On Thu, 26 Mar 2009, wren ng thornton wrote:

Thomas Hartman wrote:

Luke, does your explanation to Guenther have anything to do with
coinduction? -- the property that a producer gives a little bit of
output at each step of recursion, which a consumer can than crunch in
a lazy way?

It has more to do with "tying the knot" (using laziness to define values in terms of themselves), though there are similarities. Take the function:

infZipWith f ~(x:xs) ~(y:ys) = f x y : infZipWith f xs ys

What about using a custom list type, that has only one constructor like (:), that is, a type for infinite lists?

Yes, that would be more correct. However, the lazy pattern match would still be necessary, because single-constructor types are lifted. And as long as you're doing that, you might as well go all the way to an infinite binary trie.

Luke