Change names of logarithm functions

[Titaniumtown]

Usually log refers to taking the logarithm of a function with base 10. But currently this returns the logarithm with base e (e being Euler's number).

This PR fixes that issue by making log refer to log10, and ln referring to the actual function ln refer to logarithm with base e.

I believe I did this properly. but do let me know!

[bertiqwerty]

Thanks for the pull request!

1. My undergraduate analysis professor had and Wolfram Alpha has a different opinion about the default meaning of log. (https://www.wolframalpha.com/input?i=exp%28log%28x%29%29)
2. However, in order to avoid confusion I am fine with renaming log to ln for the natural logarithm. But log should not refer to log10. log would then not be available anymore.
3. You have to adapt partial/mod.rs according to the change, here and here.

[Titaniumtown]

1. My undergraduate analysis professor had and Wolfram Alpha has a different opinion about the default meaning of `log`. (https://www.wolframalpha.com/input?i=exp%28log%28x%29%29)

Ah lol. That's not what I was taught lol. But if that's the way of doing it 🤷🏻

2. However, in order to avoid confusion I am fine with renaming `log` to `ln` for the natural logarithm. But `log` should not refer to `log10`. `log` would then not be available anymore.

Sounds good!

3. You have to adapt `partial/mod.rs` according to the change, [here](https://github.com/bertiqwerty/exmex/blob/cb73fa8481edaecb0c604928c4b362e8388b4618/src/partial/mod.rs#L811) and [here](https://github.com/bertiqwerty/exmex/blob/cb73fa8481edaecb0c604928c4b362e8388b4618/src/partial/mod.rs#L943).

Got it.

[Titaniumtown]

I think what I pushed addresses everything 👍🏻

[bertiqwerty]

Almost there, I think. As indicated by the compilation error, you have to add another line

unary_name!(log10, Float);

for log10 after https://github.com/bertiqwerty/exmex/blob/cb73fa8481edaecb0c604928c4b362e8388b4618/src/value.rs#L334

[bertiqwerty]

And some documentation needs to be changed. https://github.com/bertiqwerty/exmex/blob/9c5d5e4edbc8a6b302eb67874442a4fbaecb56ae/src/lib.rs#L20

[Titaniumtown]

As indicated by the compilation error

I didn't get any compilation error. but I implemented the changes you mentioned.

[bertiqwerty]

Can you run

cargo test --all-features

on your side and fix the errors? I think, some test-strings need to be adapted. See https://github.com/bertiqwerty/exmex/runs/5496830706?check_suite_focus=true

[Titaniumtown]

cargo test --all-features

Oh yes. My bad.

[Titaniumtown]

Just something I noticed: derivatives of log2 and log10 don't seem to work. the derivative of log of x with base n should be equal to 1/(x*ln(n)).

[bertiqwerty]

Ah. Yes. Right. They are not implemented. Let's first merge this pull request. I will add them later. Shouldn't be a big thing.

[bertiqwerty]

Perfect. Checks have passed. Thanks for your contribution.

[bertiqwerty]

I have added the missing derivatives. Commit ad082c9759304649bd8c5ccf00ac110878106a09.

[Titaniumtown]

Thank you!