[Grace-core] minor language issues

[James Noble]

Hi Andrew

we did talk about this a bit in the teleconference. We confirmed we’ll permit “()” for null varargs lists,
which addresses the immediate problem. 

> The thing that you refer to as “built in sequence” is not part of the Grace language.

right. but we could put it or something like it back in. 

>  You may be confused because minigrace still accepts it; 
> that’s because the minigrace compiler still uses it, and when I took it out, the compiler slowed down unacceptably.  

there is also the “what *varargs” get bound to “sequence” or whatever. 

> Removing it altogether is still on my list, but not a really high priority.

I wouldn’t have it has a high priority. 

> If we make various kinds of brackets user-definable methods, then we could have uniform syntax and use [ ] for sequences.   But that would mean using more brackets, which you don’t like doing … although there are lots of them.

right, or combinations of operator brackets [+ +] or [- -] or something. 

talking briefly after the telecon, basically the issues are (as we known)
 - ambiguity between < > as “operators" and as generic parameters
       requiring space around binary operators, and delimited arguments resolves this...

 - ambiguity between [ ] (or other brackets) as “indexing” vs as “collection constructors” (matchfix / circumfix operators) 
       IF those brackets can count as delimited then there is a real ambiguity
       we could resolve with spaces (as I think minigrace did)   a[x] -> indexing, a [x] -> pass collection of [x] to a 
        but as Michael (I think) pointed out that’s to subtle a distinction
 
       we could give up on indexing (which many of you have reached already) which resolves this...

 - we’d still have to have some basic varargs functionality anyway, 
    to gather up the contents of the collection constructors / matchfix operators 
    although it could be restricted to just those operators. 
    
  I still fantasize about occasionally simplifying things. 

James