Ken Tilton <[EMAIL PROTECTED]> writes: > Alexander Schmolck wrote: > > Ken Tilton <[EMAIL PROTECTED]> writes: > > > > >>In Common Lisp we would have: > >> > >> (defvar *x*) ;; makes it special > >> (setf *x* 1) > >> (print *x*) ;;-> 1 > >> (let ((*x* 2)) > >> (print *x*)) ;; -> 2 > >> (print *x*) ;; -> 1 > > You seem to think that conflating special variable binding and lexical > > > variable binding is a feature and not a bug. What's your rationale? > > Transparency.
That's is circular. You might be right, but you failed to provide a rationale and not just a restatement. > That is where power comes from. I did the same things with Cells. Reading a > slot with the usual Lisp reader method transparently creates a dependency on > the variable. Let me see if I understand it right -- if an instance of class A has a ruled slot a that reads an instance of class B's slot b then it is noted somewhere that A's a depends on b? > To change a variable and have it propagate throughout the datamodel, Just > Change It. > > > Exposed wiring means more work and agonizing refactoring. Well, you claim that in that instance python suffers from exposed wiring and I claim that CL suffers from a (minor) booby trap. You can't typically safely ignore whether a variable is special as a mere wiring detail or your code won't work reliably (just as you can't typically safely ignore whether something is rigged or not even if booby-trapness is pretty transparent) -- it's as simple as that (actually its a bit worse because the bug can be hard to detect as lexical and special variables will result in the same behaviour in many contexts). So in the case of booby traps and special variables, I generally prefer some exposed wiring (or strong visual clues) to transparency. I'd like to see a demonstration that using the same binding syntax for special and lexical variables buys you something apart from bugs. 'as -- http://mail.python.org/mailman/listinfo/python-list
