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NAMED-LAMBDA, REC, DEFINE
In the spirit of fanatic minimalism, I would prefer to
remove both NAMED-LAMBDA and REC.
From: Chris Hanson
Re: prefering LETREC in the expansion of (DEFINE (FOO ...) ...)
I claim (and I believe that there will be support for this claim) that
the INTENT of the author of such a self referential procedure was that
the name FOO refer to the procedure itself, not the binding of the
variable FOO. This is because the binding is normally assumed to be
fixed; interactive definitions are something that the language has
because we recognize the need for debugging and evolution of our
I agree (except that I think of redefinition as provided by the
development environment, not the language).
And the more naive the user, the more confusing it will be
if the procedure FOO depends on the value of the variable FOO, rather
than meaning "self reference".
I am not convinced that introducing self references behind the naive user's
back is doing him or her a great service. LETREC-introducing DEFINE
provides what you consider to be the intuitive behavior only in the simple
(DEFINE (FOO N) ...(FOO...)...)
(SET! BAZ FOO)
<subsequent redefinition of FOO>
the value of BAZ will be "consistent" because BAZ is the old version of
FOO, and the old version of FOO will recur by calling the old version.
But, in this case:
(DEFINE (FOO N) ... (BAR N) ...)
(DEFINE (BAR N) ... (FOO N) ...)
(SET! BAZ FOO)
<subsequent redefinition of FOO and BAR>
the value of BAZ will be inconsistent because the old version of FOO will
call the new version of BAR, which will call the new version of FOO.
Of course, a novice can still achieve confusion when defining and
redefining procedures using the simple DEFINE syntax. Furthermore, you
have to explain the difference between variable references that are self
references and those that are not.