cousin_it comments on No coinductive datatype of integers - Less Wrong

4 Post author: cousin_it 04 May 2011 04:37PM

You are viewing a comment permalink. View the original post to see all comments and the full post content.

Comments (138)

You are viewing a single comment's thread. Show more comments above.

Comment author: cousin_it 04 May 2011 08:52:16PM *  4 points [-]

Right. In fact, this phrase from Harper's blog was one of the inspirations for my post:

In Carollian style there are types called naturals and lists, but that’s only what they’re called, it’s not what they are.

ETA: it seems you slightly misunderstood Harper's point. The problem with defining "data Nat = Zero | Succ Nat" is not that bottom is in Nat, but rather that laziness allows you to write the circular definition "omega = Succ omega" (note that pattern-matching on omega doesn't hang), which is similar to the unary example in my post.

Comment author: jsalvatier 04 May 2011 11:35:22PM 1 point [-]

Thanks for correcting me :) I imagine there's a lot of Harper I don't understand correctly.