i'm trying to figure out how to think out the circular definition for an infinite list and would appreciate suggestions. consider ones = 1 : ones this essentially says 1 : (1 : (1 : (1 : ones))) with ones being given by the original def. however, i had trouble with this one fib = 1 : 1 : [ a+b | (a,b) <- zip fib (tail fib) ] initially, i tried building it element by element and got stuck when i thought of what was fib tail fib and what was being zipped so i thought it out differently by assuming the infinite list was already created in the following fashion. fib is [1,1,a,b,c,d,e, ..] tail fib is [1,a,b,c,d,e,f, ..] to find a, we zip fib and tail fib getting (1,1) and add getting 2: fib is [1,1,2,b,c,d,e, ..] tail fib is [1,2,b,c,d,e,f, ..] get b from the next zip (1,2) and add giving 3: fib is [1,1,2,3,c,d,e, ..] tail fib is [1,2,3,c,d,e,f, ..] c comes from (2,3) which adds to 5: fib is [1,1,2,3,5,d,e, ..] tail fib is [1,2,3,5,d,e,f, ..] this way of thinking about it makes sense to me, but i'd be curious to know if it is proper thinking. it seems to me that if we consider the list to be already built, we can apply zip successively to get the next part of it, but if we think recursively we start at the beginning at each recursive level and go nowhere. -- In friendship, prad ... with you on your journey Towards Freedom http://www.towardsfreedom.com (website) Information, Inspiration, Imagination - truly a site for soaring I's