H->HMS conversion HP-15C vs. HP42S vs HP67

[Thomas Okken]

(09-07-2018 09:43 AM)Werner Wrote:  

(09-06-2018 05:31 PM)Dieter Wrote:  it looks like the usual binary roundoff problem.

Yet Free42 binary (of which I must be the only user?) gets it right ;-)

The approach I chose for ->HR for the binary version is robust but not very pretty: multiply x by 1e12, round to nearest integer, and then do everything using integer math. Plus, there is a special case in for |x| < 0.01, where the conversion reduces to a simple division by 0.36.

The idea was to make sure that it will never get anything wrong that the HP-42S gets right, but the simplistic approach I chose does mean a bit of precision is lost. If someone has a better algorithm lying around for IEEE-754 double precision binary, I would be interested.