Ted Nelson Comments...

From ted@xanadu.net  Wed Dec  2 11:50:17 1998
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Date: Thu, 03 Dec 1998 01:26:55 +0900
To: "Eric S. Raymond" 
From: Ted Nelson 
Subject: COME FROM statement considered asymmetrical  (CFasym.d6
Cc: ted@sfc.keio.ac.jp, marlene@xanadu.net, erik@xanadu.net, xanni@xanadu.net,
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Hi Eric--

I consider it marvelous that you have enhanced the world's
 most obscure computer language, Intercal, by adding
 Peter Ingerman's COME FROM statement.

However, I should point out that COME FROM is not
 a precise inverse of the GO TO statement.  True,
 they are similar when each is one-to-one,
 i.e. when each GOTO target/sink is pointed to by
 only one GO TO, and each COME FROM receiver
 is the unique recipient of its antecedent donor routine. 

But the many-to-one case is asymmetrical: a number of
 different GOTOs can have the same target, but a
 COME FROM statement can only have a unique source.
 And conversely: in the case of the GO TO, it is the antecedent
 routine which can have only one target but can share it
 with others; while in the case of the COME FROM,
 it is the successor routines which can only share a single source.  

This *could* be considered to be a deeper symmetry:
 the possible many-to-one relation of the GO TO could be seen
 as remapping into the possible one-to-many use of the COME FROM.

But the asymmetry is stronger than that, being temporal
 (and in some sense causative-- but this discussion must
 skirt theology, and we know that A Programmer exists)--:
 GO TO may only be temporally one-to-one or many-to-one,
 while COME FROM may only be temporally one-to-one
 or one-to-many.  If we took sexual behavior as an analogy,
 the possible many-to-one relation of the GO TO is like being
 gang-banged, with a relatively small variety of possible outcomes
 (progeny), while the COME FROM is more like a bee going
 from... oh, never mind.

I hope this brings some measure of analytic rigor to a hitherto,
 and justifiably, unknown problem area, where such rigor may
 hitherto have been, and still may perhaps be, unwelcome.

Best regards, Ted
Gee, maybe I should submit this to Communications of the ACM...


____________________________________________________
Theodor Holm Nelson, Visiting Professor of Environmental Information
 Keio University, Shonan Fujisawa Campus, Fujisawa, Japan
 Home Fax from USA: 011-81-466-46-7368  (If in Japan, 0466-46-7368)
http://www.sfc.keio.ac.jp/~ted/  (Professorial page)
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Quotation of the day, 98.12.02:
Mike McNally, president of the Air Traffic Controllers Union, yesterday
assured the press that air traffic controllers can take over from computers
in case Y2K bugs hit the system.  
     "I'm not trying to indicate that when our computers shut down that
everything is hunky-dory.  There is a major transition period where the
heart is beating and things are happening fast, and people are yelling and
screaming to try to get a handle on it," he said.  (cnn.com, dateline
98.12.01)