<rocco.rossi@gmail.com> wrote:
+---------------
| I think I've found the answer to that last question (Hyperspec):
| "Common Lisp provides no operation on a symbol that can have any
| effect on a lexical variable or on a lexical function definition."
+---------------

That's because by the time the code runs lexical variabless don't
even *have* any "symbols" any more, at least not once the code is
compiled [or even just pre-processed for "fast interpretation"].
They're [usually] just converted to stack offsets in the resulting
code. E.g., try this in your favorite CL compiler:

    (disassemble
      (lambda (x)
	(declare (type (integer -1000 1000) x)
		 (optimized (speed 3) (safety 0) (debug 0)))
	(let ((y 5))
	  (+ y (* x 37)))))

See if you can find the "Y" anywhere...  ;-}


-Rob

p.s. In CMUCL on x86, the only trace left of Y is this
single instruction:

    ADD     EDX, 20

[In CMUCL, fixnums are 30-bit signed ints shifted left two,
hence 5 => 20.]


-----
Rob Warnock			<rpw3@rpw3.org>
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