DM 42

[toml_12953]

(05-26-2017 07:24 AM)Thomas Okken Wrote:  

(05-26-2017 05:33 AM)Ángel Martin Wrote:  Again, couldn't agree more.
The way the prime makes those assumptions is not a good approach to follow.
The domain matters!

Isn't this a bit of a pointless discussion? The HP-42S has CPXRES and REALRES modes for precisely this reason. In REALRES mode, SQRT(-1) and ACOS(3) return Invalid Data, while in CPXRES mode, they return i and 0+1.76274717404i. And in either mode, they'll return complex results when given complex arguments, i.e. SQRT(-1+0i) and ACOS(3+0i). Does anyone actually think that there is anything wrong with that kind of behavior?

No, nothing at all wrong with that. Prime can turn that ability on or off. It has a checkbox that allows or disallows complex results from real input also. In my work I need answers whether real or complex. If I was an civil or mechanical engineer or surveyor, I'd probably want an error message rather than a complex result. An electrical engineer likes complex results.

Tom L