On Mon, Jun 16, 2008 at 10:31:22AM +0800, Magicloud Magiclouds wrote:
Hello, I am getting familiar with FP now, and I have a "program design" kind of question. Say I have something like this in C: static int old; int diff (int now) { /* this would be called once a second */ int ret = now - old; old = now; return ret; } Because there is no "variable" in Haskell. So how to do this in a FP way?
Thanks.
I think that "called once a second" suggests that you perhaps should not do that in a FP way. A state-changing function called frequently suggests that you are perhaps doing something with a notion of time, maybe a game? Then FRP is your FP approach. Or I would recommend you to explain your problem, because FP approach could lie on much more higher level than one can figure out looking at your short snippet.
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-- pierre