Daniel Fischer
Well, I guess you could get pretty far using 'interact' - far enough in an educational setting to do lists and Maybe, and then monads, before introducing monadic IO.
Pretty far, yes, and in an educational setting, at a university, it is quite common, I believe, to use an interpreter for a while, not producing executables (that's how I met Haskell, write pure functions and type expressions at the Hugs prompt). But what about a tutorial for programmers? How would you do
Well, yes, some things do get complicated, and I'm not suggesting that "interact" will suffice for real programs. I still agree with the faction that thinks monadic IO should be taught after non-IO monadics - which, especially for programmers, can be quite early in the curriculum. After all, lists and algebraic data types are central and simple concepts. I don't think you *need* to teach input-print sequential programs, though. This is functional programming after all, why not build a compiler instead?
I doubt you could keep many interested without telling them how to create standalone programmes, including reading input from stdin and printing output to stdout.
Well, my first "real", standalone haskell program was reading my telephone log from stdin, matching against an internal database, and outputting calls with time and name to stdout. I used standard features like shell IO redirection in and 'tee' to integrate with the rest of the system. I then moved on to monadic IO, but wish I'd done monads in general first. YMMV. -k -- If I haven't seen further, it is by standing in the footprints of giants