Re: EVAL at macroexpansion time - use *VENV* too?

[Bruno H. <br...@cl...>]

Sam wrote:

> here is another example:
>
> (symbol-macrolet ((foo 12))
>   (macrolet ((bar (x y) `(+ ,x ,(1+ y))))
>     (bar 10 foo)))
>
> see
> <http://groups.google.com/groups?dq=&hl=en&lr=&ie=UTF-8&threadm=sfwn0eifn0s
>.fsf%40shell01.TheWorld.com&prev=/groups%3Fas_ugroup%3Dcomp.lang.lisp> for
> some discussion - it appears that indeed the first form should macroexpand
> to 22 and the second to (+ 10 13).

About the second form, I don't agree. During the macroexpansion call,
   X  gets bound to              10
   Y  gets bound to the symbol   FOO
and then you just write (1+ y) - it must give an error "FOO is not a number".

Remember that no processing occurs to macro arguments before the macro
expander is invoked (except the destructuring, provided by DEFMACRO
and MACROLET). See CLHS 3.1.2.1.2.2.

The citation about "The macro-expansion functions defined by macrolet are
defined in the lexical environment in which the macrolet form appears."
only means that you can write

   (symbol-macrolet ((foo 12))
     (macrolet ((bar (x) `(+ ,x ,(1+ foo))))
       (bar 10)))

Bruno