Right, I read more about it and found this out. The 'main' function is
apparently magical at runtime and allows you to break the with pure
functionality just once but since it can call other functions this allows for
useful programs to be written.
----- Original Message ----
From: Jules Bean <[EMAIL PROTECTED]>
To: Gregory Propf <[EMAIL PROTECTED]>
Cc: haskell-cafe@haskell.org
Sent: Monday, July 2, 2007 1:40:09 AM
Subject: Re: [Haskell-cafe] Re: Parsers are monadic?
Gregory Propf wrote:
> Thanks, that was helpful. I didn't realize that there were pure
> functional monads.
Actually, it's stronger than that. All monads are pure functional, even
IO. Haskell is an entirely 100% pure functional language[*]. The IO
monad allows you to build up, in a pure, referentially transparent way,
an object call an 'IO action' which you have no way of actually
executing, per se.
Fortunately, this isn't as useless as it sounds since the runtime system
contains the support to "actually run" the special IO action called
'main', which bootstraps the whole setup.
Jules
[*] non-functions like unsafePerformIO are not technically part of the
haskell language!
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