[Haskell-cafe] Lazy Evaluation in Monads

[Stephen Tetley]

2011/5/31 Scott Lawrence <bytbox at gmail.com>:

> Evaluation here also doesn't terminate (or, (head $ unfoldM (return .
> head)) doesn't), although I can't figure out why. fmap shouldn't need to
> fully evaluate a list to prepend an element, right?

I'm afriad fmap doesn't get to choose - if the monad is strict then
both definitions are equivalent (probably...).