embedded python - cancel "while 1: pass"

[Moshe Zadka]

On Wed, 3 Jan 2001 13:48:29 -0500, D-Man <dsh8290 at rit.edu> wrote:
> 
> Just brainstorming here:
> 
> you could inspect the code for such constructs and not execute those

Ummmmmm.....so far, no one has been able to solve the halting problem:
identifying a piece of code which never ends. In fact, one of the
central results of Computer Science is that it is impossible to do so.

The proof goes as follows: suppose finishes() is a function which is
given a function and answers whether that function returns or not (assume
only functions which don't receive parameters).

Now write the following function:

def foo():
	if finishes(foo):
		while 1:
			pass

Now, if foo finishes, then foo loops. But that means foo loops, so
finishes(foo) returns false, so foo doesn't loop. This is a contradiction,
so finishes() cannot exist.
-- 
Moshe Zadka <sig at zadka.site.co.il>
This is a signature anti-virus. 
Please stop the spread of signature viruses!