Gwern Branwen wrote:

On 0, Andrew Coppin scribbled:

...

I've seen comments in various places that monads allow you to "borrow things from the future".

That sounds completely absurd to me... can anybody explain?

Take a look at issue 6 of The Monad Reader; search for time travel. http://www.haskell.org/haskellwiki/The_Monad.Reader

Mmm... yes... I've read this before. It didn't make any sense then either. (The example is too big and complicated. It obscures the thing it's trying to illustrate...)