[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Update, near finalization
| Date: Fri, 08 Apr 2005 10:34:54 -0700
| From: Per Bothner <per@xxxxxxxxxxx>
| David Van Horn wrote:
| > The draft of SRFI 63 Homogeneous and Heterogeneous Arrays has been
| > updated to resolve the Issues section (cf previous drafts). This draft
| > will be finalized if there are no concerns raised in the next couple of
| > days.
| > http://srfi.schemers.org/srfi-63/srfi-63.html
| I strongly object. array-set! is inconsistent with srfi-25, and you
| cannot distinguish between the variants by their arguments types.
This works by the implementation knowing the difference between
SRFI-25 arrays and SRFI-63 arrays. This difference can be hidden
entirely from the user.
I claim that SRFI-25 and SRFI-63 can coexist -- not that they
| This is a recipe for disaster.
| (array-set! array k ... obj)
| (array-set! array index obj)
| (array-set! array obj k1 ...)
| It is claimed that "Type dispatch on the first argument to
| array-set! could support both SRFIs simultaneously." I don't
| believe that.
| How would you handle:
| (define array (vector 'a 'b))
| (set! array 1 0)
| Is the result #(a 0) or #(1 b)?
It is not required that vectors not be arrays. It is not required
that they be, either.
For your example to be ambiguous, you would be depending on
unspecified behavior of SRFI-25.
But vectors are mandated to be arrays in SRFI-63. So the result of
your example would be #(1 b).
| make-array is also inconsistent:
| (make-array shape)
| (make-array shape obj)
| (make-array prototype k1 ...)
| It is claimed that: "Type dispatch on the first argument to
| make-array could support both SRFIs simultaneously." I don't
| believe that is correct, as written, since a SRFI-25 shape is a d*2
| array, and a SRFI-67 prototype can also be an array. Thus they can
By vectors being SRFI-63 arrays, not SRFI-25 arrays; and by the
implementation knowing the difference between SRFI-25 arrays and
SRFI-63 arrays, there is no conflict.
| (define v (shape 0 1))
| (make-array v 10)
Shape returns a SRFI-25 array, not a vector. Your example would
return a SRFI-25 array.
| The conflict can be avoided by requiring that prototypes have rank 0
| or 1, which seems a reasonable restriction.
| Much cleaner would be to choose a different name.
Bawden arrays predate SRFI-25 by a decade. SRFI-25 should have chosen