Grafting Functional Support on Top of an Imperative Language

[Bill Baxter]

Simen Kjaeraas wrote:
> On Sat, 05 Apr 2008 01:09:14 +0200, Jason House 
> <jason.james.house at gmail.com> wrote:
> 
>> bearophile wrote:
>>> P. 31: >writeln(i);<
>>>
>>> Can you put (temporary) debugging writeln/putr inside a pure function?
>>
>> That's always bothered me about this stuff.  I don't want to lose
>> debugging/logging ability!
> 
> 
> Just use multiple return types, and have the caller do the printing.
> 
> --Simen


Monads!

Or at least I think that's what I read somewhere.  I can't understand 
the buggers for the life of me.  I think maybe it's just a fancy word 
for "loophole".  If someone here has a good explanation for what a monad 
is and how it allows mutable state in FP without making thing non-FP, 
I'd love to hear it.  Because I just don't get it.

--bb