[Grace-core] collections interface for new classes

[James Noble]

>  They are operators.   For type parameters, we should use something like ⟦ and ⟧ or [| and |]  as ASCII equivalents.

people have to be able to copy-type Grace by reading code and looking at their keyboards.
I don’t what to change that principle now. 
We can have [| |] either for type params or literals (or both) if we want to, if we don’t think it’s too ugly.

def suits : Sequence[String] = [ “hearts”, “clubs”, “diamonds”, “spades” ]
def suits : Sequence[|String|] = [ “hearts”, “clubs”, “diamonds”, “spades” ]
def suits : Sequence[String] = [| “hearts”, “clubs”, “diamonds”, “spades” |]

def suits : Sequence<String> = [ “hearts”, “clubs”, “diamonds”, “spades” ]

(note that if  [ ] builds something like a literalSequece<Dynamic> then this won't do what you expect. at all) 
and if neither Kernan nor (a)mg check types on arguments, perhaps this is all moot anyway.


> (We can’t use [[ and ]], because they now mean a sequence containing a sequence …)

sure we can, given that we already have “>” and “>>” as separate operators… 

> Neither I nor Kim use [ ] with the meaning of `.at` when teaching.   The notation a[i] := expr is actually misleading, when compared to a.at (i) put (expr).  The latter is clearly an operation on the object a.  The former makes a[i] look like a variable.   

well that’s the point.  after all, "a:= expr” makes a look like a variable :=)

I noted somewhere in passing that some early Smalltalks allowed the equivalent of   a.at(i) := expr.
I think we can do this in Grace if we want to. 

(the actual Smtalltalk syntax was a ◦ i ← expr  and I had to open my character viewer to enter that!) 

> There will always be matters of taste in spacing.  Do you put spaces in requests like `at (i) put (expr)`?  How many?  Where? Do we want to legislate this, or leave it up to students to develop their own sense of style.  

we can decide what we want to do. 

> Yes, we do require a certain pattern of indentation, although to date we have refrained from insisting that all { indents are 4 spaces,

we did say > 1 space at Pomona…

J