David A. Wheeler scripsit:

> I have several concerns about cycle-detection in R7RS, which I think
> is otherwise shaping up pretty nicely.  Trying to deal with equal? led
> me to realize some weirdnesses with equal?, write, and display.  I'll
> see what I can do quickly.

Just to update you on what will appear in draft 7, based on the sixth
ballot:

Write is being split into three procedures:

    write, which detects loops and prints datum labels (#n=, #n#) for
    them.

    write-simple, which does not detect loops (same as R5RS write).

    write-shared, which detects both loops and shared structure, printing
    datum labels for both.

Display will be the same as write.

> Fair enough.  But will *Scheme* ignore it properly when it IS the
> first character of a file? Guile, clisp, and many other Lisps will
> ignore #!...!# so that you can create Scripts in Scheme / Common Lisp
> / whatever.  That is really useful functionality, and one that I hate
> to interfere with.

I don't see that you're interfering with it.  What happens with shebang
lines is implementation-dependent.  If you are writing portable code,
you need to avoid them.  In any case, we already have #!fold-case and
#!no-fold-case in both R6RS and R7RS, as well as #!r6rs in R6RS (there
is no R7RS analogue).

> #!srfi-105
> #!c-expr
> ...something else...

C-expr could mean anything.  SRFI 105 is a unique name and tells you
where to look.

--
John Cowan  xxxxxx@ccil.org  http://www.ccil.org/~cowan
Thor Heyerdahl recounts his attempt to prove Rudyard Kipling's theory
that the mongoose first came to India on a raft from Polynesia.
        --blurb for Rikki-Kon-Tiki-Tavi