On Mon, 14 Feb 2011 15:07:01 +0100
Gábor Lehel
I'm not completely sure, but I suspect another part of it (or maybe I'm just rephrasing what you said?) has to do with the fact that in Haskell, basically everything is an expression.
Yes, the fact that control statements (e.g. if-then-else) are expressions makes type checking much more effective. However, I think this is somewhat lost when programming imperative code in Haskell using a state or I/O monad (because a monadic type such as "IO t" does not discriminate what effects might take place, only the result type t). Of course one can use a more specialized monad (such ST for mutable references, etc.). I don't think that my imperative programs are automatically made more correct by writing them as monadic code in Haskell --- only that in Haskell I can opt for the functional style most of the time. BTW (slightly off topic) I found particularly annoying when teaching Python to be forced to use an imperative style (e.g. if-then-else are always statements). Scala is must better in this regard (altought it is not purely functional language); a statement is simply an expression whose return is unit. Pedro