[Haskell-cafe] Re: Left fold enumerator - a real pearl overlooked?

Henning Thielemann schlepptop at henning-thielemann.de
Tue Mar 3 19:18:04 EST 2009

John A. De Goes schrieb:

> Elsewhere, laziness can be a real boon, so I don't understand your
> question, "Why have laziness in Haskell at all?"

As I have written, many libaries process their data lazily (or could be
changed to do so without altering their interface) but their interface
can forbid application to data that is fetched from the outside world.
Say you are used to 'map', 'filter', 'foldr' - you cannot use them on
data fetched by the iteratee/enumerator approach.

Actually, Lazy I/O and exceptions can work together if you drop the
exceptions that are baked into IO monad and use explicit exceptions
(synchronous and asynchronous ones) as I develop them in the
explicit-exception package. I'm however still searching for a good set
of combinators.

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