dsandler.org/wp

One more April Fool’s gag that I missed last week: (it’s a double gag,
look out!)

From: Paul Steckler (…@ccs.neu.edu)
Subject: New PLT utility
Newsgroups: comp.lang.scheme, comp.lang.functional
Date: 2004-04-01 10:21:21 PST
Message-ID: <c4hmj0$5io$1@camelot.ccs.neu.edu>

After many years of effort, I’ve finally finished
work on a utility that will soon be available from PLT.

The utility is called “down”, for reasons that will
become clear. It takes as input an arbitrary S-expression,
and returns a boolean, as follows. If the S-expression
input would return a Scheme value in finite time, when supplied
to PLT Scheme’s “eval”, “down” returns #t; otherwise it
returns #f. The time needed for “down” to perform this calculation
is not specified. The name “down” is used, because a downward
arrow is used to denote termination, which is what the utility
detects.

The algorithm was kind of tricky to work out, but dang,
it works!

Look for this utility in the next PLT distribution.
More information about the program will be available
in the manual page, plt/man/man1/plt-down.man.

- Paul