>>>>> "Alex" == Alex Martelli <[EMAIL PROTECTED]> writes:
Alex> I've always liked the (theoretical) idea that assertions
Alex> (including of course contracts) could be used as axioms used
Alex> to optimize generated code, rather than (necessarily) as a
Alex> runtime burden. E.g. (and I don't know of any
Alex> implementation of this concept, mind you), inferring (e.g.
Alex> from such assertions) that x>=0, and that y<0, the compiler
Alex> could simply cut away a branch of dead code guarded by "if
Alex> x<y:" (maybe with a warning, in this case;-)...
I realize that your example is theoretical, but efficiency impact of
such optimizations would be dwarfed (speedwise) by optimization on
type, so that "if x < y" yields native object code for integer
comparison. Also, to get real benefits the functions called would need
to be inline-expanded so that the implications of x < y are taken in
account deeper in the call chain; a programmer that does
def f(x,y):
assert x > y
if x < y:
blah(y,x)
needs a slap on the wrists anyway. Doing "if x < y" in blah() would
make sense, but then there would need to be a special version of
blah()...
I could think of one worthwhile example as well:
def foo(l):
assert issorted(l)
if "hi" in l: # in does a bsearch because the list is sorted
blah()
but things like this probably belong to languages like Lisp where the
user gets to expand and mess with the compiler.
--
Ville Vainio http://tinyurl.com/2prnb
--
http://mail.python.org/mailman/listinfo/python-list
