pow() fix for ud60x18

[FoxDev12]

Made pow(x, y) work for x < 1. No need to replicate in sd59x18 because log2(]0,1[) is defined there.
Doesnt waste gas on doing math for 1^y when x = 1, and does 1/((1/x)^y) to get x^y when x < 1

[PaulRBerg]

Can we move this equation in the NatSpec comments, and use MathJax?

[PaulRBerg]

Thank you very much for the PR, @FoxDev12, but to merge this, tests have to be written to cover the expanded function domain:

https://github.com/PaulRBerg/prb-math/blob/95eb710da421ea013cfaf14e16c38a6462afc7bf/test/ud60x18/math/pow/pow.t.sol

[FoxDev12]

Sure enough. Will do when i have a little time in my hands, hopefully tomorrow.

[PaulRBerg]

TY!

Lint checks aren't passing; you need to make sure they do by configuring forge fmt to work in VSCode. Install this extension and add this to your global settings (the local settings in this repo would take care of the rest):

{
  "editor.formatOnSave": true,
}

Alternatively, you could try running forge fmt from the terminal.

[PaulRBerg]

@FoxDev12 I have recently performed a significant rebase on the main branch. Sorry, it looks like that messed up your PR.

The easiest way to patch this would be to cherry pick your existing commits on a new temporary branch, rename it to the current branch, and force push to remote.

[PaulRBerg]

@FoxDev12 are you planning on re-opening this PR (or creating another one)?

[FoxDev12]

@PaulRBerg Apologies, i'm quite busy lately. I will reopen the PR this weekend.

[PaulRBerg]

@FoxDev12 I started working on this myself. While reading your implementation, I got confused by this comment on this line:

will overflow for very small x values

I don't understand why that code would overflow just for small values of x. With a small x, the result of log2(x) would be high, but another pre-requisite for an overflow is a high y. If y is comparatively small, there is no overflow in mul.