Tamas K Papp wrote:
The code in the subject generates an error. I understand why this is (- is treated as part of the number), but I don't know how to solve it, ie how to tell Haskell that - is a function/binary operator?
Actually looking at the Haskell98 report, -2 seems to be treated as (negate (2)), which I find really strange because there does not appear to be any way of specifying negative literals, and the range of negative values is always 1 more than the range of positive values (when you use a fixed bit-length representation eg Int instead of Integer) I'd have thought it would have been simpler to just make the rule that -2 (no spaces between '-' and '2') would be a single lexeme, and then people could just use (negate x) or (0 - x) instead of having a special rule and a whole lot of confusion just for one arithmetic operator, which is never actually needed in the first place (just as we don't need /x because it is simple enough to write 1/x). I see with great disappointment that Haskell' Trac ticket#50 [1] looks as if it will not be accepted [2] so we're likely to be stuck with this for years to come... [1] http://hackage.haskell.org/trac/haskell-prime/ticket/50 [2] http://hackage.haskell.org/trac/haskell-prime/wiki/StrawPoll-2 So in answer to your question, you can't (except for workarounds already posted). Regards, Brian. -- Logic empowers us and Love gives us purpose. Yet still phantoms restless for eras long past, congealed in the present in unthought forms, strive mightily unseen to destroy us. http://www.metamilk.com