So for the past year or two I have been reading up on functional
programming. I still haven't written anything useful with it but I hope
that will change soon. Here is an exchange I had with Chris Seberino on
IRC last night which I thought some of you might enjoy.
<tessier> |seb|_: Have you looked at Stackless python? I just suddenly
realized it's potential.
<|seb|_> tessier: what is the potential of it? i don't know
<tessier> |seb|_: No stack. Stackless. You can do recursion much more
easily without worrying about overflowing the C stack. Also makes
threads and coroutines etc much cleaner. EVE Online uses it to script
their game engine. BIG MMORPG.
<|seb|_> tessier: yea but how often do you do a massively deep
recursion? it may have great use in a few situations...kinda like lisp
and haskell
<|seb|_> tessier: also, i try to avoid threads in general and use event
driven paradigm
<tessier> |seb|_: Well, there are lots of times you can do massively
deep recursion. But you were not taught to use it. You were taught
imperative.
<tessier> For example, check out this recursion to add up all of the
values of an array in Haskell...
<tessier> sum :: [int] -> Int
<tessier> sum [] = 0
<tessier> sum (x:xs) = x + sum xs
<tessier> You would do that instead of a for loop and an accumulator
variable and a counter variable to index the array in C like languages.
<tessier> This way is less code, fewer variables, mathematically
provably correct, less chance of accidentally reusing a loop variable or
having scope issues etc.
<tessier> to a functional coder this is just as clear and obvious as a
for loop doing the same thing to an imperative coder.
<tessier> And really only that last line is necessary to do the work.
<tessier> The first two lines are boilerplate.
<tessier> Not really boilerplate as they could change but they aren't
the guts of it.
<tessier> The first line means this function takes a list of ints and
returns an int
<tessier> The second line says if the list is empty the sum is 0
<tessier> The third line implements the actual summing and recursion
<tessier> The (x:xs) part assigns the first int in the list to x and the
remainder to xs. This is like car and cdr in Lisp.
<tessier> But each time we call it the first int changes.
--
Tracy R Reed Read my blog at http://ultraviolet.org
Key fingerprint = D4A8 4860 535C ABF8 BA97 25A6 F4F2 1829 9615 02AD
Non-GPG signed mail gets read only if I can find it among the spam.
--
[email protected]
http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-lpsg
