Re: Comments Wolfgang Corcoran-Mathe 04 Sep 2020 20:10 UTC

On 2020-09-04 15:36 -0400, Wolfgang Corcoran-Mathe wrote:
> The sentence "if the canvas does not exist, it
> is created" seems a little vague in its current position.  Does this apply
> to canvas-cleanup, i.e. does it create a canvas to delete?
> I think it's sufficient merely to add a note to rogers about canvas
> creation.  You've already done this for draw-line and draw-bezier.

I realize after re-reading that I interpreted part of the `rogers'
spec as a general requirement.  Apologies.  The rest of the above
can be ignored.

An additional comment:

I'm not exactly sure what this paragraph means:

> v-list may be one of the possible implementations of a frame, in the
> SICP terminology.  However, in order to avoid nudging the potential
> users of the library into a particular implementation of frames, we
> opted to specify one of the possible underlying data structures
> directly.  Converting between this representation, as well as any
> other representation, should be a relatively simple exercise.

From what comes before, I gather that a v-list is a list of three or
more length-two numeric lists.  Maybe such a simple structure and its
operations should just be described at the head of the specification.
(Accessors would also be helpful, to eliminate the need for the
hand-rolled cadr and caddr in the `rogers' spec.)

Wolfgang Corcoran-Mathe  <>

"It is better to forget time altogether.  Time plays no role at the
fundamental level of physics." --Carlo Rovelli