logₓy

[Dieter]

(01-13-2019 11:07 AM)Paul Dale Wrote:  All of the programming languages I used that have log to a specified base, put the base second. I.e. log(x, b).

The 34S did originally calculate log_xy, but we changed the arguments around. I have a vague memory that this was to be consistent with y^x, but I could be wrong.

?!? – all 34s versions I ever used calculate log_xy. That's also what is shown on the emulator skins.

I remember well the discussion about the argument order. My point is that you usually have a number in X and then you want to calculate the base-x-log of it. For a base-5-log you now simply enter 5 [log_xy]. Just as you do it with powers: 5 [y^x].

5 [ENTER] 3 [y^x] =>125
5 [log_xy] => 3

So this is similar to he mentioned log(x, b) function in the programming languages: enter x first, then the base. It's only that in RPN the x-value happens to end up in Y and the base b in X. ;-)

Dieter