30 Dec
2009
30 Dec
'09
8:59 p.m.
On Wed, Dec 30, 2009 at 05:49:12PM -0800, Joe Van Dyk wrote:
What's the appropriate way to write this in Haskell?
# Ruby code, ignore the thread-unsafety for now. class Ticker @@tick = 0 def self.update! @@tick += 1 end def self.current return @@tick end end
Ticker.update! # 1 Ticker.update! # 2 Ticker.current # 2
If you really want a global ticker, use the State monad: tick :: State Int () tick = modify (+1) -- increment the counter twice then return its new value mainStuff :: State Int Int mainStuff = tick >> tick >> get -Brent