1 Oct
2012
1 Oct
'12
5:34 a.m.
"Albert Y. C. Lai"
On 12-09-30 06:33 PM, Jake McArthur wrote:
When discussing monads, at least, a side effect is an effect that is triggered by merely evaluating an expression. A monad is an interface that decouples effects from evaluation.
I don't understand that definition. Or maybe I do subconsciously.
I have
s :: State Int () s = do { x <- get; put (x+1) }
Is there an effect triggered by merely evaluating s?
I have
m :: IO () m = if True then putStrLn "x" else putChar 'y'
Is there an effect triggered by merely evaluating m?
What counts as "evaluate"?
Evaluation! Consider m `seq` 42. m is evaluated, but to no effect. -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk