Add logbase function

[Former user]

Originally reported on Google Code with ID 486

A logbase function allows using a number other than 10 or 2 as the base. It can be useful
for getting the exponent that a number has been raised by (aka. the inverse operation
of raising a number to a power).
Suggested expression implementations (the former [<<] may be easier to understand):
* logbase(x, base) <<
* logbase(base, x)
Example problems:
* logbase(512, 8) = 3
* logbase(64, 2) = 6

Reported by richWiki101 on 2014-02-28 22:59:28

[Former user]

Thanks for your feedback. Now that I think about it, this is how I think we should have
it (according to ISO): https://en.wikipedia.org/wiki/Logarithm#Particular_bases

And then, we'd finally have log(x, base). What do you think?

Reported by helder.pereira.correia on 2014-03-01 00:03:48 - Status changed: Accepted - Labels added: Type-Enhancement, Priority-High, Milestone-0.12

[Former user]

Also: http://en.wikipedia.org/wiki/ISO_31-11#Exponential_and_logarithmic_functions

Reported by helder.pereira.correia on 2014-03-01 00:05:24

[Former user]

I think I may be OK with what you suggest, but I have just a few concerns to address:

* What will happen if someone wants to do only log(x)? Will an error result if, after
you implement your suggestion, one inputs only log(x)?
* Or will this expression be moved to a new one (Such as lb(x) needs to become the
new binary logarithm, so that lg(x) can become the new logarithm)?
* If you do implement what you suggested, I feel like that some confusion may arise
for some users, so you may need to document this change somewhere, such as a changelog.

Reported by richWiki101 on 2014-03-01 01:07:24

[Former user]

Just like the ISO standard, there would be no log with only one argument. The application
already tells the user on-the-fly about function usage. log(x) would not be accepted
and the users would know why. Also, the next version will come with a user manual where
all this would be documented, of course.

Reported by helder.pereira.correia on 2014-03-01 01:14:09

[Former user]

Finally, if you type just "l", the completion box will hint you about the changes, since
you'll see the new names and descriptions immediately.

Reported by helder.pereira.correia on 2014-03-01 01:15:41

[Former user]

Okay now, I WILL LET YOU implement your suggestion. I raised my concern earlier not
for just myself but for other people who may be ignorant. I trust that the users will
be informed of these changes by the next release.

Reported by richWiki101 on 2014-03-01 02:26:05

[Former user]

Browsing older entries on this tracker lead me to issue 381 which asks for ISO notation.

Reported by helder.pereira.correia on 2014-03-01 02:35:17

[Former user]

Function log(base; x) added in revision 2ee3d586.

Reported by helder.pereira.correia on 2014-03-06 06:07:53 - Status changed: Fixed