[Grace-core] Some comments from Tijs on parsing Grace

[Michael Homer]

On Wed, Jul 27, 2016 at 10:23 PM, James Noble <kjx at ecs.vuw.ac.nz> wrote:
> On 27/07/2016, at 22:14PM, Tijs van der Storm <storm at cwi.nl> wrote:
>> Moreover, I can't define my own brackety things, so the analogy with operators is only partial.
>
> you could once, in Kernan.
>
>> Btw, reminds me, I once had a language design where , (comma) was just an infix binary operator, and bracketing using [] was unary around-fix operator. The comma then would create a shallow line-up like object, the bracket converted it to a list/array; same with {} for sets. (You weren't allowed to use comma expressions in param lists directly, but with parentheses you'd just get the shallow line-up). The only problem is that you couldn't write empty lists or set using the bracket notation.
>
> Ha!  Andrew will probably tell us Smalltalk does that.
> Self did something similar with && which was a sort of "flat cons"
> it lifed two objects into a "collection building" except that two collection buildrers flattened themselves out (aka flat cons). I'd say it was Monadic
> except that Tim & Wadler would yell at me.
>
> I can't remember if Kernan supported empty lists operators: wouldn't surprise me.
It still permits circumfix definitions of mirrored bracket pairs with
arbitrary parameter and argument lists, including empty and variadic,
which is what's used for defining method circumfix[ *x ] { x } in the
prelude.
-Michael