25 Jun
2007
25 Jun
'07
8:58 a.m.
On Mon, 25 Jun 2007, Tomasz Zielonka wrote:
On Mon, Jun 25, 2007 at 10:29:14AM +0200, Henning Thielemann wrote:
Imagine all performActions contain their checks somehow. Let performActionB take an argument.
do x <- performActionA y <- performActionB x z <- performActionC return $ calculateStuff x y z
Now performActionB and its included check depend on x. That is, the check relies formally on the result of performActionA and thus check B must be performed after performActionA.
IIUC, this limitation of Monads was one of the reasons why John Hughes introduced the new Arrow abstraction.
How would this problem be solved using Arrows?