚀 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... *)

No problem -- the program is a syntax error.

In the absence of other delimeters, a `case' eats all the clauses it can,
so in fact this program should have been indented this way:

	fun testcase (x,y) =
	  case x of
	    Alpha _ => ()
	  | Beta _ =>
	      case y of
	        Happy _ => ()
	      | Dopey _ => ()
	      | Grumpy _ => ()
	      | Gamma _ => ();

to correspond to the way it's parsed.  That in turn generates a type error.
-- 
				--Andrew Koenig
				  ark@europa.att.com