On Tuesday 10 August 2010 19:12:57, michael rice wrote:
OK, then there's also an implicit *in* after the *let* in this code.
Yes. do let x = foo bar baz is desugared to let x = foo in (bar >> baz)
Must the implicit (or explicit) *in* actually use the calculated value(s)?
No, and if the values aren't used, they're not calculated (unless you force the calculation in the bindings, e.g. with bangs).
And, the monad can "continue on" after the *let* (with or without the *in*) as below, i.e., the *let* needn't be the last statement in the *do*?
It *mustn't* be the last statement; the last statement in a do-block must be an expression (return blah, putStrLn whatever, ...)
main = do gen <- getStdGen let code = genCode gen putStrLn $ "Code is " ++ show code putStrLn "..."
Michael