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Re: semantics of DEFINE (why use it at all on the top level?)
In article <890503-103409-9762@Xerox> Pavel.pa@XEROX.COM writes:
>-- A program is a mixed sequence of definitions and expressions.
>-- The meaning of a program P is the same as that of the following expression:
> ((lambda (I*) P') <undefined> ...)
>where I* is the set of variables defined in P (i.e., appearing as the CADR
>of a DEFINE form), P' is the sequence of expressions obtained by replacing
>each definition in P with the corresponding assignment, and <undefined> is
>an expression producing some useless value.
Then why not actually do this?
-- The scheme top-level environment has each variable bound to a unique
location. Many of these locations will be assigned the value #\undefined.
-- The user can assign other values to variable locations using "set!".
A "define" on top level will be an error, since the variable is
already bound on that level.
-- Allow the syntax "(set! (first cell) (car cell))" to mean the analogue
of the comparable "define" syntax
Biep. (email@example.com via mcvax)
Who am I to doubt the existence of God? I am
only a simple man, I already have trouble
enough doubting the existence of my neighbour!