Doug McNutt wrote: > Jonathan Lang wrote: > >Technically, the result set is one element (the principle value), > >since a mathematical function - by definition - produces a single > >result for any given input. > > Please be careful of "definitions" like that. Computer science has quite > different ideas about mathematics than those of chalkboard algebra.
...which is why I specified "mathematical function"; I was intentionally referring to the chalkboard algebra meaning. But I can see where the confusion came from. > x^(1/2) is a multivalued function and x^2 is a single valued > function but they are both pow(x ,y). Actually, that's an interesting point: I didn't find a pow() function in the s29 draft. There was an exp() function which could do the same thing, albeit with the arguments in reverse order: exp($exp, $base) := $base ** $exp; but if you want to do a function that places the arguments the other way around, you apparently have to say something like "infix:<**> ($base, $exp)". I'd recommend adding a pow() function such that pow($base, $exp) := $base ** $exp; it's redundant, but it's a very useful bit of redundancy. > The likes of yacc have > other ideas causing -2^2 to become +4 (thankfully not in > perl) Oh? Last I checked, prefix:<-> was a higher-priority operator than infix:<**>; so -2**2 is equivalent to (-2)**2, not -(2**2). > and sqrt(x) to become single valued positive definite. > -2^(1/2) is not the same as -sqrt(2) in some implementations. I should hope not. That said, I really hope that "sqrt($x)" will effectively be the same as "$x ** 0.5": I want both of them to return a single value in scalar context, and for each to behave like the other when in list context. -- Jonathan "Dataweaver" Lang
