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Re: Psi Calculus
Sorry it's taken me so long to respond. I've been
trying to read up on mathematics of arrays (mostly
unsuccessfully) so that I might have more intelligent
things to say. In addition to SAC, the FISh langauge
is worth a look.
and I need to take a better look at APL derivatives.
--- Jussi Piitulainen <jpiitula@xxxxxxxxxxxxxxxx>
> It doesn't provide sharing as a primitive
> notion. I suppose it
> relies on a compiler to avoid a lot of unnecessary
I believe so.
> I think,
> 1) modarray single element case in Scheme would _be_
> array-set!, not
> make it redundant;
Not quite. modarray is functional in SAC. It returns
a new array.
> 2) reshape is partly provided by share-array and
> partly not provided
> in current srfi-25; the row major stuff mentioned
> in Issues would
> provide the latter part;
I think there needs to be something to get all the
data from the array. Maybe
(flatten array) -> vector
Gets the data part of an array in row-major order.
> 4) there is no way around Scheme being an imperative
> language with
> runtime typing; static compiler optimisations are
> not in reach, nor
> is anything restricted to single assignment.
Hmmm...I don't want to start a bun-fight here.
Optimisation is more difficult in Scheme because the
language hasn't been designed to make certain
properties obvious, but it is not impossible. See,
A few more issues:
I think the basic procedures should all work on
vectors as arguments. E.g. instead of
(array-ref array x1 x2 ...)
I'd vouch for
(array-ref array index-vector)
Why? To preserve symmetry. With functions returning
lists there is the nice symmetry that those results
can be immediately applied as the arguments to another
function. No such symmetry exists with array-ref as
it currently stands. You can't, e.g., get an array
slice representing an index and then apply that to
I also think there is a need for a simple array slice
primitive (equivalent to the psi function in SAC).
The provided function, though expressive, is complex
and makes writing simple array slices unduly
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