On 12-10-01 05:34 AM, Jon Fairbairn wrote:
"Albert Y. C. Lai" <tre...@vex.net> writes:
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.
Sure thing. So s has no side effect, and m has no side effect. Since
they have no side effect, there is no effect to be decoupled from
evaluation.
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