Re: [stack] Combining Combinators

On 6/28/07, Manfred Von Thun <[email protected]> wrote:
> On 20/6/07 6:47 PM, "Christopher Diggins" <[email protected]> wrote:
> > On 6/19/07, Manfred Von Thun <[email protected]> wrote:
> >> On 19/6/07 1:05 AM, "William Tanksley, Jr" <[email protected]> wrote:
> >>> Manfred Von Thun <[email protected]> wrote:
>
> [..]
>
> >> At level one there are functions which take zero level entities
> >> as arguments.
> >
> > In Cat this would be the set of functions with types matching: ('A 'b -> 'C)
>
> But also binary operators such as +, <, cons and so on, also ternary
> operators such as + +, ..., also operators returning several items:
> + + dup, which consumes three and yields two.

I see. That is indeed not a category that can be represented using a
single Cat type then.

> I don¹t know the
> upper/lower case conventions of your type notation to say whether
> these cases are already included in (A b -> C).

Lowercase letters are types, and uppercase letters are type vectors
(or the type of a stack of values if you prefer).

[snip]

Thanks for the clarification.

> > If you are concerned about eliminating any possibility of level-3
> > combinators in Joy, can't you rewrite the definitions of the level-2
> > primitives so that they accept combinators or non-combinators? I don't
> > see the reason that "dip" can't accept straight values like "5" on the
> > top of the stack, if "i" can accept them.
>
> Correction: Joy does not allow any of the following:
>
> 5 i
> 5 dip
> 5 map
> 2 3 + i
> 2 3 + dip
> ...
> [..]
>
> > I believe it is either good to go all the way one direction or the
> > other: either non-combinator values can be "evaluated" or they can't.
> > As far as I can see (and I could be mistaken) Joy is somewhat
> > ambiguous about what exactly can and can't be evaluated.
>
> can or can¹t ‹ where is the ambiguity in Joy?

My mistake, I thought "5 i" was defined in Joy.
Sorry about the confusion.

Christopher


 
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