Jon Schneider wrote:
Good morning all,
I think I've got the hang of the way state is carried and fancy operators work in monads but still have a major sticky issue.
With lazy evaluation where is it written that if you write things with no dependencies with a "do" things will be done in order ? Or isn't it ?
Is it a feature of the language we're supposed to accept ?
Is it something in the implementation of IO ?
Is the do keyword more than just a syntactic sugar for a string of binds and lambdas ?
You have to distinguish between *evaluation order*, which dictates how a Haskell expression is evaluated, and something I'd like to call *execution order*, which specifies how the IO monad works. The point is that the latter is very much independent of the former. Evaluating the expression `getLine :: IO String` and "executing" the expression `getLine :: IO String` are two entirely different things. I recommend the tutorial Simon Peyton Jones. "Tackling the awkward squad: monadic input/output, concurrency, exceptions, and foreign-language calls in Haskell" http://research.microsoft.com/en-us/um/people/simonpj/papers/marktoberdorf/ for more on this. Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com