On 10 Aug 2007, at 6:42 am, David Roundy wrote:
do x1 <- e1 if x1 then do x2 <- e2 xx <- if x2 then e3 else do x4 <- e4 x5 <- e5 e6 x4 x5 e7 xx x1 else do x8 <- e8 x9 <- e9 e10 x8 x9 x1 x11
Granted. If you desugar nested dos then you need extra parentheses. (Basically, the invisible curly braces turn visible as parentheses.) But then, I don't regard this example as readable, and in true "lots of little functions" style would name the steps. I especially dislike the irregular indentation one gets with do/if/do. Anyone remember when Haskell extended list comprehension syntax to monads? Just as I was about to get my head around it, it went away.
This is the beauty of the do notation, it allows one to write actual real complicated monadic code in a form that is actually comprehensible.
It seems we are now in complete agreement except for "comprehensible".