Apparently: Prelude> let r = (fmap (1:) r) :: IO [Integer] Prelude> fmap (take 5) r *** Exception: stack overflow
Thanks - I'll just have to stay out of IO for this, then. On Tue, May 31, 2011 at 17:05, Stephen Tetley <stephen.tet...@gmail.com> wrote: > 2011/5/31 Scott Lawrence <byt...@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...). > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- Scott Lawrence _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
