[r6rs-discuss] Hashes in the number syntax

From: William D Clinger <will>
Date: Sun Nov 19 14:51:31 2006

I am posting this as an individual member of the Scheme
community. I am not speaking for the R6RS editors.

Jens Axel Soegaard wrote:
> My understanding is that # to some degree means
> "digit unknown". That is, an implementation
> is free to parse 1## as any inexact number
> between 100 and 199.

The # indicates an inexact number. Although most systems
happen to treat the # as a 0, the 1## notation is more
specific than 100. because the latter doesn't tell you
that the two zero digits are insignificant.

> Is this syntax used by anyone?

I don't know. IIRC, Sussman suggested this syntax, so
it might be used more at MIT than elsewhere.

> I'd prefer the syntax is removed, since the syntax can
> not be used in portable programs.

I don't understand that comment. All R5RS-conforming
implementations accept the syntax. They may parse the
syntax as different values, but the same is true of all
notations for inexact numbers.

Will
Received on Sun Nov 19 2006 - 14:51:23 UTC