XPost: alt.usage.english

Newsgroups: alt.usage.english, comp.lang.haskell
Followup-To: comp.lang.haskell

Jack Campin <bogus@purr.demon.co.uk> writes:

In pure functional programming, one does not have
such effects as object creation.

You do. That's what monads are for.

Monads are merely used to express the /combination/ of
action values using the »bind« operation. But the
action values used in Haskell, like the value of
»putStr "hello"« clearly have an /operational/ meaning:

»putStr :: String -> IO ()
base Prelude, base System.IO
Write a string to the standard output device«

www.haskell.org

and thus they are /not/ what I call »purely function«
anymore.

One can write a Haskell function that deals with an
action value representing object creation. Such a function
would still be what I call »purely function«, but it never
will /create an object/ on its own. The moment one wants
to actually /perform/ the action value, one is leaving
the realm of pure functional programming.

Newsgroups: alt.usage.english, comp.lang.haskell
Followup-To: comp.lang.haskell

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