On 9/3/07, Vimal <j.vimal@gmail.com> wrote:

Hi
In my Paradigms of Programming course, my professor presents this piece of code:

while E do
  S
  if F then
     break
  end
  T
end

He then asked us to *prove* that the above programming fragment cannot
be implemented just using if and while statement, even if S and T can
be duplicated a finite number of times

But it IS possible. Just add a boolean flag:

done = False
while E and not(done) do...

I'll let you work out the rest. Unless I am missing something here... are you not allowed to introduce extra variables? It's a strange thing for your professor to ask, since under reasonable assumptions, anything that is computable can be done only using if and while. goto (which is essentially what break is) is never necessary.

-Brent