Re: [Haskell-beginners] howto reason infinite lists

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 6/21/10 17:43 , Chaddaï Fouché wrote:

On Mon, Jun 21, 2010 at 8:58 PM, prad wrote:

...

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.

That's a funny way to say it : to me recursive thinking has always been about assuming I already have a function that works on smaller (in some sense) cases, writing the function knowing that and then figuring what's the base case we're tending toward and handling it non-recursively. That's what recursion is about for me and I've always found easier to think about it like that rather than always expansing the recursive calls (I also find it easier than thinking iteratively nowadays but YMMV).

I think of it a bit like proofs: prove the base case, prove the inductive case, therefore the proof applies to all cases (which is equivalent to being infinite). -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkwf3boACgkQIn7hlCsL25UI9ACeM7OBLjSZnUuzHmfC0ZKge4ti n2UAoLn09TYwvUAvSTCOeJHMAQZa/3FI =rDt7 -----END PGP SIGNATURE-----