From: Jim Pryor Date: Tue, 5 Oct 2010 03:21:43 +0000 (-0400) Subject: week4 tweaks X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=commitdiff_plain;h=6d58ca4a1e34835770dcb3213cc95470209b06ec week4 tweaks Signed-off-by: Jim Pryor --- diff --git a/week4.mdwn b/week4.mdwn index fca995e3..8353afb7 100644 --- a/week4.mdwn +++ b/week4.mdwn @@ -593,15 +593,15 @@ detail](http://okmij.org/ftp/Streams.html#enumerator-stream). > > Well, the right fold of `f` over a list `[a;b;c;d;e]`, using starting value z, is: > -> f a (f b (f c (f d (f e z)))) +> f a (f b (f c (f d (f e z)))) > > The left fold on the other hand starts combining `z` with elements from the left. `f z z` is then combined with `b`, and so on: > -> f (f (f (f (f z a) b) c) d) e +> f (f (f (f (f z a) b) c) d) e > > or, if we preferred the arguments to each `f` flipped: > -> f e (f d (f c (f b (f a z)))) +> f e (f d (f c (f b (f a z)))) > > Recall we implemented v3 lists as their own right-fold functions. We could > instead implement lists as their own left-fold functions. To do that with our