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I don't know if this is the right forum to raise this issue. But, I wonder
why make-environment works the way it does. If I define
(define (complex x y)
(define re x)
(define im y)))
(define a (complex 1 2))
not only does a have re and im bound in it, but it also has x and y
bound in it. So,
(access x a)
yields 1. From the description of make-environment in Abelson and Sussman,
it appears that only re and im should be bound in a. Is this a bug, or a
feature, or am I missing something? If this is the way make-environment
is supposed to work, is there some other primitive that binds re and im
and forgets about x and y?
You have misunderstood section 4.3.1 of S&ICP. If you read it
carefully, you will notice
"For use in conjunction with EVAL, Scheme provides an operation called
MAKE-ENVIRONMENT that constructs an environment, evaluates a
designated sequence of expressions within this environment, and
returns the environment as the value of the MAKE-ENVIRONMENT
expression. The enclosing environment of the new environment is the
environment in which the MAKE-ENVIRONMENT expression was evaluated."
The last sentence in the above quote makes it quite clear that this
environment is built on top of the one in which the MAKE-ENVIRONMENT
expression was evaluated, and therefore all these names are visible to
You ask about ACCESS, which is not in S&ICP, so I assume you are
talking about MIT Scheme instead of the restricted subset used in
There are two possibilities for ACCESS:
Make it compatible with EVAL, and therefore make all the names (like X
and Y in your example) visible. This is the current implementation.
Make ACCESS look only at the "topmost" frame of the environment. This
means that all the names that can be exported from a package must be
defined in that package itself, and there is no "export" inheritance
between packages built on top of packages.
We tried the latter approach for a while and it was a total mess. We
quickly changed it to its alternative.