Bug: HP Prime can't do Log's

[Tim Wessman]

(12-14-2015 09:36 PM)davimle Wrote:  @TW, she was using the Solver app before, but it would only return one root and would require some guessing on a "seed" to return the other root. Again, as you know as a "teaching" calculator, the others put in a more "easy to use" function.

Well, since you are in the solve application, try pressing the "plot" button and you can quickly see a graph. That can be helpful in situations like this. NUM will switch back to the solve screen.

Currently, solving in the solve app will just return the single result like you've mentioned. That is in fact the identical numerical solver found in your 28S (speaking from an algorithm and behavior perspective).

One other thing you might not have discovered yet (but I suspect your daughter already has), press the LOG key and then press the "HELP" button. It will pull up contextual help for nearly everything in the system. I suspect she found it there. There are about 250-300 pages of documentation built into the calculator. :-)

For anyone interested, the code originally was like this:

Code:


  THPObj *ln[2];
  ln[0]= CallLN(f, Params, 1);
  ln[1]= CallLN(f, Params+1, 1);
  THPObj *ret= CallDIV(f, ln, 2);
  ln[0]->Delete(); ln[1]->Delete();

We've added a special case right before the first code for real inputs as the benefit outweighs any downside here.The _L on the div function returns the "user" 12 digit normalized result.

Code:

// case of LOG in base b...
  HP_Real r1, r2;
  if (Params[0]->GetReal(&r1) && Params[1]->GetReal(&r2))
  { Errors er; 
    if (!fError(er= filn(&r1, &r1)) || !fError(er= filn(&r2, &r2))) return THPObj::NewError(er);
    return THPObj::NewReal(fidiv_L(&r1, &r2, &r1), &r1);
  }