Re: painter implementation for picture language in SICP

[Taylor R Campbell]

> Date: Wed, 25 Dec 2019 13:15:57 -0500
> From: David Liu <address@hidden>
> 
> The book's website [1] gives the "primitive painter" support files for the
> picture language, and one of the files is prmpnt.scm. One problematic line
> in that file is this:
> 
> (define floating-vector-ref
>     (access floating-vector-ref
>         (->environment '(student pictures))))
> 
> The "student pictures" part probably indicates an environment that a
> special 6.001 version of MIT-scheme provided. I left MIT less than a year
> ago, so I'm still able to ssh into my Athena account; I did `add 6.001`,
> and looked in the Athena locker at `/mit/6.001`, and was not able to find
> any true definitions of the floating-vector-ref function.

The definition of floating-vector-ref in the (student pictures)
package, in src/6001/picture.scm in the source code, appears to have
been removed back in 2001 in CVS revision 1.30 of picture.scm (now git
commit 5ab526814d6757638fbdaf0d98fa82e2539588d4).  The name for the
procedure is now flo:vector-ref; similarly for flo:vector-set!.

We haven't carefully maintained the src/6001 code base, and it is in
desperate need of automatic tests particularly since there aren't many
manual testers of it these days, but feel free to ask if anything else
comes up with it.