Am 23.03.2014 09:50, schrieb Bart Massey:
* The multiplicity of exponentiation functions, one of which looks exactly like C's XOR operator, which I've watched trip up newbies a bunch of times. (Indeed, NumericPrelude seems to have added more of these, including the IMHO poorly-named (^-) which has nothing to do with numeric negation as far as I can tell. See "unary negation" above.)
It is unfortunate, but there really is a distinction being made.
I get that. I even get that static-typing exponentiation is hard. (You should see how we did it in Nickle (http://nickle.org) --not because it's good but because it calls out a lot of the problems.) What I don't get is why the names seem so terrible to me, nor why the typechecker can't do more to help reduce the number of needed operators, ideally to one. It might mean extra conversion operators around exponentiation once in a while, I guess?
I think the power functions of Haskell are the best we can do, and mathematics is to blame for having only one notation for different power functions. http://www.haskell.org/haskellwiki/Power_function I like to compare it to division. In school we first learnt natural numbers and that division cannot always be performed with natural numbers. Instead we have division with remainder. In contrast to that we can always divide rational numbers (except division by zero). In Haskell this is nicely captured by two different functions div and (/). The same way I find it sensible to distinguish power functions. I found the infix operator names (^^) and (**) not very intuitive and defined (^-) and (^/) in NumericPrelude, in order to show, that the first one allows negative exponents and the second one allows fractional exponents. Unfortunately the first one looks like power function with negated exponent and I had no better idea for an identifier so far.