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From: jonl%kuwait@lucid.COM (Jon L White)
Newsgroups: comp.lang.scheme
Subject: Destructuring / pattern-matching (was: Multiple return values)
Message-ID: <9104130136.AA06792@kuwait>
Date: 13 Apr 91 01:36:05 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 31

In isssue Scheme Digest V3 #184, Jeff Dalton recounts the ways that 
LET, DESTRUCTURING-BIND, and MULTIPLE-VALUE-BIND could be unified
by a single user-defined macro:

    Nonetheless, I think the best way to proceed would be for people to
    write macros that they find useful, let others use them, and see what
    solutions evolve. 

I know this sort of topic has already been flamed-out on this list, but 
the irresitable force of macro power does come up against the immovable 
object of a community of programmers.  That is to say, as long as I was 
working only by myself, or with a VERY small set of hackers, Jeff's 
suggestion for extra macrofication works fine.  But somehere around 
the 20-person "industrial quality" project you find that the number 
of idiosyncratic, personalized syntax macros is too large for anyone 
to comprehend.  It just takes one conservative member of the team to 
demand that no macros be used for trivial extensions; and this rules 
out the one-liner JONL-BIND in favor of the three-lines involving LET, 
DESTRUCTURING-BIND, and MULTIPLE-VALUE-BIND.

The above paragraph is based on hard experience (my own) with a group
considerably smaller than 20.

Of course, it is easier to bear if all 20 persons believe that the
macro in question is about to be "a standard" in the language.  (This
may explain why there are so many constructs being suggested for
standardization; but let us drink no standards before their time.)



-- JonL --