[Grace-core] [Minigrace] In praise of consistency

[Michael Homer]

On Fri, May 18, 2012 at 12:11 PM, Andrew P. Black <black at cs.pdx.edu> wrote:
> I've been playing with James' example
>
>        print "hello".reversed on output.mainStream
>
> This _looks_ ambiguous to me:  I though that it meant
>
>        request method print()on()                                                              (1)
>        from (implicit) receiver self
>        with arg1 = "hello".reversed
>        and agr2 = output.mainStream
>
> So, the rule I proposed in today's meeting — that we require parenthesis whenever there is an ambiguity — would require parens, right?  And that would solve the problem, right.  Unfortunately, no.
>
> The problem is that while it's easy to come up with a parenthesisation for the second interpretation:
>
>        print ( "hello".reversed on output.mainStream ) ,
>
> I can't see a way of adding parenthesis that will make it mean the first.
Surely:
  print("hello".reversed)on(output.mainStream)

The rule that came up when I asked exactly this with multi-part names
last year [1] was that arguments had to be parenthesised. That was
later extended to include delimited/literal arguments. Anything else
is ambiguous - particularly, identifiers and method requests can't be
unparenthesised or you don't know whether the next word of the name
goes, or sometimes even if whether is a mixfix name or not.
-Michael

[1] The thread starts here:
https://mailhost.cecs.pdx.edu/mailman/private/grace-core/2011-May/000261.html