Here is some relevant discussion: http://lambda-the-ultimate.org/node/2003 http://lambda-the-ultimate.org/node/2003 Also, codata doesn't solve everything. You

Here is some relevant discussion: http://lambda-the-ultimate.org/node/2003 http://lambda-the-ultimate.org/node/2003 Also, codata doesn't solve everything. You still can't filter infinite data. Filtering with \x -> x > 0 won't terminate for all infinite lists of numbers since [0 0 0 0 0 ...] is a potential case.