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Re: Internal definitions as a combination of LETREC's and LET*'s.
In article <41415@linus.UUCP> ramsdell@linus.UUCP (John D. Ramsdell) writes:
>Yet at top level, it is okay to define values in terms of other
>definitions. An obvious way of making internal definitions behave
>more like top level definitions, is to specify the order in which the
>init bodies are evaluated. I call this interpretation internal
>definitions as a combination of LETREC's and LET*'s; a definition
>becomes equivalent to the following combinations of LET's and SET!'s:
> (DEFINE <var-0> <init-0>)
> (DEFINE <var-n> <init-n>)
>(LET ((<var-0> <undefined>)
> (<var-n> <undefined>))
> (SET! <var-0> <init-0>) ; init's must be evaluated
> ... ; in the order presented.
> (SET! <var-n> <init-n>)
Here's one possible problem, at least with the suggested expansion:
(define x 5)
(define y x)
(define x 'any)
Then wouldn't the result be unspecified, even though the intuitive
answer is 5?
-- Brad Pierce
P.S. Something else I'm curious about...
Also, is one allowed to declare the same identifier more than once in the same
lambda closure in official Scheme? The Scheme I am currently using doesn't give
an error message when I try to do this: ((lambda (x x) x) 1 2)
And is it officially legal to "define" something more than once at top level.
The reason that I ask is that the expansion looks a little shaky in the case
that one would re"define" an identifier in such a clause.