On May 13, 2011, at 14:37 , David Nolen wrote: > On Fri, May 13, 2011 at 2:04 AM, Heinz N. Gies <he...@licenser.net> wrote: > Hearing Pattern Matching, > do you mean Erlang like Pattern matching? > > Regards, > Heinz > > Erlang, OCaml, SML, Haskell, Scala all have the kind of pattern matching I'm > talking about. One important point is that they all support guards on > patterns. It's not clear to me that current implementation actually use > guards to shape the tree, but that is my plan. In the system I'm proposing > guards are actually logical predicates that can be reasoned about. > > (match n > ([x] :guard [(number? x)] > ...) > ([0] ...)) > > This is not ok in OCaml, SML, or Haskell (or Scala and Erlang as far as I > know). This would be ok in the system I'm proposing since number? is a > logical predicate and we can test for such cases and reorder the pattern. Erlang not only allows predicate functions, simple math is also just fine like
f(x) when x < 0 -> ... then again erlangs reasoning for only allowing certain BIF's and simple arithmetics in guards is speed, those are writtin in plain C so are blazing fast compared to erlang functions ^^. That is a issue Clojure does not have to face so I don't think it would make sense to limit the code you can put in guard expressions. Regards, Heinz
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