On Tue, Apr 1, 2008 at 1:02 PM, Bulat Ziganshin
Hello Simon,
Tuesday, April 1, 2008, 2:18:25 PM, you wrote:
How can one answer the question--why choose Haskell over Scheme?
Well as a longtime Scheme and OCaml programmer, and Haskell-cafe lurker, I'll take a stab at this...
1. static typing with type inference - imho, must-be for production code development. as many haskellers said, once compiler accept your program, you may be 95% sure that it contains no bugs. just try it!
I think this is the biggest, and most obvious, difference to consider when choosing either Scheme or Haskell over the other -- for a particular problem. Dynamic and static typing each have their advantages, depending on the context. I think it's dangerous to try to answer the question "Scheme or Haskell?" without a problem context.
2. lazy evaluation - reduces complexity of language. in particular, all control structures are usual functions while in scheme they are macros
Well, if I don't have side effects (and don't mind extra, unneeded evaluations), I can write my conditionals as functions in Scheme too. Heck, now that I think of it I can even avoid those extra evaluations and side-effect woes if i require promises for each branch of the conditional. No macros required... I think some problems are just more naturally modeled with lazy thinking, and a language with implicit support for lazy evaluation is a _huge_ win then. I written plenty of lazy Scheme, and OCaml for that matter, code where I wished and wished that it just supported lazy evaluation semantics by default. Again, I think this is highly problem dependent, though I think you win more with lazy evaluation in the long run. Do more experienced Haskellers than me have the opposite experience? I mean, do you ever find yourself forcing strict evaluation so frequently that you just wish you could switch on strict evaluation as a default for a while?
3. great, terse syntax. actually, the best syntax among several dozens of languages i know
I think this is possibly the weakest reason to choose Haskell over Scheme. Lispers like the regularity of the syntax of S-expressions, the fact that there is just one syntactic form to learn, understand, teach, and use. For myself, I find them to be exactly the right balance between terseness and expressiveness. For me, Haskell syntax can be a bit impenetrable at times unless I squint (and remember I'm also an OCaml programmer). Once you "get it," though, I agree that the brevity and expressiveness of Haskell is really beautiful.
4. type classes machinery, together with type inference, means that code for dealing with complex data types (say, serialization) is generated on the fly and compiled right down to machine code
This is obviously related to #1, and Haskell sure does provide a lot of fancy, useful machinery for manipulating types -- machinery whose functionality is tedious at best to mimic in Scheme, when even possible. In short, I think the orginal question must be asked in context. For some problems, types are just a natural way to start thinking about them. For others dynamic typing, with _judicious_ use of macros to model key aspects, is the most natural approach. For the problems that straddle the fence, I usually pick the language I am most familiar with (Scheme) if there are any time constraints on solving it, and the language I'm least familiar with (Haskell, right now) if I have some breathing room and can afford to learn something in the process. Cheers, -Andy
-- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe