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 He also asked us to state our assumptions if any. 1. We have assignment statements (to create a flag and check) 2. The execution of E or F does not affect execution of S or T... Well, learning Haskell, I quickly realized that even if S and T have to be expressions and came up with this, assuming that 1. There are boolean operations 2. Boolean expressions are evaluated from Left to Right 3. Boolean expressions can be short-circuited while E and (S or 1) and F and (T or 1) do (* Nothing *) end But I would also like to consider an option of proving that its impossible, under the given constraints... Any thoughts? Vimal